Contactor holding circuit with Push Button Switch

Hey, in this article we are going to see the contactor holding circuit with NO and NC push button switches. This contactor holding circuit is mostly used in the motor controller or motor starter circuit such as DOL Starter, Star Delta Starter, etc. The main objective of this holding circuit is to keep the contactor On condition even if we release the pressure from the NO push button switch. Basically, when we push the start button(NO) the contactor will close its contacts and it keep closed until we press Stop(NC) push button.

Why holding circuit required with the Contactor?

We know that the push-button switch used for the motor starter has a construction as that, it only makes or breaks contact when we press the switch, once we release the pressure from the switch, its contact will come to its old position.

So when we use a NO pushbutton with a contactor, the contactor will be turned on only when we press the switch. So we need to make an external connection that will keep on the contactor until we press the NC pushbutton switch.

Contactor Holding Circuit and Wiring Connection

Equipment used for this Circuit:

• Three Pole, 440V Contactor(having four auxiliary contacts) - 1 no
• NC Push Button Switch - 1 no
• NO Push Button Switch - 1 no

Step 1

Make the three-phase power connection as shown in the below figure. Then connect the neutral wire with the Contactor Coil A2 terminal as shown below.

Step 2

Take a connection from the 'R' phase and connect the NO and NC Push button switches in series as shown in the below figure. Then connect another terminal of the NO push button switch with the contactor coil A1 terminal.

Step 3

Connect the NO auxiliary contact terminal with the coil A1 terminal as shown in the below figure.

Step 4

Connect another terminal of the NO auxiliary contact with the incoming terminal of the NO push button switch. See the diagram below to better understand.

Step 5

Now your connection is ready. Check your connection again with the below figure.

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