What is a contactor and how is it used in aircraft electrical systems?

What is a contactor and how is it used in aircraft electrical systems?

• A. A high-current switching device used to control large loads like pumps or motors.
• B. A low-power speaker in the cabin.
• C. A device used to regulate voltage.
• D. A fuse.

Answer: (A)

A contactor is a high-current switching device that is operated by an electrical coil, built to turn large loads such as pumps or motors on and off. In aircraft electrical systems, the coil is energized by a low-power control circuit (often from the cockpit or an automated control system), which closes normally open contacts to connect the power from the aircraft’s electrical bus to the load. This setup lets the crew or the system control powerful equipment without routing high current through control switches, improving safety and reliability. Contactor contacts can be arranged in multiple poles to feed several circuits at once, and they’re commonly used with protective or interlock features to coordinate starting and operation of pumps, motors, or other high-current devices such as engine or APU start circuits, hydraulic pumps, or environmental control system pumps. They are not fuses, which only protect by opening the circuit during faults; nor are they voltage regulators, which maintain voltage levels, or speakers, which serve an unrelated function.

A contactor is a high-current switching device that is operated by an electrical coil, built to turn large loads such as pumps or motors on and off. In aircraft electrical systems, the coil is energized by a low-power control circuit (often from the cockpit or an automated control system), which closes normally open contacts to connect the power from the aircraft’s electrical bus to the load. This setup lets the crew or the system control powerful equipment without routing high current through control switches, improving safety and reliability. Contactor contacts can be arranged in multiple poles to feed several circuits at once, and they’re commonly used with protective or interlock features to coordinate starting and operation of pumps, motors, or other high-current devices such as engine or APU start circuits, hydraulic pumps, or environmental control system pumps. They are not fuses, which only protect by opening the circuit during faults; nor are they voltage regulators, which maintain voltage levels, or speakers, which serve an unrelated function.