A heavy-duty relay designed to repeatedly open and close high-current power circuits. Unlike a standard control relay, a contactor is built with arc suppression mechanisms and robust contacts to handle the heavy inrush currents of electric motors, lighting banks, or heating loads. It is typically controlled by a lower voltage circuit, allowing a small switch or PLC to safely command a massive load.
The main pump won't start because the coil on the motor contactor has burned out.
Do not mix it up with
- Circuit breaker: A contactor is designed for millions of normal operational switching cycles but cannot interrupt a short circuit; a circuit breaker is designed to interrupt fault currents but is not meant for frequent switching.
Related terms
Circuit breaker
A mechanical switching device capable of making, carrying and breaking currents under normal and fault conditions.
Switchgear
Assemblies of breakers, switches, fuses, busbars and enclosures that control and protect power circuits.
86 relay
Lockout relay that latches after a serious trip and holds breakers open until someone resets it by hand.
Squirrel-cage motor
An AC induction motor featuring a rotor made of parallel conductive bars shorted by end rings.