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.
I don't understand. Your saying that you have a single 200 amp lighting contactor with multiple coils? The contactors I have used only have one coil. I would make sure that the coil is rated for the control voltage as that would surely smoke it. Improper voltage, incorrect wiring, or really cheap quality of coil is all I can come up with.
[This message has been edited by RobbieD (edited 10-02-2006).]
#70245 - 10/02/0609:13 PMRe: need lighting contactor help
I worked on an ASCO lighting contactor with the electricians a few years ago. I seem to remember a cam of sorts that would internally open up the closing coil path once closed, and opening coil path once open. This allowed using one photocell controlled relay with form "c" contacts to control intermittent duty contactor coils. The cam getting messed up could explain letting the smoke out but only with the control ckt connected.
Now I seem to remember ASCO sending us a bunch of 24 volt ATS coils that didn't much like the 120 volt control ckts. Dealing with them is like walking into a room of 400 people, all named Bob. You might recognize him if you see him again but the label on the shirt doesn't help that much. Joe
#70248 - 10/02/0609:59 PMRe: need lighting contactor help
RobbieD--1 coil to open, 1 coil to close. 120v coil and 120v control circuit.
Grover and Larry C--Internal jumper for grounded conductor only. Power from A-phase to photo-cell to reversing relay then to contactor. Contactor is a GE. They have been involved in this for the past 3 years and can't figure this one out.
What gets me is the coils smoking tonight after I took ALL control wiring out of the picture. No power to coil, photo-cell, relay at all, and it still showed voltage on the coil. Could the coils be acting like an isolation transformer somehow? Richard
#70249 - 10/02/0610:38 PMRe: need lighting contactor help
Lets assume contactor is OK. What changes from day (when you tested it) and night (when it lets out the magic smoke).
Is it possible that the neutral for the lighting circuits shifts under load? This might overvoltage the coil. Perhaps the neutral ground bond is missing? Are the lighting circuits fed from a dedicated transformer? Is there the possibility that one of the lighting circuits is accidentally tied into another power source?
I would suspect that if the factory has been involved and they are coming up blank, then perhaps it is a facility issue.
What is downstrean of this contactor?
#70250 - 10/03/0606:19 AMRe: need lighting contactor help
LarryC, Contactor feeds a 200 amp lighting panel that feeds all the parking lot lights, pole sign and building exterior neon. This is a car dealership, so quite a bit if lighting. In December of 05, I megged all branch circuits out of this panel and found nothing wrong. I replaced the feeders to this panel at that time also. The only transformers are the pole mounetd utilitys.
I also thought somthing had to be different at night that I wasn't seeing during the day. I have spent hours checking during the night and can find nothing different. I agree it is a facility rather than contactor problem. I will take pics today and post them after work. Maybe you guys will see somthing that I dont. Thanks, Richard
#70251 - 10/03/0607:14 AMRe: need lighting contactor help