MXPA99001389A - Generator that has output capacity of primary source of impedance adapter for operation with maximum efficiency to max - Google Patents

Abstract

In a unit of electric power generation with a primary source that has a motor shaft that rotates at a speed (which ends an output energy function having in each value of (an energy-output slope / (Md, and a generator that develops electrical energy sensitive to shaft rotation, an electric generator impedance selected to provide a slope of generator power-output / (Mg to approximate the slope Md, thus (can be controlled to maximize efficiency)

Description

GENERATOR THAT HAS OUTPUT CAPACITY OF PRIMARY SOURCE OF IMPEDANCE ADAPTER FOR OPERATION WITH ONE INCREASED EFFICIENCY AT MAXIMUM The present application relates to generators driven by primary sources and, more particularly, to a new generator having a selected internal impedance to adapt the output drive capacity of the primary source all along the source speed range. to obtain maximum efficiency and minimum emissions.

ANTEC DENTES DE LÁ? NVEÑCÍÓN It is well known to drive an electric generator with a primary source connected to the rotor shaft of the generator. Typically, the electrical output of the generator is provided responsive to the excitation of a field coil in the generator; The field coil itself and the separate field excitation electronics are both expensive and undesirable. In addition, the use of excited field coils will often cause the generator to operate at reduced efficiency. This is not normally desirable, and it is especially so when the combination of the primary source and the electric generator is contained in an electric vehicle, wherein the wheels are driven by a motor receiving power provided directly or indirectly from the generator; The maximization of efficiency will not only improve fuel consumption, but may also result in the minimization of pollution and other undesirable characteristics. It is therefore desirable to provide a permanent magnet generator, devoid of the field coil and field excitation means, which are driven, with maximum efficiency, directly by the primary source.

