Optimal Design Of Rotor Geometry In Interior Permanent Magnet Machine To Broaden Speed Range

Permanent magnet synchronous motor?PMSM?has so much advantages,including small size,light weight and high-power factor,which make it widely used in ship propulsion,locomotive traction,aerospace and other fields.With its unique magnetic circuit structure,the interior permanent magnet synchronous motor?IPMSM?makes the magneto-resistance of the d-axis magnetic circuit greater than that of the q-axis magnetic circuit,thus producing the magneto-resistive torque.Therefore,compared with the surface PMSM,IPMSM has a wider constant power range of speed and excellent speed expansion capability of flux-weakening,which make IPMSM suitable for electric vehicle environment of low-speed and large-torque,high speed constant power wide range.However,the flux of permanent magnet is difficult to attenuate,which restricts the further increase of speed to some extent.Therefore,a series of researches are carried out to improve the speed range of the IPMSM from the point of view of body design.The mathematical model of d-axis and q-axis of PMSM is introduced.Furthermore,the operation principle of motor is analyzed,including the maximum torque per ampere control operation principle below the base speed and the flux-weakening control operation principle above the base speed.The relationship between the torque,current,voltage and speed of the motor is derived,and the relationship between the ideal maximum speed and parameters of the motor is obtained.It provides a theoretical basis for improving the motor structure.An 20kW IPMSM with V-shape permanent magnet has been researched and an improved rotor structure which conclude segment permanent magnet and protrudins from centers of every magnetic poles toward air gap has also been proposed.Meanwhile,the Taguchi method is utilized to optimize this structure.Finally,the latest optimized structure has been validated by finite element method.By comparing the optimized rotor structure with the initial structure,the d-axis inductance is effectively increased,the speed range is also greatly increased,and the electromagnetic torque ripple and the cogging torque are reduced to a certain extent.The sinusoidal property of air gap flux density of optimized is better than that of initial structure,and the main harmonic frequency(3^rd,5^th,7^th)is obviously decreased.The finite element model of the motor in ANSYS Maxwell environment,the power loop model in ANSYS Simplorer environment,and the flux-weakening control strategy model in Simulink are built,respectively.Meanwhile,the speed of simulation can be accelerated by replacing the traditional finite element model with ECE scanning model of motor.In fact,The ECE model is in good agreement with the finite element model.Then,the ECE model,the power loop model and the control strategy model are organically combined to realize the co-simulation of the 20kW IPMSM under the flux-weakening control including the latest optimized structure and the initial structure.Finally,the effectiveness and rationality of the proposed improved structure are verified by the co-simulation results.