Glossary · Electrical engineering and control panels
Contactor
Also known as: Power contactor, Motor contactor
German: Schütz
In electrical engineering, a contactor is an electromagnetically operated switching device designed for frequent switching of load currents, such as motors, heaters or capacitors, under normal operating conditions, including specified overloads.
- Control panels
In one sentence
A contactor is an electromagnetically operated switch for frequent switching of loads such as motors under normal operating conditions.
Example
The PLC switches the pump motor through a contactor; an auxiliary contact reports the contactor state back to a digital input.
How it applies
- Engineering: Select contactors by utilization category (for example AC-3 for squirrel-cage motors), rated current and coil voltage. Auxiliary contacts provide feedback; mirror contacts are used when a contactor is monitored in a safety function.
- Safety: Contactors can be part of safety functions, for example two contactors in series with feedback monitoring for a Stop category 0 stop. Whether that is adequate depends on the required performance level or SIL, not on the contactor alone.
- Documentation: List utilization category and rating in the parts list. Maintenance manuals should note that contact wear depends on switching cycles and load, and describe replacement.
Contactor vs. relay
A contactor switches load currents, typically motors. A Control relay switches signals and small loads. Construction principles are similar, but ratings and standards differ. Note: the list's German term "Schütz" (contactor) must not be confused with "Schutz" (protection).