Varnish insulation; generator windings

[Microbeman]

It appears a mouse has ventured into our 25 KW generator and chewed off some of the varnish insulation on the winding bundles (about a square inch). Does anyone know if we can just patch the spot with spray on air dry varnish and recommend a good brand?

Sorry for going off topic but I need some help.

 

[JackTheGrower]

I'm going to bet you are in the wrong forum for that.. Inductance is effected I'm thinking so you need to get a professional opinion.

On a side note I'd hope so.. That's an expense to replace. Any suggestions on protecting? It would be nice to spray something on but how would we know all wires are still isolated?

 

[Mr-B]

Turn the generator off and get yourself a marine grade shellac.
Using a small brush, apply the varnish over the exposed area. Let dry for 6 hours. You can help the drying time by adding a heater to the area.

The windings will be fine, no harm done. The varnish is there to protect from rust buildup by moisture in cold weather.


Good luck

B

 

[Microbeman]

Turn the generator off and get yourself a marine grade shellac.
Using a small brush, apply the varnish over the exposed area. Let dry for 6 hours. You can help the drying time by adding a heater to the area.

The windings will be fine, no harm done. The varnish is there to protect from rust buildup by moisture in cold weather.


Good luck

B

Thanks B!

 

[JackTheGrower]

Cool to know...

I was thinking that it also isolates the wires electrically since they are copper after all yes?

Can wires touching each other cause a problem for the magnetic field?

 

[imnotcrazy]

The varnish IS an insulation, without it the winding would have multiple thousands of short circuits.

If you are going to attempt to re-varnish the windings, you MUST ensure you get a good coat of varnish, of a PROPER DIELECTRIC (insulating property) RATING, between any potentially shorted windings. I sincerely doubt marine varnish will suit this purpose.

Short circuited windings would be similar to wiring a 9 lead motor (dual voltage 3 phase) for the wrong voltage and can damage the windings further.

 

[Microbeman]

http://www.kpg-industrial.com/products/insulating_varnish/

Jack; the wires in a winding are touching each other but are insulated from the opposing magnetic field (I think).

 

[imnotcrazy]

Current passing through the windings produces a magnetic field. This can't occur properly if the windings are short circuited.

Short circuiting a motor winding turns any shorted windings into a short circuited transformer secondary. The primary winding (rest of the motor) will attempt to supply the current the "secondary" is calling for, which is unlimited current being that it is short circuited.

This will cause EXTREMELY HIGH winding currents which you can be sure will damage the windings further.


I'm not trying to be a dick, but "I Think" can get you killed......

 

[JackTheGrower]

I was worried about that too..

I'd let a professional do the repair if it is possible.. Safety is really important.

It should be tested to be sure it has the correct impedance and ohms I believe.. Not that I am an expert .. Not even close..

 

[imnotcrazy]

Resistance of the windings should be negligible, they are just a piece of wire.

Your repair must have as good, or better insulation rating than original.

 

[JackTheGrower]

Resistance of the windings should be negligible, they are just a piece of wire.

Your repair must have as good, or better insulation rating than original.

well, maybe it's the 100,000 mile time anyway. Whatever is correct be safe.. See wrong forum..

Best Wishes on a cheep repair but a proper one..

 

[Microbeman]

Its a matter of repairing the insulation. Everything else looks good and the machine shuts down if there is a problem. I don't have a megger (or whatever its called) to check the insulation but we have fixed everything around the farm, so far successfully. When you live 2 hours from the closest town you can't bring people in to fix stuff and also eat.

 

[JackTheGrower]

Well the best advice is be safe.. I can't see it and maybe it's minor.

Better to do it right than ruin a really big generator I was thinking.

 

[Microbeman]

We will be safe. Rewinding services cost more than buying a new generator, if you can believe that.

 

[maryjohn]

The mj award for best totally off topic thread ever goes to this one.

And kudos to microbe for assuming there would be lurkers around who know electric motors.

 

[imnotcrazy]

The mj award for best totally off topic thread ever goes to this one.

And kudos to microbe for assuming there would be lurkers around who know electric motors.

Except there are, and they gave him solid advice, minus the Marine Varnish suggestion................

 

[Microbeman]

Just so you know, the windings are coated with electrical grade varnish at the factory. We would be trying to match this.

 

[JackTheGrower]

That's a big unit isn't it?

Take care...

I'm wanting to call chuck and check on that Burn1...

 

[JackTheGrower]

The mj award for best totally off topic thread ever goes to this one.

And kudos to microbe for assuming there would be lurkers around who know electric motors.

Eh.. we get older and collect bits of this and that.. Good to use my memory while I have it.

Then again your post was the most off topic in an off topic thread.. So you win!

Funny bit of high humor..

 

[maryjohn]

Lol true enough.


Don't get me wrong, microbe was very wise to post here. We get quality lurkers who know all kinds of stuff.