CN1675730B - Electrostatic fluid accelerator and method for controlling fluid flow - Google Patents

Abstract

A spark management device comprising: a high voltage power supply to provide electrical power to a load device; a sensor to monitor an electromagnetic parameter within the load device; a first detector to identify a pre-spark condition in the load device in response to the electromagnetic parameter; a second detector is connected to the first detector to cause the high voltage power supply to change electrical power to a level that prevents sparking in response to the pre-spark condition. A method of controlling spark: supplying high voltage power to a load device; monitoring an electromagnetic parameter of the high voltage power; the high voltage power is changed to a level that prevents sparking in response to an electromagnetic parameter that identifies a pre-spark condition. An electrostatic fluid accelerator comprising: a corona discharge electrode and a collector electrode; a high voltage power supply for supplying high voltage power to the corona discharge electrode; a sensor monitoring an electromagnetic parameter of the high voltage power; a first detector responsive to identification of a pre-spark condition; a second detector connected to the first detector varies the high voltage power to a level that prevents sparking.

Description

Electrostatic fluid accelerator and method for controlling fluid flow

related application

The entire contents of the following patents are incorporated herein by reference: Serial No. 10/187,983, "Spark Control Method and Apparatus," filed July 3, 2002; Serial No. 10/352,193, "Electrostatic Fluid Accelerators and Methods of Controlling Fluid Flow"; "Electrostatic Fluid Accelerators," Serial No. 09/419,720, filed October 14, 1999; "Electrostatic Fluid Accelerators," Serial No. 10/175,947, filed January 21, 2002. Method and Apparatus for Controlling Fluid Acceleration"; Serial No. 10/188,069, "Electrostatic Fluid Accelerator and Method of Controlling Fluid Flow," filed July 3, 2002.

technical field

The present invention relates to methods and apparatus for generating corona discharges, and in particular to methods and apparatus for fluid acceleration to provide velocity and momentum to a fluid, especially air, using ions and such electric fields for motion , and the control of such fluids.

Background technique

A number of patents (see, eg, US Patent Nos. 4,210,847 to Shannon et al. and 4,231,766 to Spurgin) have recognized the fact that corona discharges can be used to generate ions and charged particles. Such methods are widely used in electrostatic precipitators and fans as described in the book "Practical Electrostatic Precipitators" published by Chapman & Hall (1997). Corona discharge devices can be formed by applying a high voltage across a pair of electrodes (eg, a corona discharge electrode and an attraction electrode). Among them, a high-voltage power supply is applied to the paired electrodes, thereby generating a corona discharge. The electrodes are constructed and arranged to produce an inhomogeneous electric field near one of the electrodes (called the corona discharge electrode), thereby producing a corona and a charge towards the nearby complementary electrode (called the collecting or attracting electrode). The resulting corona current. The required geometry of a corona discharge electrode typically requires a point or front to face the direction of corona current flow, eg, towards the collecting or attracting electrode.

Therefore, at least the corona discharge electrode should be small or include a point or edge in order to create the required electric field gradient in the vicinity of the electrode. Corona discharge occurs over a relatively narrow voltage range, between a lower voltage for a corona onset and a higher breakdown (or spark) voltage. Below the corona onset voltage, no ions are emitted from the corona discharge electrodes and, therefore, no acceleration of air occurs. On the other hand, if the applied voltage is close to the dielectric breakdown or sparking level, sparks and arcs can be caused which interrupt the corona discharge process and create an unpleasant arcing sound. Therefore, it is generally advantageous to maintain a high voltage between these values, in particular close to but slightly below the spark level, so that fluid acceleration is most efficient.

There are many patents addressing the problem of sparking in electrostatic devices. For example, US Patent No. 4,061,961 to Baker describes a circuit for controlling the duty cycle of a two-stage electrostatic precipitator power supply. The circuit includes a switching device connected in series with the primary winding of the power transformer and a circuit operable to control the switching device. A capacitive network adapted to monitor the current in the primary winding of the power transformer is provided to operate the control circuit. Under normal operating conditions, ie when the current in the primary winding of the power transformer is within nominal limits, the capacitive network operates the control circuit to allow current to flow through the primary winding of the power transformer. However, upon detection of the increased primary current associated with the high instantaneous voltage generated by the arc, the arc occurs between the components of the precipitator and is reflected by the secondary winding of the power transformer to the primary winding of the power transformer. At this time, the capacitor network to operate the control circuit. In response thereto, the control circuit causes the switching device to inhibit current flow through the primary winding of the transformer until arcing conditions associated with high transient voltages are suppressed or otherwise suppressed. The switching device automatically re-establishes power to the primary winding after a certain time interval after the termination of the high transient voltage, thereby resuming normal operation of the electrostatic precipitator power supply.

US Patent No. 4,156,885 to Baker et al. describes an automatic current overload protection circuit for an electrostatic precipitator power supply that operates after detection of a sustained overload.

US Patent No. 4,335,414 to Weber describes an automatic electronic recovery current cut-off for an electrostatic precipitator air cleaner power supply. A protection circuit protects the power supply using an iron resonant transformer having a primary power winding, a secondary winding providing a relatively high voltage, and a tertiary winding providing a relatively low voltage. In the event of an overload in the ionizer or collector unit, the protection circuit operates to inhibit the operation of the power supply by detecting a voltage from the high voltage and comparing the detected voltage with a fixed reference value. When the sensed voltage drops below a predetermined value, current flow through the primary of the transformer is suppressed for a predetermined time. Current is automatically restored and the circuit will cycle the power off until the fault is cleared. The reference voltage is taken from the tertiary winding voltage, resulting in improved circuit sensitivity and shortened overload conditions.

As is known in the art, the application of any high voltage presents a risk of electric discharge. Discharge is ideal for some applications. As with many other high voltage applications, sparking is an undesirable event that should be avoided or prevented. This is especially the case in applications where high voltages are maintained close to a spark level (ie, dielectric breakdown voltage). For example, electrostatic precipitators operate at the highest possible voltage levels, and as such, sparks are unavoidable. Electrostatic precipitators typically maintain a spark rate of 50-100 sparks per minute. When a spark occurs, the output of the power supply typically drops to zero volts and only resumes operation after a predetermined period of time called the "ionization time" during which the air discharges and the spark is re-established front resistance. Each spark event reduces the overall efficiency of the high voltage device and is one of the main causes of electrode degradation and aging. The generation of sparks also creates an unpleasant sound that is unacceptable in many environments and related applications, for example, electrostatic air accelerators, filters and appliances used in the home.

In addition to the undesired noise produced by sparks, other inefficiencies also plague the prior art. For example, pairs of corona discharge and attraction electrodes should be constructed and arranged to produce a non-uniform electric field, with at least one electrode, the corona discharge electrode, typically being relatively small and/or Provide a suitable electric field gradient nearby. There are several known arrangements for applying a voltage between electrodes to effectively generate the required electric field for ion production. US Patent No. 4,789,801 to Lee and Patent Nos. 6,152,146 to Taylor et al. describe applying a pulsed voltage waveform across paired electrodes with a duty cycle between 10% and 100%. These patents describe that such voltage generation reduces ozone generation by means of a generated corona discharge compared to the application of steady state D.C. power. Regardless of the actual benefit of this voltage generation for reducing ozone generation, the air flow generation, the resultant pulsating air flow being considered unpleasant, is significantly reduced by using a duty cycle of less than 100%.

US Patent No. 6,200,539 to Sherman et al. describes the use of a high frequency high voltage power supply to generate an alternating voltage at a frequency of approximately 20 kHz. Such high-frequency high-voltage generation requires a large rather expensive power supply, which usually incurs high energy losses. US Patent No. 5,814,135 to Weinberg describes a high voltage power supply that produces very narrow (ie, steep, short duration) voltage pulses. Such voltage generation can produce airflows of only relatively small quantities and ratios, and is not suitable for acceleration or movement of high airflows.

US Patent Nos. 4,789,801 to Lee, 5,667,564 to Weinberg, 6,176,977 to Taylor et al. and 4,643,745 to Sakakibara et al. also describe air moving devices that use an electrostatic field to accelerate air. The air velocities achieved in these devices are too low to be practical for commercial or industrial applications.

US Patent Nos. 3,699,387 and 3,751,715 to Edwards describe the use of multiple stages of electrostatic air accelerators (EFAs) placed in succession to enhance the flow of air. These devices use a conductive mesh as the attracting (collecting) electrode, which mesh separates nearby corona electrodes. The mesh presents a considerable air resistance and slows air flow, thereby preventing the EFA from reaching the required higher flow rates.

Unfortunately, these devices have not been able to generate commercially viable airflows. Traditional air moving devices that provide multiple stages cannot provide an answer by themselves. For example, five tandem stages of electrostatic fluid accelerators placed one behind the other supply only 17% more gas flow than a single stage accelerator. See, eg, US Patent No. 4,231,766 to Spurgin. Likewise, changing the relative position of the electrodes relative to each other provides only limited improvements to the performance and fluid velocity of the EFA. For example, US Patent No. 4,812,711 reports producing air velocities of only 0.5 m/s, well below what can be expected and delivered by commercial fans and blowers.

Accordingly, there is a need for a practical electrostatic fluid accelerator that produces commercially useful flow rates while minimizing undesirable and parasitic effects such as sparks.

It has been found that the spark initiation voltage level does not have a constant value even for the same set of electrodes. A spark is an unexpected event that cannot be predicted with certainty. The occurrence of a spark is generally an unpredictable event that can have many causes, many if not all of which are transient. Spark initiation tends to vary with fluid (ie, dielectric) conditions such as humidity, temperature, contamination, and the like. The spark voltage can vary with an onset margin of as much as 10% or more for the same set of electrodes.

High voltage applications and devices known in the industry typically deal with sparks only after they have occurred. The operating voltage must be kept relatively low if all sparking is to be avoided. The necessary reduced voltage levels reduce the air flow rate and also reduce the device performance of associated devices such as electrostatic fluid accelerators and dust collectors.

As noted above, existing techniques and devices only address spark events after spark initiation; there is no commercially practical solution to prevent sparks from occurring. Providing a dynamic mechanism to avoid sparking (instead of just extinguishing an existing arc) while maintaining voltage levels within the range where sparking can occur will result in a more efficient device operation while avoiding accompanying sparking The sound of arcing occurs.

Contents of the invention

The present invention includes features related to ion generating devices and processes to provide high efficiency, high output, and reduce or eliminate parasitic effects such as reduced sparking and ozone generation.

The invention provides a spark control device, comprising:

a high voltage power supply operative to provide electrical power to the load device;

a sensor operative to monitor one or more electromagnetic parameters within said load device;

a first detector responsive to the one or more electromagnetic parameters to identify pre-spark conditions within the load device; and

A second detector coupled to said first detector enables said high voltage power supply to rapidly vary the magnitude of said electrical power to a level that prevents sparking in response to said pre-spark condition.

The present invention also provides a kind of method of controlling spark, comprises the following steps:

supplying high voltage power to a load device;

monitoring an electromagnetic parameter of the high voltage power to detect a pre-spark condition of the load device; and

controlling the high voltage power in response to one or more electromagnetic parameters identifying the pre-spark condition to rapidly vary the magnitude of the high voltage power to a level that prevents sparking from occurring in order to control the pre-spark condition The occurrence of the associated spark event.

The present invention also provides an electrostatic fluid accelerator, comprising:

a corona discharge electrode and a collector electrode in an array;

a high voltage power supply electrically connected to said array for supplying high voltage power to said corona discharge electrodes;

a sensor configured to monitor an electromagnetic parameter of said high voltage power;

a first detector, responsive to identifying a pre-spark condition, to control the supply of said high voltage power to a load device; and

a second detector connected to said first detector, said second detector being operable to control said high voltage power supply to rapidly vary the magnitude of said high voltage power in response to said pre-spark conditions to a level that prevents sparks from occurring.

It is a feature of the present invention to provide high voltage generation for devices such as, but not limited to, corona discharge systems. The present invention provides for detecting the onset of a spark some time before full dielectric breakdown and spark discharge. Using a "inertialess" high voltage power supply, a feature of the present invention controls electrical discharges associated with sparks. Therefore, it is practical to use a high voltage level that is substantially closer to the spark initiation level while preventing sparking from occurring.

Features and aspects of the invention also relate to spark control in situations, for example, where absolute spark suppression is not required, or may not even be required.

According to one aspect of the invention, a spark control device includes a high power supply and a detector configured to monitor a parameter of current supplied to a load device. Pre-spark conditions are identified in response to these parameters. A switching circuit is responsive to identification of the pre-spark condition to control current supplied to the load device.

According to a feature of the invention, the high voltage power supply may include a high voltage power supply configured to transform a primary power supply into a high voltage power feed for supplying current.

According to another feature of the invention, the high voltage power supply may include a step-up power transformer, and the high voltage power supply includes an alternating current (ac) pulse generator having an output connected to a primary winding of the step-up power transformer. A rectifier circuit is connected to the secondary winding of the step-up power transformer to provide current at a high voltage level.

According to another feature of the invention, the high voltage power supply may comprise a high voltage power supply having a low inertia output circuit.

According to another feature of the invention, the high voltage power supply may include a control circuit operable to monitor current flow. In response to the detected pre-spark condition, the voltage of the current is reduced to a level that does not induce sparking to occur (eg, a level below that of sparking).

