Cleaning a rotor on an electric motor

[Bobby Robbinett]

So I have one of my large 7.5HP 3ph electric motors apart changing the bearings. The rotor has gotten a little dirty and is a little rough. I know that I can use a green scotchbright pad to clean it but what kind of liquid could I use to clean and lube the scotchbright pad with that will dry quickly and not damage any thing? Could I use like a Kurd Kutter or Simple Green? Or just soap and water? Or nothing at all? What ever you guys suggest that I use, how long should I let the rotor dry before reinstalling it?

[Paul F Franklin]

I use electric motor cleaner or contact cleaner and an old toothbrush. They both dry quickly and don't leave any residue after wiping. I think it best to avoid anything with water.

[Bill Dufour]

Clean the stator while you are at it. Climate? I would use ivory soap and water. A soft cloth. Let it sit outside all day in the sun when it is over 100 degrees. Consider flooding on some varnish where needed.
Bill D

[johnny means]

When I work on motors, I clean them with water and whatever soap is handy (I like dish soap a lot),dry them with compressed air, then flood them with denatured alcohol. The alcohol takes care of any residual water and evaporates almost instantly. This is also my procedure for computer and automotive stuff. Despite what common knowledge would tell you, water isn't all that harmful to electrical components.

[wayne booker]

Isopropyl alcohol. It dries quickly and thoroughly, does not damage the winding sealant, and only needs to be wiped off. And if you do use water, go over it with IPA and it will dry the water.

[Lee Schierer]

If it were my motor I wouldn't use water.....

[Bill Dufour]

I would not use alcohol. The shellac on the wiring may be damaged by it. I suppose a newer motor may not use real shellac.
Bill D

[Frank Pratt]

When I work on motors, I clean them with water and whatever soap is handy (I like dish soap a lot),dry them with compressed air, then flood them with denatured alcohol. The alcohol takes care of any residual water and evaporates almost instantly. This is also my procedure for computer and automotive stuff. Despite what common knowledge would tell you, water isn't all that harmful to electrical components.

Anytime motor windings are flooded with water, you must bake them off. Rinsing in alcohol will not ensure that all the water has been removed. There are thousands of tiny pockets inside the windings and an alcohol rinse is very unlikely to get in there & drive all the water out.

[Bobby Robbinett]

The windings and wiring on the inside are coated with shellac? This is a 20 year old 3 phase motor.

[Jerry Bruette]

The windings and wiring on the inside are coated with shellac? This is a 20 year old 3 phase motor.

Nope. They're coated with a type of varnish which is baked on and provides insulation.

I suspect if they were coated with shellac contact cleaner would make a real mess.

I'd clean the motor with contact cleaner and gently scrub with a plastic bristled brush if needed followed by a blow down with compressed air.

[Bill Dufour]

The windings and wiring on the inside are coated with shellac? This is a 20 year old 3 phase motor.


The first electric motor the wires were insulated by ripping strips of silk fabric and winding that around as insulation. The silk came from his wife's wedding dress.
Bill D

[Matt Day]

Air compressor and a toothbrush or scotch brite (lightly) is all I do.

[Bill Dufour]

The windings and wiring on the inside are coated with shellac? This is a 20 year old 3 phase motor.


Age of you motor was never mentioned. My bench grinder is from 1930-1937. i have no idea what varnish was used then on wires. My 1949 house the insulation crumbles if you move it and it is better then the older stuff they used.
Bill D.

[johnny means]

Anytime motor windings are flooded with water, you must bake them off. Rinsing in alcohol will not ensure that all the water has been removed. There are thousands of tiny pockets inside the windings and an alcohol rinse is very unlikely to get in there & drive all the water out.
Any reason why the alcohol is also not getting into these same tiny pockets? Also, minute amounts of moisture on insulated windings isn't going to any damage. Any old brushed motor will run completely submerged as long as the water is not made to be highly conductive.

[Bill Dufour]

Others disagree but I would not heat the windings over 200 F. that way no chance of steam pressure messing things up.
My old Neighbor was involved in drying out flooded generators. He said they built a sealed house over them and pulled a vacuum. They had electric heaters inside and kept the temperature below the boiling point. Had to watch temp/pressure curves closely. Took 12-16 months to dry out all the way. They measured water content of the vacuum pumps. These generators were the size of a house, supplying power to a county or two.
It was still quicker then getting new ones custom made. A big flood destroyed many generating stations on the river. I think it was the Tennessee? It would have taken several weeks just to get delivered from the factory after it was made.
Bill .