High temperature motors: Investigations on the voltage distribution in windings at a short scale times for a PWM supply

Most of electrical machines are wound with enameled copper wires insulated by a thin polymer layer, which has excellent mechanical and insulation properties. However, the organic nature of these insulating layers limit their operating temperatures to more or less 280° C for the best polymers. It is possible to operate at much higher internal temperatures with an inorganic Electrical Insulation System (EIS) made without any polymer. Unfortunately, the available inorganic wires made with a thin ceramic insulating layer have poor electrical and mechanical performances. Therefore, the design of High Temperature (HT^°) coils, able to work with standard PWM inverters is more difficult. The paper presents a method for computing the voltage spikes that follow each voltage fast edge with a high frequency (HF) equivalent circuits.