Maintenance of MITSUBISHI A800, F740 and E540 inverter

Failure phenomenon: the starting operation shows OC alarm
Fault analysis: MITSUBISHI inverter failure phenomenon OC causes are mainly the following:
(1) the aging of the components will inevitably lead to the aging of the components due to the use of a long period of life, thus causing the distortion of the driving wave and the instability of the output voltage, so the OC alarm is often appeared at the same time.
(2) the damage of the IPM module will also cause the OC alarm D700 series of MITSUBISHI inverter power module not only contain over current, undervoltage and other detection circuits, but also contain amplifier drive circuit, so whether the damage of the detection circuit, the damage of the driving circuit, and the damage of the large power transistor can cause the OC. Call the police.
(3) most of the reasons for failure to display faults are due to the damage of thick film of switching power supply.
(4) the ERR fault is an undervoltage fault, which is usually caused by the problems of the resistance or connection of the voltage detection circuit, but not the actual input voltage. The OC failure of the F700 series is mostly caused by the damage of the driving circuit. Its driving circuit uses a thick film circuit of ceramic package, which brings some difficulties to maintenance, and its thick film circuit is based on a circuit designed by a drive optocoupler.
(5) in addition, we will also encounter some LV failures, and the failure of the undervoltage is mostly due to the failure of the bus detection circuit, and the MITSUBISHI inverter also designed a thick film circuit for detecting voltage and current. The damage of the switching power supply pulse transformer is also a common fault of the F700 series inverter. Due to the short circuit of the output load of the switching power supply, or the mutation of the bus voltage, the primary and secondary windings of the pulse transformer are damaged.
Fault repair: after disassembling the machine, it was found that the voltage of the power supply substrate was normal. After inspection, it was found that the drive circuit had a normal output. After dismantling the optocoupler, the inspection found that the circuit was broken. The IGBT module was normal, and the failure was eliminated after the replacement of the above parts.