Coupling failure with no motor trip 6

[EEENGRX]

A 75 Hp centrifugal pump in operation suddenly lost its coupling plus the coupling guard. The bolts were dislodged and the motor kept spinning but did not trip. All motor control set points appeared normal. Can anyone explain why there was no trip when this occurred as the motor had to be turned off via a local STOP button. Thanks

 

[EEENGRX]

Thanks guys.. well notes

 

[jraef]

We used to monitor actual power used by our pumps, and we set high and low trip points based on power (as well as current).

Yes, power (kW) monitoring is much better than current alone, because current can be affected by line voltage fluctuations whereas kW is always shaft load. It's just that a solid state OL relay that ALSO monitors the phase angle to determine power factor is more complex and expensive than people are sometimes willing to pay for.


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