Phase-monitoring relay avoids motor burnout
01 August 2006
New from Finder is the 72.31 three-phase monitoring relay, which detects loss of phase or incorrect phase rotation. The unit ensures that motors do not become permanently damaged due to phase loss, as well as avoiding potential hazards or damage due to incorrect motor rotation. The relay features positive safety logic, which triggers the contact to open if an error is detected, allowing the system to fail to a safe condition. The relay provides reliable monitoring of phase loss, even under conditions where the lost phase may be 'regenerated' by the action of the rotating motor. This phenomenon is not uncommon, and many monitoring relay units falsely detect this phase regeneration and thus fail to disconnect the supply. The 72.31 can discriminate phase regeneration up to 80% of the line voltage.
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