Three-phase motor single-wire remote commutation circuit

In some occasions, it is necessary to control the starting, stopping and reversing operation of the motor at a place far away from the motor. The circuit shown in the figure is designed to adapt to this requirement. Set up a wire (single line) as shown in the figure and control the selector switch SA "offsite". When SA is set to position "1", the local motor stops; when set to "2", the local relay K1 forms a loop through VD3, ground wire, VD1, SA, transformer T, and single line. K1 acts, and its contact K1 Turn on the coil circuit of AC contactor KM1, and the motor will rotate forward; when SA is set to "3", relay K2 will act, AC contactor KM2 will act (KM1 loses power), and the motor will rotate reversely. The relay can be JRX-13F24V, and the transformer can be a 36V power transformer. Considering the long line and large voltage drop, the low-voltage output voltage of the transformer should be higher.