How to repair the inverter DC bus fault

Appearance inspection

· Check whether the DC bus capacitor has bulging or leakage. If so, replace the capacitor in time.

· Check whether the bus connection bar is loose or has signs of ablation. If so, tighten the connection bolts and clean the ablated parts or replace the connection bar.

Voltage detection

· Use the DC voltage range of the multimeter to measure the voltage across the DC bus. Under normal circumstances, the DC bus voltage should be within a certain range of the rated DC voltage of the inverter (usually ±10%).

· If the voltage is too high, it may be due to an abnormal increase in the input power supply voltage or a failure in the brake unit, causing the brake resistor to be unable to consume energy normally. The input power supply and brake unit need to be checked.

· If the voltage is too low, it may be caused by a rectifier bridge failure, capacitor damage or excessive load. The output voltage of the rectifier bridge can be further checked. If the output of the rectifier bridge is normal and the DC bus voltage is low, focus on checking the capacitor.

Resistance detection

· Disconnect the inverter from the load and use the resistance range of the multimeter to measure the DC bus resistance to ground. Under normal circumstances, the resistance value should be within a certain range (different for different inverter models). If the resistance value is significantly smaller, it means that there is a grounding fault, and the grounding location needs to be found and eliminated.

·Measure the resistance value of the brake resistor to see if it matches the nominal value. If the resistance value deviation is too large, it means that the brake resistor is damaged and needs to be replaced.

Component detection

·Check whether the diodes of the rectifier bridge are normal. Use the diode range of the multimeter to measure the forward and reverse conduction of each diode of the rectifier bridge.

·Check whether the IGBT module is normal. You can use a multimeter to measure the resistance value between the gate, collector and emitter of the IGBT module to determine whether it is damaged.

Control board detection

·Check whether the relevant circuits on the control board have component damage, short circuit or open circuit. Focus on checking the circuit components related to the DC bus voltage detection and control, such as resistors, capacitors, chips, etc.

·Check whether the software parameter settings on the control board are correct. Incorrect parameter settings may cause the inverter to have incorrect control strategy for the DC bus and cause failures.