Inverter overvoltage and undervoltage fault causes and treatment - Database & Sql Blog Articles

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Fault phenomenon 1: Overvoltage (OU): Overvoltage alarm is generally present at the time of shutdown.

1. The main cause of the failure is that the deceleration time is too short or the braking resistor is damaged.

2. Example: A Taian N2 series 3.7kW inverter jumps “OU” when it stops. Analysis and maintenance: Before repairing this machine, we must first understand the reason of the "OU" alarm. This is because when the inverter is decelerating, the speed of the rotor winding of the motor is faster, and the electromotive force and current of the rotor increase. The motor is in a power generation state, and the energy of the feedback flows to the DC link through the diode connected in parallel with the high-power switch tube in the inverter link, so that the DC bus voltage is increased.

3, fault handling: so we should focus on checking the brake circuit, measuring the discharge resistance is no problem, when the brake tube (ET191) is measured, it has been broken down, after the replacement, the power is running, and there is no problem with fast parking. Valve imported pump industrial washing machine

Fault phenomenon 2: Undervoltage (Uu): It is also a problem that we often encounter in use.

1. The main reason for the failure: Because the main circuit voltage is too low (220V series is lower than 200V, 380V series is lower than 400V), one of the rectifier bridges is damaged or the thyristor three channels are not working properly, which may cause undervoltage The fault occurs, and the main circuit contactor is damaged. The DC bus voltage loss may cause undervoltage on the charging resistor. There is also a problem that the voltage detection circuit is faulty and undervoltage occurs.

2. Example: A DANFOSS VLT5004 inverter, the power-on display is normal, but after adding the load, jump “DC LINK UNDERVOLT” (the DC link voltage is low). Analysis and maintenance: This inverter is quite special in terms of phenomena, but if you analyze the problem carefully, it is not so complicated. The inverter also completes the charging process through the charging circuit and the contactor. It is not found when the power is turned on. Any abnormal phenomenon is estimated to be caused by the voltage drop of the DC link when the load is applied, and the voltage of the DC link is rectified by the full-wave rectification of the rectifier bridge, and then provided by the capacitor after the wave is applied.

3, fault handling: so should focus on the inspection of the rectifier bridge, after the measurement found that the rectifier bridge has a bridge arm open circuit, the problem is solved after replacing the new product.