Three-phase alternating current three-potential rectifying circuit

Abstract

The utility model discloses a three-phase alternating current three-potential rectifying circuit, which is particularly applied to a power supply circuit of a three-phase alternating current combination switch. According to the three-phase alternating-current composite switch powered by the three-phase alternating-current three-potential rectifying circuit, three phase line relays are respectively powered by three non-common-ground power supplies, so that the problem of sparking between relay contacts and coils is fundamentally solved, the problem of interphase short circuit of the three-phase alternating-current composite switch is effectively solved, and the service life of the three-phase alternating-current composite switch is prolonged. The reliability of the switch is greatly improved, the cost is reduced, and a reliable guarantee is provided for wide application of the three-phase alternating-current composite switch in the field of reactive compensation.

Description

Technical Field

[0001] The utility model relates to a three-phase alternating current three-potential rectifying circuit, in particular to a relay power supply circuit for a three-phase alternating current composite switch. Background Art

[0002] Three-phase alternating current composite switches are widely used in switching on and off three-phase alternating current capacitors for reactive power compensation. Existing three-phase alternating current composite switches all use one power supply to supply power to the relays on three phase lines. Since there is a large voltage difference between the contacts and coils of the switch, once the withstand voltage between the contacts and coils of two relays drops and arcing occurs, it will cause a phase-to-phase short circuit, which is commonly known as the switch blowing up. Generally, the solutions are to increase the distance between the contacts and coils of the relay, or to completely isolate the contacts and coils, or to increase the insulation of the coils. The above three methods to improve the withstand voltage between the contacts and coils of the relay will greatly increase the volume and cost of the relay, and there is no substantial improvement effect on some relays with a small volume. Summary of the Utility Model

[0003] In order to solve the problem that the existing three-phase alternating current composite switch is prone to arcing due to insufficient withstand voltage between the relay contacts and coils, the utility model provides a three-phase alternating current three-potential rectifying circuit, so that the voltage difference between the contacts and coils of the relays working on three phase lines is very small, and even ordinary relays can avoid the phenomenon of arcing between the contacts and coils.

[0004] To achieve the above object, the technical scheme adopted by the utility model is as follows: The three-phase alternating current three-potential rectifying circuit of the utility model is composed of three rectifier bridges Qa, Qb, and Qc for three phases A, B, and C and two step-down capacitors Ca and Cb. One end of the AC input of the rectifier bridge Qa for phase A is connected to phase A, and the other end is connected to an AC input terminal of the rectifier bridge for phase C through the capacitor Ca. One end of the AC input of the rectifier bridge Qb for phase B is connected to phase B, and the other end is connected to an AC input terminal of the rectifier bridge for phase C through the capacitor Cb. One end of the AC input of the rectifier bridge Qc for phase C is connected to phase C, and the other AC input terminal is connected to the capacitors Ca and Cb. The DC output of each rectifier bridge is connected to the coil of the corresponding relay, and the DC output of the rectifier bridge for phase C also provides power for the control circuit.

[0005] The utility model has the following advantages:

[0006] The three-phase alternating current three-potential rectifying circuit of the utility model provides a power supply circuit for the relays of three phases of a three-phase alternating current composite switch, which can ensure that arcing cannot occur between the contacts and coils of the relays, thereby ensuring that no phase-to-phase short circuit occurs inside the three-phase alternating current composite switch. It enables the three-phase alternating current composite switch to achieve higher reliability with ordinary low-cost relays. Description of the Drawings

[0007] Figure 1 is one of the schematic diagrams of the three - potential rectification circuit for three - phase alternating current of the present utility model;

[0008] Figure 2 is the second of the schematic diagrams of the three - potential rectification circuit for three - phase alternating current of the present utility model. Specific embodiments

[0009] As Figure 1 shown, a three - potential rectification circuit for three - phase alternating current of the present utility model: consists of three rectifier bridges Qa, Qb, and Qc of three phases A, B, and C and two step - down capacitors Ca and Cb. One AC input terminal of the rectifier bridge Qa of phase A is connected to phase A, and the other AC input terminal is connected to one AC input terminal of the rectifier bridge Qc of phase C (the input terminal not connected to phase C) through the capacitor Ca. One AC input terminal of the rectifier bridge Qb of phase B is connected to phase B, and the other AC input terminal is connected to one AC input terminal of the rectifier bridge Qc of phase C (the input terminal not connected to phase C) through the capacitor Cb. One AC input terminal of the rectifier bridge Qc of phase C is connected to phase C, and the other AC input terminal is connected to the capacitors Ca and Cb. The DC outputs of each rectifier bridge Qa, Qb, and Qc are connected to the coils of the corresponding relays Ja, Jb, and Jc. The DC output of the rectifier bridge of phase C also provides power for the control circuit.

