Press the start button SB2, contactor KM1 coil get electricity and self lock, KM3 coil power, which normally open the main contact closure, motor access power supply, and Y connection to start running. At the same time, the time relay KT coil power, after the delay, the normally closed contact is disconnected, cut off the power supply of the KM3 coil, making the KM3 power loss, normally open contact off, normally closed contact closure. KT of the normally open contact is closed and a contactor km2 coil power, km2 main contact closure makes motor by Y connection switching method for delta connection operation.
Relay control circuit
PLC control program design