Cooling of Integrated Electric Motors

Reduction of carbon emissions and energy savings are driving the development of lightweight, high efficiency, electric motor systems containing integrated power electronics. Thermal management is one of the major obstacles in high power density electric motor development. For high power interior permanent magnet motors, the heat loss is mainly generated in three locations: the stator core, the stator windings and the power electronics that are used to drive the motor. A compact thermal management system is developed and presented in this paper, which consists of a manifold microchannel cooling jacket, used for cooling both the stator core and power electronics, and a direct winding cooling approach employing hollow conductors.The cooling jacket has an overall ring-shaped structure, with the inner surface in contact with the stator core, and the outer surface in contact with the power electronics. A complex fluid path is designed inside the cooling jacket to lower the pressure drop and pumping power while increasing its thermal performance. For directly cooling the windings, hollow conductors allow the coolant to flow inside the conductor. This direct contact means it can handle very high heat loss. It also decouples the thermal and electrical aspects for choosing a wire insulation material. Since the heat generated in the conductor flows inwards without passing through the electric insulation, thermal conductivity doesn’t need to be a constraint to the choice of insulation material. Four different hollow conductor configurations, including one circular hollow conductor and three rectangular hollow conductor shapes, are evaluated and discussed in this study.