In motor control circuits, which device acts as the main switch controlled by control signals to energize or de-energize the motor?

• A. Contactor
• B. Fuse
• C. Circuit breaker
• D. Transformer

Answer: (A)

The device used as the main switch in motor control circuits is the contactor. It’s a heavy-duty, electrically operated relay designed to handle the high current that a motor draws. When the control circuit sends a signal to energize the coil, the contactor closes its main contacts and connects the motor to the supply, starting it. When the coil is de-energized, the contacts open and the motor stops. This arrangement lets a low-current control circuit safely control a high-current motor circuit.

Fuses and circuit breakers act as protection devices. They interrupt current to protect wiring and equipment during faults, but they aren’t the primary switching element controlled by the control signals to run or stop the motor. A transformer simply changes voltage levels; it isn’t used to switch the motor on and off.