Combined type arc-free alternating-current (AC) contactor with function of thyristor fault diagnosis

Abstract

The invention provides a combined type arc-free alternating-current (AC) contactor with the function of thyristor fault diagnosis. The combined type arc-free AC contactor comprises an AC contactor body, parallel shunt branch circuits and a detection control device, wherein the parallel shunt branch circuits are respectively connected to the two ends of each three-phase main contact of the AC contactor body in parallel; the parallel shunt branch circuit of each phase comprises a current detection unit, a bidirectional thyristor, a thyristor self-check relay, a thyristor self-check resistor and an electromagnetic relay; the detection control device comprises a three-phase voltage detection unit, an A-phase voltage zero-crossing detection unit, a three-phase current detection unit, an A-phase current zero-crossing detection unit, a solenoid excitation unit, a thyristor drive unit, an electromagnetic relay drive unit, a current detection unit, a resistance-capacitance buck power supply and a microcontroller. The combined type arc-free AC contactor is used for frequently connecting or disconnecting an AC main circuit, and the generation of electric arcs during each action of the contactor is inhibited through the instant current shunting of power electronic devices, so that the erosion to the main contacts of the contactor caused by the electric arcs is reduced greatly.

Description

technical field [0001] The invention belongs to the technical field of low-voltage switches, in particular to a composite arc-free AC contactor with a thyristor fault diagnosis function. Background technique [0002] The existing compound AC contactor is based on the complex of AC contactor and thyristor. The electromagnetic coil excitation method is mostly AC mode, that is, it directly takes power from the 380V bus bar, and the magnetic flux in the magnetic circuit alternates, which will cause core loss in the core. And it emits noise, which reduces the efficiency of electrical equipment and the power factor of the grid, poor controllability, low operating frequency, and consumes a lot of electric energy when maintaining the electromagnet. [0003] The stable and reliable operation of the AC contactor directly affects the power quality. With the development of new materials and new processes and the rapid advancement of power electronics technology, intelligence and arc-fr...

AI Technical Summary

Problems solved by technology

[0004] Electromagnetic coils also use DC excitation, but the hardware circuit is large in size, low in cost performance, and the processor has poor real-time performance and simple control strategy

The thyristor is the weak link of the existing composite switch, and it is prone to failure. It is necessary to take effective measures to detect and remove the failure in time, otherwise, it will be a great safety hazard in practical applications.

[0005] The actual application of the engineering project found that the long-term operation of the composite AC contactor also has potential safety hazards

Usually, the problem of no-arcing is solved by connecting the bidirectional thyristor in parallel with the contactor, but the thyristor needs to withstand a large voltage change rate (dv / dt) during the transient process of the thyristor conducting and shunting, and it is easy to break down short circuit or open circuit

If the two-phase or three-phase thyristors in the shunt branch break down and short-circuit, it will cause the motor load to short-circuit or lose phase, and the motor winding will burn out quickly.

At this time, the load cannot be broken. Even if the staff finds out, it will take some time to deal with it, which will lead to serious production accidents, so it cannot be ignored.

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