OT contactor

faehigkeit1 · Jul 23, 2009

Hi All, I have a cutler hammer contactor that is suppling power to a 75hp motor. The motor runs fine and is not hot.
The problem is that the coil that pulls in the contactor is over heating. It's a 110volt ac coil. I checked the voltage to the coil and its good. Also there is no chattering going on but it does have a vibration, kinda feels like an electric razor type of vibration. Not sure what else to check.
Thanks for any suggestions.
Dean

OkiePC · Jul 23, 2009

Most likely, the shading coil in the contactor is failing, allowing it to bounce slightly, but enough to overheat due to excess current or from the vibration itself. I'd suggest that you replace the coil.

Paul

faehigkeit1 · Jul 23, 2009

Thanks Paul, the two shading coils seem to be in tact but there are some signs of wear.
Dean

milldrone · Jul 23, 2009

faehigkeit1 said:
Thanks Paul, the two shading coils seem to be in tact but there are some signs of wear.
Dean

Presuming the wear is on the magnet laminations. If this is true, the armature and the stationary part of the electromagnet can no longer seal (magnetically). The vibrations will get louder and louder and the coil will get hotter and hotter.

Does this contactor have a high number of cycles?

faehigkeit1 · Jul 23, 2009

Hi Vaughn,
This contactor stays on all the time.

Roy Matson · Jul 23, 2009

It sounds as though you should think about replacing the contactor, changing the coil may not help. Are you sure the shading coil doesn't have a tiny crack?
Roy

faehigkeit1 · Jul 23, 2009

If the shade coil is damaged can you replace them?
If so, what holds them in place?

milldrone · Jul 23, 2009

faehigkeit1 said:
If so, what holds them in place?

All of the ones I have seen are welded while they are in placed in the lamination slot.

leitmotif · Jul 24, 2009

If the relay is maybe 50 amp or less and is over 10 years old then it may be least expensive to replace the whole thing.

On other hand if over say 100 amp and over 10 years old maybe it is rebuild time.

Dan Bentler

Stationmaster · Jul 24, 2009

As others have said, position is the key. One problem I see from time to time is a little rust built up on the mating faces of the laminates. It can be just enough to keep them from reaching their "position" and therefore they vibrate. I use a little fine sandpaper to remove the rust.

Stationmaster

brucechase · Jul 24, 2009

Stationmaster said:
I use a little fine sandpaper to remove the rust.

Stationmaster

One thing I've tried to teach our maintenance guys is to NEVER use sandpaper on anything electrical. The silica is an insulator and any residue on the contact surfaces will do more harm than good. I have always used scotch bite cloth, it is not supposed to leave anything behind.

leitmotif · Jul 24, 2009

brucechase said:
One thing I've tried to teach our maintenance guys is to NEVER use sandpaper on anything electrical. The silica is an insulator and any residue on the contact surfaces will do more harm than good. I have always used scotch bite cloth, it is not supposed to leave anything behind.

Bruce
Mostly agree BUT
I would prefer using a sandpaper that is insulator ie silica or garnet (if I recall correct) than one that is conductive ie carborendum.

I prefer schotchbrite to sandpaper for many applications but you still have to clean things up of course. You still leave chunks of scotchbrite and the dirt oxide etc etc.

Sandpaper especially for larger DC equipment seats brushes quickly and does not affect the "chocolate" finish on commutator as will seating stone. Smaller equipment seating stone is sometimes the only choice.

Dan Bentler

Stationmaster · Jul 24, 2009

brucechase said:
One thing I've tried to teach our maintenance guys is to NEVER use sandpaper on anything electrical. The silica is an insulator and any residue on the contact surfaces will do more harm than good. I have always used scotch bite cloth, it is not supposed to leave anything behind.

Brucechase, your point is taken, but I wasn't talking about the contacts.... I was talking about the laminate faces.

Still, I understand how residue could cause harm... and I failed to mention in my post that the OP should REMOVE any residue after cleaning off the rust. I actually sort of figured that was obvious, given that I was talking about RUST as a foriegn material in the first place... but if YOU couldn't figure it out, maybe he wouldn't have either.

I will say that I've done this many times, and it works just fine. I will ALSO say that I don't have room on my service trucks for every product that is available to do a perfect job, and ONCE in a while I/we have to make do with a product from which we can get multiple uses.

I'm sorry if I led anyone astray here.... most of the guys are pretty clever.

Stationmaster

brucechase · Jul 25, 2009

Stationmaster said:
Brucechase, your point is taken, but I wasn't talking about the contacts.... I was talking about the laminate faces.

... but if YOU couldn't figure it out, maybe he wouldn't have either.

..most of the guys are pretty clever.

Stationmaster

There is no need to be insulting.

Stationmaster · Jul 25, 2009

brucechase said:
There is no need to be insulting.

A better choice of words might have been "If my post didn't make it clear to YOU, then it may not have made it clear to HIM".

I wasn't trying to be insulting, just acknowledging that my failure to include "remove residue" in my post may have made it unclear to some.

Stationmaster

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