Compatibility of alternative refrigerants with varnished magnet wire

The compatibility of 24 motor materials with 11 pure refrigerants and 17 refrigerant-lubricant combinations has been determined. A summary of the effect of refrigerants on varnished magnet wire is presented. The greatest effect on the motor materials is caused by absorption followed by desorption of refrigerants at higher temperatures. The high internal pressure of the absorbed refrigerants and the tendency of these refrigerants to evolve from the materials results in blisters, cracks and internal bubbles in the varnish and magnet wire insulation. The degradation of the insulation results in changes in the bond, dielectric and burnout strength of the varnished magnet wire. Desorption of HCFC-22, and to a lesser extent HFC-32, HFC-134 and HFC-152a, has the greatest effect on insulation integrity. Of the refrigerants tested, exposure to HCFC-22 produces the most deleterious effects on the magnet wire insulation and varnishes