Industrial sewing machine no-load self-stop power-saving circuit

Working principle of the circuit : As shown in Figure 4-18, a set of three-phase AC
non-contact switch is installed on the sewing machine. When the springboard is stepped on, the travel switch SQ is turned on; when the car is stopped, SQ
is turned off and the relay is released. The thyristor loses the trigger signal and turns off, and the motor stops supplying
power, achieving no-load power consumption. According to actual measurement, the motor has more than 1 minute of inertial operation,
so the current will not be very large each time it is restarted, and it will not have a big impact on the motor .