Research On Stator Iron Loss And Temperature Distribution Characteristics Of Low Temperature And High Speed Permanent Magnet Motors

The application of low-temperature high-speed permanent magnet motors in LNG pumps has advantages such as high power density,high reliability,and strong adaptability.However,changes in the mechanical and electromagnetic properties of motor materials in low-temperature environments have a significant impact on the strength,electromagnetism,and temperature of the motor,requiring recalculation and analysis.This dissertation focuses on the above issues and takes a 40 k W,35000r/min low-temperature high-speed permanent magnet motor as an example to study its rotor strength,stator core loss,and motor temperature.On the basis of considering the influence of temperature,an analytical model and a three-dimensional finite element simulation model for the stress of the motor rotor were established.The stress distribution of the rotor in low and high temperature environments was obtained using these two methods,and the correctness of the calculation results was verified through comparison;Based on the finite element method,the variation law of the strength of permanent magnets and rotor shielding sleeves under different rotational speeds and temperatures was studied,and the working conditions towards the critical strength of the material were determined.At this limit working condition,the influence of shielding sleeve thickness and interference on rotor strength was analyzed,and the feasible range of shielding sleeve size was further determined.To address the issue of changes in the electromagnetic properties of motor materials in low-temperature environments,based on a finite element simulation model,the no-load air gap magnetic density and load torque changes of the motor at low and room temperatures were compared,and the magnetic field distribution characteristics of the stator core of the low-temperature motor were studied;On this basis,the variable coefficient iron loss model considering skin effect is selected to improve the fitting accuracy of silicon steel sheet loss curve,and the iron loss calculation model considering rotating magnetization and harmonic effect is used to calculate the stator core loss;Further elaborated on the distribution characteristics of stator iron loss and the impact of low temperature on iron loss.The low-temperature high-speed permanent magnet motor works in LNG fluid.Considering the influence of low-temperature fluid on the temperature distribution of the motor,the temperature field of the motor needs to be studied;On the basis of calculating the heat generation rate of each component based on the finite element method,the thermal conductivity of the core silicon steel sheet is equivalent to the windings and insulation in the stator slot,and a three-dimensional fluid solid coupling solution model considering the rotor rotation is constructed,which further reveals the temperature Degree distribution distribution law of the fluid and key components in the motor.The research content of this dissertation can provide reference for the research of low-temperature high-speed permanent magnet motors used in shielded LNG pumps.