Proposition for Improving the Design of Motor Windings for Low-Pressure Environment

A new approach is proposed for designing coils free of partial discharges (PDs) for compact machines operating at high altitudes. The proposed method consists in using an enameled wire made with a thin additional resistive layer on the outer surface, which strongly reduces the electrical field in the voids between the wires of random coils. With such a wire, PDs occur only in specific zones situated near the wire connections and a local reinforcement of the insulation can strongly increase the partial discharge inception voltage. The article proposes a theoretical method for determining the properties of the resistive layer. The local reinforcement of the insulation is analyzed with an electrostatic simulation and Paschen's law. Measurements confirm the effectiveness of the proposed method.