Common faults and corresponding solutions of high frequency quenching equipment

1. Fault phenomenon The equipment is operating normally, but many KP thyristors and fast fuses are burned when the normal overcurrent protection operates. In order to release the energy of the smoothing reactor to the power grid during overcurrent protection, the rectifier bridge changes from the rectification state to the inverter state. At this time, if α=150?, it may cause the active inverter to overturn and burn down multiple thyristors and fast fuses. , The switch trips, accompanied by a huge current short-circuit explosion sound, which will generate a large current and electromagnetic force impact on the transformer, and will damage the transformer in severe cases.

2. Fault phenomenon The high-frequency quenching equipment is operating normally, but the equipment is unstable near a certain point in the high-voltage area, the DC voltmeter shakes, and the equipment is accompanied by a creaking sound. This situation can easily cause the inverter bridge to overturn and burn the thyristor. . This kind of fault is difficult to rule out and mostly occurs when a certain part of the equipment is ignited by high voltage:

(1) The screws of the copper bar joints are loose and cause ignition;

(2) Oxidation of the main connector of the circuit breaker leads to ignition;

(3) The screw of the wiring pile of the compensation capacitor is loose, which causes the ignition compensation capacitor to discharge the internal discharge resistance and capacitance absorption capacitor to ignite;

(4) The insulating part of the water-cooled radiator is too dirty or carbonized and sparks to the ground;

(5) The induction coil of the furnace body is facing the furnace shell furnace. The turn spacing of the induction coil of the base plate ignition furnace body is too close, and the insulation column of the induction coil of the furnace body is ignited due to high-temperature carbonization discharge due to ignition between turns or arcing.

(6) Fire inside the thyristor.

3. Fault phenomenon The high-frequency quenching equipment operates normally, but sharp beeps can be heard from time to time, and the DC voltmeter swings slightly at the same time. Use an oscilloscope to observe the voltage waveform at both ends of the inverter bridge DC. It can be seen that the inverter is periodically short-lived, and one cycle failure or an indefinite period of short-term failure. The short-term failure of the parallel resonant inverter circuit can be self-recovery. The periodic short-term failure is generally inverter control Some of them are disturbed by the rectification pulse, and the non-periodic short-term failure is generally caused by the poor insulation between turns of the intermediate frequency transformer.

4. Fault phenomenon After the high-frequency quenching equipment has been in normal operation for a period of time, the equipment has abnormal sound, and the reading of the electric meter is shaking, and the equipment is unstable. After the equipment has been working for a period of time, there is abnormal sound and the work is unstable. The main reason is that the thermal characteristics of the electrical components of the equipment are not good. The electrical part of the equipment can be divided into two parts: weak current and strong current, and the control part should be detected first to prevent damage. When the power device of the main circuit is not connected to the main power switch, only the power supply of the control part is turned on. After the control part has been working for a period of time, use an oscilloscope to detect the trigger pulse of the control board to see if the trigger pulse is normal.

On the premise of confirming that there is no problem with the control part, turn on the equipment. After the abnormal phenomenon occurs, use an oscilloscope to observe the voltage drop waveform of each thyristor to find out the thyristor with poor thermal characteristics; if the thyristor The voltage drop waveform of the thyristor At this time, it is necessary to pay attention to whether there are problems with other electrical components, and pay special attention to circuit breakers, capacitors, reactors, copper bar contacts and main transformers.