A heavy-duty stator core and coil assembly that can accommodate severe input voltage spiking and harmonics may include a coat of varnish applied to the stator core and coil assembly by steps of dipping the stator core and coil assembly end-first along a longitudinal axis into a first tank of liquid epoxy resin having a relatively low viscosity, baking the coating, inverting the stator core and coil assembly and applying a second coat of varnish in the same manner, then dipping the core and coil assembly into a second tank having a liquid epoxy resin of a relatively high viscosity, then baking the second coat.