According to another feature of the invention, the load circuit is connectable to the high voltage power supply to selectively accept a substantial portion of the current in response to the identified pre-spark condition. A load circuit may be an electrical device used to dissipate electrical energy (eg, a resistor that converts electrical energy into heat) or an electrical device used to store electrical energy (eg, a capacitor or an inductor). The load means may also include certain working means, for example, different stages of corona discharge means, which include a plurality of electrodes configured to accept electrical current to form a corona discharge. Corona discharge devices may be in the form of electrostatic air accelerators, electrostatic air cleaners and/or electrostatic precipitators.

According to another feature of the invention, the switching circuit may include circuitry for selectively powering auxiliary devices in addition to powering the primary load device from the power source. Thus, if an incipient spark is detected, at least a portion of the power regularly supplied to the primary device may be shunted to the auxiliary device in response to the identified pre-spark condition, thereby reducing the voltage within the primary device and Avoid sparks. One or both primary load devices may be electrostatic air handling devices configured to accelerate fluid under the influence of electrostatic forces generated by the corona discharge structure.

According to another feature of the invention, the detector is sensitive to phenomena including changes in current levels or waveforms, changes in voltage levels or waveforms, or magnetic, electrical or optical events related to pre-spark conditions .

According to another aspect of the invention, a method of controlling sparking may include supplying a high voltage current to a device, and monitoring the high voltage current to detect a pre-spark condition of the device. The high voltage current is controlled in response to the pre-spark conditions to control the occurrence of spark events related to the pre-spark conditions.

According to another characteristic of the invention, the step of monitoring may comprise detecting current spikes in the high voltage current.

According to a feature of the invention, the step of supplying a high voltage current may include shifting a power supply from a primary voltage level to a secondary voltage level higher than the primary voltage level. The power supply at the secondary voltage level is then rectified to supply high voltage current to the device. This may include reducing the output voltage or voltage at the device, for example, the voltage level on the corona discharge electrodes of a corona discharge air accelerator. The voltage can be reduced to a level at which no pilot spark occurs. Control may also be achieved by routing at least a portion of the high voltage current to an auxiliary load device. The above arrangement can be implemented by switching a resistor into an output circuit of a high voltage power supply supplying high voltage current.

According to another feature of the invention, the additional steps include directing the fluid to a corona discharge electrode, energizing the corona discharge electrode with a high voltage current, generating a corona discharge into the fluid and accelerating it under the influence of the corona discharge fluid.

According to another aspect of the invention, an electrostatic fluid accelerator may include an array of corona discharge and collector electrodes, and a high voltage power supply electrically connected to the array for supplying high voltage current to the corona discharge electrodes. A detector may be configured to monitor the current level of the high voltage current and responsively identify pre-spark conditions. A switching circuit controls the high voltage current in response to the identified pre-spark condition.

According to a feature of the invention, the switching circuit may be configured to inhibit the supply of high voltage current to the corona discharge electrodes by the high voltage power supply in response to pre-spark conditions.

According to another feature of the invention, the switching circuit may include a bleeder resistor configured to accept at least a portion of the high voltage current in response to the identified pre-spark condition.

Corona sparking has been found to be preceded by an observable electrical event that exposes a sparking event to occur and can be monitored to predict when dielectric breakdown is imminent. The indicative precursor to sparking may be an increase in current, or a change or variation (eg, an increase) in the magnetic field near the corona discharge, or other monitorable condition within the circuit or electrode environment. In particular, it has been determined experimentally that a spark event is usually preceded by an increase in corona current. This increase in current occurs a short time (ie, 0.1-1.0 milliseconds) prior to the spark event. The increase in current may be in the form of a short duration current spike that appears about 0.1-1.0 milliseconds (msec) before the associated electrical discharge. This current increase is substantially independent of the voltage change. In order to prevent a sparking event, it is necessary to detect the initial current spike event and sharply drop the voltage level applied to and/or at the corona discharge electrodes below the sparking level.

Two conditions should be met in order to be able to control such sparks. First, the high-voltage power supply should be able to rapidly ramp down the output voltage before a spark event occurs, ie, within the time period from event detection until the start of the spark event. Second, the corona discharge device should be capable of discharging and storing electrical energy, ie, discharge before spark.

The time between corona current increase and spark is on the order of 0.1-1.0 msec. Therefore, the electrical energy stored in the corona discharge device (comprising the power supply and the energized corona discharge electrodes) should be able to dissipate the stored energy in a relatively short time, ie in the sub-millisecond range. In addition, the high voltage power supply should have "low inertia" characteristics (ie, capable of rapidly changing a voltage level on its output) and circuitry to interrupt voltage generation, preferably in the sub-millisecond or millisecond range. Such a rapid voltage drop is practical, which can be done using a high frequency switching high voltage power supply, operating in the range of 100kHz to 1MHz, with low stored energy and circuitry to quickly drop or turn off the output voltage. To provide such capability, the power supply should operate at the high voltage switching frequency for an "off" period (i.e., the time required for discontinuous high voltage output) that is less than the detection of corona current spikes and any generation of The time between spark events. Since state of the art power supplies can operate at switching frequencies up to 1 MHz, in particular, a properly designed (eg, inertialess) power supply can interrupt current generation in the sub-millisecond range as needed. That is, it is possible to shut down the power supply and reduce the output voltage significantly to a safe level, ie well below the level at which electrical discharge in the form of a spark begins.

There are different techniques used to detect electrical events preceding the spark. A current sensor can be used to measure peak or average, or RMA (root mean square), or any other quantity or value of output current, as well as the rate of change of current, ie, dI/dt. Alternatively, a voltage sensor may be used to detect the voltage level of the power supply or the voltage level of an AC component. Another parameter that can be monitored to identify an impending spark event is the drop in output voltage, or the first derivative of voltage with respect to time (ie, dV/dt) of the AC component of the output voltage. Electric or magnetic field strengths or other changes within the corona discharge preceding the electrical discharge in the form of a spark may also be detected. A common feature of these technologies is that the increase in corona current spikes is not accompanied by an increase in output voltage or any significant power supply fluctuations.

Different techniques can be used to quickly reduce the output voltage generated by the power supply. A preferred method is to turn off the power transistor, or SCR, or any other switching component of the power supply that forms the pulsating high frequency ac current supplied to the primary of the step-up transformer, in order to interrupt the process of electric power generation. In this situation, the switching components become inactive and no electrical power is generated or supplied to the load. The disadvantage of this method is that the residual energy accumulated in the power supply components, especially in the output filtering stages such as capacitors and inductors (including stray capacitance and leakage inductance) must be released somewhere, i.e. discharge to a suitable energy dissipation device, commonly referred to as "grounding". Without some sort of fast draining mechanism, the residual energy stored by the power supply could be discharged into the load, thus slowing down the rate at which the output voltage drops (ie, "droops"). Alternatively, a preferred structure and method electrically "shorts" the primary windings (i.e., the terminals of the interconnected windings) of the magnetic components (transformers and/or multi-turn inductors) to dissipate the magnetic field to break down the stored Any energy, thereby ensuring that no energy is transferred to the load. Other more basic methods short circuit the output of the power supply to a lower value resistor. However, this resistance should be much higher than the spark resistance and, at the same time, should be smaller than the operating resistance of the corona discharge device to be powered, as it would be at the moment before the spark event occurs. For example, if a high voltage corona device (e.g., an electrostatic fluid accelerator) draws 1 mA of current just prior to spark detection, and passes a current limiting device (e.g., series current limiting resistor) to limit the output current from the power supply to 1A, the "bleeder" resistor applied across the load (i.e. between the corona discharge electrode and the attractor electrode of the corona discharge device) should progress progressively to greater than 1mA (ie, provide a lower resistance and thereby conduct a current greater than the normal operating load current), but less than 1A (ie, less than the maximum short circuit current limit). This additional bleeder resistor can be connected to the power supply output through a high voltage reed type relay or other high voltage high speed relay or switching component (eg, SCR, transistor, etc.). A common and very important feature of an inertialess high voltage power supply is that it interrupts the occurrence of electrical power for a short time and at a time less than the time between the preceding electrical event and the indication of an initial spark event, The instant is when the sparking has actually occurred without some intervention, ie typically in the sub-millisecond or millisecond range.

Another important feature of such an inertialess power supply is that any residual energy accumulated and stored within the power supply components should not significantly slow down or otherwise impede the discharge process within the load, such as a corona discharge device. For example, if the corona discharge device discharges its own electrical energy within 50 milliseconds, and the minimum expected time before the spark event is 100 milliseconds, then the power supply should not add more than 50 milliseconds to the discharge time so that the actual discharge time does not exceed 100 milliseconds. Therefore, high voltage power supplies should not use any energy storage components like capacitors or inductors that discharge their energy into corona discharge devices after active components such as power transistors are turned off. To provide this capability and functionality, any high voltage transformer should have a relatively small leakage inductance and either little or no output filter capacitance. It has been found that conventional high voltage power supply layouts including voltage amplifiers and flyback inductors are generally not suitable for such spark control or prevention.

The present invention also addresses the deficiencies of the prior art to recognize or evaluate the fact that the ionization process is more complex than just applying a voltage to two electrodes. In contrast, prior art systems and methods generally do not produce comparable airflows while at the same time failing to limit ozone production.

The processes associated with corona have three common aspects. The first aspect is the generation of ions within the fluid medium. The second aspect is the release of fluid molecules and foreign particles by the emitted ions. The third aspect is the acceleration (ie along the lines of electric force) of emitted particles towards an opposing (collector) electrode.

The acceleration of air or other fluids caused by ions depends on the number (ie number) of ions and their ability to be in the vicinity of fluid ions and thus repel the induced charge of fluid ions towards the opposite electrode. At the same time, the generation of ozone is substantially proportional to the power applied to the electrodes. When ions are induced into a fluid, they tend to attach themselves to particles and charge-neutral fluid molecules. Each particle can accept only a limited amount of charge depending on the size of the particular particle. According to the following formula, the maximum charge (then called saturation charge) can be expressed as follows:

Q _p ＝{(1+2λ/d _p ) ² +(1/(1+2λ/d _p ))*((εr-1)/(ε _r +2))*πε _o d _p ² E, where , _dp = particle size, _εr is the dielectric constant of the dielectric material between the electrode pair, and _εo is the dielectric constant in vacuum.

From this equation it follows that a given amount of ions introduced into a fluid will charge nearby molecules and surrounding particles to some maximum level. The number of ions represents the amount of charge flowing from one electrode to the other and determines the corona current flowing between the two electrodes.

Once charged, fluid molecules are attracted to the opposite collector electrode in the direction of the electric field. This directional spatial movement of molecules with a charge Q, upon which an electric field force F is applied, depends on the electric field strength E, i.e., which in turn is proportional to the voltage applied to the electrodes:

F＝-Q*E

Rr If the maximum number of ions is introduced into the fluid by the corona current, and the generated charges are accelerated by the voltage applied alone, a comparable gas flow is produced and the average power consumption drops significantly. This can be achieved by controlling how the value of the corona current varies from a certain minimum value to a certain maximum value, while at the same time keeping the voltage between the electrodes substantially constant. In other words, it has been found that the high voltage ripple (or, alternating component) of the supply voltage applied to the electrodes (as part of the average high voltage applied) is minimized, while at the same time, the overall average or RNS amplitude of the current It is beneficial to keep the current ripple fairly high and idealized compared to the value. (Unless otherwise noted or implied by usage, as used herein, the term "ripple" and the phrase "alternating component" refer to the time-varying component of a signal, including signals such as sine waves, square waves, sawtooth waves, All time-varying signal waveforms, irregular waves, complex waves, etc., also include bidirectional waveforms (also known as "alternating current" or "ac") and unidirectional waveforms such as pulsating direct current or "pulsating dc". Furthermore, unless the context indicates otherwise, adjectives such as "small,""big," etc., used in conjunction with such terms including, but not limited to, "ripple,""accomponent,""alternatingcomponent," etc., describe The relative or absolute magnitude of particular parameters such as signal potential (or "voltage") and signal flow rate (or "current").) Because of the reactivity of the corona and corona-generating arrays of the attractor electrodes ( capacitive) components, so such distinctions between voltage and current waveforms are possible in corona-related techniques and devices. The capacitive component results in a relatively low-amplitude alternating component of the voltage, producing a correspondingly large alternating component of the current. For example, a power supply that generates high voltage with small ripples can be used in a corona discharge device. These ripples should be of relatively high frequency "f" (ie, greater than 1 kHz). The electrodes (i.e., corona and collector electrodes) are designed such that their mutual capacitance C is high enough to present a relatively small impedance _Xc when a high frequency voltage is applied, which is expressed as follows:

X _c =1/2πfC

The electrodes may represent or be viewed as a parallel connection of a non-reactive dc resistance and a reactive ac capacitive impedance. Ohmic resistance causes corona current to flow from one electrode to the other. The magnitude of this current is approximately proportional to the magnitude of the applied voltage and is substantially constant (dc). The capacitive impedance is responsible for the ac part of the current flow between the two electrodes. This portion is proportional to the magnitude of the ac component ("ripple") of the applied voltage and inversely proportional to the frequency of the alternating component of the voltage. Depending on the magnitude of the ripple voltage and its frequency, the magnitude of the ac component of the current between the two electrodes can be smaller or larger than the dc component of the current.