BRIEF DESCRIPTION OF THE INVENTION According to the invention, a primary source has an output motor shaft, whose rotation at a speed? determines an output energy function having in each value of? an exit-e? éfgíá / pending? Md, and is coupled to a generator for the development of electrical energy sensitive to the rotation of that motor shaft, then an electric generator impedance is selected to have an output-energy / slope generator? Mg, to approach the slope d, to facilitate the maximum increase in efficiency. In a currently preferred mode, the slope of the generator is within a factor of of the slope of the primary source. When used in a hybrid electric vehicle having a primary source diesel engine with an operating curve slope Mg in the order of 0.15 hp / rev. , the electrical impedance of generator Z is selected to give an operating curve slope Mg of between about 0.075 hp / rev. and around 0.3 hp / rev. Accordingly, it is an object of the present invention to provide a motor driven electric generator having a selected impedance to adapt the operating characteristics of the generator to those of the driving motor and thereby maximize efficiency. This and other objects of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description, when read in conjunction with the accompanying drawings, in which like elements are designated with similar reference designations.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic block diagram of a motor driven generator and a typical load therein, as can be found in a hybrid electric vehicle and the like; Figure 2 is a group of coordinated graphs illustrating the voltage and current provided by the motor-driven adapted impedance generator of the present invention; Figure 3 is the Thevenin equivalent circuit of the new adapted generator of the present invention; Figure 4 is a graph that illustrates: the net and maximum energy curves of a particular diesel engine; the operating curve of a generator not adapted from the prior art: and a group of operating curves for a new generator adapted according to the present invention; and Figure 5 is a graph illustrating a group of voltage-current operating curves, and a constant load-energy curve for a particular operational scenario, illustrating the manner in which the efficiency of the primary source generator is increased to maximum according to the principles of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring initially to Figure 1, a system 10, such as the motor system for a hybrid electric vehicle and the like, uses a 1 1 motor as the primary source. A fuel source 12 is connected to a fuel input 1 1 a of the engine, whose fuel is burned in the engine to cause a drive shaft 1 1 s to rotate at a rotation speed, or frequency,?. The rotation speed? of the motor shaft 1 1 s is set sensitive to the signals provided in a motor control input 1 1 b from an output 14b of motor / load control means 14. The means 14 have at least one input / output port 14a connected to receive and transmit electrical signals over an electrical wiring link 16 to and from generator load means 18, which may contain sensors, switches and similar transducers and / or effectors coupled to at least one end effector means, such as wheel drive motor in a hybrid electric vehicle and the like. The motor shaft 1 1 s is directly connected to a rotor shaft 20s of a generator means 20 to produce an AC voltage output Vg between the output terminals of the generator 20a and 20b, for the connection to the load 18. Generally, generator 20, hitherto, has been of the field-excited type, having a field coil 20f (shown in line of shadows) within the generator and connected to an excitation field output 22f of a field excitation means 22 The means 22 would typically have inputs 22a / 22b connected to the electrical output of the generator, to monitor the AC voltage from there, and also have a control input port 22c to receive commands, other captured parameters and similar signals, so that all of the input signals can be used, in a manner well known for the electric generator technique, to set the generator voltage Vg by controlling the excitation signal characteristics of the field coil 20f. According to one aspect of the present invention, the generator 20 is a type of permanent magnet, completely devoid of any field excitation coils 20f and the system 10 is completely similarly devoid of any form of field excitation means. , and any special sensors, triggers and special electrical connections associated with such field excitation means. An illustrative generator load 18, as can be found in a hybrid electric vehicle and the like, can include a full wave rectifier means (FWR) 20 for receiving the AC voltage Vg from the generator terminals 20a and 20b, for rectification in a pulsed-DC voltage V that appears through a storage battery 26. A controlled switch means 28 is connected in series with a variable load 30, such as a DC electric motor and the like, through battery means 26 The media combination series 28 and the means 30 is thus connected in parallel with the battery means 26, and through the output of the means FWR 24. The electrical potential at the input of the control means of switch 28a is selectively coupled to its output 28b (and therefore to load 30) responsive to the state of a control signal at an input 28c, whose signal is typically provided through a link 16 and the like. Referring now to Figure 2, the generator voltage Vg is always a bipolar AC voltage 20w of some peak value (which will have a maximum value of Voc, the open circuit voltage of the generator, and will typically be of a smaller magnitude, due to the voltage drop caused by the flow of current from the generator through to a series impedance of the generator Z). At the voltage output V of the means 24, the half-cycles of negative polarity 20n (shown in dashed line) are inverted by the full-wave rectification process; the unipolar voltage V has polarity-positive lobes only 20p. The current I 'does not flow when the rectifier diodes of the means 24 are inversely biased, which occurs whenever the instantaneous magnitude of the voltage V is less than the voltage Vb of the battery means 26 connected through the output of the FWR media. However, as soon as the voltage V is instantaneously of a value greater than the battery voltage V, the medium diodes FWR 24 become forward biased and the pulses 32 of the current flow I ', as shown in the form of lower wave in figure 2, at some peak value lp. If the switch means 28 is not conductive, the entire current I 'charges and recharges the battery 26; if the switch means 28 is conductive, the current flows from each or both of the means 24 or the battery 26, through the medium 28 and into the electrical load 30. The permanent magnet generator (PMG) means 20 has a Thevenin equivalent circuit as shown in Fig. 3, with a sinusoidal source 20y having a value Voc (which is a function of the rotation speed? of the input shaft of the generator 20s) in series, between the terminals of the generator 20a and 20b with a generator impedance 20z consisting of a series resistor 