Utilize self-induced electromotive force to realize instantaneous protection circuit

The circuit is shown in Figure 3-73. This circuit uses the self-induced electromotive force generated by the motor to achieve instantaneous shutdown protection when the power supply fails instantaneously.     When the power supply fails instantaneously, the contactor KM loses power and is released, the motor rotates inertly, and the normally closed auxiliary contact of KM is closed. The self-induced electromotive force between the V and W phases of the motor supplies power to the DC relay KA through the diode VD . KA is powered on and its normally open contact is closed. If the power supply is restored at this time, contactor KM is powered on and locks itself, and the motor is reconnected to the power supply and runs.