CMD Contactor Monitoring Relay

Redundant contactor design a thing of the past

Plant sections in virtually all applications are implemented nowadays with safety in mind.

Safety-oriented control sections are used for disconnection in the event of a hazard such as an open safety guard or when an Emergency-stop button is actuated. A redundant disconnection facility is often provided to prevent failure in these plant sections. In the event of a hazard, a contactor is typically used to provide the disconnection.

However, contactors tend to weld towards the end of their service life and so two contactors are often connected in series. This is a particularly expensive measure, especially with large contactors.

Moeller's CMD contactor monitoring device makes this redundant contactor design a thing of the past. It monitors the contactor for welding. The backup circuit-breaker is disconnected if the contacts are welded.

• The CMD can be used in Emergency-stop applications for safety category 3 in compliance with EN 945-1 and the performance level d in compliance with EN ISO 13849-1.


• Moeller contactors are used in combination with Moeller circuit-breakers.

Further information see Downloads – Product Information