20r and a 20x series reactance. According to one aspect of the present invention, the Z value of the generator impedance 20z is selected to set a particular operating slope Mg, which is defined as the change in energy P (in horsepower) with respect to the speed of engine S (in revolutions per minute), and desirably adapts the slope Md of the P / S curve of the engine, as will be discussed in detail hereinafter. The slope Mg can be established by manipulation of the amount of resistive component R and / or the magnitude of reactive component X. Referring now to figure 4, graph 40 has the rotational speed S of the engine 1 1, in revolutions per minute (rpm ), drawn along the abscissa 41, and the energy output of the engine P, in horsepower, drawn along the ordinate 42. For a particular 1 1 diesel engine, a maximum energy P-ma can be obtained ? and also, with a known coupling between the motor and its motor shaft load, a net power curve Ppet 44 '. Curve 44 'runs near curve 44; for this particular engine, the energy versus speed curve 44 has an Md slope of about (240-60) hp / (2000-800) rpm = 0.15hp / rev. The generator 20 has an operating curve 46 which is determined by its output voltage Vg, the same being the same, when rectified, to the battery voltage Vb; thus, the generator has a first operating curve 46a of output power vs. the speed S of the axis 20s, for a minimum limit of battery voltage (here, around 450 Vdc), and has other operating curves 46b, 46c, 46d and 46e, respectively, for higher values Vb (here, of about 500, 540, 580 and 620 Vdc, respectively). According to the invention, the generator impedance Z is selected to cause an operational curve of generator 46 to have an Mg slope approaching the operating slope of the engine Md. Typically, the slope Mg of generator curve 46 for any speed S will be related with the slope Md of the motor curve 44 at the same speed by not more than a factor of two, for example, a slope of the minimum generator operating curve Mg, min of approximately Md / 2 and a slope of the generator operating curve maximum Md, mx of approximately 2Md. Illustratively, for a motor having an Md of 0.15, the minimum generator curve slope 46 will be around 0.075 (as in the upper end of curve 45a) and the maximum generator slope Mg will be about 0.3 (as in the lower end of curve 46e). In the motor-generator combinations known so far, the traditional generator 48 operational curve has had a typical Moid slope of about 0.4 horsepower per revolution. It will be appreciated that an adapted motor-generator pair, in accordance with the present invention, will have a slope of operating curve less than the operational slope of a traditional generator two or three times lower than the traditional generator slope. For a particular combination of a horsepower 240 horsepower diesel engine and a permanent magnet generator 20 supplying power output at AC voltage peaks between about 450 volts and about 620 volts, it will be appreciated that the generator 20 is selected not only for an impedance matching to the primary source, but also to cause the generator to substantially not provide output power for rotational speeds below about 1,000,000 rpm; appreciable electric power, which can be defined as more than about 5% peak energy, is only thus provided at selected speeds to be above the low velocity region where the highest emissions and other undesirable characteristics are found for the particular engine used. According to another aspect of the invention, having a start of appreciable generator output energy at motor speeds between 1, 000 and 1, 200 rpm allows for engine emissions reduced to a minimum while at the same time does not place a load on the motor. 1 1 diesel engine until the turbo diesel has increased in speed sufficiently to not reduce the overall diesel operating speed; this also allows the diesel engine fuel injection system to be adjusted to gradually bring the engine up to about 1,200 rpm prior to the increased fuel flow to meet the lower end torque requirements and thus reduce emissions gas and motor particles 1 1. Referring finally to Figure 5, a graph 50 has a load current l drawn along the abscissa 51 and load voltage VL drawn along the ordinate 52. The load (motor 30) is a constant energy load having a curve Vl 53 shown in a dashed line. This curve is the energy distributed to the load motor and is the product of an operating voltage, approximately equal to the generator voltage Vg, multiplied by and the operating current, at any point on the curve 53. At a set speed, the generator 20 it will operate along a generator energy curve producing an energy determined by the voltage point of the battery system Vb. For illustration purposes, let's assume a first operating speed generator curve given by the full line curve 55. This curve will be for a speed greater than (ie, say, 2,000 rpm) than the average speed (ie 1, 800 rpm) of a second curve 56, which will be even greater than the lower speed of a third operating curve 57 (ie at 1, 600 rpm). If the generator energy demand is significantly lower than the generator capacity at the given speed, ie 2,000 rpm along curve 55, current I will naturally decrease causing the system to operate at a less efficient point. In curve 55, maximum efficiency is obtained at a point 55a, with an increase in rotor losses occurring in the direction of arrow A and an increase in losses l2R occurring in the direction of arrow B. The only points possible operatives are found where curves 53 and 55 intersect, at points 55p and 55p '; The relatively high generator voltage will normally dictate operation at point 55p, with much less than the maximum efficiency for that generator curve 55. Controller 14 recognizes operation at voltage V0 ,? , and the current l * _ ,? , well separated from point 55a, and sets the speed of the diesel engine 1 1, for example, decreasing the speed, to increase the efficiency of the generator. A little later, the generator speed has decreased until the generator 20 is operating along the generator curve 56. The exact operating point will be the point 56p, where the curves 53 and 56 intersect. Operating point 56p is still quite far from the maximum efficiency operating point 56a of the generator at this new speed. Accordingly, the controller means 14 continues to reduce the speed of the motor until a speed is reached by producing the curve 57, where the generator is operating at 57p, very close to the point of maximum operational efficiency 57a. It has been found that a minimum efficiency of about 94% can be obtained by adapting generator impedance Z to the motor by rotating the generator shaft, contrary to a typical 85% efficiency of the generators having operating curves such as curve 48. While the present invention has been described with respect to a currently preferred embodiment thereof, many variations and modifications will become apparent to those skilled in the art. It is the intention, therefore, to limit it only to the scope of the following claims, and not by the details and instrumentations presented here by way of description.

