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Discussion Starter #1
Wasn't sure where to put this - so decided on the "Shed"

I'm repairing a Coleman 5kw Powermate Generator that I believe was overloaded during Storm Irene. 3 separate homes had plugged in to run freezers or refrigerators and I was told there was a screeching noise and sparks coming out of the endbell while it ran; the output had quit so they shut the genny down and although the motor would run; they couldn't use it for power.

I removed the endbell to discover that the area between where the brushes ride was burned / gouged away. I'm not familiar enough to know if this was caused by extreme heat or what..?
The components in the end bell appear fine visually with some mild to moderate surface rust on one of the 2 diodes.

Here is a link to photos.
First page shows the rotor;
Second page shows the endbell
https://skydrive.live.com/P.mvc#!/view.aspx/generator%20rotor%20end.pptx?cid=baf5c12816bfeed9&sc=documents

I'm assuming that the ringed area was fairly hot from the overload and that somehow the insulating material between the rings failed.
I've never done a repair of this nature. Can I fill the area between the rings with something like epoxy?

I see no other obvious damage to the rotor, endbell or stator;
Can this be repaired?
I'm really need of some guidance.
Appreciate your help.
-br
 

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That's some pretty nasty damage there BR... That plastic melted out due to extreme heat but I'm thinking that's not the root cause of the genny failing to produce now; the melted plastic is a sign of significant heat damage, but shouldn't prevent the brushes from contacting the rings. My money says that it also burned out a winding due to the overload. Use a meter and read the ohms across the coils. I'll bet you find one has burned open! If the coils are ok, check the regulator circuit. you may be able to repair the damage by filling it with something non-conductive like JB Weld... won't guarantee that'll work though, as the rinds need to be in correct alignment with the brushes.
 

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Discussion Starter #3 (Edited)
That's some pretty nasty damage there BR... That plastic melted out due to extreme heat but I'm thinking that's not the root cause of the genny failing to produce now; the melted plastic is a sign of significant heat damage, but shouldn't prevent the brushes from contacting the rings. My money says that it also burned out a winding due to the overload. Use a meter and read the ohms across the coils. I'll bet you find one has burned open! If the coils are ok, check the regulator circuit. you may be able to repair the damage by filling it with something non-conductive like JB Weld... won't guarantee that'll work though, as the rinds need to be in correct alignment with the brushes.
Thanks for the reply, JR.
I'm thinking that the plastic melted enough from the heat of overloading that the dielectric strength of the plastic failed and it began to arc from one ring to the other ring, totally bypassing the brush circuit etc. My uncle said he saw sparks coming from the vent holes in the plastic endbell before he shut it down. (they had put 3 electric cords on the genny at the same time)
2 - in the 120v receptacles and one cord on a "pigtail" plugged into the 220v one.
This of course is all guesswork on my part
Can you walk me thru checking the coils - this is all kind of new to me.
I'm not sure I'd know offhand a good read from a bad.:thanku:
-br
 

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First thing in reading coils is to determine how your meter shows a direct short; turn the meter to the Ohms setting and short both leads together. My Radio Shack meter reads 0.8 Ohm sorted, yours may read 0.0 or something close. Next touch one lead to each ring with the brushes off, if you see the SAME reading as shorting the meter the coil is shorted out and bad, if you really high reading (over a few dozen ohms) I'd suspect a burned out (open circuit) coil. You'll also want to check the field coils, you should find 2 or 3 wires coming out of the field, disconnect them (noting how they were connected!) and check across all of them... if anything is shorted out to another wire OR shorted to chassis ground you have a problem too! Perhaps someone more familiar with that particular model can chime in as to the field wiring details.
 

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Keep in mind that the Coleman was an entry level generator even when they were in business. If this will require a lot of parts, you may be better off putting the $ toward a better unit. Another option is to scout to repair outfits in your area and find one in the junk pile with a blown engine. I've salvaged LOTS of good stuff from the place I visit.
 

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Discussion Starter #7
Some progress - and more questions.

OKay - I've put my meter on the 2 rings that the brushes normally ride on,
on the end of the stator. (brushes are removed when I removed the endbell.)

I get 25.9 ohms.

I haven't checked the field coil - is that the coil that is in the stator?

I assume in order to check that coil I have to remove the rotor.
ie. the stator wire, though copper in color, is coated and I cannot simply put the test leads on whatever wire in the bundle is handy.
Am I correct on this?

(btw thank you for the chime in rscurtis.)

So anyway how shall I proceed?
-br
 

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Nothing wrong with the Coleman Powermate's, what do you mean when they were in business? Still sold at every store around me.

I have a 6500w Coleman that i bought a few years ago, wired up with a manual transfer switch. Normally i only have a few days a year that i need it, but after the tornado July 1st i ran it for three days straight keeping the refrigerator, freezer, tv's for the kids, and fans and lights on. If i unplugged the fridge and freezer i could run the AC unit in the living room and keep an oasis of cool available to take breaks in from the cleanup.

It has served me well!
 

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http://www.powermate.com/generators/

They redesigned them a bit... Mine is the older style frame.

My guess is the generator head is shot on this one. Looks like it was severely overloaded and overheated. Not the generators fault. You need to monitor the current/wattage being used. I run a transfer switch which has wattmeters built in. But there is a few companies that sell addon units as well.
 

