Influence Of Rotor Structure Of High-Speed Permanent Magnet Synchronous Motor On Multi-Physics Field

High Speed Permanent Magnet Synchronous Motor(HSPMSM)has the advantages of high power density,high efficiency and fast dynamic response,so it is widely used in high speed grinder,flywheel energy storage system,high speed centrifugal compressor and other fields.However,the ultra-high speed of the HSPMSM makes the design and analysis of the HSPMSM have some new features,such as the high frequency of the HSPMSM makes the time and space harmonics are much greater than that of the conventional permanent magnet motor,resulting in a large eddy current loss on the rotor surface.In addition,it also leads to poor cooling and heat dissipation conditions of the rotor.In a comprehensive consideration,the high temperature rise of the rotor of the HSPMSM can easily cause the high temperature magnetic damage of the permanent magnet.Therefore,the accurate calculation of the rotor eddy current loss and the accurate analysis of the rotor temperature field are of great significance for the design of the HSPMSM.Secondly,the centrifugal force on the surface of the rotor is large when the rotor rotates at high speed.The conventional permanent magnet sleeve scheme cannot satisfy the safe and stable operation of the permanent magnet rotor.,and may even cause permanent magnet fracture and sleeve deformation.Therefore,it is urgent to carry out in-depth research on the rotor sleeve structure scheme of HSPMSM to ensure the safe and stable operation of rotor and permanent magnet.In addition,the HSPMSM has a wide operating frequency and needs to pass through a large frequency band from start-up to stable operation.In this process,the HSPMSM is extremely prone to resonance.If it cannot pass through the resonance frequency domain quickly,it will easily cause the resonance deformation of the rotor body and induce the rotor scanning and boring failure.Therefore,the rotor dynamics analysis in the full frequency domain of the HSPMSM is carried out to provide data support for the start and operation control of the HSPMSM.In view of the above problems,the thesis focuses on the simulation analysis of the electromagnetic field,temperature field,stress field and rotor dynamics of the HSPMSM.The specific contents are as follows.Taking a 200 kW,15 000 r/min high-power HSPMSM as an example,the thesis establishes a two-dimensional transient electromagnetic field mathematical analysis model.The rotor sleeve is discretized by radial equal-ratio asymptotic method.The above-mentioned analytical model is used to calculate accurately the loss distribution of each component of the motor,and the influence of sleeve thickness on the loss distribution of the rotor is studied.On this basis,the mathematical analysis model of the global temperature field of HSPMSM is established.The influence of different air gap length and temperature on the equivalent thermal conductivity of air gap under high-speed rotation is studied.The calculated equivalent thermal conductivity of air gap is used to study the rotor temperature field of HSPMSM.The results show that the equivalent thermal conductivity of the air gap decreases with the increase of the air gap temperature and the decrease of the air gap length.Finally,it studies the influence of sleeve thickness on temperature distribution in the motor.A three-dimensional mathematical model of mechanical stress field of HSPMSM was established to solve the stress safety problem of surface-mounted rotor structure designed by the combination of circumferential partitioned permanent magnet and austenitic stainless-steel sleeve.The effects of the number of axis-circumferential partitioned permanent magnet on the structural strength of permanent magnet and the stress of each component of the motor rotor were studied comparatively.On this basis,the structure of permanent magnet with 10 axially and 2 circumferentially is adopted to further study the influence of the matching size of permanent magnet and sleeve,motor speed and sleeve thickness on the stress distribution of each component of motor rotor.The safety threshold values of austenitic stainless-steel sleeve and permanent magnet stress are determined,which provides a reference for the subsequent design of high-speed motor.Aiming at the problem that the rotor of a HSPMSM needs to pass through a large frequency band from start-up to stable operation,which is prone to resonance and induces boring and sweeping faults,a mathematical model for analyzing the dynamic characteristics of the rotor of the HSPMSM is established.By comparing and analyzing the Campbell diagram of the rotor structure of the motor with different jacket thicknesses the critical speed of the rotor structure and its corresponding modal changes are studied.The modal analysis of a 50kW,30000r/min HSPMSM is carried out to verify the correctness of the simulation results.