It has been found that a power supply capable of generating a high voltage with a small magnitude ripple (i.e., a filtered dc voltage) but providing a current with a relatively large ac component (i.e., a large magnitude current ripple) across the electrodes provides improved Ion generation and fluid acceleration, while, in the case of air, significantly reducing or minimizing the generation of ozone. Therefore, the current ripple is expressed as a ratio or fraction defined as the magnitude of the ac component of the corona current divided by the magnitude of the dc component of the corona current (ie, I _ac /I _dc ), the current ripple should be considerably larger than Voltage ripple (i.e. at least 2 times), preferably at least 10 times, 100 times, even more preferably 1000 times, voltage ripple is similarly defined as the time-varying component of the voltage applied to the corona discharge electrode Or the magnitude of the ac component divided by the magnitude of the dc component (ie, V _ac /V _dc ).

It has also been found that corona discharge devices perform best in the following situations: the output voltage has an alternating component of a voltage of small magnitude relative to the average voltage magnitude, while the electrodes and intervening dielectric substances (i.e., Accelerated fluid) current is at least 2 times, preferably 10 times (relative to a dc current component) greater than the alternating component of the voltage (relative to a dc current component), ie, the ac/dc ratio of the current is much greater than A factor of 2, 10, or even greater than the ac/dc ratio of the applied voltage. That is, it is preferable to generate a voltage across the corona discharge electrodes such that the generated current satisfies the following relationship:

V _ac ＜＜V _dc and I _ac ～I _dc

Or V _ac /V _dc <<I _ac /I _dc

Or V _ac < V _dc and I _ac > I _dc

Or V _RMS ≈ V _MEAN and I _RMS > I _MEAN

If any of the above requirements are met, the resulting corona discharge device will consume less power per cubic foot of fluid moved and produce less of ozone (in the case of air).

In order to meet these requirements, the power source and corona generating device should be suitably designed and constructed. In particular, the power supply should produce a high voltage output with only minimal and at the same time relatively high frequency ripple. The corona generating device itself should have a predetermined value of stray or parasitic capacitance designed to provide a relatively high frequency current through the electrodes (ie from one electrode to the other). If the power supply produces low frequency ripple, X _c will be quite large and the magnitude of the alternating component current cannot be compared with the magnitude of the dc component of the current. Alternating current is not comparable to DC if the power supply produces very little or no ripple. If the corona generator (ie, the electrode array) has a low capacitance (including parasitic and/or stray capacitance between the electrodes), then again the alternating current will not be comparable in magnitude to the direct current. If a large resistor is installed between the power source and the electrode array (see, for example, Figures 1 and 2 in U.S. Patent No. 4,789,801 to Lee), the magnitude of the ac current ripple will be suppressed (i.e., dropped), and the It cannot be compared in magnitude to the ripple of the dc (ie, constant) component of the current. Therefore, the corona generator will only function optimally to provide sufficient air flow, increased operating efficiency and desired ozone levels if certain conditions are met such that a predetermined voltage and current relationship exists. The resulting power costs are also lower.

In particular, a waveform-generating power supply does not require substantial output filtering, which would otherwise be relatively expensive to provide and connect physically large high voltage capacitors at the output of the power supply. This alone makes the power supply less expensive. In addition, such a power supply has less "inertia", ie, less stored energy that tends to reduce amplitude changes in the output, and is therefore capable of rapidly changing output voltage than a high inertia power supply with no or negligible ripple.

The present invention also addresses several deficiencies in the prior art, the limitations of which are air flow and the general inability to achieve theoretically optimal characteristics. One of these deficiencies includes the excessive size requirements for multi-stage EFA devices, since several stages of EFA are placed consecutively, requiring considerable length along the air passage (ie, in the direction of air flow). The longer channel also presents greater resistance to air flow.

Additional problems arise when stages are placed close to each other. Reducing the spacing between stages creates "back corona" between an attractor electrode of one stage and a corona discharge electrode adjacent the next stage, which results in reversed air flow. In addition, there are parasitic currents between adjacent stages due to the capacitance between adjacent stages. This current is caused by asynchronous high voltage ripples or high voltage pulses between adjacent stages.

Using large or multi-stage EFAs, such that each separate (or grouped) stage is provided with its own high voltage power supply (HVPS), further problems arise. In this case, the high voltages required to create a corona discharge can lead to an unacceptable level of sparking between the electrodes. When a spark occurs, the HVPS must be completely shut down for the time required to deionize and extinguish the spark before resuming operation. When the number of electrodes is increased, sparks occur more frequently than with one set of electrodes. If an HVPS feeds several sets of electrodes (ie several stages), it must be shut down more frequently to extinguish the increased number of sparks that occur. This results in undesirably increased power interruptions for the overall system. To solve this problem, it is advantageous to feed each stage from its own dedicated HVPS. However, the use of separate HVPSs requires that successive stages be spaced wider to avoid undesirable electrical interactions caused by stray capacitance between electrodes of adjacent stages and to avoid back corona.

The present invention proposes an innovative solution to increase air flow by closely spaced EFA stages while minimizing or avoiding the introduction of undesirable effects. Embodiments of the invention include a combination of electrode geometry, mutual position, and voltage applied to the electrodes to provide enhanced performance.

According to a feature of the invention, a plurality of corona electrodes and collecting electrodes are positioned parallel to each other, or extend between corresponding planes perpendicular to the air flow direction. All electrodes of adjacent stages are parallel to each other so that all electrodes of the same type (i.e., corona discharge electrodes or collecting electrodes) are placed in the same parallel planes, the parallel planes being orthogonal to electrodes of the same type or in which the electrode edges are located the planes. According to another feature, the stages are closely spaced to avoid or minimize any corona discharge between the poles of adjacent stages. If the closest spacing between adjacent electrodes is "a", the potential difference (V1-V2) between the voltage V1 applied to the first electrode and the voltage V2 applied to the closest second electrode, and the distance between the electrodes The ratio of the distance between them is a normalized distance "aN", then aN=(V1-V2)/a. The normalized distance between the corona discharge wires of one stage and the nearest part of the adjacent stage shall exceed the corona onset voltage applied between these electrodes, which in practice means that the corona onset voltage shall not be less than 1.2 to 2.0 times the normalized distance from the corona discharge electrode to the corresponding associated (ie closest) attraction electrode, thereby preventing back corona formation.

Finally, the voltages applied to adjacent stages should be synchronized and in phase. That is, the ac components of the voltages applied to the electrodes of adjacent stages should rise and fall simultaneously and have substantially the same waveform and magnitude and/or amplitude.

The present invention increases EFA electrode density (typically measured on the order of per unit length) and eliminates or significantly reduces parasitic currents between electrodes. At this point, the present invention eliminates corona discharge (eg, back corona) between electrodes of adjacent stages. This is accomplished in part by powering adjacent EFA stages with substantially the same voltage waveform, i.e., the potentials on adjacent electrodes have the same or very similar alternating components, so as to eliminate or reduce any ac between stages differential voltage. Working between stages in such a synchronized manner, the potential difference between adjacent electrodes of adjacent EFA components remains constant and any generated parasitic currents from one electrode to the other are minimized or completely avoided. Synchronization can be implemented by different methods, but the easiest way is to power adjacent EFA components with corresponding synchronous and in-phase voltages from corresponding power supplies, or with synchronous power supplies to provide similar The ac component of the magnitude. This can be achieved with the same power supply connected to adjacent EFA components, or with different (preferably matched) power supplies generating synchronized and in-phase ac components of the applied voltage.

The present invention also addresses other deficiencies of the prior art, including airflow limitations and the general inability to achieve theoretically optimal characteristics. Additional aspects of these deficiencies include the limited ability to generate large volumes of fluid flow for commercial use. Yet another disadvantage is that a large electrode structure (beyond the corona electrodes) must be used to avoid generating high electric fields. Using physically large electrodes also increases fluid flow resistance and limits EFA capacity and efficiency.

Other problems arise when an EFA is operated near or at maximum capacity, namely, a certain maximum applied voltage and power consumption. In this case, the applied operating voltage is characteristically kept close to the dielectric breakdown voltage, so that undesired electrical events such as sparks and/or arcs can occur. If one of the electrodes is contacted unintentionally, further disadvantages can arise that a large current can flow through the person, which is both unpleasant and often dangerous.

The usual use of thin wires for corona electrodes also causes other problems. Such wire must be relatively thin (typically about 0.004" diameter) and fragile, thus, difficult to clean or otherwise work on.

Other problems also arise when a stronger fluid flow (eg, higher fluid flow rate) is necessary or required. Conventional multipole arrangements result in a relatively low multipole density (and therefore insufficient for the maximum achievable electrical power), since the corona electrodes must be located at a minimum distance from each other in order to avoid mutual interference with their corresponding electric fields. Spacing requires increased bulk and limits electrode density.

A feature of the present invention provides an innovative solution utilizing high resistive materials in the construction and processing of the accelerating electrodes to enhance fluid flow by using an innovative electrode geometry and optimized mutual electrode placement (i.e., interelectrode geometry) .

According to a feature of the invention, a plurality of corona electrodes and acceleration electrodes are positioned parallel to each other, some electrodes extending between corresponding planes perpendicular to the direction of the gas flow. Corona electrodes are made of conductive material, eg metal or conductive ceramic. Corona electrodes can be in the form of thin wires, blades or strips. It should be noted that the corona discharge occurs over narrow areas of the corona electrodes, these narrow areas are referred to herein as "ionization edges". These edges are usually located on the downstream side of the corona electrode with respect to the direction of desired fluid flow. Other electrodes (for example, accelerating electrodes) are in the shape of rods or thin ribbons extending in the main direction of fluid flow. Generally, the number of corona electrodes is equal to the number of accelerating electrodes+1. That is, each corona electrode is located relative to and parallel to one or two adjacent accelerating electrodes.

The accelerating electrodes are made of a high resistance material providing a high resistance path, ie of a high resistivity material that readily conducts the corona current without incurring a significant voltage drop across the electrodes. For example, accelerating electrodes are made of relatively high-resistance materials, such as carbon-filled plastic, silicon, gallium arsenide, indium phosphide, boron nitride, silicon carbide, cadmium selenide, and the like. These materials should generally have a resistivity p in the range of 103 to 109 Ω-cm, preferably between 105 and 108 Ω-cm, more preferably between 106 and 107 Ω-cm.

At this point, the geometry of the electrodes is chosen such that local events or disturbances such as sparks or arcs can be terminated without significant current increase or noise generation.

The present invention increases EFA electrode density (commonly measured in 'electrode length' per volume) and significantly reduces the aerodynamic fluid drag caused by the electrodes relative to the physical thickness of the electrodes. A further advantage of the present invention is that it provides virtually spark-free operation no matter how closely the operating voltage applied to the electrodes approaches a dielectric breakdown limit. Still another advantage of the present invention is that it provides a more robust shape of the corona electrode, making the electrode more stable and reliable. The design of the electrodes is such that it creates a "failure-free" EFA, i.e. there is no safety hazard if someone touches it inadvertently.

A still further advantage of the present invention is that the corona discharge is provided using electrodes other than solid materials. For example, a conductive fluid can be effectively used for corona discharge emission, supporting greater electrical power handling capabilities and, therefore, increasing the velocity of the fluid. In addition, fluids can change electrochemical processes near the sheath of a corona discharge, e.g., producing less ozone (in the case of air) than from solid corona materials, or providing a chemical change through the fluid (transient Harmful gas destruction).

Brief description of the drawings

Figure 1 is a schematic circuit diagram of a high voltage power supply (HVPS) with a low inertia output circuit that can be controlled to rapidly reduce a voltage output level to a certain margin below the dielectric breakdown initiation level The level of the degree, the breakdown start level also produces a high-amplitude dc voltage, which has a low-amplitude high-frequency voltage ripple;

Figure 2 is a schematic circuit diagram of another high voltage power supply configured to prevent spark events within a high voltage device such as a corona discharge device;

3 is a schematic circuit diagram of another high voltage power supply configured to prevent spark events within the high voltage device;

4 is a schematic circuit diagram of a high voltage power supply configured to prevent spark events within the high voltage device;

Figure 5 is an oscilloscope trace of an output corona current and output voltage at the corona discharge electrodes of an electrostatic fluid accelerator receiving power from a HVPS configured to anticipate and avoid spark events;

Figure 6 is a diagram of a HVPS connected to an HV power supply supplying an electrostatic device;

Figure 7A is a schematic diagram of a power supply generating dc voltage and dc+ac current;

Figure 7B is a waveform of the power supply output showing voltage and current magnitudes versus time, respectively;

Figure 8A is a schematic diagram of a corona discharge device with insufficient interelectrode capacitance to (i) optimize air flow, (ii) reduce power consumption and/or (iii) minimize ozone generation;

Figure 8B is a schematic diagram of a corona discharge device optimized to benefit from and cooperate with a power source such as that shown in Figure 1;

Figure 9 is an oscilloscope trace of the high voltage applied to the corona discharge device and the resultant corona current;

Figure 10A is a schematic diagram of an electrostatic fluid accelerator (EFA) assembly with a single high voltage power supply feeding an adjacent corona discharge stage;

Figure 10B is a schematic diagram of an EFA assembly with a pair of synchronous power supplies feeding each adjacent corona discharge stage;

Figure 11A is a timing graph of voltage and current between electrodes of adjacent EPA stages without ac differential voltage components between stages;

Figure 1 IB is a timing graph of voltage and current between electrodes of adjacent EPA stages, where there is a small voltage ripple between stages;

12 is a schematic diagram of a power supply unit including a pair of high voltage power supply subassemblies with synchronized output voltages;

13A is a schematic top view of a two-stage EFA assembly implementing a first electrode arrangement geometry;

13B is a schematic top view of a two-stage EFA assembly implementing a second electrode arrangement geometry;

14 is a schematic diagram of an EFA assembly with corona electrodes formed as thin wires electrically spaced from opposing high-resistance accelerating electrodes;

Figure 15 is a schematic diagram of an EFA assembly with a corona electrode formed as a thin wire and an accelerating electrode formed as a high resistance rod, the conductive portion of the latter being completely enclosed within the housing;

16 is a schematic diagram of an EFA assembly with a corona electrode formed as a thin line and an accelerating electrode formed as a high resistance rod with adjacent segments of varying or stepped conductivity along the width of the accelerating electrode;

17 is a schematic diagram of an EFA assembly with corona electrodes in the shape of thin ribbons positioned between electrically opposing high-resistance accelerating electrodes;

FIG. 18A is a graph showing corona current distribution within a fluid and within the bulk of corresponding accelerating electrodes;

FIG. 18B is a diagram showing the path of current generated by a spark or arc event;

Figure 19 is a schematic diagram of a comb-shaped accelerating electrode; and

Figure 20 is a schematic illustration of a hollow droplet corona electrode filled with a conductive fluid and inserted between high resistance accelerating electrodes.

