AC contactor self-locking principle

- Jul 17, 2019-

AC contactor principle is to get electro-absorption, main contact closed on, motor operation, this article introduces the AC contactor self-locking circuit, what is contactor self-locking? First let's look at the picture.

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Principle introduction: The figure we can see the circuit breaker, contactor, two buttons, a stop button, a start button, since it is the contactor self-locking circuit, we use the start button, since can start certainly to stop, so we use the stop button often closed.

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Wiring steps: circuit breaker 2p, blue zero line into contact coil A1, fire line into the red button , stop button normally closed, act stop circuit, after the stop button is often closed out two lines, one into the contactor's auxiliary contacts often open NO (here is the contactor L1-L2---L3 contactor main contact). The other intake button is normally open and the action starts. The start button often opens the coil A2 of the wire-in contactor.

Run the demo: Press the start button SB2, the contactor coil is powered, while the contactor main contact is closed and the auxiliary contact is closed. The mainline power supply passes through the fuse to the contactor contact, to the thermal relay, to the circuit, and the contactor auxiliary contact is closed, when the contactor is powered by the auxiliary contact closed control circuit.

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Wiring steps: circuit breaker 2p, blue zero line into contact coil A1, fire line into the red button , stop button normally closed, act stop circuit, after the stop button is often closed out two lines, one into the contactor's auxiliary contacts often open NO (here is the contactor L1-L2---L3 contactor main contact). The other intake button is normally open and the action starts. The start button often opens the coil A2 of the wire-in contactor.

Run the demo: Press the start button SB2, the contactor coil is powered, while the contactor main contact is closed and the auxiliary contact is closed. The mainline power supply passes through the fuse to the contactor contact, to the thermal relay, to the circuit, and the contactor auxiliary contact is closed, when the contactor is powered by the auxiliary contact closed control circuit.

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Principle analysis: control circuit, because the control circuit string thermal relay often closed contacts, so the power supply through the hot relay normally closed contactcontact KM auxiliary contact, when we press the start button, contactor auxiliary contact closed power supply through the contactor auxiliary contact to the contactor coil. So the contactor sits on and the motor stays in operation.

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Stop pressing stop button SB1, the control circuit because the stop button is often closed and open, so the entire control circuit is out of power, contactor coil is out of power, the main contact back to the initial state, the auxiliary contact back to the initial state, this is the contactor self-locking circuit. If you need to start again, press the start button and the workflow is the same as above.