In-slot Cooling for High Power Density Electric Motor with Encapsulation Channels

The desire to reduce carbon emissions, noise, and fuel consumption is driving recent research on electrification of traditional combustion power units. High power density motors are essential for large-scale, heavy-duty applications. To achieve high power density, thermal management systems are critical as, at elevated temperatures, electric motors are susceptible to reduced performance or even catastrophic failure.The stator winding is the primary heat source in high power motors and is the major challenge in cooling system design. Not only is controlling the temperature important for safe operation, but also the resistance of the winding increases with higher temperature, lowering the motor efficiency. As there is a high thermal conductive resistance between the windings and traditional cooling structures built on the outer surface of the motor, direct in-slot cooling is required to achieve the needed thermal management. In this paper, a novel in-slot cooling approach is discussed for a permanent magnet motor with power density higher than 22 kW/kg, based on active mass. In this approach, the stator slot, including the winding within, is encapsulated with high thermal conductivity potting material. Fluid channels are built directly into the winding turns by an investment casting process, reducing the thermal resistance between the winding and the coolant. A manufacturing process is proposed, and five different configurations are simulated and compared.