Detailed ways

FIG. 1 is a schematic circuit diagram of a high voltage power supply (HVPS) 100 configured to prevent spark events within a high voltage device such as an electrostatic fluid accelerator. HVPS 100 includes a high voltage step-up transformer 106 with a primary winding 107 and a secondary winding 108. The primary winding 107 is connected to an ac voltage provided by the DC voltage source 101 through the half-bridge converter (power transistors 104, 103 and capacitors 105, 114). A gate signal controller 111 generates control pulses at the gates of transistors 104, 113, the frequency of which is determined by the values of resistor 110 and capacitor 116 forming an RC timing circuit. The secondary winding 108 is connected to a voltage rectifier 109 comprising four high voltage (HV), high frequency diodes configured as a full wave bridge rectifier circuit. HVPS 100 generates a high voltage between terminal 120 and ground, which are connected to an HV device or electrode (eg, a corona discharge device). The AC component of the voltage applied to the HV device (eg, across an array of corona discharge electrodes) is detected by high voltage capacitor 119 , while the detected voltage is limited by Zener diode 122 . When the output voltage exhibits pre-spark voltage fluctuation characteristics, the characteristic AC fluctuation component results in a substantial signal level across resistor 121, turning on transistor 115. Transistor 115 is grounded to pin 3 of signal controller 111 and interrupts the voltage across the gates of power transistors 104 and 113 . By rendering transistors 104 and 113 non-conductive, an almost instantaneous voltage interruption affects the primary winding 107 and, therefore, passes to the closely coupled secondary winding 108 . Since a similar rapid voltage drop at the corona discharge device results in below a spark initiation level, any imminent arcing or breakdown of the dielectric material is avoided.

Spark prevention techniques consist of two steps or stages. First, the energy stored in the stray capacitance of the corona discharge device is discharged down to the corona inception voltage by the corona current discharge. This voltage is always well below the spark initiation voltage. If this discharge occurs in a time period shorter than about 0.1 msec (ie, less than 100 mksec), the drop in voltage will effectively prevent a spark event from occurring. It has been determined experimentally that the voltage drop from the higher spark inception voltage level to the corona inception level can preferably be achieved within about 50 mksec.

After the mains voltage reaches the corona onset level and the corona current stops, the discharge process becomes much slower and the voltage falls to zero over a period of several milliseconds. Power supply 100 voltage recovery occurs after the same predetermined time defined by resistor 121 and the inherent capacitance of the gate-source of transistor 115 . The predetermined time is usually on the order of a few milliseconds and has been found to be sufficient for the ionization process and the resumption of normal operation. In response to reapplying power to the transformer 106, the voltage supplied to the corona discharge device rises from the corona power starting level to the normal operating level in a matter of milliseconds. With such a structure, sparking events do not occur even when the output voltage exceeds a value that would otherwise cause frequent sparking across the same corona discharge arrangement and structure. The power supply 100 can be formed using the electronic components provided; no special components are required.

FIG. 2 is a schematic circuit diagram of an alternative power supply 200 with reed contacts 222 and additional load 223 . The power supply 200 includes a high voltage two-winding inductor 209 with a primary winding 210 and a secondary winding 211 . Primary winding 210 is connected to ground through power transistor 208 and to a dc power supply provided at terminal 201 . PWM controller 205 (eg, a UC3843 current mode PWM controller) generates control pulses at the gate of transistor 208 whose operating frequency is determined by an RC circuit including resistor 202 and capacitor 204 . Typical frequencies can be 100kHz or higher. Secondary winding 211 is connected to a voltage doubler circuit comprising HV capacitors 215 and 218 , and high frequency HV diodes 216 and 217 . The power supply 200 generates HV dc power between 10 and 25 kV, and typically 18 kV, between output terminals 219 and 220 connected to a HV device or pole (ie, load). When the current through the shunt resistor 212 exceeds a preset level and allows a current to flow through a control coil 221 of a reed type relay including reed contacts 222, the control transistor 203 is turned on. When current passes through coil 221, for a certain time determined by resistor 207 and capacitor 206, reed contact 222 closes, shunting the HV output to HV bleed resistor 223, loading the output and lowering the output voltage level. Use of this spark control circuit in combination with various EFA components and/or devices can result in virtually all spark elimination during normal operation. Reed relay 203/222 may be ZP-3 produced by Ge-Ding Information Inc. of Taiwan.

FIG. 3 is a schematic circuit diagram of another HVPS structure similar to the structure shown in FIG. 2 . However, where the HVPS 300 includes reed contacts 322 and an additional load 323 connected directly to the output terminals of the HVPS, the HVPS 300 includes a high voltage transformer 309 with a primary winding 310 and a secondary winding 311. Primary winding 310 is connected to ground through power transistor 308 and to a DC source connected at power input terminal 301 . PWM controller 305 (eg, a UC3843) generates control pulses at the gate of transistor 308 . The operating frequency of these control pulses is determined by resistor 302 and capacitor 304 . Secondary winding 311 is connected to a voltage doubler circuit comprising HV capacitors 315 and 318 and high frequency HV diodes 316 and 317 . The HVPS 300 produces a high voltage output of approximately 18 kV at output terminals 319 and 320 connected to the HV device or electrode (load). The spark control transistor 303 is turned on when the current through the shunt resistor 312 exceeds some predetermined preset level and allows current to flow through the control coil 321 . When current flows through coil 321, reed contact 322 closes and shunts the HV output of HVPS to HV bleed resistor 323, thereby reducing the output voltage for a period of time determined by resistor 307 and capacitor 306 level. Using this initial spark detection and mitigation structure results in virtually no sparks occurring over extended operating times.

FIG. 4 shows a power supply structure similar to that shown in FIG. 2 . The HVPS 400 also includes a relay and a power discharge load 423 . The relay includes a normally open contact 422 and a coil 421 . HVPS 400 includes a power transformer 409 with a primary winding 410 and a secondary winding 411 . Primary winding 410 is connected to ground through power transistor 408 and to a dc power supply at terminal 401 . A PWM controller 405 (eg, a UC3843) generates a train of control pulses at the gate of transistor 408 . The operating frequency of these control pulses is set by resistor 402 and capacitor 404 . The secondary winding 411 is connected to a voltage multiplier circuit including HV capacitors 415 and 418 and high frequency HV diodes 416 and 417 to supply a high voltage (eg, 9kV). The power supply 400 produces a high voltage output at terminals 419 and 420 connected to HV devices or corona electrodes (loads). When the current through shunt resistor 412 exceeds some preset level predetermined to be characteristic of an initial spark event and allows current to flow through coil 421 , spark control transistor 403 turns on. When current flows through coil 421 , relay contact 422 closes, shorting primary winding 410 through bleeder resistor 423 . The additional load provided by bleeder resistor 423 rapidly reduces the output voltage level for a period of time determined by resistor 407 and capacitor 406 .

FIG. 5 is an oscilloscope display including two sweep traces of the power supply output represented by corona current 501 and output voltage 502 . As can be seen in the figure, the corona current has a characteristic narrow spike 503 representing an initial spark event within a time period of about 0.1 to 1.0 msce, here shown about 2.2 msce after the current spike. Detection of a current spike 503 within a corona discharge or similar HV device activates the control circuit, disconnects the HVPS, and preferably discharges any stored energy needed to drop an electrode potential to or below dielectric breakdown safety level. Therefore, in addition to interrupting the primary power supply to the HVPS by, for example, blocking the operation of a high-frequency pulse generator (e.g., PWM controller 205), other steps can be taken to quickly reduce the voltage applied to the HV device to a level below the spark initiation or dielectric breakdown potential. These steps and supporting circuitry may include "draining" any stored charge into a suitable "sink", eg, a resistor, capacitor, inductor, or some combination thereof. The receiver may be located within the physical confines of the HVPS, and/or at an energized device, ie, a HV device or load. If located at the load, the receiver can accept the charge stored in the load more quickly, while a receiver located at the HVPS can be directed to reduce the voltage level of the HVPS output. It should be noted that with HV resistors, the receiver can dissipate power to reduce the voltage level applied to or at the load. Alternatively, energy may be stored and reapplied after the spark event has resolved to quickly return the device to optimal operation. Furthermore, it is not necessary under any circumstances to reduce the voltage to a zero potential level, but it is desirable to reduce the voltage level to some known or predetermined value in order to avoid sparking events. According to one embodiment, the HVPS includes processing and memory capabilities to correlate the characteristics of specific pre-spark indicators (e.g., current spike magnitude, waveform, timing, etc.) Avoid or minimize the chance of a spark event. For example, the HVPS can be used to selectively interpolate multiple previously determined loads in response to an absolute magnitude or area under a current spike (i.e., ∫ _t1 ^t2 (it-i _average )dt) to provide a required The amount of sparking event control, for example, avoiding a sparking event, delaying or reducing the intensity of a sparking event, providing a desired number or rate of sparking events, etc.

Referring again to Figure 5, if the output of the HVPS is all interrupted and no current flows into the corona discharge device, the voltage across the corona discharge device drops rapidly as shown in Figure 5 and as described above. After some short time, a current spike 504 may be observed, indicating that no action was taken to reduce the voltage level applied to the HV device at the time the actual spark event had occurred. Fortunately, since the output voltage is well below the spark level, no sparking or arcing occurs. Instead, only a moderate current spike is visible, which is small enough not to cause any disturbance or undesirable arc noise. After a certain period of time on the order of 2-10 msec after the detection current spike 504, or 1-9 msec after the current spike 503, the HVPS switches on and resumes normal operation.

Figure 6 is a diagram of a HVPS 601 connected to supply HV power to an electrostatic device 602, eg, a corona discharge fluid accelerator, in accordance with the present invention. The electrostatic device 602 may include a plurality of corona discharge electrodes 603 connected to the HVPS 601 through a common connection 604 . The attractor or collector electrode 605 is connected by connection 606 to the HV output of the complementary HVPS 601 . After the HV potential is applied to the corona discharge electrode 603, a corresponding corona discharge electron cloud forms near the electrode, charging the intervening fluid (e.g., air) molecules, which act as an intervening corona discharge electrode 603 and the opposite charged attractor or collector electrode 605. The ionized fluid molecules are accelerated towards the opposing charge of the collector/attractor electrode 605, resulting in a desired fluid motion. However, due to various environmental and other disturbances, the dielectric properties of the fluid can change. This variation may be sufficient so that the dielectric breakdown voltage may drop to a point where arcing may occur between sets of corona discharge and attractor electrodes 603,605. For example, dust, moisture, and/or changes in fluid density can reduce the dielectric breakdown level to a point below the operating voltage applied to the device. By monitoring the electrical characteristics of the power supply signal (eg, current spikes or pulses, etc.) for pre-spark signal events, appropriate steps can be implemented to control the occurrence of the event, eg, reducing the operating voltage in those situations where it is desirable to avoid sparking.

While the invention described above is directed to eliminating or reducing multiple spark events and/or spark event magnitudes, other embodiments may provide other spark control facility capabilities and functionality. For example, a method according to an embodiment of the invention may control spark events that rapidly change voltage levels (e.g., change the duty cycle of the PWM controller) to make the spark discharge more uniform, providing a desired spark intensity and / or rate, or for any other purpose. Therefore, other applications and implementations of embodiments of the present invention include pre-spark detection and rapid voltage changes to a specific level to achieve desired results.

In accordance with the above and other features of the invention, three features are provided to effectively control spark events. First, the power supply should be inertialess. This means that the power supply should be able to rapidly change an output voltage in a time period that is less than the time period between the pre-spark indicator and the occurrence of the spark event. This time is usually a millisecond or less. Second, an effective and fast pre-spark detection method should be included in the power shutdown circuit. Third, the load device (eg, a corona discharge device) should have a low inherent capacitance that can discharge in a time period that is less than the time period between the pre-spark signal and the actual spark event.

