CMO Series AC Over Current Monitoring Relay

The CMO Series AC Over Current Monitoring Relay from the ATC Diversified Electronics division of Marsh Bellofram is an AC over current monitoring relay with adjustable time delay, designed to prevent damage and premature equipment failure in pumps, motors and other critical machinery and equipment. The internal relay of the CMO series energizes (pick-up) when monitored AC current exceeds the preset trip point for longer than the preset adjustable time delay. The delay is incorporated to prevent nuisance tripping caused by motor inrush currents. In addition, the CMO series has an automatic reset feature. The internal relay de-energizes (drop-out) when the current drops 5% below the preset trip for longer than 0.2 seconds. An external CT may be used to extend the AC current range.



  • AC over current monitor
  • Models available from 0.05 to 10 amps
  • Plug-in or surface mount enclosure
  • Adjustments for:
    • Current trip point
    • Response time
  • Automatic reset feature


  • Current demand level monitoring
  • Conveyor or motor load jam detection
  • Dull bit or blade detection
  • Remote motor sensing
  • Broken fan belt or chains detection
  • Feed rate to keep two loads at their most efficient point