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CM-MSx Thermistor Motor Protection Relays

Protecting motors against overheating
The CM-MSx thermistor motor protection relays are used to monitor the temperature of motors equipped with PTC temperature sensors.

ABB’s CM-MSx range of thermistor motor protection relays monitor the winding temperature of motors. PTC sensors integrated in the motor windings directly measure the motor heat. This direct temperature measurement enables the thermistor motor protection relays to evaluate various motor conditions such as overheating, overload and insufficient cooling. ATEX approval is also available for products used in hazardous areas.


  • Reliable motor operation
  • Easy status indication and troubleshooting
  • Operation in hazardous areas possible


  • Dynamic interrupted wire detection
  • Wide control supply voltage range of 24-240 V AC/DC
  • Short circuit monitoring of the sensor circuit
  • Non-volatile fault storage
  • Remote reset
  • Screw connection or Easy Connect push-in technology available