In motor control, what is the role of a contactor?

• A. To monitor motor temperature.
• B. To remotely switch a motor circuit on and off.
• C. To provide overload protection.
• D. To limit starting current via soft-start.

Answer: (B)

A contactor’s job in motor control is to act as an electrically controlled switch that remotely turns a motor circuit on and off. When the control circuit energizes the contactor coil, its power contacts close and supply line voltage to the motor. This arrangement lets you start and stop a motor from a distant switch, PLC, or control panel while keeping the high-current motor path separate from the control circuitry. In practical setups, a contactor is often used together with an overload relay in a motor starter—the overload protects the motor, while the contactor handles the switching.

Temperature monitoring isn’t the role of a contactor; that’s handled by sensors or thermal overload devices. Overload protection is provided by an overload relay (or similar device) that trips if current or temperature gets too high, not by the contactor itself. Limiting starting current via soft-start is achieved with a soft starter or VFD, not just a contactor, which by itself only opens or closes the circuit.