Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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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).

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: IEC 60947-4-1, Low-voltage switchgear and controlgear — Part 4-1: Contactors and motor-starters — Electromechanical contactors and motor-starters

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Knowledge and are not part of any standard.

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