Motor Design And Torque Optimization Of Low-Speed High-Torque Permanent Magnet Synchronous Motor

Aiming at the direct-drive traction low-speed and high-torque permanent magnet synchronous motor for drilling,considering that the application requires large and stable torque,this dissertation takes a 48-slot 40-pole 160kW low-speed and high-torque permanent magnet synchronous motor as the research object.In the motor design process the different tooth widths of the stator are used to weaken the cogging torque and the opening of the rotor yoke to increase the electromagnetic torque to improve the torque characteristics of the motor.The research work of this dissertation is mainly focused on the following aspects:First of all,the main size of the motor was determined according to the performance constraints of the drilling traction occasion,the stator and rotor structure design is carried out,and the pole slot when the fractional slot concentrated winding was used was studied.In accordance with the selection principle,the length of the magnetizing direction of the permanent magnet and the width of each pole of the permanent magnet were selected according to the maximum demagnetization operating point of the permanent magnet and the no-load back EMF,and then the design plan was given and the prototype is manufactured.The parameters and performance indicators such as power factor,efficiency and electromagnetic torque were compared and analyzed through experiments.Secondly,Fourier decomposition was performed on the air gap flux density of the motor and an analytical formula for cogging torque under unequal tooth width was derived.The corresponding number of poles under each slot is an integer and a fraction and the unit motor The total cogging torque in the case of a non-unit motor.The stator slot grouping method was proposed and the offset method was given to realize the unequal tooth width of the stator.The finite element method was used to verify the effect of unequal tooth width on cogging torque.It was found that unequal tooth width could effectively weaken the cogging torque.The variation law of the weakening effect of the cogging torque with the offset angle of the stator teeth and the optimal offset angle are obtained.Finally,according to the mechanism of electromagnetic torque generation,the quadrature axis inductance is increased by opening a hole in the rotor yoke without affecting the direct axis inductance to increase the electromagnetic torque.The finite element method was used to analyze the influence of the shape,size and quantity of holes on the electromagnetic torque,and the optimal hole shape and size were given.Combining the two schemes of unequal tooth width and rotor yoke opening,optimize the motor design,analyze its electromagnetic performance and compare it with the original prototype,and verify that the unequal tooth width and rotor yoke opening can suppress torque ripple and torque Improved effectiveness.After that,the stator solid-state frequency and rotor mechanical strength of the optimized scheme were analyzed,and it was proved that the mechanical strength of the optimized motor meets the requirements and the scheme was feasible.