Study Of Electromagnetic Design And Rotor Structure For High Speed Permanent Magnet Motor

High speed permanent magnet motor(HSPMM)with merits of high efficiency,high power density and compact structure,which makes it more and more widely used in industrial drive,aerospace and other fields.The high power supply frequency of HSPMMs results in large loss in the stator region,small size of the motor and difficulty in cooling the stator,which may lead to excessive temperature rise in the motor,resulting in irreversible demagnetization of the rotor permanent magnet.At the same time,the high-speed rotation of the rotor brings large centrifugal force,which puts forward higher requirements for the strength of the rotor and the protection of permanent magnets.In addition,the resonance of the rotor system may lead to the unsafe operation of the motor.Therefore,reasonable electromagnetic design and rotor structure research of HSPMM are of great significance to the safe operation of high speed motor.Firstly,the background and the current research status of HSPMM were summarized.In order to solve the problem of large magnetic leakage and poor mechanical properties of the built-in HSPMM,the electromagnetic design and rotor structure of the HSPMM were studied.According to the characteristics and design indexes of HSPMM,the stator and rotor structure design of the motor was carried out,including the determination of the main size of the motor,the selection of rotor pole number,the selection of permanent magnet materials and the selection of stator winding form.The electromagnetic verification was carried out using the circuit calculation formula,and the design scheme of the motor was determined.According to the design scheme of the motor,the equivalent analysis model of the rotor strength was established.According to the analytical calculation formula of rotor strength,the maximum stress of the rotor at rated speed was calculated.The finite element analysis model of motor rotor strength was established,and the finiteelement calculation results and the analytical calculation results were compared.The influence of rotor pole structure on the rotor stress was analyzed.The influence of the number of permanent magnet blocks and the size of stiffeners on the maximum stress of the rotor and the magnetic leakage coefficient of the rotor was analyzed.An improved built-in rotor structure was proposed.The rotor strength and electromagnetic performance of the new rotor structure were verified by finite element method,and the effect of motor speed on rotor stress was analyzed.According to the improved rotor structure scheme,the simplified analysis model of rotor stiffness was established,and the analysis calculation of the rotor stiffness was carried out.The maximum deformation of the rotor was calculated.The finite element analysis model of the rotor stiffness was established,and the finite element calculation results and analytical results were compared.The dynamic model of the rotor system was established,and the modal analysis of the rotor was carried out.The natural frequency and critical speed of the rotor were obtained.The influence of the rotor structure on the critical speed was analyzed,and the variation rule of the first critical speed with the extension length of the shaft was obtained.