Numerical Modeling Method of Turn-to-Turn Transient Voltages Taking Into Account the Common Mode Interactions

Electrifying future aircraft requires the development of advanced embedded electrical power systems. To achieve this objective, increasing on-board voltage levels are needed, beyond the conventional reference values of 230VAC/540VDC. In More-Electric Aircraft (MEA) and All-Electric Aircraft (AEA) applications, rotating electrical machines powered by PulseWidth Modulation (PWM) inverters are widely used. However, the use of these fast-switching PWM inverters combined with the presence of non-negligible cable lengths leads to significant overvoltages at the machine terminals (caused by waveform reflection phenomena) and non-uniform voltage distribution within stator windings. This leads to an increased risk of Partial Discharge (PD) inception, as turn-to-turn voltages may exceed the Partial Discharge Inception Voltage (PDIV). The risk is further exacerbated by the use of Wide Band Gap (WBG) inverters, which enable higher switching frequencies and faster voltage rise times. Combined with the harsh environmental conditions associated to high-altitude operations, these factors further increase the probability of PD inception and insulation breakdown in machine windings. This paper presents a time-domain validation of a High-Frequency (HF) model of an electrical machine stator windings. The method uses a two-time-scale approach, accounting for the electrical machine’s operating environment to predict turn-to-turn and turn-to-ground voltage distributions. In order to take into account the HF behavior of the different elements constituting the stator winding, an experimental validation is carried out using three systems of increasing complexity: an elementary air-core coil, an intermediate ferrite core coil, and a more representative coil with a laminated-iron core to simulate the materials of electrical machines.