Design Of Novel Reverse Salient Pole Permanent Magnet Synchronous Motor

Different from traditional electric excitation synchronous motor,permanent magnet motor uses rare earth permanent magnet as the excitation source,which has the advantages of light weight,high power density,simple structure and low rotor side losses.Therefore,it is widely used in the industrial field,especially PMSM with salient pole effect,which is easy to expand the speed of weak magnetic field and has a wider range of speed regulation.Because the permanent magnets are placed inside the rotor of traditional salient pole PMSM,the d-axis magnetic resistance is larger than the q-axis magnetic resistance,while the d-axis inductance is smaller than the q-axis inductance.When the power angle is less than 90°,the reluctance torque component is negative,and the maximum value of torque appears between 90°and 180°.Therefore,there is a certain risk of demagnetization of permanent magnets when the motor is under load or overload operation.In addition,the q-axis magnetic circuit of the motor is relatively easy to saturate in this state,which will increase the core loss,resulting in the decrease of the efficiency of the motor.In this thesis,the basic theory of PMSM is firstly analyzed,and a novel reverse salient pole PMSM is proposed based on the conventional salient pole PMSM.Secondly,a novel reverse salient pole permanent magnet synchronous motor with a capacity of550W is designed by using the magnetic circuit analysis method.The finite element software Ansoft was used to simulate and analyze two kinds of motors.The air-gap magnetic density,back-EMF,d-q axis inductance characteristics,and torque angle characteristics of the two motors are obtained.The analysis results show that compared with conventional salient pole PMSM,the novel reverse salient pole PMSM has less air-gap magnetic density and back-EMF harmonic content,and the waveform is closer to a sine wave.At the same time,the reverse salient pole characteristic(L_d>L_q)is shown by the new motor.Thirdly,from the analysis speed,torque curves and losses of the two motors under no-load and rated load,it can be seen that speed and torque ripple of novel reverse salient pole PMSM are smaller than that of conventional salient PMSM in the steady state,and the loss and efficiency performance are more superior.Prove the correctness and superiority of the new structure motor proposed in this thesis.Finally,some basic performance tests were carried out on the prototype of the new motor,which verified the correctness of the simulation analysis.Using Workbench software to analyze the temperature field of two motors.Firstly,the heat generation rate of each part is calculated according to the copper and iron losses under the rated load obtained by electromagnetic field simulation.Then,the thermal conductivity of each part material and the heat dissipation coefficient of different surfaces are determined by formula calculation and other references.Finally,the steady-state temperature field distribution under the rated load of the two motors is obtained by finite element solution.Because six semi-circular air slots are opened on the rotor core side of the novel reverse salient pole PMSM,which facilitates the heat dissipation of the rotor and plays a role in reducing the temperature of the motor.Therefore,it can be seen that the temperature of the novel reverse salient pole PMSM is lower than that of the conventional salient pole PMSM,which protects the important components such as permanent magnets and stator windings of motor.Showing the superiority of the new structure motor in heat dissipation performance.The thesis has 59 figures,10 tables,and 73 references.