CN1068968C - Switchgear control apparatus - Google Patents

Abstract

A control device for switching equipment, particularly contactors or relays, typically has a magnetic system comprising a coil with an armature and a yoke. In the past, it has been suggested to employ a device that adjusts the magnetic flux in the magnetic system over time according to a rated curve, which is precisely calculated for a magnetic model. According to the present invention, the magnetic flux is adjusted within a predetermined range independent of time and travel using the adjusting device (10). It is preferable to use the adjusting device (10) to adjust the magnetic flux through the coils (1, 21). In particular, the narrow range of coil magnetic flux adjustment is independent of time and travel, which is not possible with the prior art.

Description

Control gear for switchgear

The invention relates to a control device for switching devices, in particular for contactors or relays, with a magnetic system and an adjusting device, the former comprising an armature and a yoke with a coil, the latter for adjusting The magnetic flux in the magnetic system, using the control device, can adjust the magnetic flux in the magnetic system within a predetermined range, such a control device has been disclosed by GB2112213A.

The drive of the switching device is usually operated by means of a magnetic system, which has to be adapted to the voltage level and/or the type of operation of the switching device. A large number of coil variants are necessary for this.

Especially when using DC-driven contactors, it is known that a high current is necessary during the pull-in phase of the magnetic system in order to overcome the spring force. In contrast, a significantly lower current is sufficient for a secure hold when the magnetic system is closed. In order to reduce the holding power when using DC-driven contactors, different techniques have been used: for example it is known to use two solenoid coils, one for the pull-in phase and the other for the hold-in phase, where the The coil is accessible via an auxiliary switch. In addition, pulsed coil voltages have been proposed for the holding phase. The pulse performance determines the effective coil current. When the contactor is reliably connected, switch over after a fixed time.

A circuit arrangement for an electromagnetic switching device is known from DE 30 47 488 A1, in which a two-point regulator is used to regulate the current flow through a holding coil in the closed state of a holding magnet. To reduce the holding power, after a given period of time, the threshold for current regulation is switched. The measured variable for current control is ascertained here by means of a magnetic flux measurement via a Hall probe. Furthermore, DE 41 29 265 A1 discloses an electromagnetic switching device with a pivoted armature system, in which the leakage flux is measured by means of a Hall detector and the power supplied to the coil is regulated via the calculated flux proportional parameter. In DE 3637133 the leakage flux is also measured by forming a magnetic shunt for detecting the smallest air gap. Finally, a switching contactor with a flux sensor is known from DE 3246739, in which a Hall sensor is located in the yoke of the magnetic system, the signal of which is used to control the electrical actuation of the switching contactor when a predetermined magnetic flux is reached.

In addition, due to the fact that the 13th research class of the University of Karlsruhe held the contactor seminar held on October 4-6, 1995, in page 101 below, the control and regulation by different principles were studied. Contactor drive mechanism. In particular there is also described a device for regulating the magnetic flux in a magnetic system, in which the magnetic flux is determined by integrating the induced voltage in a coil wound on the magnet legs and is used with the aid of an accurate magnet model The inverse simulation method is used to calculate the rated predetermined value of the magnetic flux. A specific time-dependent flux rating curve is thereby set. This magnetic flux generates the driving force and thus establishes a causal link with the mechanical movement.

The aforementioned patent GB 2112213A discloses a switching device with an electromagnetic drive, which has a magnetic flux sensor in the magnetic system and an analog control circuit for the magnetic flux. As a result, the high power losses of the control elements required for the analog regulation are converted, resulting in an increase in heat, which necessitates the use of a cooling body. Furthermore, US Pat. No. 3,579,052 A discloses a control device for switching devices, in which the suction force is adjusted over time.

The object of the present invention is to simplify the control device used in the above-mentioned type of switchgear, on the one hand to reduce the holding power of the magnetic system, and on the other hand to increase its mechanical and electrical service life. Furthermore, the simplified control device can be used in different switching devices, so that only few coil modifications are necessary and the magnetic system itself can be made smaller than before.

The object of the invention is achieved with a control device of the type mentioned in the preamble in that the magnetic flux in the coil is regulated for a time- and travel-independent control by means of a regulating device, wherein an upper threshold value and a lower threshold value of the predetermined range are specified. Threshold, and according to the desired switching frequency, the width of the range in which the magnetic flux of the coil is regulated can be selected.

