generator slip rings

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joshgarcia

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Hello,

Besides the usual bad brush, bad spring tension, etc...What would cause the generator slip ring brushes to spark on a 6 meg turbine/generator?
 
Any nicks on the ring to cause the brush to loose solid contact?
 
joshgarcia said:
Besides the usual bad brush, bad spring tension, etc...What would cause the generator slip ring brushes to spark on a 6 meg turbine/generator?
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Check the current to each brush. If some are more heavily loaded than the rest, the ones carrying more power can spark up a storm.

Check to make sure the brushes move freely in the holder, if they stick and don't make full contact, same problem.

Check to see that the brush face is curved to match the ring. If they're installed backwards, or the brush face is flat-smooth (like when the brush is new), then there's a very small surface area carrying all the power and you can get sparking.

Look for any grooves in the ring or cracks in the brushes.

Check for abnormal runout on the slip ring. It's not likely, because you'd see the vibration somewhere else in the unit, but that can also cause arcing (along with a whole lot of other problems!)

-John
 
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Thank you. I will check all those items. Another interesting thing i noticed that may be very interesting to you fellas is, there are three different brushes that are sparking and if i apply pressure to one brush the sparking goes away on all three brushes.
 
joshgarcia said:
...There are three different brushes that are sparking and if i apply pressure to one brush the sparking goes away on all three brushes.
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I would bet money that you have a couple of sticky brush-holders. When you press down on a brush, you're making really solid contact, and I'll bet that you'd see a pretty fair current increase on that brush. This would reduce the current on the other brushes enough that the sparking would stop.

I'd be interested to hear what the current readings were if you take 'em

-John
 
There are 4 brushes sparking and no matter which brush you apply pressure to all the sparking stops. The current readings on all 6 brushes are as follows: 11.8, 18.8, 16.1, 12.9, 19.6 Amps DC. (the 5th one I was unable to get a clamp around) My guess is the lower current brushes may be the culprits...would this be a safe assumption?
Now I think I will begin by taking the down the turbine and cleaning all components, checking spring tension, and tightening eveything up. Just wondering if you have any other suggestions while I have the unit down?
I appreciate all the advice.
 
joshgarcia said:
My guess is the lower current brushes may be the culprits...would this be a safe assumption?
Click to expand...
That's definitely where I'd start. Check spring tension like you said, but also check to see how easily the brush moves in the holder. Pull it out and look for chips or cracks that might roughen the edges and cause them to stick.

Also, there are soms silly questions: Are all the brushes the same model? Were these changed recently? Did the old ones spark?

If you can't find any obvious problems, I'd just replace the low current brushes with new, sanded brushes. See if the arcing goes away, that would at least eliminate the brush itself as the problem.

-John
 
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