Moeller Electric Ends Contactor Redundancy!

The innovative CMD modules operate by monitoring the state of the contactor’s main contacts, and comparing 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 starter’s motor protection circuit breaker via an undervoltage release.

This mode of operation ensures that, even if the main contacts of the contactor weld, the motor it is controlling is safely brought to a stop.

Moeller Electric’s CMD monitoring relay can be used to implement Category 3 and Category 4 safety circuits in line with EN 954-1, as well as safety circuits with Performance Level d, as prescribed by the more recent EN ISO 13849 standard.

To ensure functional reliability of the starter – comprising contactor, circuit breaker and CMD unit – under all operating conditions, the CMD monitoring relay is approved only for use with specified Moeller Electric contactors, circuit breakers and switch disconnectors. The contactors that can be used with the CMD range from the DILM7, which has an AC3 rating of 7A, to the DILM1600 with an AC3 rating of 1,600A.

These contactors, all of which are equipped with mirror auxiliary contacts that can be used for monitoring purposes, are complemented by PKZ2 motor protection circuit breakers, NZM1 to NZM4 circuit breakers and N1 to N4 switch disconnectors. When used with the CMD, all of these devices must be fitted with an undervoltage release.

The CMD module carries the CE marking, and is also approved by the German trade association for use as a safety module. In addition, it also has UL and CSA approvals, allowing it to be used in the North American markets.