Dual-Processor Motor Safety Relay Is Self-Monitoring
01 March 2003
Dual-processor motor safety relay is self-monitoring
Castell's CMM200 motor safety relay monitors the back EMF generated by a
motor to detect whether it is safely at rest or in motion, and is claimed
to be the only back EMF device to include dual processors for monitoring
the state of the motor and the condition of the relay itself. The two
independent channels are connected to separate motor windings, the relay
contacts closing only when both sense a zero speed condition.
The processors communicate with one another via an optically isolated
link. If a fault is detected in either one, the unit reverts to a
fail-safe condition. They also monitor the condition of the sensing
cables connected to the motor. If one becomes disconnected, the relay
again reverts to a fail-safe condition and provides a local indication of
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