Here's the deal. I have a customer with a 200 amp lighting contactor. 208v 3ph. All 3 phases draw less than 140 amps. First contactor lasted 15 years with no problems. In the last 4 years the coils have burned up 9 times. Twice in the past 7 days.
It has a photo cell controlling a small control relay that powers the coils on the contactor. I have replace all controll wireing, photo cell and relay. I installed new coils this afternoon, tested and watched for about an hour. Everything was OK. Tonight the lights did not come on. Had power to the close coil, but it would not close. I removed all control wires, and manually turned on the contactor. Coils started smoking with no electrical connection to them. Also showed 120 volts to ground on both open and close coil terminals. This was checked with a DMM and A Wiggy.
Any ideas what could cause this?