With the present invention, a soft closing of the switching device can be achieved in a simple manner, resulting in a longer service life of the contacts and thus of the entire switching device due to the reduction of contact bouncing. Furthermore, it is advantageous that only one magnetic flux range is necessary for pulling and holding, which range can be set to a narrower range. The width of the range in which the magnetic flux of the coil is regulated is generally between 0.01% and 10% of the magnetic flux, preferably between 0.05% and 5%. The width of the range of coil flux is determined by the switching frequency.

The invention is based on the unusual insight that the desired value of the magnetic flux in the coil is preferably selected independent of state and position. Tests carried out on a specific contactor have shown that the magnetic flux must have approximately equal values in order to achieve the attracting force of the magnetic system in the open state and the holding force of the magnetic system in the closed state. In the closed state, a significantly lower current is sufficient to generate such a large magnetic flux, because there is a larger inductance and a smaller magnetic resistance. In a given magnetic system, the value of the magnetic flux is independent of the voltage level by adjusting the number of turns of the coil.

In this way a considerable advantage is obtained over the prior art, in which, while simplifying the construction of the magnetic system, the magnetic flux has to be preselected as a function of time. It is also advantageous that the properties obtained on a specific contactor can also be transferred to contactors of other sizes. In particular by varying the forced air gap in the yoke of the magnetic system, a correspondingly adapted performance can also be obtained.

Further details and advantages of the invention are obtained from the following description of embodiments with the aid of the accompanying drawings and other subclaims, in which:

Figure 1 shows the schematic structure of a control device for a magnetic system;

Figure 2 is a diagram of the flux and current curves adjusted within a narrow range;

Figure 3 shows a schematic diagram of measuring the magnetic flux of the coil in the magnetic system through an auxiliary coil;

Figure 4 is a schematic diagram of measuring the magnetic flux of a coil by a magnetic field probe;

Figure 5 shows the construction of a magnetic system consisting of a yoke and an armature, where a forced air gap can be seen.

Identical or identically acting elements in the various figures bear the same reference symbols. These figures are partially illustrated together.

In these figures, reference numeral 1 designates a coil which is part of a magnetic system for the switchgear. FIG. 1 specifically shows a coil 1 as an inductance, which is connected via a rectifier bridge 5 to the terminals of the AC network. The coil 1 is equipped with a sensor 2 for detecting the magnetic flux.

In Fig. 1, 10 denotes the means originally used for regulating the magnetic flux. It contains a threshold detection unit 11 and a voltage monitoring unit 12 as well as a controllable switching element 13 . Through the controllable switching element 13 , such as a transistor, the coil 1 is connected to the rectified terminal voltage.

The voltage monitoring in the unit 12 is used to initiate the switch-on process when the voltage exceeds a certain switch-on threshold, for example 70% of the rated voltage. This prevents the contactor from hanging and welding at the main contacts.

After release, the magnetic flux through the coil 1 , ie, the coil flux, is measured, but not in the working gap of the magnetic system during switching-on, and the measured value is then used for the regulation control. An upper threshold and a lower threshold are determined for the coil magnetic flux. The switching element 13 remains closed as long as the coil flux remains below the upper threshold. When the upper threshold value is exceeded, the switching element 13 is switched off, and the coil magnetic flux decreases again. The switching element 13 is closed again when the lower threshold value falls below.

By such an adjustment it is possible to maintain the magnetic flux through the coil 1 within predetermined limits, so that the coil magnetic flux can be adjusted within such a range, that is, between 0.01% and 10% of the coil magnetic flux, especially between 0.05% and 5%. .

In order to further standardize the adjustment range, the test was carried out on the contactor 3TF56 of Siemens to obtain the basic data for the simulation calculation. The results of this experiment are shown in Figure 2, where the magnetic flux φ and the associated current I are shown respectively as a function of time. As shown in the legend, for a magnetic flux of 1.35 to 1.4 V.s, a switching frequency of 400 Hz achieves a window width of about 3.6%. Since it is desirable that the frequency is as far as possible outside the high range, ie above about 20 KHz, the window width value is below 0.01%. A narrow range which has not been considered so far can thus be determined in this way.

It can be further known from Figure 2 that the coil magnetic flux φ(t) has nothing to do with time. The opposite is true for the current curve I(t), according to which the current I drops after about 50 ms.

