Research On Hybrid Rotor Structure Of Permanent Magnet Motor For Screw Pump

Currently,the main trend in oil extraction is the use of permanent magnet motor direct drive screw pumps,due to the use of permanent magnet excitation,higher power factor than asynchronous motors,and the use of direct drive reduces the intermediate device,with the advantages of reliable operation and simple structure.However,the price of rare earth permanent magnet materials,which are strategic materials,is increasing in recent years,causing higher motor costs and bringing uncertainty to motor manufacturing.Therefore,in the field of permanent magnet motors,the use of rare earth-free and rare earth less permanent magnet materials has become a research direction,and the use of hybrid rotor structure using more ferrite and a small amount of Nd Fe B permanent magnet materials can reduce the motor cost and the motor performance is better.The research content of this thesis is as follows:Firstly,two types of single-pole motors,surface-type Nd Fe B permanent magnet motors and built-in ferrite permanent magnet motors,are designed to improve motor performance by optimizing parameters such as rotor opening slot width,spacer bridge,and permanent magnet size,so that the performance of built-in ferrite motors can be improved and compared with the performance obtained from surface-type permanent magnet motors.Then,due to the poor electromagnetic performance of the built-in ferrite motor,a hybrid rotor structure is considered to improve the motor performance.The influence of the length of magnetization direction of the permanent magnets on the air gap magnetic density,cogging torque and torque fluctuation is compared and analyzed,and the change law is analyzed.Considering the small length of Nd Fe B magnetization direction and analyzing its anti-demagnetization ability.Finally,based on the motor design requirements,the design of the permanent magnet motor is carried out,comparing the characteristics of air gap magnetic density,counter-electromotive force and tooth slot torque under different pole-slot fits,as well as optimizing the size of air gap length and stator inner diameter,analyzing the electromagnetic characteristics of the motor,and verifying the correctness and reasonableness of the design method of this type of motor by comparing the design value with the experimental value of a Nd Fe B permanent magnet motor for a surface screw pump.Finally,the mechanical strength of the motor is analyzed.