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Seems like its breaker should have tripped if overloaded.

Another factor in repairing it - even if you get the insulating material fixed, you have to make sure the slip rings run true and flat, otherwise the brushes will be bouncing up and down, making poor contact, and maybe arcing and ruining themselves.
 

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Discussion Starter #11
Seems like its breaker should have tripped if overloaded.

Another factor in repairing it - even if you get the insulating material fixed, you have to make sure the slip rings run true and flat, otherwise the brushes will be bouncing up and down, making poor contact, and maybe arcing and ruining themselves.
Thank you for the reply FC.
I think what happened was the cumulative load was too much - but was spread over 3 circuits.

-br
 

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Thank you for the reply FC.
I think what happened was the cumulative load was too much - but was spread over 3 circuits.

-br
That would make sense as i know with mine each outlet has its own seperate breaker. So if none of the outlets were over their rating but the combined load was too much then you still get a meltdown.

I would say that generator head is dead, for if you repaired it you would probably find another weakness. I know one guy that had a burnt up rotor and replaced it and the brush assembly then ran it again and the stator coil failed because it was previously overheated badly.
 

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That would make sense as i know with mine each outlet has its own seperate breaker. So if none of the outlets were over their rating but the combined load was too much then you still get a meltdown.

I would say that generator head is dead, for if you repaired it you would probably find another weakness. I know one guy that had a burnt up rotor and replaced it and the brush assembly then ran it again and the stator coil failed because it was previously overheated badly.
:ditto: :ditto: :ditto: :ditto:

Personally when I see the type/severity of damage as you have to the ring assembly I just issue a death certificate on the spot. The diode assembly has also been severely overloaded and likely to fail, brushes overheated and will wear quickly, stator overheated making future breakdown of the insulation inevitable, etc.. As others have said, find one with a blown motor and a good genny head...
 

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Discussion Starter #14 (Edited)
Hmm...

Well I certainly understand the point of view;
But the gentleman doesn't want a new genny; he wants his fixed if possible.
Further I have no access to a blown motor genny.
Assuming the rings are still true (they appear to be)
My intent is to proceed.
If any of you are willing to help with additional thoughts,
I would appreciate it.

This to me is an odd repair in that the endbell shows no damage and the rings have what according to one kind poster is a good reading.
I'm thinking that once the insulating plastic failed; one ring simply arced to another. This of course by-passes all the endbell circuitry; in essence preserving it from further damage.

Once the first arc occurred electricity took the path of least resistance; no longer flowing out the receptacles to the load.

Anyhow this is my laymens diagnosis (helped by all your initial comments.)

As far as "knowing a guy..." I can't compare his genny to this one because I can't see his "before and after". Perhaps the genny that failed had much more damage or abuse.

Like I say, this gentleman wants it repaired if at all possible; I would not counsel him to have me install a replacement rotor for $210 if it could be properly/adequately repaired with jb weld or some other epoxy.
Again, thanks for the help so far and your additional comments/concerns/ideas are certainly welcome.:trink39:
-br
 

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Well i think where this is going is that the best you can do is "try" to repair it. And once its up and running and you have voltage then put a load on it, a few thousand watts or so of electric heaters is a good cheap load, or a portable or window air conditioner that would stress it good. Whatever you use for a load put an equal amount on each side or use a 220/240v appliance/load to make it even.

Test it until it smokes basically.
 

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Discussion Starter #16
Well i think where this is going is that the best you can do is "try" to repair it. And once its up and running and you have voltage then put a load on it, a few thousand watts or so of electric heaters is a good cheap load, or a portable or window air conditioner that would stress it good. Whatever you use for a load put an equal amount on each side or use a 220/240v appliance/load to make it even.

Test it until it smokes basically.
Thank you Kb;
Not sure I understand the last line though, can you 'splain?

-br
 

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LOL...

Well we don't know if anything else is stressed or damaged... So basically put a good load on it and see what happens. If you can run it for an hour and nothing goes BOOM, then you should be ok.
 

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Discussion Starter #18
Got it. Ha!
Thanks Kb;
I'll let you know how it goes.
Might turn out to be a weenie roast:biglaugh:
I really appreciate the help and humor.
:trink39:
-br
 

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Looked at the pictures again... Very odd how that failed indeed... Oh well it happened now to see what happens with it!
 

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Before you patch the plastic insulator witht he JB Weld be sure to clean out ALL the burned plastic. I've seen carbon tracking in old PLC and IO cabinets in mills; once an arc jumps across a plastic insulator it will burn it slightly, leaving a carbon conductive path behind. The carbon path makes it easier for the next arc leaving more carbon, eventually it will arc enough to blow the fuse! Any carbon (burnt plastic) between those two rings needs removed down to clean plastic; a dremal would be great for this. After the filler is cured, I'd clean the rings carefully up using 1000-2000 grit sandpaper.

You may well find the unit dead once you fire it up; get an old single-speed non-reversing electric drill, plug it in to the running genny, and turn the drill backwards by hand (it should immediately come to life and begin turning forwards). This should re-energize the field since it likely lost all its magnetism when it failed.
 
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