End‐winding wire‐insulation heat conduction model for precise thermal predictions of permanent magnet synchronous machines

Abstract

Accurate thermal calculations of end‐winding temperature rises are the key issue in designing and developing cooling systems of permanent magnet synchronous machines (PMSMs). Due to the complex connections of the end‐windings, it is challenging to precisely predict the heat dissipation capacities through a traditional wire‐insulation equivalent model. Numerical simulations and lumped parameter thermal networks (LPTN) are used by the authors to develop thermal models that illustrate the end‐winding properties of a 2.1‐kW PMSM. As multi‐strand end wires are bent and bound together by ribbons, they have thermal interrelations which can hardly be considered in LPTN models. An equivalent coefficient enhancing the axial heat conduction capacities of end‐windings is proposed for LPTN calculations to model the aforementioned thermal interrelations with circumferential symmetric structures. To correctly model the mutual thermal coupling between various strands of end‐windings, the thermal conductivity of the equivalent insulation sheets between the multi‐strand end‐windings is determined for exact numerical calculations. The external insulation sheet thickness is calculated based on the equivalent thermal conductivity. After developing heat conduction models for LPTN and numerical simulations, LPTN and FEA are used to determine the PMSM's temperature rise characteristics. To verify the approaches, the computation findings are contrasted with experimental ones.