Figure 7A is a block diagram of a power supply suitable for powering a corona discharge device consistent with an embodiment of the present invention. A high voltage power supply (HVPS) 705 generates a supply voltage 701 of variable magnitude Vac+dc (FIG. 7B). Voltage 701 has superimposed on the average dc voltage of Vdc an alternating component of ac or magnitude Vac having an instantaneous value represented by distance 703 (ie, the alternating component of voltage). A typical average dc component (Vdc) of the voltage 701 is in the range of 10kV to 25kV, preferably equal to 18kV. The ripple frequency "f" is typically about 100 kHz. It should be noted that low frequency harmonics, eg various 60 Hz mains frequencies including 120 Hz may be present in the voltage waveform. The calculations below consider only the most important harmonics, ie the highest frequency harmonics, in this case 100 kHz. The peak-to-peak amplitude 703 of the ripple (Vac being the ac component of the voltage 701) may be in the range of 0 to 2000 volts peak-to-peak, preferably less than or equal to 900V, with an RMS value of approximately 640V. A voltage 701 is applied to a pair of electrodes (ie, a corona discharge electrode and an attractor electrode). Resistor 706 represents the internal resistance of HVPS 705 and the resistance of the wires connecting HVPS 705 to the electrodes, which typically have a relatively small value. Capacitance 707 represents the stray capacitance between the two electrodes. It should be noted that the value of the capacitor 707 is not constant, but can be roughly estimated to be on the order of about 10pF.

Resistor 708 represents the non-resistive dc ohmic load resistor R characteristic of the air gap between the corona discharge electrode and the attractor electrode. This resistor R depends on the applied voltage and usually has a typical value of 10 MΩ.

The dc component flows from HVPS 705 through resistor 708 , while the ac component flows mainly through capacitor 707 , which presents a considerably lower impedance than resistor 708 in the 100 kHz operating range. In particular, the impedance Xc of capacitor 707 is a function of the ripple frequency. In this case it is approximately equal to:

Xc＝1/(2πfC)＝1/(2*3.14*100,000*10*10 ^-12 )＝160kΩ

The ac component I _ac of the current flowing through capacitor 707 is equal to:

I _ac =V _ac /X _c =640/160,000=0.004A=4mA.

The dc component _Idc of the current flowing through resistor 708 is equal to:

_Idc = _Vdc /R = 18kV/10MΩ = 1.8mA.

Therefore, the ac component of the resultant current between the electrodes is approximately 2.2 times the dc component of the resultant current.

The operation of device 700 can be described with reference to the timing diagram of FIG. 7B. When the ionizing current reaches a certain maximum magnitude (Imax), ions are emitted from the corona discharge electrodes to charge the surrounding molecules and particles of the fluid (ie, air molecules). At this point, maximum power is produced and maximum ozone production (in air or oxygen) occurs. When the current is reduced to I _min , less power is generated, and virtually no ozone occurs.

At this point, charged molecules and particles are accelerated towards the opposite electrode (attractor electrode) with the same force as in the case of maximum current (since the voltage remains substantially constant). Therefore, fluid acceleration rates are largely unaffected, and not to the extent that ozone generation is reduced.

The acceleration of the surrounding fluid is produced by the torque of the ions forming the corona discharge electrode to the attractor electrode. This is because ions are emitted from the corona discharge electrodes under the influence of the voltage 701 forming an "ion cloud" surrounding the corona discharge electrodes. The ion cloud moves towards the opposing attractor electrode in response to the electric field strength, which is proportional to the value of the applied voltage 701 . The current applied by power supply 705 is approximately proportional to output current 702 (assuming voltage 701 remains substantially constant). Therefore, the pulsating nature of the current 702 results in lower energy consumption than a pure dc current of the same magnitude. Such a current waveform and relationship between the ac and dc components of the current is ensured by having a low internal resistance 706 and an alternating component 703 of the output voltage of small magnitude. It has been determined by means of experiments that the most efficient is achieved when the relative magnitude of the alternating component of the current 702 (i.e., Iac/Idc) is greater than the relative magnitude of the alternating component of the voltage 701 (i.e., Vac/Vdc). Electrostatic fluid acceleration. Furthermore, as these ratios vary, additional improvements are achieved. Thus, if Vac/Vdc is considerably less than Iac/Idc (i.e., not more than half), and preferably not more than 1/10, 1/100, or even preferably not more than 1/1000 of Iac/Idc (where , Vac and Iac are measured similarly, eg, both RMS, peak-to-peak, or similar), then additional efficiency in fluid acceleration can be achieved. To express it mathematically in another way, the product of the constant component of the corona current and the time-varying component of the applied voltage is divided by the time-varying component of the corona current and the constant component of the applied voltage. species, the resulting quotient should be minimal, and for some initial steps, each discrete step provides a significant improvement in magnitude:

Figure 8A shows a corona discharge device that does not satisfy the above equation. It includes a needle-shaped corona discharge electrode 800 whose sharp geometry provides the necessary electric field to generate a corona discharge near the tip of the needle. The opposite collector electrode 801 is much larger, in the form of a smooth rod. A high voltage power source 802 is connected to the two electrodes through high voltage supply wires 803 and 804 . However, because of the relative orientation of the discharge electrodes perpendicular to the central axis of the collector electrode 801 , this structure does not create any significant capacitance between the electrodes 800 and 801 . In general, any capacitance is proportional to the effective area facing between the electrodes. This area is very small in the device shown in Figure 8A because one of the electrodes is in the shape of a needle tip with the smallest cross-sectional area. Therefore, the current flowing from electrode 800 to electrode 801 will not have a significant ac component. Corona discharge device structures similar to those shown in Figure 8A show very low air acceleration capabilities and relatively significant amounts of ozone generation.

Figure 8B shows another corona discharge device. A plurality of corona discharge electrodes are in the shape of long thin corona discharge wires 805 , and their opposing collector electrodes 806 are in the shape of much thicker rods, which are parallel to the corona wires 805 . A high voltage power source 807 is connected to corona discharge wire 805 and collector electrode 806 through corresponding high voltage current wires 809 and 810 . This structure provides a much larger area between the electrodes and therefore a much larger capacitance formed therebetween. Therefore, the current flowing from the corona wire 805 to the collector electrode 806 will have a significant ac component if the high voltage power supply 807 has sufficient current supply capability. The structure of a corona discharge device as shown in Figure 8B provides greater air acceleration capability and a lower Less ozone is generated.

Referring again to FIG. 1, the high voltage power supply circuit 100 may be configured to generate a high voltage with small high frequency ripple. As mentioned above, the power supply 100 includes a high voltage two-winding transformer 106 with a primary winding 107 and a secondary winding 108 . The primary winding 107 is connected to a dc voltage source 101 via a half bridge converter (power transistors 104, 113 and capacitors 105, 114). A gate signal controller 111 generates control pulses at the gates of transistors 104 , 113 through resistors 103 and 117 . The operating frequency of these pulses is determined by the selected resistor 110 and capacitor 116 values. The secondary winding 108 of the transformer 106 is connected to a bridge voltage rectifier 109 comprising four high voltage high frequency power diodes. Power supply 100 produces a high voltage output between terminal 120 and ground, which is connected to the electrodes of the corona discharge device.

Figure 9 shows the oscilloscope scan traces of the waveforms of the output current and voltage, the high voltage 901 at the corona discharge device and the resultant current 902 generated and flowing through the array electrodes. It can be seen that voltage 901 has a relatively constant magnitude of approximately 15,300V with little or no alternating component. Current 902, on the other hand, has a relatively large current alternating component (ripple) of over 2 mA, well in excess of the current average value (1.189 mA).

Thus, in addition to the features described above, the present invention also includes embodiments in which the low inertia power source incorporates an array of corona discharge elements which present a high resistive load to the power source. That is, the capacitive loading of the array greatly exceeds any impedance components within the output of the power supply. This relationship provides a constant, low ripple voltage and high ripple current. The result is an efficient electrostatic fluid accelerator and reduced ozone generation.

10A is a schematic diagram of an electrostatic fluid accelerator (EFA) device 1000 comprising two EFA stages 1014 and 1015 according to another embodiment of the present invention. The first EFA stage 1014 includes a corona discharge electrode 1006 and an associated accelerating electrode 1012 ; the second EFA stage 1015 includes a corona discharge electrode 1013 and an associated accelerating electrode 1011 . The two EFA stages and all electrodes are shown schematically in the figure. Only one set of corona discharge and collector electrodes is shown for each stage for ease of illustration, but it is contemplated that each stage may include a large number of arrayed pairs of corona electrodes and accelerating electrodes. An important feature of EFA1000 is that the distance d ₁ between the corona discharge electrode 1006 and the collector electrode 1012 is comparable to the distance d ₂ between the collector electrode 1012 of the subsequent stage 1015 and its corona discharge electrode 1013, namely The closest distance between elements of adjacent stages is no greater than the distance between electrodes within the same stage. Generally, the interstage distance _d2 between the collector electrode 1012 and the corona discharge electrode 1013 of the adjacent stage is the interstage distance _d1 (or electric 1.2 and 2.0 times the distance between the corona discharge electrode 1013 and the collector electrode 1011). Because of this consistent spacing, the capacitance between electrodes 1006 and 1012 and between 1006 and 1013 is of the same order. It should be noted that in this configuration, the capacitance coupled between the corona discharge electrodes 1006 and 1013 may allow some stray current to flow between the electrodes. This stray current is of the same magnitude as the magnitude of the capacitive current between the electrode pair 1006 and 1012 . In order to reduce unnecessary current flow between electrodes 1013 and 1006, each electrode should be supplied with a synchronized high voltage waveform. In the embodiment shown in FIG. 10A, the two EFA stages are powered by a common power supply 1005, ie, a power supply with a single voltage conversion circuit (eg, current transformer, rectifier, filter circuit, etc.) feeding two stages in parallel. This ensures that the voltage difference between electrodes 1006 and 1013 remains constant relative to electrodes 1006 and 1011 so that no or only very little current flows between electrodes 1006 and 1013 .

FIG. 10B shows another configuration of an EFA 1001 that includes a pair of EFA stages 1016 and 1017 powered by separate power supplies 1002 and 1003, respectively. The first EFA stage 1016 includes a corona discharge 1007 and a collector electrode 1008 which form a pair of complementary electrodes within the stage 1016 . The second EFA stage 1017 comprises a corona discharge electrode 1009 and a collector electrode 1010 which form a second pair of complementary electrodes. The two EFA stages 1016, 1017 and all electrodes 1007-1010 are shown schematically in the figure.

The first EFA stage 1016 is powered by the power supply 1002 , while the second EFA stage 1017 is powered by the power supply 1003 . The two EFA stages and the two power supplies 1002 and 1003 may be of the same design to simplify synchronization, but different designs may be used to accommodate alternative arrangements as appropriate. The power sources 1002 and 1003 are synchronized by the control circuit 1004 to provide synchronized outputs. The control circuitry ensures that the two power supplies 1002 and 1003 produce synchronized and substantially equal in-phase output voltages such that the potential difference between electrodes 1007 and 1009 remains substantially constant (eg, with no or very small ac voltage components). (Note: Although the term "synchronous" generally includes frequency and phase agreement between signals, the requirement for phase alignment is further emphasized by using the term "in-phase," which requires that signals be in phase with each other at corresponding locations, e.g., as Applied to and present in each stage.) Keeping this potential difference constant (i.e., minimizing or eliminating any ac voltage component) limits or eliminates the flow of any capacitive current between electrodes 1007 and 1009 to achieve An acceptable value is, for example, typically less than 1 mA, and preferably less than 100 μA.

Referring to the waveforms shown in FIGS. 11A and 11B , a reduction in parasitic capacitive currents between electrodes adjacent to the EFA stage can be seen. As shown in FIG. 11A , the voltage V1 ( FIG. 10B ) presented on electrode 1007 and the voltage V2 presented to electrode 1009 are synchronous and in phase, but not necessarily equal in dc magnitude. Because of perfect synchronization, the difference V1-V2 between the voltages presented on electrodes 1007 and 1009 is nearly constant, indicating only a dc offset between the signals (ie, no ac component). The current Ic flowing through the capacitive coupling between electrode 1007 and electrode 1009 is proportional to the time rate of change (dV/dt) of the voltage across the capacitance:

Ic=C*(d(V1-V2)/dt).

It follows directly from this relationship that if the voltage across any capacitance is held constant (ie, no ac component), then no current will flow through that path. On the other hand, if the voltage changes rapidly (ie, d(V1-V2)/dt is large), even small voltage changes can create large capacitive currents. In order to avoid excessive current flow from different electrodes of adjacent EFA stages, the voltages applied to the electrodes of these adjacent stages should be synchronized and in phase. For example, referring to FIG. 11B , the corona voltages V1 and V2 are slightly out of sync, resulting in a small ac voltage component in the difference d(V1-V2)/dt. This small ac voltage component results in a significant parasitic current Ic flowing between adjacent EFA stages. An embodiment of the invention includes synchronization of power applied to all stages to avoid current flow between stages.

The closest spacing of electrodes of adjacent EFAs can be approximated as follows. Note that typical EFAs operate efficiently over a rather narrow voltage range. The voltage _Vc applied between the corona discharge electrode and the collector electrode of the same stage should exceed the so-called corona _onset voltage Vonset for proper operation. That is, when the voltage V _c is less than V _onset , no corona discharge occurs and no air movement occurs. At this time, V _c should not exceed the dielectric breakdown voltage V _b to avoid arcing. Depending on the electrode geometry and other conditions, V _b can be twice V _onset . For typical electrode configurations, the ratio of V _b /V _onset is about 1.4-1.8, so that any particular corona discharge electrode should not be located at a distance from adjacent collector electrodes where a "back corona" could occur. Therefore, the normalized distance aNn between the closest electrodes of adjacent stages should be at least 1.2 times the normalized distance "aNc" between the corona discharge electrode and the collecting electrode of the same stage, preferably not greater than 2 times the distance "aNc". That is, the electrodes of adjacent stages should be spaced apart to ensure that the voltage difference between the electrodes is less than the corona inception voltage between any electrodes of adjacent stages.

