2.The principle of analysis
Positive rotation control: press the positive rotation button SB1→ charging of contactor KM1 coil → main contact closure of KM1 → positive rotation of the motor; at the same time, the self-locking contact closure of KM1 and the interlock contact disconnect of KM1.
Reverse control: first press the stop button SB3→ the contact KM1 coil loses power → the interlock contact of KM1 closes.Then press the reverse button SB2→ generate power in the contactor KM2 coil → then the main contact of KM2 closes, and the motor starts to reverse. At the same time, the self-locking contact of KM2 closes and the interlock contact of KM2 disconnects.
For this line, to change the motor's direction, must first press the stop button, then press the reverse button, to make the motor reverse.