What is a contactor and how is it used in LV control circuits?

• A. A relay designed to switch high-current loads under control of a low-current circuit.
• B. A device that reduces voltage to control circuits.
• C. A device that stores energy for backup.
• D. A ground fault detector.

Answer: (A)

A contactor is a heavy-duty relay used to switch high-current loads using a low-current control signal. In low-voltage control circuits, the coil of the contactor is energized by a small voltage from the control side (like a PLC output or push button), and this energizes the coil to close the main contacts that carry the large current to motors, heaters, or other power devices. This separation lets you control powerful equipment without running high-current wiring through the control devices, improving safety and reliability. Contactor designs often include multiple poles and both normally open and normally closed contacts, and they’re built to handle the load currents and voltages typical in LV control circuits. They aren’t for reducing voltage, storing energy, or detecting faults, which is why the described heavy-duty switching function is the best fit.