Double-Circulatory Thermal Analyses of a Water-Cooled Permanent Magnet Motor Based on a Modified Model

This paper presents a modified thermal model-based double-loop circulatory technique for the thermal analyses of permanent magnet synchronous machines. The inner loop of the circulation procedure is employed to guarantee the energy conservation of the air enclosed in the endcaps and modify the temperature-dependent heat convection coefficients, while the outer loop is used to correct the heat conductivity coefficients and the electromagnetic losses that change with temperatures. The thermal model based on finite formulation method is modified to simplify the modification process of the outer loop. The temperature estimation techniques are then applied to analyze the temperature distribution of a permanent magnet motor with a spirally mounted water-cooling system. A novel ventilation structure is established to maintain the temperature rise of the rotor parts. The analyses based on the proposed methodologies are validated by experiments.