Cleaning solvent for motor windings

Usually, the dry ice approach is the best bet because it leaves no real residue from the cleaning material. If the insulation is "fluffing", the likely problem is that the air pressure used to move the dry ice particles is too high.

A second alternative that can be used is "corn cob blasting". The media is reusable, biodegradable particles of corn husks. Again, a relatively low pressure air stream is required. It WILL damage the insulation if the pressure is too high, just as in the dry ice case.

Most solvents will aggressively attack the insulation systems used for windings: this is specifically true for the larger machines where mica tapes are coated / filled with a resinous material (vacuum pressure impregnation). However, it is equally true for smaller machines where the primary insulation is at the strand level and is essentially a varnish or enamel coating on the wire. If you're worried about how the solvent will affect the insulation system, get in touch with the motor supplier for their suggested approach.

If a solvent-based cleaner must be used, it should be applied sparingly - BY HAND - on the areas to be cleaned to break up the oily / greasy contaminant and then rewashed with some other (non-solvent) approach to clean away any solvent residue. This also will require a "dry out" of the equipment after the second washing. This three-stage approach tends to minimize damage done by solvent that may be left behind to "eat away" at the varnishes, enamels, and resins comprising the insulation system.

One last thing - pretty much ALL solvents are going to be designated as hazardous materials in most regions, due to health concerns. Therefore it is more a case of "pick your poison"!