Research On High Power Density Design Of Permanent Magnet Synchronous Motor For All Electric Aircraft Propulsion

The electrification of aircraft is a big trend in the development of aircraft and electric machine is one of its key component.Therefore,high power density,reliability and efficiency are essential to motor design.Ultra light all electric aircraft are driven by propellers so that the motor has to operate in a peculiar cycle,which is different from factory or electric vehicle motors.Besides,propeller driving motor enjoys good air cooling conditions at a high altitude.In order to design a high power density electric motor,consideration of electromagnetic field,temperature rise,and structural design have to be combined within the optimization process.By summarizing current experimental model data,the operation profile of drive motor is obtained which comprise taxiing,taking off,climbing,cruising,descending and landing.The variation in speed is limited,but the torque required in climb phase is almost twice as it is in cruise phase.However,the cooling condition is weaker in climb phase.A novel design procedure is proposed that magnetic circuit and heat circuit are combined in order to compare various motor configurations that satisfy temperature rise limit.The surface heat transfer capacity is analyzed with finned motor shell.By predicting motor loss and heat transfer,using simplified lumped parameter motor model,the transient temperature rise of different motor dimensions are presented more intuitively than traditional method which use heat loading value as indication.Two improvements in stator design are presented to help fulfill the high power density design.One is to use auxiliary tooth to alleviate thermal stress in the slot center,and the other one is to double the teeth number by duplicate the winding with offset position which eliminate some higher frequency MMF harmonic waves.Lumped parameter heat network is modeled to assist electromagnetic design.Novel rotor pole configuration is used to improve torque and decrease eddy current loss by changing pole arc proportion and magnetization angle.CFD models are constructed to improve fin design and thermal phenomena inside the electric motor.Hollow shaft and hollow rotor are used to reduce weight which facilitate rotor cooling.The heat transfer and temperature distribution in proposed motor structures are calculated and compared throughout take-off and cruise mission.In this dissertation,three motor thermal models are used to facilitate motor design from preliminary design to final optimization.Shell heat dissipation,stator and rotor configuration,as well as shaft design are optimized to realize high power density design.Finally,a total enclosed surface mount five phase permanent magnet synchronous motor suitable for electric aircraft propulsion with high power density is design.