Research On Rotor Loss Of Permanent Magnet Synchronous Motor With Fractional Slot Concentrated Winding

Due to its short end turns,high slot fill factor,high efficiency and high power density,low cogging torque and excellent flux-weakening capability and fault tolerance,fractional slot concentrated winding permanent magnet synchronous motor is widely used in many fields such as electric vehicles/hybrid electric vehicles,ships,wind turbines and so on.Different from distributed-winding permanent magnet synchronous motors,for fractional-slot concentrated-winding permanent magnet synchronous motors,the production of the torque results from the interaction between rotor magnets and a certain high-order harmonic of the stator winding magnetomotive force,while the other low-order and high-order harmonics will cause high losses on the rotor due to the relative motion with the rotor,including the rotor core loss and the magnet eddy current loss.In addition,the heat dissipation condition of the motor’s rotor is usually very poor.These losses may cause irreversible thermal demagnetization of permanent magnets.Therefore,it is of great significance to study the rotor loss of fractional slot concentrated winding permanent magnet synchronous motor for the safe and efficient operation of the motor.Firstly,this paper deduces the magnetomotive force produced by the fractional slot concentrated winding in detail and analyses the characteristics of the harmonics of the magnetomotive force which lays the foundation for the analysis of the rotor loss.Then the principles to choose the pole number and slot number are provided.In order to solve the problem of higher rotor loss of single-layer fractional slot concentrated winding permanent magnet motor due to high content of harmonics,the stator winding is improved and the surface-mounted and interior permanent magnet rotors are designed.Based on the two-dimensional transient finite element method,the rotor losses with improved stator winding surface-mounted and interior permanent magnet motors under the optimal current control conditions are studied and compared with the traditional motor’s rotor loss.Also the effects of dq axis slotting and permanent magnet segments on the rotor losses are studied.