A: The motor is mainly caused by the formation of over-voltage as long as the speed of the motor is bigger than the inverter's output speed, the motor will produce a power generation effect, charging the inverter. In engineering, the inverter over-voltage phenomenon is complicated, but we follow the motor as long as there will be a power generation effect, external energy interference, as long as to find out the interference to the motor, the problem is solved. Negative pressure, the formation of cavitation phenomenon, the negative pressure of the water from the frequency conversion pump inhalation, driving the impeller rotation, so that the motor speed is higher than the inverter output speed, motor power generation.

Solution: add braking units and resistors on the inverter.