[0010] The working principles of the three rectifier bridges are as follows: The rectifier bridge Qa of phase A is provided with an AC input voltage by phases A and C through the step - down capacitor Ca. The rectifier bridge Qb of phase B is provided with an AC input voltage by phases B and C through the step - down capacitor Cb. The rectifier bridge Qc of phase C is provided with an AC input voltage by phases A, C, B, and C through the step - down capacitors Ca and Cb. When Ca and Cb are of the same size, the output current of the rectifier bridge Qc of phase C is about 1.7 times that of the rectifier bridges Qa and Qb of phases A and B, and the extra part just provides current for the control circuit.

[0011] The outputs of the three rectifier power supplies Qa, Qb, and Qc are not grounded. The grounds of the three rectifier power supplies are the potentials of the corresponding phase voltages respectively. The DC ground of the rectifier bridge Qa is the potential of phase A, the DC ground of the rectifier bridge Qb is the potential of phase B, and the DC ground of the rectifier bridge Qc is the potential of phase C. The three relays Ja, Jb, and Jc of the three phases are respectively powered by power supplies with three different ground potentials. In this way, the voltage between the contacts and the coils of the three relays Ja, Jb, and Jc is only the DC voltage output by the rectifier bridges Qa, Qb, and Qc. This voltage cannot cause arcing between the contacts and the coils of the relays. Using this three - potential power supply circuit has basically no requirements for the withstand voltage between the contacts and the coils of the relays. Even very small - sized relays can meet the withstand voltage requirements between the contacts and the coils.

[0012] The control circuit controls relays Ja and Jb through an optocoupler to meet the withstand voltage requirements between the control circuit and Ja and Jb. As for Jc, since there is no voltage difference, it can be directly controlled. Figure 1 It is not shown in the figure, and its principle is easily achievable by those with ordinary skills in the art, so it will not be elaborated here.

[0013] Figure 2 This is the second embodiment of the three-phase AC three-potential bridge rectifier circuit of the present utility model. Phase A rectifier bridge Qa takes power from phases AB through step-down capacitor Ca, phase B rectifier bridge Qb takes power from phases BC through step-down capacitor Cb, and phase C rectifier bridge Qc takes power from phases AC through step-down capacitor Cc. The characteristic of this circuit is that the output current of the rectifier bridge for each phase is determined by the size of the step-down capacitor for each phase. Similarly, the phase C rectifier bridge can supply power to the control circuit. At this time, the step-down capacitor Cc of phase C should be larger than Ca and Cb because the output of the phase C rectifier bridge not only needs to provide power for the relay but also for the control circuit.

[0014] The withstand voltage between the contacts and the coil of a relay is an important indicator of a power relay. Too low withstand voltage will cause arcing between the contacts and the coil. To prevent the problem of arcing between the contacts and the coil of the relay, the general solution is to increase the distance between the contacts and the coil and improve the insulation on the surface of the coil. The result of this is that on the one hand, it will increase the volume of the relay, and on the other hand, it will also increase the cost of the relay. The solution provided by the present utility model is to reduce the voltage between the contacts and the coil through the power supply design, which will provide a new idea for the design of three-phase power switches.

[0015] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit them. Although the present utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present utility model.

Claims

1. A three-phase AC three-potential rectifier circuit, characterized in that, It is composed of three rectifier bridges Qa, Qb, and Qc for three phases A, B, and C, and two step-down capacitors Ca and Cb. One AC input terminal of the rectifier bridge Qa for phase A is connected to phase A, and the other AC input terminal is connected to one AC input terminal of the rectifier bridge Qc for phase C through the capacitor Ca. One AC input terminal of the rectifier bridge Qb for phase B is connected to phase B, and the other AC input terminal is connected to one AC input terminal of the rectifier bridge Qc for phase C through the capacitor Cb. One AC input terminal of the rectifier bridge Qc for phase C is connected to phase C, and the other AC input terminal is connected to the capacitors Ca and Cb. The DC outputs of each rectifier bridge Qa, Qb, and Qc are connected to the coils of the corresponding relays Ja, Jb, and Jc. The DC output of the rectifier bridge for phase C also supplies power to the control circuit.

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