If the above-mentioned conditions are not fulfilled, the necessary consequence is that adjacent stages must be spaced further and wider than would otherwise be the case. Such increased spacing between stages leads to several conditions that adversely affect air movement. For example, increased spacing between adjacent stages results in longer ducts and, therefore, greater resistance to airflow. The overall volume and weight of the EFA also increases. For both synchronous and in-phase HVPS, these negative aspects can be avoided by reducing the spacing between HFA stages without reducing efficiency or increasing sparking.

Referring to FIG. 12 , a two-stage EFA 1200 includes a pair of HVPSs 1201 and 1202 associated with corresponding first and second stages 1212 and 1213 . The two stages are essentially identical and are powered electrically by the same HVPS1201 and 1202. HVPS 1201 and 1202 include respective pulse width modulation (PWM) controllers 1204 and 1205 , power transistors 1206 and 1207 , high voltage inductors 1208 and 1209 (ie, filter chokes), and voltage multipliers 1201 and 1202 . HVPS 1220 and 1221 provide power to the corresponding EFA corona discharge electrodes of stages 1212 and 1213 . As noted above, although the EFA electrodes of stages 1212 and 1213 are shown schematically as a single pair of one corona discharge electrode and one accelerating (or attractor) electrode, stages will typically include multiple pairs of electrodes configured in a two-dimensional array of . The PWM controllers 1204, 1205 generate (and supply at pin 7) high frequency pulses to the gates of the respective filter transistors 1206 and 1207. The frequency of these pulses is determined by a corresponding RC timing circuit comprising resistor 1216 and capacitor 1217 and resistor 1218 and capacitor 1219 . In general, slight differences between these component values between stages can result in slightly different operating frequencies for the two HVPS stages. However, even a slight change in frequency can result in asynchronous operation of stages 1212 and 1213 of EFA1200. Therefore, in order to ensure that the power supplies 1201 and 1202 are synchronous and in-phase (i.e., zero phase shift or phase difference) operation, the connection controller 1205 is connected to the PWM controller 1204 from pin Pin 1 accepts a sync signal pulse. This structure synchronizes PWM controller 1205 to PWM controller 1204 so that both PWM controllers output voltage pulses that are both synchronized (same frequency) and in phase (same phase).

13A and 13B are cross-sectional views of two different configurations of a two-stage EFA device. Although only two stages are shown, the principles and structural details are the same. Referring to FIG. 13A , the first EFA device 1311 is composed of two series or tandem stages 1314 and 1315 . The first stage 1314 comprises a plurality of parallel corona discharge electrodes 1301 aligned in first vertical columns, and collector electrodes 1302 aligned in a second column parallel to the columns of corona discharge electrodes 1301 . All electrodes are shown in sections extending longitudinally into and out of the paper. The corona discharge electrodes 1301 may be in the form of wires as shown, although other structures may be used. Collecting electrodes 1302 are shown extending horizontally as conductive rods. Also, for purposes of illustration, other geometries and configurations may be implemented consistent with various embodiments of the invention. The second stage 1315 similarly contains an aligned corona discharge electrode 1303 (also shown as a thin wire extending perpendicular to the paper), and a collector electrode 1304 (also a rod). All electrodes are installed in the air duct 1305. The first and second stages 1314 and 1315 of the EFA 1311 are powered by respective individual HVPSs (not shown). The HVPS is synchronous and in-phase so that the corona discharge electrode 1303 of the second stage 1315 can be placed at the closest possible normalized distance from the collecting electrode 1302 of the first stage 1314 without adversely interacting and Reduced EPA properties.

For the sake of illustration, we assume that all voltages and their components (eg, ac and dc) applied to the electrodes of adjacent stages 1314 and 1315 are equal. It is further assumed that a high voltage is applied to corona discharge electrodes 1301 and 1303 while collector electrodes 1302 and 1304 are grounded, ie maintained at a common ground potential relative to the high voltage applied to corona discharge electrodes 1301 and 1303 . All electrodes are arranged in parallel vertical columns such that corresponding electrodes of different stages are horizontally aligned and vertically offset from complementary electrodes of staggered columns within their own stage. The normalized distance 1310 between the corona discharge electrode 1301 and the leading edge of the vertically closest adjacent collector electrode 1302 is equal to aN1. The normalized distance aN2 (1313) between the corona discharge electrode 1303 of the second stage and the trailing edge of the collecting electrode 1302 of the first stage should be slightly greater than aN1, and the actual distance depends on the specific voltage applied to the corona discharge electrode . In any case, aN2 should be just larger than aN1 , ie in the range of 1 to 1.2 times aN1 , preferably 1.1 to 1.65 times aN1 , even more preferably approximately 1.4 times aN1 . In particular, as shown in FIG. 13A, the distance aN2 is just larger than necessary to avoid forming a voltage between the corona inception voltages through which a current flows. Let us assume that the normalized "stant" distance aN2 is equal to 1.4*aN1. Then, the horizontal distance 1312 between adjacent stages is less than the distance aN2 (1313). As shown, the inter-stage spacing is minimized when electrodes of the same type in adjacent stages lie within a plane 1320 (as shown in FIG. 13A ). Plane 1314 may be defined as a plane (plane 1317 in FIG. 13A ) that is normal to the plane containing the edges of the corona discharge electrodes. If electrodes of the same type in adjacent stages lie in different but parallel planes, e.g., planes 1321 and 1322 (as shown in FIG. 13B ), the resulting minimum spacing between electrodes of adjacent EFA stages is equal to aN2 shown. It should be noted that the length of line 1319 is the same as distance 1313(aN2) and greater than distance 1312 so that the inter-stage spacing is increased.

Accordingly, these features of the invention include structures that satisfy one or more of the three conditions in various embodiments:

The electrodes of adjacent EFA stages are powered with substantially the same voltage waveform, ie the potentials on adjacent electrodes should have substantially the same alternating component. These alternating components should be close or identical in magnitude and phase.

Adjacent EFA stages should be closely spaced, the spacing between adjacent stages being defined and determined by a distance just sufficient to avoid or minimize any corona discharge between electrodes of adjacent stages.

Electrodes of the same type on adjacent stages should lie in the same plane, which is normal to the plane in which the electrodes (or electrode leading edges) are located.

14 is a schematic diagram of an EFA device 1400 that includes linear corona electrodes 1402 (three are shown for the sake of this example, but other numbers may be included, a typical device having tens or hundreds of electrodes to provide a desired characteristic) and accelerating electrodes 1409 (two in this simplified example). Each accelerating electrode 1409 includes a relatively high resistance portion 1403 and a low resistance portion 1408 . The high resistance portion 1403 has a resistivity p in the range of 10 ¹ to 10 ⁹ Ω-cm, preferably in the range between 10 ⁵ and 10 ⁸ Ω-cm, more preferably in the range of 10 ⁶ to 10 ⁷ Ω-cm range.

All electrodes are shown in section. Thus, the corona discharge electrodes 1402 are in the form and shape of thin wires, while the accelerating electrodes 1409 are shown in the shape of rods and plates. The "downstream" portion of the corona electrode 1403 closest to the accelerating electrode 1409 forms an ionization edge 1410 . The corona electrode 1402 and the low resistance portion 1408 of the accelerating electrode 1409 are connected to opposite polarity terminals of a high voltage power supply (HVPS) 1401 through wire conductors 1404 and 1405 . The low-resistance portion 1408 has a resistivity ρ≤10 ⁴ Ω-cm, and preferably not greater than 1 Ω-cm, even more preferably not greater than 0.1 Ω-cm. EFA 1400 creates a fluid flow in the desired fluid flow direction indicated by arrow 1407 .

HVPS 1401 is configured to generate a predetermined voltage between electrode 1402 and collector electrode 1409 so as to create an electric field between the electrodes. This electric field is represented by dotted flow lines 1406 . When the voltage exceeds a so-called "corona onset voltage", a corona discharge event starts in the vicinity of the corona electrode 1402, resulting in a process of corresponding emission of ions from the corona electrode 1402.

The corona discharge process causes fluid ions to be emitted from the corona electrode 1402 and accelerated along and following the lines of electric force 1406 towards the accelerating electrode 1409 . Corona current in the form of free ions and other charged particles is near the proximal-most end of the accelerating electrode 1409 . The corona current then flows along the path of least resistance through the electrodes opposite some of the higher resistance paths of the surrounding fluid. Since the high-resistance portion 1403 of the accelerating electrode 1409 has a lower resistance surrounding the ionized fluid, the main part of the corona current flows through the body of the accelerating electrode 1409, i.e., through the high-resistance portion 1403 to the low-resistance portion 1408, to The return path of HVPS 1401 is accomplished by connecting wire 1405 . Since the current flows along the width of the high resistance portion 1403 (see FIG. 14) (parallel to the main direction of air flow 1407, a voltage drop Vd is formed along the current path). This voltage drop is proportional to the product of the corona current Ic multiplied by the resistance R of the high resistance part 1403 (the resistance of the low resistance part 1408 and the connecting wire are omitted for this moment). Then, the actual voltage Va applied between the corona wire 102 and the corresponding nearest end of the accelerating electrode 1409, due to the voltage drop caused by the resistance, the applied actual voltage Va is smaller than the output voltage V _{out of} the HVPS1401, that is,

Va = V _out - V _d = V _out - I _c *R (1).

Note that the corona current is non-linearly proportional to the voltage Va between the ends of the corona electrode 1402 and the accelerating electrode 1409, ie the current increases faster than the voltage. The voltage-current relationship can be approximately expressed as the following empirical expression:

Ic=k ₁ *(V _a -V _o ) ^1.5 , (2)

where V _o = corona onset voltage and k ₁ = empirically determined coefficient. This non-linear relationship provides an ideal feedback which, in fact, automatically controls the resultant voltage value Va appearing across the electrodes and prevents, minimizes, slows or mitigates corona discharge disturbances and irregularities. Noting that the corona discharge process is considered "irregular" by its nature (i.e., "unpredictable"), the corona current value depends on a variety of environmental factors that are subject to change, such as temperature, contamination, humidity, Foreign matter etc. If for some reason the corona current becomes greater at one location in the interelectrode space than at some other location, the voltage drop _Vd along the corresponding high resistance portion 1403 will become larger and, therefore, the actual voltage at this location Va will go low. This in turn limits the corona current at this location and prevents or minimizes the occurrence of sparks or arcs.

The following example is for illustration purposes, using typical component values as used in an embodiment of the invention. In one embodiment of the EFA 1400 as schematically shown in FIG. 14 , a corona onset voltage is assumed to be equal to 8.6 kV to achieve a minimum electric field strength of 30 kV/cm in the vicinity of the corona electrode 1402 . This value can be determined by calculation, measurement or other methods, and for a corona/accelerating electrode spacing of 10 mm and a corona electrode diameter of 0.1 mm, this value is usually a corona onset value. The total resistance R _total of the high resistance portion 103 for the acceleration electrode 1409 is equal to 0.5 MΩ, and the width of the high resistance portion 1403 along the airflow direction 1407 (see FIG. 14 ) is equal to 1 inch. The length of the accelerating electrode 1409 transverse to the airflow direction (ie, into the plane of the drawing) is equal to 24 inches. Therefore, for each inch of accelerating electrode 1409 the resistivity R _inch is

_Rinch ＝ _Rtotal *24＝12MΩ

The empirical coefficient k ₁ for this particular design is equal to 22*10 ⁻⁶ . At an applied voltage Va equal to 12.5kV, the corona current Ic is equal to

Ic=4.6×10 ⁻⁹ *(12,500V−8,600V) ^1.5 =1.12 mA.

However, the corona current Ic _/inch flowing through each inch of the semiconductor portion 103 is equal to

1.12mA/24inches=47μA/inch.

Therefore, the voltage drop _V across the one-inch length of semiconductor portion 103 is equal to

V _d =47*10 ⁻⁶ A*12*10 ⁶ Ω=564V.

_Vout from the HVPS 1401 is equal to the sum of the voltage _Va applied to the electrode and the voltage drop _Vd across the semiconductor portion 1403 of the accelerating electrode 1409, expressed as follows:

_Vout ＝12,500+564＝13,064V

For some reason, say the corona current in some local area increases to twice the overall distribution value of 47μA/inch, so that it equals 94μA at some point, the resultant voltage drop _Vd will reflect this change and equal to 1,128V (ie, V _d =94×10 ⁻⁶ μA*12×10 ⁶ Ω). Then, V _a =V _out -V _d =13,064-1,128=11,936V. Therefore, the increased voltage drop V _d slows down the actual voltage level at the local area and limits the corona current in this area. According to formula (2), the corona current _Ic through the length of one inch can be expressed as 4.6*10 ^-9 (11,936-8,600V) ^1.5 /24inch=0.886mA, relative to 1.12mA. Even if there are some local irregularities, whereby this "negative feedback" effect works to restore normal EFA work. In the extreme case of a short circuit caused by a foreign object (eg, dust, etc.) entering the interstage space, the maximum current through the circuit is effectively limited by the resistance of the local area where the foreign object contacts the electrode.

