Which device is a heavy-duty electrical switch used to control large motor loads?

• A. Bearing
• B. VFD
• C. Overload
• D. Contactor

Answer: (D)

Identifying the device used to switch large motor loads in industrial power circuits. A contactor is built as a heavy‑duty electrical switch that can carry the high current drawn by motors, including the surge when starting. It’s actuated by a control coil—typically powered by a low-voltage control circuit—which pulls in the main contacts to connect power to the motor. This arrangement is the standard way to turn large motors on and off remotely and safely, and it’s often paired with overload protection to form a complete motor starter.

The other options don’t fit this role. Bearings are mechanical components that support and guide rotating parts, not switches. A variable frequency drive changes motor speed by controlling voltage and frequency, so it’s more than a simple switch. An overload device protects the motor by interrupting current when overheating or overcurrent occurs, but it does not serve as the device that switches the motor on or off.