A Layered Thermal Model for Concentrated Windings of Electric Machines

In electrical machines, the end winding usually has high temperature and complex structure. Therefore, it is very important to establish an accurate thermal model of the end winding. Through simulation, it is found that the commonly used homogenization winding model is not sufficiently accurate for the end winding. This paper presents a layered thermal model for both end winding and slot winding of electric machines which are equipped with concentrated windings. According to the winding parameters such as the wire diameter and the fill factor, the layer number and the layer thickness of the layered model are calculated with a proposed analytical method. In addition, calculation of the thermal conductivity of the insulation layer is introduced for the analytical method. Steady-state temperature field simulations using the actual winding geometric model and its layered model were carried out respectively, and the simulation results are compared to verify the accuracy of the proposed layered model. Comparison with existing layered models and sensitivity analysis across typical machine design parameters further verify the superiority and robustness of the proposed layered model. Three winding samples with different wire diameters and fill factor are fabricated to measure the steady-state and transient temperature. The results are in agreement with the calculated results with the layered model, which further verifies the reliability of the proposed layered model.