The CMD Contactor Monitoring Device - A World Innovation: Moeller Contactor Monitoring Device Makes Redundant Contactor Designs 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 failure of these plant sections is mostly unacceptable even in the event of an error. Special precautionary measures therefore have to be taken, such as the implementation of redundant disconnection. A contactor functions as a typical disconnection device in the event of a hazard. However, contactors tend to weld towards the end of their service life at the latest and so two contactors are often connected in series. This is a particularly expensive measure, especially with large contactors. The CMD contactor monitoring device makes this redundant contactor design a thing of the past.

The CMD monitors the main contacts of a contactor for welding. It compares the contactor control voltage with the state of the main contactors and indicates this reliably with a mirror contact (IEC EN 60947-4-1 Ann. F). If the contactor coil is de-energized and the contactor does not drop out, the CMD trips the backup circuit-breaker, motor-protective circuit-breaker or switch-disconnector via an undervoltage release.

The CMD also monitors the functioning of the internal relay using an additional auxiliary make contact of the monitored contactor. For this the auxiliary make and break contact is positively driven. The break contact is designed as a mirror contact.

To ensure the functional reliability of the entire unit, consisting of contactor, circuit-breaker and CMD, the CMD is only approved for use with specific Moeller contactors as well as motor-protective circuit-breakers/circuit-breakers/or switch-disconnectors. CMD can be used for monitoring the welding of all contactors DILM7 to DILH2000 of the Moeller contactor range. All auxiliary break contacts of these contactors are designed as mirror contacts and can be used for monitoring tasks. The PKZ2 motor-protective circuit-breakers can be used as backup motor-protective circuit-breakers / circuit-breakers or switch-disconnectors when fitted with a U-PKZ2 (18VDC) undervoltage release. This also applies to NZM1 to NZM4 circuit-breakers or N1 to N4 switch-disconnectors with an NZM..-XUV undervoltage release.

These kinds of combinations are used in Germany and Europe for safety-oriented applications. Previously the series connection of two contactors was recommended for circuits of safety category 3 and 4. Now one contactor and Moeller's CMD is enough. The CMD contactor monitoring relay is used for Emergency-stop applications in compliance with EN 60204-1. It can also be used in the US automotive industry where solutions are required that can reliably detect the welding of the motor starters and safely disconnect the motor feeder. Further applications are possible with crane applications that still prefer bar-mounted contactors: In these applications EN 60204-32 requires type 2 coordination for contactors. Moeller's vacuum contactors can also be used with the CMD.

In addition to the CE mark, the CMD is approved by the German trade association for use as a safety module. As a world market device, it also has UL and CSA approval for the North American market.

Moeller GmbH, 53105 Bonn
Tel.: +49 (0)228 602-0
Fax: +49 (0)228 602-2275
E-Mail: presse@moeller.net
Internet: www.moeller.net
Please direct your enquiries to:
Corporate Communications, Tel.: +49 (0)228 602-2915

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