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Bulletin 440R CU3 Back EMF Monitors

CU3 Back EMF Monitors

The Guardmaster® CU3 control unit detects stopped motion and is ideal for use with guard-locking interlock switches. It interfaces with single- or three-phase induction motors by measuring the drive voltage and the back electro-magnetic field (EMF) of the motor. Note that Guardmaster Safety Relays have been marketed by Rockwell Automation under the trade name "Minotaur" in the past.

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  • Category 1 per EN 954-1
  • Stop category 1
  • Two N.O. safety outputs
  • One N.C. auxiliary output
  • Supports automatic/manual and monitored reset
  • Motor voltage up to 500V max.


  • CU3 Back EMF Monitors


  • CE marked for all applicable directives, cULus, c-Tick, and TÜV

Certifications apply when product is marked. See our Product Certification site for Declarations of Conformity, certificates and other certification details.

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CU3 Motor Stopped Motion/Slow Speed Detector Installation InstructionsCU3-IN001
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