Design and Optimization of High-Power Density Permanent Magnet Motor with Integrated Cooling for Aircraft Propulsion
Thirumalai Ananthanpillai, Aravindakshan
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There is a critical need for the electrification of transportation systems. While power density required for ground-based vehicles can, to some extent, be met by current off-the-shelf motors and generators, aircrafts require significant improvements both in terms of power density and efficiency. The concept relies on the tight integration of a high-power density dual-rotor permanent magnet motor, high power density SiC power converters, and a shared closed loop cooling system rejecting the heat in the propulsion ducted fan air stream. The motor is based on a dual-rotor configuration using permanent magnets forming ideal Halbach arrays allowing for high magnetic loading without needing iron. The permanent magnet rotors are based on “continuous flux directed” magnets (PM-360™) and an air-gap stator with direct liquid cooling allowing for high electric loading and unprecedented specific torque and specific power. The heat is removed by a closed loop of liquid shared by the motor and power converter. The heat is rejected in the propulsion air stream. Integrating the motor and power converter will help achieve very high density, which is paramount in aircraft applications. A high efficiency three-level SiC inverter along with the double-sided direct cooling features with high switching frequency is used to reach high specific power. Using the novel motor and drive designs, a 250 kW electric powertrain is designed with a specific power of 16.9 kW/kg at an efficiency of 93%, thus paving the way for electric aircrafts for commercial transportation.