Three-phase motor contactor auxiliary contact interlock commutation circuit

As shown in the figure, two AC contactors KMF and KMR are used. KMF is used for forward rotation and KMR is used for reverse rotation. Since the main contact wiring phase sequence of the AC contactor is different, when the two contactors work separately, the direction of the motor is exactly opposite. Because of this, selenium is not allowed to attract KMF and KMR at the same time during operation. For this reason, in the forward and reverse control circuits, a normally closed contact of the other party is connected in series. The circuit adds contactor self-protection auxiliary contacts KMF and KMR. When the button STF or STR is released, the contact The device can still keep itself closed.