Let us consider a foreign object like a finger or a screwdriver shorting the two electrodes together, i.e., providing an electrical path of relatively low resistance (compared to that of the intervening fluid) between the corona electrode 1402 and the accelerating electrode 1409 . It is reasonable to assume that current will flow through an area of width approximately equal to the width of high-resistivity portion 1403 (ie, 1 inch). Therefore, a foreign object can cause a maximum current I _max , which is equal to

I _max ＝V _out /R _total ＝13,064V/12*10 ^6Ω ＝1.2mA

It is just slightly greater than the nominal operating current of 1.12mA. Such a small increase in current should not create any risk of electric shock or produce any unpleasant noises (eg arcing and popping). At this time, the maximum operating current of all EFAs is limited to:

_Imax ＝13,064V/0.5MΩ＝26mA

This value is sufficient to generate a large fluid flow, eg, at least 100 ^ft3 /min. If the accelerating electrode is made of metal or has relatively low resistivity (for example, ρ≤10 ⁴ Ω-cm, preferably ρ≤1 Ω-cm, and more preferably ρ≤10 ^-1 Ω-cm,) other materials, the short-circuit current will be limited only by the maximum current (i.e., maximum current capability) of the HVPS1401, and/or by any energy stored in its output filter (e.g., filter capacitor), determined by This presents a significant shock hazard to the user, produces an unpleasant "click" or "pop" sound caused by sparks, and/or produces electromagnetic disturbances (eg, radio frequency interference or radio frequency interference). In general, the resistivity characteristics and geometry (length to width ratio) of the high-resistivity region 103 are chosen so as to provide unhindered operation while not imposing current limitations on EFA operation. This can be achieved by providing a relatively large ratio (preferably if at least 10) between (i) the overall length of the accelerating electrode (dimension transverse to the main flow direction of the fluid) and (ii) the The accelerating electrode is its width (dimension along the direction of fluid flow). In general, the length of the electrodes should be greater than the width of the electrodes. Optimal results can be achieved by providing multiple accelerating electrodes, preferably within a range equal to the number of corona electrodes plus or minus one, depending on electrode location and configuration. It should be noted that although FIG. 14 shows two accelerating electrodes and three corona electrodes for illustration purposes, other electrode configurations may include three of the four accelerating electrodes facing the same three corona electrodes, Alternatively, other quantities and configurations of alternative electrode configurations are included.

It should also be considered that localized excessive current flow can cause degradation of high resistivity materials. This is especially the case if a foreign object is lodged between the electrodes for some extended period of time (eg, more than a few milliseconds prior to cleaning). To prevent electrode damage and associated failure due to overcurrent conditions, the HVPS may be equipped with a current sensor or other device that can detect such an overcurrent event and rapidly interrupt power generation or otherwise prevent current flow. After a predetermined reset or inactive time _Toff , generation may resume for some minimum predetermined time _Ton sufficient to detect any remaining or residual short circuit condition. If the short circuit condition persists, the HVPS may shut down or otherwise stop, again for at least the time period T _off . Therefore, if the overcurrent problem persists, the HVPS 1401 can continue this on-off cycle several times (eg, ten or more) to make T _off sufficiently larger than T _on , in order to ensure safe operation of the EFA and life of the electrodes. It should be noted that in some cases, cycling will have the effect of clearing certain short conditions without manual intervention.

Figure 15 shows another embodiment of an EFA with accelerating electrodes having high resistivity sections. The main difference between EFA 1400 shown in FIG. 14 and EFA 1500 is that in the latter, low-resistivity portion 1505 is completely contained within high-resistivity portion 1503 of accelerating electrode 1509 (i.e., completely surrounded by surrounding high-resistivity material). package). This modification provides at least two advantages to this embodiment of the invention. First, completely encapsulating the low-resistivity portion 1508 within the high-resistivity portion 1503 increases EFA safety by preventing inadvertent or accidental direct contact with the high voltage "hot" terminals of the HVPS 1501. Second, the structure forces the corona current to flow through a larger portion or volume of the high-resistivity portion 1503 rather than just a surface area. Although surface conductivity is of the same order of magnitude as bulk (i.e., internal) conductivity for most high-resistivity materials (e.g., plastic or rubber), surface conductivity can vary widely due to gradual contamination and deterioration of the surface (eg, the variation over time may increase by several orders of magnitude).

EFA has an inherent ability to collect particles present in the fluid at the surface of the accelerating electrode. When a certain amount of particles is collected or otherwise accumulates on the accelerating electrode, the particles can cover the surface of the electrode with a solid layer (eg, a continuous film) of contiguous contaminants. The conductivity of this contaminant layer may be higher than the conductivity of the high resistivity material itself. In such a case, corona currents can flow through the contamination layer and detract from the advantages offered by the high resistivity material. The EFA 1500 of FIG. 15 avoids this problem by completely encapsulating the low-resistivity portion 1508 within the high-resistivity portion 1503 . It should be noted that the low-resistivity portion 1508 need not be continuous, or have any point in direct contact with the supply terminal of the HVPS 1501 or the wire 1505 that provides power from the HVPS 1501 . It should be appreciated that the primary function of these conductive portions is to equalize the potential along the length of the accelerating electrode 1509, ie, to distribute current so that the high resistivity portion 1503 contacting the low resistivity portion 1508 remains at some equipotential. Furthermore, if the corona electrode 1502 (including the ionizing edge 1510) is grounded, there is substantially less or no chance of inadvertent or accidental exposure to dangerous current levels that could cause injury due to high operating voltages and/or electrocuted because there is no "hot" potential to contact the entire structure.

16 is a schematic diagram of an EFA assembly 1600 with a corona electrode 1602 (preferably formed as a longitudinally oriented wire with an ionizing edge 1610) and an accelerating electrode 1603 consisting of a plurality of horizontally stacked high resistivity rods, The rods each have a different resistance value and descend along the width of the accelerating electrode. The accelerating electrode 1603 is made of several segments 1608 to 1612, each in intimate contact with its immediately adjacent segment. Each of these segments is made of a material, or otherwise orchestrated, to have a different resistivity value pn. It has been determined that as the resistivity decreases progressively in the direction towards the HVPS 1601 terminal connection (i.e., decreasing from segments 1608 to 1609, 1611, and 1612), the resulting electric field becomes more linear with respect to the main direction of fluid flow. uniform. Note that in Figures 14 and 16, the electric field lines shown between the corona electrodes 1402/1502 and the accelerating electrodes 1403/1503 are preferably not parallel to the main direction of fluid flow, but arcuate. This arc causes ions and other charged particles to be accelerated in a range of directions, thereby reducing the efficiency of the EFA. By accelerating the gradual progression of electrode resistance, it has been found that when the corona current reaches a certain maximum value, the trajectories of the ions are aligned with the main direction of fluid flow. It should also be noted that, for purposes of illustration, although the accelerating electrode 1603 is shown as comprising a plurality of discrete segments with resistivity values _pn , the resistivity values may vary continuously across the width of the electrode. The gradual change in resistivity across the width can be achieved by a variety of processes including, for example, ion implantation of suitable impurity materials at suitable varying concentration levels to achieve a gradual increase or decrease in resistivity.

17A and 17B are schematic diagrams of yet another embodiment of an EFA 1700 in which the accelerating electrode 1703 is made of a high resistivity material. Although for purposes of illustration, Figures 17A and 17B show a particular number of corona electrodes 1702 and accelerating electrodes 1703 distributed, other numbers and configurations may be used consistent with various embodiments of the invention.

Accelerating electrodes 1703 are made of one or more thin strips or layers of high resistivity material. The corona electrode 1702 is made of a low resistivity material such as metal or conductive ceramic. HVPS 1701 is connected to corona electrode 1702 and accelerating electrode 1703 through wires 1704 and 1705 . The geometry of the corona electrodes 1702 contrasts with electrodes formed as needles or thin wires, which are inherently more difficult to hold and install, and prone to damage during normal operation of the EFA. The downstream edge of each corona electrode 1702 includes an ionizing edge 1710 . Like other small items, the thin wires that are often used as corona electrodes are fragile and therefore unreliable. In contrast, the present embodiment shown in Figures 17A and 17B provides corona electrodes in the shape of relatively wide metal strips. While these metal strips must be thin at the corona discharge end in order to easily corona discharge along their "downstream" edges, the strips are relatively wider (in the direction of the gas flow) and thus less brittle than corresponding thin wires.

Another advantage of the EFA 1700 shown in Figure 17A includes that the accelerating electrodes 1703 are substantially thinner than electrodes used in prior art systems. That is, existing accelerating electrodes are generally much thicker than associated corona electrodes in order to avoid creating an electric field around the accelerating electrodes and the edges of the accelerating electrodes. By placing the edge of the corona electrode 1702 opposite or against the flat surface of the accelerating electrode 1703 (in this illustration, the right "falling" edge of the corona electrode), the structure shown in FIG. Any electric field generated by the electrodes 1703 is accelerated. That is, at least a portion of the body of the corona electrode 1702 extends downwardly past the leading edge of the accelerating electrode 1703 in the direction of desired fluid flow, whereby an active portion of the corona electrode 1702 extends along its trailing edge along the length of the accelerating electrode 1703. A corona discharge is generated between and near planar surfaces. This orientation and structure provides an electric field strength near such a planar surface that is substantially lower than a corresponding electric field strength formed around the trailing edge of the corona electrode 1702 . Therefore, a corona discharge is formed near the trailing edge of the corona electrode 1702 and not at the surface of the accelerating electrode 1703 .

Just at the onset of the corona discharge, by the generation of ions and charged particles in the fluid, and the transfer of such charges to the HVPS 1701 along the accelerating electrode 1703 through the wire 1705, the corona current flows through the corona electrode 1702 and the accelerating electrode 1703 The accelerated fluid (for example, air, insulating liquid, etc.) between. Since no current flows in the opposite direction (ie, from the accelerating electrode 1703 through the fluid to the corona electrode 1702), no back corona is generated. It has also been found that this structure results in an electric field (represented by line 1706) that is more linear with respect to the direction of desired fluid flow (shown by arrow 1707) than would otherwise be provided. The increased linearity of the electric field is caused by the voltage drop across the accelerating electrodes 1703, which create equipotential lines of the electric field transverse to the main direction of fluid flow. Since the electric field lines are orthogonal to such equipotential lines, the electric field lines are more parallel to the main direction of fluid flow.

Another advantage of the EFA 1700 shown in FIG. 17A is provided by the structure of the intervening accelerating electrode 1703, by isolating the active portion of the corona electrodes 1702 from each other (ie, the right edge as shown). Accordingly, the corona electrodes "do not see" each other, and therefore, the corona electrodes 1702 can be positioned in close proximity to each other (ie, in a vertical direction as shown in FIG. 17A ) compared to prior systems. By using the design features shown in FIG. 17A, two major obstacles to fluid flow that occur are avoided. The first of these hurdles is the high air resistance caused by the relatively thick front of conventional accelerating electrodes. The present structure provides both the corona electrode and the accelerating electrode with a low drag geometry, ie, an aerodynamically "friendly" shape. For example, these geometries provide a drag coefficient Cd for air not greater than 1, preferably less than 0.1, more preferably less than 0.01. The actual geometry or shape must depend on the desired fluid flow and the viscosity of the fluid being accelerated, factors that vary from design to design.

A second obstacle overcome by this embodiment of the invention is that a composite low density of electrodes is possible due to the conventional inter-electrode spacing requirements necessary and observed from existing structures. For example, US Patent No. 4,812,711, which is incorporated herein by reference in its entirety, shows four corona electrodes spaced apart from each other by a distance of 50 mm. Not surprisingly, this relatively low density and small number of electrodes can accommodate only very low power levels, with a resultant low level of fluid flow. In contrast, this embodiment accommodates a distance from the corona electrode to the attractor electrode of less than 10 mm, preferably less than 1 mm.

Still another configuration of electrodes is shown in EFA 1700 of FIG. 17B. In this case, the corona electrode 1702 is placed at a predetermined distance from the accelerating electrode 1703 in the desired fluid flow direction as indicated by arrow 1707 . Furthermore, the combined electric field is basically linear, starting from the corona electrode 1702 toward the accelerating electrode 1703 as shown by the dotted line. It should be noted, however, that the corona electrode 1702 is not placed "inside" the accelerating electrode 1703 with respect to the desired direction of fluid flow.

The various embodiments of the present invention as shown in FIG. 17A aim to achieve closer spacing of corona electrodes (i.e., smaller high-density electrodes). That is, extremely thin and short electrodes can be easily fabricated by a single fabrication process or step, for example, that is compatible with modern microelectromechanical systems (MEMS) and related semiconductor technologies and capabilities. Referring again to FIG. 17A , it can be seen that adjacent corona electrodes 1702 may be vertically spaced apart from each other by a distance of less than 1 mm, or even by only a few μm from each other. The resulting increase in electrode density provides increased fluid acceleration and flow rate. For example, US Patent No. 4,812,711 describes a device capable of producing air velocities of only 0.5 meters per second (m/sec). Conversely, if the electrode spacing is 1 mm, a 50-fold increase in electrode density and increased current capability can be achieved to provide a corresponding increase in air velocity, ie, to about 25 m/sec or 5,000 ft/min. In addition, several EFA stages can be placed in series, or one behind the other along the desired horizontal direction of fluid flow, with the stages also accelerating the fluid as it flows through the successive stages. The stages are located a predetermined distance from the nearest stage determined by the maximum voltage applied to the opposing electrodes of the stages. In particular, when the corona discharge electrodes and accelerating electrodes of a stage are placed closer together, lower voltages are required to initiate and maintain the corona discharge. Therefore, the EFAs of all stages can similarly be placed closer to each other in view of the low operating voltage used within that stage. This relationship results in the density of stages along the horizontal direction being approximately proportional to the electrode density within a stage (eg, along the vertical direction). Therefore, it can be expected that an increase in electrode "vertical" density will provide a similar increase in "horizontal" density such that fluid flow acceleration is inversely proportional to the square of the distance between electrodes.

