big john
Senior Member
- Location
- Portland, ME
Had an interesting problem involving an Over/Undervoltage protective relay that was preventing an ATS system from working.
Everything pointed back to the relay not actuating, went and bench-tested it and the relay would pick up at 102VAC when slowly ramped.
In service it was getting instantaneous 114VAC applied, but the contacts would not pull in reliably. It's obviously a weak coil because if I give the relay the slightest tap, it will close and maintain.
I've read foot-notes for voltage relays that warn when the "actuating quantity" is too close to the pickup voltage, this may happen, but I was hard pressed to explain why it worked on the bench and not in service, and I don't think it impressed the customer much.
Any ideas?
Everything pointed back to the relay not actuating, went and bench-tested it and the relay would pick up at 102VAC when slowly ramped.
In service it was getting instantaneous 114VAC applied, but the contacts would not pull in reliably. It's obviously a weak coil because if I give the relay the slightest tap, it will close and maintain.
I've read foot-notes for voltage relays that warn when the "actuating quantity" is too close to the pickup voltage, this may happen, but I was hard pressed to explain why it worked on the bench and not in service, and I don't think it impressed the customer much.
Any ideas?