Lighting Contactor Stuck

[edt]

I have a problem with one particular pole light failing to go off when its switched "off". Its operated by a Cutler-Hammer 5-pole,100 amp magnetic latched-type lighting contactor (A202K3EAM (?), 5277C15G26 Model M, C030911 as it's labeled).
In the "on" position, contactor pulls in and stays in okay. When its turned off the contactor fails to release.
The switch, coil, contacts,all appear in good shape. No obstructions. When I opened it up though, i did find some fine bits and pieces of metalic chips and plastic below the coil. Otherwise quite clean. I noticed some small indentions on the core and similar markings on contact block - what appears to might have been a small screw was bouncing around in there, hence the metal pieces.
If this were the case, I could see it not pulling in deep enough to make contact closure. But releasing is the problem. Switched to off, energized coil, should throw out the contact block, but its not. I suppose this "unintended gap"(created by a possible screw)could ruin the module or coil? Any suggestions?

 

[charlie tuna]

Re: Lighting Contactor Stuck

edt,
you said it was a "latching" contactor. that means it needs a powered signal to the trip coil to unlatch the contacts. have you checked the trip coil contacts to insure it is getting an "off" command?

 

[thinfool]

Re: Lighting Contactor Stuck

Is the 'little screw' a part of the operating mechanism? IOW, where did it come from.
In my experience, little screws are not the product of spontaneous generation.
The previous post about the clearing contact/coil is also right on.

 

[edt]

Re: Lighting Contactor Stuck

Thanks for your replies!
Yes Charlie, its magnetic latched. The voltage applied from the switch to the coil is present (120v). I took it off and applied it to another - it worked fine. I thought perhaps "mechanically" something in there was holding it back, but didn't know what. Should I fine somekind of dielectric lube or what?
Thinfool, Scews? what have you? All terminal screws, mounting hardware, etc. are accounted for(doesn't mean it wasn't before, does it?).
I'm wondering if the module could've been damaged internally, mechanically "binding". A replacement would be kinda pricy.

 

[flick]

Re: Lighting Contactor Stuck

I don't have a C-H catalog, but I can say that there is a good possibility that there is a mechanical problem with the contactor. It's not uncommon at all for contactors to stick or bind in the closed position, especially the older they get. I recommend disassembly of the contactor and examination of all sliding surfaces. They will get worn, sometimes with a pronounced step or bump, that can cause the armature to cock to one side, or front to back. The best thing to do to verify this is simply power the unlatch coil of the contactor, then gently tap the coil area with a screwdriver handle and see if it falls/drops down on it's own. If it does, that indicates a mechanical binding problem somewhere in the contactor. Sometimes parts can be replaced in different positions that basically presents a new unworn surface that will let an old contactor work like new again. It all depends on the internal construction of the contactor.

Make sure that the unlatch coil isn't open. You can check this with a ohmeter and compare readings with a known good coil. And make sure you're getting the correct voltage to the unlatch coil too.

John

[ December 03, 2005, 09:59 PM: Message edited by: flick ]

 

[charlie tuna]

Re: Lighting Contactor Stuck

if you are an electrician --- ? --- you should be able to troubleshoot the problem. you originally said it was a mechanically latched contactor! and that it didn't shut off. the control circuit will have auxillary contacts to allow the contactor to close and de-energize the closing coil -- and at the same time set up to recieve an "open command" ---it's an electrical interlock. trace the "open" control power signal until it disappears and thats where the problem is. if it goes all the way to the coil --the coil is bad. probibly in the auxillary contacts! and yes they are expensive! about $500.00...............