Westinghouse Contactor Relay

[burntcoil]

We have westinghouse BF84F contactor relay in one of the cabinet of a very critical system. The contactor have dual 115Vac input, primary source is energizing the coil and NO contacts whereas secondary source is connected to NC contacts of the contactor. In case of primary power failure, the secondary power shall provide uninterrupted supply to the critical I/O cards since the contacts are overlapping. Over the past few days, the primary source has failed (coil de-energized) and returned back to normal within 22msec, 12msec, 28msec on three different occasions. These primary and secondary sources are from UPS panel. But similar contactors on the other circuits of the UPS panels are not impacted during such events. Can the coil de-energize on such short voltage dips and return to normal within milliseconds as mentioned above? I doubt these are voltage dips because at these instances other contactors fed from the same panel remain un imapacted.

 

[davidbeach]

Probably. Look for a loose connection somewhere along with a source of vibration that would cause the connection to move enough. Enough may be a very small amount. I've seen loose wires cause relay inputs to drop out and pick up again in well less than 16ms.