Evaluation of Inter-Turn Stresses in Electrical Machines Considering Common Mode Elements

In the context of the more electric aircraft (MEA), and with the development of hybrid or all electric propulsion systems, future aircrafts will require electrical machines with voltage levels and switching frequencies higher than the reference values of 540 V and 10 kHz, respectively. During voltage transients, windings of electrical machines undergo overvoltages due to waveform reflection phenomena and non-uniform voltage distribution. These phenomena are amplified using modern PWM (Pulse Width Modulation) inverters built with SiC (Silicon Carbine) and GaN (Gallium Nitride) transistors. As a consequence, there is a risk that the inter-turn voltage may be higher than the PDIV (Partial Discharge Inception Voltage). In this context, it becomes crucial to precisely determine these inter-turn voltages. This paper focuses on a High Frequency (HF) model, which aims to predict the inter-turn and turn-to-ground voltages in electrical machines.