Framework for Insulation Thickness Calculation in PD-Free E-Machines for Automotive and Aerospace

This paper presents a framework for optimizing insulation thickness (IT) in electrical machines (EMs), ensuring reliability and efficiency for a fixed copper diameter and slot geometry. A validated, model-based software, grounded in the streamer inception criterion (SIC), calculates optimal IT for turn-to-turn windings in automotive and aerospace applications, incorporating enhancement factors (EFs) from IEC 60034-18-41. IT is evaluated for automotive systems (1000 mbar) across five temperatures (20°C–180°C) and four inverter DC bus voltages (1–1.6 kV). Aerospace analysis considers three air pressures (600, 400, 200 mbar) at altitudes of 13.8k–38.6k ft, the same temperature range, and four voltage levels (0.7–1 kV). The framework is applicable to all winding topologies and evaluates IT under worst-case conditions (non-impregnated insulation) and varying partial discharge inception probabilities (PDIPs). Trends in partial discharge inception voltage (PDIV) vs. IT are analyzed, with sensitivity to voltage variations examined across air pressures and temperatures. These findings support the design of reliable, high-performance insulation systems for electric transport.