Design Of Ultra High Speed Permanent Magnet Synchronous Machine

Ultra-high speed permanent magnet synchronous machine(PMSM)is widely used in micro gas turbines,flywheel energy storage,dental bearings,vacuum cleaners,centrifugal compressors and other fields because of its high efficiency,high power density,small size and being directly connected to load.This article takes a 1k W,500,000r/min ultra-high-speed PMSM as the design goal,analyzes the electromagnetic parameter design,rotor mechanical characteristics analysis,loss calculation and thermal field simulation.The main research contents are as follows:In view of the characteristics of high frequency and high speed,this paper analyzes the stator material and structure which are suitable for ultra-high frequency operation.The design process of machine parameters is determined by means of analytical method and finite element method,and the design results of three different rotor structures are given.The electromagnetic performance of the above three types of rotor structures under no-load and rated load is analyzed and compared by using Maxwell finite element software..The compressive and non-tensile characteristics of the permanent magnet make the strength of the ultra-high speed rotor very high,and the working speed of the slender rotor system needs to be far away from the critical speed.Therefore,this paper analyzes and verifies the mechanical characteristics of the ultra-high speed rotor from the aspects of the rotor strength and mode analysis.Based on the basic theory of elasticity mechanics,the rotor strength of solid permanent magnet is modeled mathematically.At the same time,the influence of temperature,rotation speed,static interference,inner diameter of permanent magnet,sheath thickness and sheath material on the rotor stress of solid,hollow and surface mounted permanent magnets is analyzed by finite element method,and the rules of rotor strength size design and stress check of rotor is summarized.According to the above analysis results,the solid permanent magnet is selected as the rotor of the final prototype,and the rotor strength is further checked by the analytical method and the finite element method.In addition,considering the slender characteristics of the ultra-high speed rotor,the paper calculates the critical speed of the flexible rotor,and analyzes in detail the change law of the critical speed of the flexible rotor considering the factors of the rotor structure,size and bearing stiffness,so as to ensure that the rotor system is in the safe speed range..This paper analyzes the loss calculation and temperature field simulation of the motor.In the aspect of stator loss,the finite element method is used to calculate the stator copper loss and core loss,and the influence of stator material and power supply mode on the loss value is considered.In the aspect of rotor loss,the eddy current loss of the rotor under different power supply mode,sheath material and sheath thickness is analyzed,and the wind friction loss of the cylindrical rotor is calculated by the classical calculation formula.Finally,the loss calculation results are used as the heat source,and the three-dimensional temperature field model of the machine is established with ANSYS Workbench software.The results show that the prototype can work normally within the material limit temperature.