Y/△ started three-phase motor stall protection circuit

The circuit as shown in the figure can prevent the starting three-phase motor from stalling due to mechanical failure. R1 is the sampling resistor. When the motor is blocked, the signal generated by the strong current passing through TA is rectified by VC2, filtered by C1, RP, and R2 divide the sampling signal, and extract part of the signal for the actuator to amplify and shape, thereby triggering the thyristor VS to conduct, causing the relay to K pulls in, its normally closed contact is disconnected, and the motor stops when it loses power to prevent the stator winding from being burned.