Hybrid impregnation process for electric vehicle motor stator using hot melt epoxy-imidazole cure system

A process for insulating an electric vehicle motor stator, comprising the steps of:

• (a) providing a one-component epoxy varnish composition comprising:
• (i) 20-30 weight percent of at least one bisphenol A based epoxy resin;
• (ii) 5-10 weight percent of at least one multifunctional epoxy resin;
• (iii) 5-10 weight percent of a non-halogenated phosphorus-containing flame retardant epoxy resin;
• (iv) 35-65 weight percent of a cycloaliphatic anhydride hardener;
• (v) 0.1-5 weight percent of an encapsulated imidazole catalyst;
• and (vi) 0-5 weight percent of a fumed silica rheological additive;
• (b) heating the composition to 40-80° C.;
• (c) dip coating a hairpin portion of the stator in the heated composition;
• (d) cooling to allow the coating to set at room temperature;
• (e) heating the composition to 60-80° C.;
• (f) applying the heated composition to a crown wire portion of the stator via trickling;
• and
• (g) curing both coated portions simultaneously at 150° C. for 1 hour.

An insulated electric vehicle motor stator, comprising:

• (a) a stator core having a hairpin portion and a crown wire portion;
• and
• (b) an insulating coating formed from a cured one-component epoxy varnish composition comprising:
• (i) 20-30 weight percent of at least one bisphenol A based epoxy resin;
• (ii) 5-10 weight percent of at least one multifunctional epoxy resin;
• (iii) 5-10 weight percent of a non-halogenated phosphorus-containing flame retardant epoxy resin;
• (iv) 35-65 weight percent of a cycloaliphatic anhydride hardener;
• (v) 0.1-5 weight percent of an encapsulated imidazole catalyst;
• and (vi) 0-5 weight percent of a fumed silica rheological additive;
• and (c) wherein the coating exhibits a glass transition temperature above 150° C.