The principle of overvoltage undervoltage protection of the inverter

- Jul 18, 2019-

The operation of the inverter has been caused by the undervoltage protection action, mostly caused by the fluctuation of the voltage of the power grid. In the drive supply circuit, if there is a direct start or stop of a heavy-duty motor, it will cause the power grid voltage to fluctuate widely in an instant, resulting in the drive overvoltage undervoltage protection action, but not normal operation. This usually does not last long and can operate normally after the voltage fluctuations of the grid.

This situation can only be avoided by increasing the capacity of the power supply transformer and improving the quality of the power grid.

In addition, the drive overvoltage fault may also be due to the drive of the inverter large inertial load, because in this case, the deceleration of the inverter is a regenerative brake, in the stop process, the output frequency of the inverter is linearly reduced, and the frequency of the load motor is higher than the output frequency of the inverter, the load motor is in the power generation state, mechanical energy converted into electrical energy , and absorbed by the flat wave capacitor on the DC side of the drive, when this energy is large enough, the voltage on the DC side of the drive will exceed the overvoltage protection adjustment value of the DC bus and trip. For this fault, the first is to set the deceleration time parameter shorter, or increase the brake resistance, or increase the brake unit, and the other is to set the drive to stop freely.

Another case is the inverter rectification part of the damage or detection of circuit damage caused by the fault alarm, voltage detection is generally through the DC bus voltage sampling, and then with the overvoltage protection rectification value comparison, and then the relatively poor value transmitted to the microcontroller. This alarm occurs if there is a problem with any device in the rectifier bridge, filter capacitor, sampling circuit, or comparison circuit.

G600-1