Research On The Influence Of Sheath Structure On Rotor Loss And Temperature Rise Of External Rotor Permanent Magnet Motor

Permanent magnet synchronous motors are widely used in various fields due to their high performance,stable operation and miniaturization.The rotor part of the outer rotor motor is located outside the motor and has good heat dissipation effect.The problems caused by its temperature rise are often ignored.However,the outer rotor permanent magnet synchronous motor itself has the characteristics of high loss density,and the outer sheath structure of the surface mounted permanent magnet is not conducive to the heat dissipation of the permanent magnet,so it is necessary to discuss the rotor loss and temperature rise of the outer rotor permanent magnet motor.In this dissertation,for the outer rotor permanent magnet synchronous motor rotor,which has the characteristics of high loss density,the structure of rotor sheath with spiral groove is proposed and analyzed.By using this structure,the eddy current loss of rotor sheath can be reduced while the heat dissipation of the motor can be improved,and the eddy current loss of rotor sheath under different number of spiral groove rings can be calculated.At the same time,the eddy current loss of the rotor sheath under different circumferential segments,axial segments and circumferential groove rings is calculated,and the above calculation results are compared with the eddy current loss of the rotor when the sheath has spiral groove.Then the eddy current loss of rotor with or without copper sheath is calculated,and the influence of copper sheath on the eddy current loss of rotor is analyzed in detail.The eddy current loss of the permanent magnet without sheath is calculated under the condition of different circumferential segments,different axial segments and axial uneven segments.The influence of different segments of the permanent magnet on the eddy current loss of the rotor is compared and analyzed.In this dissertation,the fluid field around the motor is studied under the structure of rotor sheath with spiral groove.Under the condition of keeping other variables unchanged,the fluid field around the motor with different width of spiral groove and different ring number of spiral groove is calculated,and the calculation results are compared with the calculation results around the motor without spiral groove of rotor sheath.The influence of these two variables on the distribution of fluid velocity around the motor is analyzed.Determine the loss data of the motor,and through the establishment of the fluid solid coupling model of the outer rotor permanent magnet synchronous motor,calculate the temperature field of the outer rotor permanent magnet synchronous motor in detail,and calculate the temperature rise of the motor when the rotor sheath is opened with different width of spiral groove,and compare and analyze the influence of the width of the rotor sheath opening spiral groove on the temperature rise of the motor.