Claims (20)

1. CLAIMS 1 . Apparatus for generating electric power, comprising: primary source means having a motor shaft that rotates at a speed? determining an output energy function that you have in each value of? an energy-output slope / © Md; and generator means for providing electrical power responsive to the rotation of said axis and with a selected impedance to cause a generator-energy-output slope /? Mg to approximate said slope Md.
2. 2. The apparatus according to claim 1 further comprising means for controlling the speed of the motor rotation to maximize the efficiency of the apparatus.
3. The apparatus according to claim 1, wherein the impedance of the generator provides an operating curve slope Mg not greater than about two times the slope Md.
4. The apparatus according to claim 1, in where the generator Impedance provides an operating curve slope Mg not less than about one half of the slope Md.
5. The apparatus according to claim 1, wherein said generator means provides an output of lower energy, less than about 10% of a maximum generator power output, for a rotational speed & less than around 1500 rpm.
6. The apparatus according to claim 5, wherein a generator power output for a rotational speed or less than about 1000 rpm is not provided.
7. The apparatus according to claim 1, wherein said primary source means is a hydrocarbon fuel burner engine.
8. The apparatus according to claim 7, wherein said engine is a turbo-diesel engine in a hybrid electric vehicle.
9. 9. A method to generate electric power, which comprises the steps of: (a) providing a primary source having a motor shaft that rotates at a speed? determining an output energy function that you have in each value of? an energy-output slope / © Md¡ (b) provide a generator that develops electrical energy sensitive to the rotation of the motor shaft; and (c) select a generator impedance to have a power-output generator slope /? Mg to approximate the slope Md.
10. The method according to claim 9, wherein the slope Mg is within a factor of about two of the slope Md. 1 1.
11. The method according to claim 9, which further includes the step to vary the speed? from the primary source to maximize generator efficiency.
12. The method according to claim 9, further including the step of operating the generator without an excitation field.
13. 13. The method according to claim 9, which further includes the step of also selecting the generator to provide an appreciable electrical output only above the value? minimum preselected.
14. 14. A method for generating electric power in a hybrid electric vehicle, comprising the steps of: (a) providing a primary source that has a motor shaft that rotates at a speed? determining an output energy function that you have in each value of? an energy-output slope /? M; (b) provide a generator that develops electrical energy sensitive to the rotation of the motor shaft; and (c) selecting a generator impedance to have an energy-output generator function /? with a slope Mg to approximate the slope Md.
15. 15. The method according to claim 14, wherein the slope Mg is within a factor of about two of the slope Md.
16. 16. The method according to the claim 14, which also includes the step of varying the speed © of the primary source to maximize the efficiency of the generator.
17. 17. The method according to claim 14, further including the step of operating the generator without an excitation field.
18. 18. The method according to claim 14, which further includes the step of also selecting the generator to provide an appreciable electrical output only above the value? minimum preselected.
19. 19. The method according to claim 14, further including the steps of: selecting the primary source to be a diesel engine; select the generator to be a CA generator that has an input shaft; and directly connect the output shaft of the motor to the input shaft of the generator. The method according to claim 19, further including the steps of: operating the generator without excitation field; vary the speed? from the primary source to maximize generator efficiency; and select the generator to provide an appreciable electrical output only above the value? minimum preselected.