In order to regulate the magnetic flux within a predetermined narrow range, it is necessary to detect the coil magnetic flux by various known methods.

As shown in FIG. 3 , the magnetic system 20 is composed of a coil 21 (corresponding to the coil 1 in FIG. 1 ), a yoke 22 and an armature 23 . Mounted on the yoke 22 of the magnet system 20 is an auxiliary coil 24 which serves to measure the induced voltage. The induced voltage is integrated over time to obtain a magnitude for changing the coil flux. The achievable precision is sufficient in the suction phase. Since the induced voltage in the holding stage cannot be controlled, the offset error in the measurement process may cause the drift of the integrator, so appropriate compensation measures must be taken.

As shown in FIG. 4, mounted on the same magnetic system 20 as shown in FIG. 3 is a magnetic field probe 34 which measures either the B (accelerating) magnetic field or the H (homogeneous) magnetic field. It may be necessary to provide a slot 25 in the magnetic system 20 for this purpose. The B magnetic field or H magnetic field is a measurement of the magnetic flux passing through the coil 21 . It is particularly advantageous in this case that no integrator is required.

Figure 5 is basically a combination of Figure 1 and Figure 4 . In the electrical control module, the control lines for the coil 1 shown in FIG. 1 or the coil 21 shown in FIG. 4 are bridged via a diode. A suitable magnetic field probe 34 is inserted into the slot 25 .

This is exploited in FIG. 5 by preferably having a forced air gap 30 in the yoke 22 . Such forced-air gaps are usually provided and filled with a film of insulating material during the manufacture of a yoke made of sheet iron in order to securely connect the two yoke parts.

In the arrangement shown in FIG. 5 , a magnetic voltage divider is realized between the forced air gap 30 and the slot 25 by means of the special geometry of the slot 25 and the forced air gap 30 . Magnetic properties are influenced by changing the geometry. A narrower forced air gap greatly reduces the coil flux necessary to hold, but has little effect on the coil flux necessary to apply the pull force in the off state. A variation of the width b of the forced air gap is therefore particularly useful for adapting the magnetic flux required in the closed state to have the same magnitude as that required in the open state.

Claims (11)

1. A control device for switching devices, in particular contactors or relays, having a magnetic system with a coil with an armature and a yoke, and an adjusting device for adjusting the magnetic flux in the magnetic system, using The adjustment device can adjust the magnetic flux within a predetermined range, and it is characterized in that, in order to adjust independently of time and travel, the magnetic flux in the coil (1, 21) is adjusted by the adjustment device (10), wherein the coil (1, 21 ) The magnetic flux range defines an upper threshold and a lower threshold, and selects the width of the range in which the coil magnetic flux is regulated according to the desired switching frequency. 2. The control device according to claim 1, characterized in that the width of the range in which the magnetic flux of the coil is regulated is between 0.01% and 10% of the magnetic flux, preferably between 0.05% and 5%. 3. 1. The control device as claimed in claim 1, characterized in that the magnetic flux is measured during the switch-on and holding processes and used for the regulation. 4. 1. Control device according to claim 1, characterized in that the coil (1) is connected to the terminal voltage via a controllable switching element (15) and a rectifier (5). 5. The control device according to claim 1, characterized in that the regulating device (10) comprises a voltage monitoring unit (12), with which, when the voltage exceeds a defined switch-on threshold, for example 70% of the nominal voltage, Release the switch-on process. 6. Control device according to claim 1 , characterized in that an auxiliary coil ( 24 ) with an integrator ( 26 ) is provided for measuring the magnetic flux. 7. 6. Control device according to claim 6, characterized in that the auxiliary coil (24) is arranged on the yoke (22) of the magnetic system (20). 8. 6. Control device according to any one of claims 1 to 7, characterized in that a magnetic field probe (34) is provided for measuring the magnetic flux of the coil. 9. Control device according to claim 8, characterized in that the magnetic field probe (34) is arranged in a slot (25) of the yoke (22) of the magnet system (20). 10. Control device according to claim 9, wherein the yoke of said magnetic system has a forced air gap, characterized in that said slot (25) and forced air gap (30) in the yoke (22) form a magnetic voltage divider. 11. 11. The control device of claim 10, wherein said forced air gap has a preselected width (b).

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