When the inverter circuit breaks down, it is considered that the medium frequency protection circuit is started and the inverter circuit is damaged.
It is preliminarily determined that the fault range is in the inverter control circuit. Through visual inspection, it is found that a resistor on the inverter pulse forming circuit seems to be overheated. During hand touch and shaking inspection, one foot comes out of the solder joint and is welded firmly again, and the fault is eliminated.
After the circuit has poor contact (virtual connection), it is difficult to measure directly with the instrument, and the visual inspection method is the most effective in dealing with such difficult faults.