It is suggested that the inertia effect of the load torque on the motor and the impact of the motor on the load after the voltage recovery are considered.

When the voltage is recessed, the motor will feed back the voltage to the busbar system, so the busbar of the system will be impacted.

If the recess time is long and the voltage value is low, the bus voltage and frequency may change due to motor feedback.

When the voltage is restored, the motor's speed has decreased, so the motor will have a torque shock to the load.

Therefore, it has been conventionally stipulated that a voltage depression of 200 milliseconds is a gateway. The motor is previously energized and then stopped.