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25 February, 2021

Starter monitor eliminates redundant contactors

05 August, 2008

A contactor monitoring device first shown by Moeller Electric at the 2007 Hannover Fair, is now available in the UK. The CMD module is designed to eliminate the cost of using duplicate redundant contactors in motor starters with safety functions. Instead, the same levels of safety can be achieved by using the compact, low-cost modules with each contactor, thus cutting costs and saving panel space.

Moeller CMD

The module (above) monitors the state of the contactorís main contacts, and compares this with the voltage applied to the coil. If the coil is de-energised but the main contacts are not open, the CMD opens a normally-closed output contact that can, for example, be used to trip the starterís motor-protection circuit-breaker via an under-voltage release. This ensures that, even if the main contacts of the contactor weld, the motor being controlled is brought safely to a stop.

The CMD rmonitoring elay can be used to implement Cat 3 and 4 safety circuits, as well as safety circuits with Performance Level d (EN ISO 13849). The CMD relay is approved for use only with specific Moeller contactors, circuit breakers and switch disconnectors.

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