The advantages achieved by various embodiments of the present invention are at least partially attributable to the use of a high resistivity material as part of the accelerating electrode. High-resistivity materials may include relatively high-resistance materials such as carbon-filled plastic or rubber, silicon, germanium, tin, gallium arsenide, indium phosphide, boron nitride, silicon carbide, cadmium selenide, and the like. These materials should have a resistivity in the range of 10 ¹ to 10 ¹⁰ Ω-cm, preferably in the range of 10 ⁴ to 10 ⁹ Ω-cm, more preferably in the range of 10 ⁶ to 10 ⁷ Ω-cm between. The use of high-resistivity materials supports increased electrode density. For example, closely spaced metal accelerating electrodes exhibit unstable operating characteristics that generate high frequency spark events. In contrast, high-resistivity electrodes according to embodiments of the present invention produce a more linearized electric field, thereby minimizing sparking and back corona emission from sharp edges of the accelerating electrodes. Elimination of back corona can be understood with reference to Figure 17a.

Referring again to FIG. 17A , a corona discharge event is shown occurring at or along the trailing or right edge of corona electrode 1702 , but not along the leading or left edge of accelerating electrode 1703 . This is due to the distribution of voltage and electric field created by the corona discharge process. For example, the left edge of the accelerating electrode 1703 is at least slightly thicker than the right edge of the corona electrode 1702, while the right edge of the corona electrode 1702 is thin and sharp. The corona discharge begins at the trailing edge of the corona electrode 1702 because the electric field near an electrode is approximately proportional to the thickness of the electrode. The resultant corona current then flows from the trailing edge of the corona electrode 1702 to the high voltage terminal of the HVPS 1701 through two paths. The first path is the ionized portion of the fluid passed along the electric field shown by line 1706 . The second path is through the body of the accelerating electrode 1703 . Corona current flowing through the body of the accelerating electrode 1703 causes a voltage drop along the body. This voltage drop proceeds from the high voltage terminal applied to the right edge of the accelerating electrode 1703 towards the left edge of the electrode. As the corona current increases, a corresponding increase is shown in this voltage drop. When the output voltage of the HVPS 1701dd reaches a level sufficient to initiate corona discharge along the left edge of the accelerating electrode 1703, the voltage drop at these edges is high enough to slow down any voltage increase and prevent corona discharge along the edge of the accelerating electrode.

Other embodiments of the present invention can reduce the interelectrode spacing to the order of a few microns. At such distances, a corona discharge condition can be initiated at a relatively low voltage, and the formation of corona discharge is not caused by the voltage itself, but by the high intensity electric field generated by the voltage. The electric field strength is approximately proportional to the applied voltage and inversely proportional to the distance between opposing electrodes. For example, a voltage of about 8 kV is sufficient to initiate a corona discharge at an interelectrode distance of approximately 1 cm. The distance between the poles is reduced by 1/10 to 1mm, which can reduce the voltage required for corona discharge starting to approximately 800V. A further reduction of the inter-electrode spacing to 0.1mm reduces the required corona initiating voltage to 80V, while a 10 micron spacing requires only 8V to initiate corona discharge. These low voltages provide closer spacing between poles and closer spacing between stages, thereby increasing the overall fluid acceleration several times. As noted above, this increase is approximately inversely proportional to the square of the distance between the poles, resulting in an overall increase of 100, 10,000, and 1,000,000 in air flow compared to a 1 cm spacing.

The benefits of using a high resistivity electrode structure are further explained with reference to A and 18B. Referring to FIG. 18A , the EFA 1800 includes a corona electrode 1802 and an accelerating electrode 1803 . The accelerating electrode 1803 further includes a low-resistivity portion 1804 and a high-resistivity portion 1806 . A corona current flows through the ionized fluid present between the corona electrode 1802 and the accelerating electrode 503 (i.e., through the interelectrode space) on the current path shown by arrow 1805, which continues through the High resistivity portion 1806 of electrode 1803 is accelerated. Upon the occurrence of a local disturbance, such as a spark event, the resultant discharge current is directed through the narrow path indicated by arrow 1807 in Figure 18B. The current then follows a wider path 1808 across the high-resistivity portion 1806 . Because the increased current emanating from a small area of the accelerating electrode 1803 spreads gradually outward only on the path 1808, the resulting resistance on the path 1808 is substantially higher than if such current was distributed over the entire high-resistivity portion 1806 . Thus, the spark or pre-spark event signaled by increased current flow is limited by the resistance along path 1808, thereby limiting the current flow. If the high-resistivity portion 1806 is selected to have a resistivity and width-to-length ratio, any significant increase in current flow can be avoided or slowed down. Such an increase in current can be caused by a number of events including the electrical discharge or spark described above, the presence of a foreign object (eg, dust, insect, etc.) screwdriver on or between the electrodes, or even a finger placed between and in contact with the electrodes.

Another embodiment of the present invention is shown in FIG. 19 . As shown, EFA 1900 includes a comb-shaped high-resistivity portion 1906 of accelerating electrode 1903 . Any localized event such as a spark is obviously limited to flow over a small portion of the attracting electrode 1903, for example, on a single or a small number of teeth near the event. The corona current associated with normal operating conditions is shown with arrow 1905. For example, events such as a spark shown at arrows 1907 and 1908 are restricted to flow along finger or tooth 1906 . The resistance on this path is high enough to modulate any increase in current caused by the event. It should be noted that performance is improved by increasing the number of teeth rather than choosing a width-to-length ratio. A typical width to length ratio of 1 to 0.1 may be suitable, preferably a ratio of 0.05 to 1 or less.

As noted above, the various features of the invention enable the invention to use materials other than solids to generate a corona discharge or ion emission. In general, solid materials only "barely" give off and generate ions, thereby limiting the EFA acceleration of the fluid. At this point, many fluids, such as water, can release more ions if positioned and shaped to create a corona discharge. For example, the use of a conductive fluid as a corona emitting material is described in US Patent No. 3,751,715. Therein, a tear-drop-shaped container is described as a tank for containing an electrically conductive fluid. For example, the conductive fluid may be tap water, preferably an aqueous solution including a strong electrolyte, eg, NaCl, HNO3, NaOH, etc. FIG. 20 shows the operation of an EFA according to an embodiment of the present invention, wherein the EFA 2000 includes five accelerating electrodes 2003 and four corona electrodes 2002 . All these electrodes are shown as cross-sectional views. The corona electrodes each comprise a narrow elongated non-conductive shell 2009 made of insulation such as plastic or silicon, with a slot 2011 formed at the ionizing edge 2010 in the trailing or right side of the shell. The housing 2009 of the corona electrode 2002 is connected to a conductive fluid supply or container (not shown) via a suitable supply tube. The slot 2011 formed in the trailing edge of the corona electrode 2002 is narrow enough to allow fluid to be contained within the housing 2009 by fluid molecular tension. The slot 2011 may be equipped with a sponge-like "stop" or nozzle section in order to provide a constant slow release of conductive fluid through the slot. The HVPS 2001 generates a voltage sufficient to cause a corona discharge such that the conductive fluid 2008 acts as a sharp-edged conductor and emits ions at the slot 2011 from the trailing edge of the corona electrode 2002 at the slot 2011. Ions generated by the conductive fluid 2008 migrate from the tank 2001 towards the accelerating high-resistivity electrode 2003 along the electric field represented by the line 2006 . Fluid is replenished through housing 2009 from a suitable fluid source or container (not shown) as it is consumed in the resulting corona discharge.

It should be pointed out and understood that all publications, patents and patent applications mentioned in this specification are intended to indicate the state of the art in the technical field to which the present invention pertains. All publications, patents, and patent applications are herein incorporated by reference to the same extent as if each individual publication, patent, and patent application was specifically and individually indicated to be incorporated by reference in its entirety.

Claims (26)

1. A spark control device comprising: a high voltage power supply operative to provide electrical power to the load device; a sensor operative to monitor one or more electromagnetic parameters within said load device; a first detector responsive to the one or more electromagnetic parameters to identify pre-spark conditions within the load device; and A second detector coupled to said first detector enables said high voltage power supply to rapidly vary the magnitude of said electrical power to a level that prevents sparking in response to said pre-spark condition. 2. The spark control apparatus of claim 1, wherein said high voltage power supply comprises a high voltage power supply configured to transform a primary power supply into a high voltage power feed to supply current. 3. spark control device as claimed in claim 1, is characterized in that, described high-voltage power supply comprises: the magnetic power device of the multi-winding of a step-up; One comprises the high-voltage power supply of an AC voltage generator, and this AC voltage generator has a an output connected to the primary winding of the step-up multi-winding magnetic power device; and a rectifier circuit connected to the secondary winding of the step-up multi-winding magnetic power device to provide a high voltage level of current. 4. The spark control apparatus of claim 1, wherein said high voltage power supply comprises a high voltage power supply having a low level output circuit storing electromagnetic energy. 5. The spark control apparatus of claim 4, wherein said high voltage power supply includes a control circuit operable to monitor the current of said at least one electromagnetic parameter and respond to a detected spark previous conditions, reducing the voltage of the current to a level that prevents sparking from occurring. 6. The spark control apparatus of claim 4, wherein said high voltage power supply includes a control circuit operable to monitor said electromagnetic parameter and, in response to a detected pre-spark condition, The voltage of the electrical power is reduced to a level at which sparking is not induced. 7. The spark control apparatus of claim 1 , further comprising a load circuit connected to said high voltage power supply such that said load circuit is responsive to said identification of said pre-spark condition A substantial portion of the electrical power is selectively received. 8. The spark control apparatus of claim 7, wherein said load circuit includes an electrical device for dissipating electrical energy. 9. The spark control apparatus of claim 7, wherein said load circuit includes an electrical device for storing electrical energy. 10. The spark control device of claim 1, wherein said load device comprises a corona discharge device including a plurality of electrodes configured to receive said electrical power to form a corona discharge. 11. The spark control device of claim 10, wherein said corona discharge device comprises an electrostatic air treatment device. 12. The spark control device of claim 11, wherein said electrostatic air treatment device comprises a device selected from the group consisting of electrostatic air acceleration devices, electrostatic air cleaners, and electrostatic precipitators. 13. The spark control device of claim 1 wherein said first detector includes circuitry for selectively powering an auxiliary load device in addition to said load device, Thereby, in response to said identified pre-spark condition, at least a portion of said electrical power is shunted from said load device to said auxiliary load device. 14. The spark control device of claim 13 wherein said load device and auxiliary load device each comprise an electrostatic air handling device configured to accelerate under the influence of electrostatic forces generated by corona discharge structures fluid. 15. The spark control device of claim 1, wherein the sensor is sensitive to one or more of the following phenomena: changes in current, changes in voltage, magnetic changes, occurrence of electrical events , and the occurrence of light events to identify the pre-spark conditions. 16. A method of controlling sparks, comprising the steps of: supplying high voltage power to a load device; monitoring an electromagnetic parameter of the high voltage power to detect a pre-spark condition of the load device; and controlling the high voltage power in response to one or more electromagnetic parameters identifying the pre-spark condition to rapidly vary the magnitude of the high voltage power to a level that prevents sparking from occurring in order to control the pre-spark condition The occurrence of the associated spark event. 17. The method of claim 16, wherein said step of supplying high voltage power comprises the steps of: transforming a source of electrical power from a primary voltage level to a secondary voltage level higher than said primary voltage level; and The electric power at the secondary voltage level is rectified to the high voltage power to supply the high voltage power to the load device. 18. The method of claim 16, wherein said step of monitoring includes the step of detecting current spikes in a high voltage current provided by said high voltage power. 19. The method of claim 16, wherein the step of monitoring includes the step of detecting an output voltage parameter of the high voltage power. 20. The method of claim 16, wherein the step of controlling further includes the step of reducing the voltage level of the high voltage power to a level that prevents sparking from occurring. 21. The method of claim 16, wherein said step of controlling includes the step of routing at least a portion of said high voltage power to an auxiliary load device. 22. The method of claim 21, wherein said step of sending at least a portion of said high voltage power to said auxiliary load device comprises connecting an additional load to a high voltage supply supplying said high voltage power on the output circuit of the power supply. 23. The method of claim 16, wherein said loading device comprises at least one corona discharge electrode, said method further comprising the step of: directing fluid to the corona discharge electrodes; energizing the corona discharge electrodes with the high voltage power; generating a corona discharge into said fluid; and The fluid is accelerated under the influence of the corona discharge. 24. An electrostatic fluid accelerator comprising: a corona discharge electrode and a collector electrode in an array; a high voltage power supply electrically connected to said array for supplying high voltage power to said corona discharge electrodes; a sensor configured to monitor an electromagnetic parameter of said high voltage power; a first detector to control the high voltage power in response to identifying a pre-spark condition; and a second detector connected to said first detector, said second detector being operable to control said high voltage power supply to rapidly vary the magnitude of said high voltage power in response to said pre-spark conditions to a level that prevents sparks from occurring. 25. The electrostatic fluid accelerator of claim 24, wherein said first detector is configured to prevent supply of said high voltage power to said Corona discharge electrodes. 26. The electrostatic fluid accelerator of claim 24, wherein said first detector includes a bleed resistor configured to respond to said pre-spark condition to said identifying, accepting at least a portion of said high voltage power.

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