# How does an Interlocking Control Circuit for Two Motor Contactors work?

**URL:** <https://forumautomation.com/t/how-does-an-interlocking-control-circuit-for-two-motor-contactors-work/14438>\
**Category:** Electrical\
**Tags:** electrical\
**Created:** [September 23, 2026, 6:28am UTC](https://forumautomation.com/t/how-does-an-interlocking-control-circuit-for-two-motor-contactors-work/14438 "2026-09-23T06:28:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [September 23, 2026, 6:28am UTC](https://forumautomation.com/t/how-does-an-interlocking-control-circuit-for-two-motor-contactors-work/14438/1 "2026-09-23T06:28:14Z")

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## How does an Interlocking Control Circuit for Two Motor Contactors work?

An **[interlocking](https://forumelectrical.com/what-is-electrical-interlocking/)** control circuit prevents two motor contactors from energizing at the same time, protecting motors and equipment from short circuits or reverse operation.

It combines electrical interlocking using normally closed (NC) auxiliary contacts with mechanical interlocking between the contactors for added safety.

## Main Components

**K1 & K2:** Motor contactors

**START 1 / START 2:** Push buttons for each motor

**STOP:** Common stop push button

**NC Auxiliary Contacts:** Electrical interlocking

**Thermal Overload Relay:** Motor protection

**Mechanical Interlock:** Prevents both contactors from closing together

## Working Principle

1. Press START 1 to energize K1 and run Motor 1.

2. K1’s NC auxiliary contact opens the K2 control circuit, preventing Motor 2 from starting.

3. Press START 2 only after K1 is de-energized; K2 then runs Motor 2.

4. The STOP button or overload relay de-energizes the active contactor, allowing the other motor to be started.

 ![1](https://cdn.forumautomation.com/original/2X/e/eb0c065ac86b123aeee33b52e36fd961cedc7e37.jpeg)

## Applications

1. Forward/Reverse motor control,

2. Two-pump duty/standby systems,

3. Conveyor interlocking and

4. Industrial motor control panels.