Cleaning oil contamination from older electric motor

[Dranreb]

I have a 1950 ish electric motor that has an earth fault and is throwing the w/shop trip, is an has oil film all over the inside and I've been told this could be the cause, due to trapped condensation and contaminants, if I use isopropanol alcohol to clean this off would it affect the varnish on the windings?

I'm worried it may be some sort of shellac that could be damaged, unlike a more modern type.

Bernard

 

[John Hasler]

I have a 1950 ish electric motor that has an earth fault and is throwing the w/shop trip, is an has oil film all over the inside and I've been told this could be the cause, due to trapped condensation and contaminants, if I use isopropanol alcohol to clean this off would it affect the varnish on the windings?

I'm worried it may be some sort of shellac that could be damaged, unlike a more modern type.

Bernard

If it's just tripping a GFI you might fix it by washing it out with isopropanol (which won't hurt the insulation unless it's already shot). If it's tripping a breaker you aren't going to fix it with cleaning.

Actually, you can clean the armature with soap and water as long as you thoroughly rinse it and get it completely dry before powering it up.

 

[Alan Douglas]

Alcohols aren't very good solvents for oils; mineral spirits/paint thinner would be better. But oil wouldn't cause electrical leakage. You could try heating the motor and seeing if the leakage decreases. That would point to the cause, if not actually fix it. I've never done it but you could run some current at low voltage through the windings to heat them.

I suspect rust has penetrated the insulating paper that separates the windings from the stator core.

 

[Dranreb]

Thanks for the input guys, I've dug a little further behind a Bakelite plate and found the insulation on the two wires from the starter thingy softened, bare and touching..

 

[John Hasler]

Alcohols aren't very good solvents for oils; mineral spirits/paint thinner would be better. But oil wouldn't cause electrical leakage. You could try heating the motor and seeing if the leakage decreases. That would point to the cause, if not actually fix it. I've never done it but you could run some current at low voltage through the windings to heat them.

I suspect rust has penetrated the insulating paper that separates the windings from the stator core.

The alcohol would remove any moisture that was in there. Grease and oil don't cause shorts (they can cause overheating). If you are going to use isopropanol use the 91% variety, though, and dry the armature thoroughly with heat.

The first step is to take the motor apart and look for the cause.

 

[fixit]

When I had my small (gas) motor / Compressor shop I used CRC LECTRA CLEAN on motors (electric) & switches. The spray can was good to blast the crud out of the motors. Can be purchased at ACE hardware in my area or Graingers, or Mc master-carr.

fixit

 

[CoopVA]

I just completed the rebuild/restore of my lathe motor... Took it apart, cleaned it with electric contact cleaner...

Were you able to fix the wires? I had the same issue and was able to fix it by cutting the wires back and soldering in a new length of wire.


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[Alan Douglas]

The alcohol would remove any moisture that was in there.

We'll have to agree to disagree on that one. While it might combine with the moisture, the alcohol would have to be flushed out or replaced with fresh alcohol, or it will simply evaporate and leave the original water behind. I doubt you could flush it all out of buried insulation, particularly if there is oil in it too.

 

[CoopVA]

The only reliable way to remove moisture from electrical windings is to bake it...


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[John Hasler]

We'll have to agree to disagree on that one. While it might combine with the moisture, the alcohol would have to be flushed out or replaced with fresh alcohol, or it will simply evaporate and leave the original water behind. I doubt you could flush it all out of buried insulation, particularly if there is oil in it too.

Yes, of course you have to flush it with more alcohol. That's how the alcohol removes the water.

You still need heat to get all the alcohol out, of course.

However, water will only cause leakage current. If it's tripping a breaker there is a short. Cleaning will not fix that.