Thermal Analysis Of High Speed Permanent Magnet Motor For Flywheel Energy Storage System

In order to improve the quality of power supply to the communication system,computer systems,precision medical devices,semiconductor manufacturing who demand for high power quality,various uninterruptible power systems are widely used.Compared with traditional chemical battery,flywheel energy storage system has the advantages of fast charging and discharging,high power,high efficiency,Suitable for frequent charging and discharging,long service life and easy maintenance,is widely used in uninterruptible power systems.Because high speed permanent magnet synchronous motors has the advantages of small size,high power density and high efficiency,they are very suitable for flywheel energy storage system.The temperature rise and temperature field distribution will directly affect the performance and reliability of the motor.In the operation of high speed motor,rotor loss created by time and space harmonics of stator winding current can not be ignore.Considering the motor rotor is arranged in the stator,heat dissipation condition is very limited,So the gradual accumulation of its losses may lead to greater temperature rise of the rotor.Because the Curie temperature of the permanent magnet is relatively low,high temperature may lead the magnetism loss of permanent magnet.This not only affects the performance of the motor,but also affects the service life and reliability of the motor.In this paper,a 150kW/9000r/min permanent magnet synchronous motor is studied.The simulation of electromagnetic field and temperature field of the motor are carried out.According to the principle of thermodynamics,the heat transfer mode and the heat dissipation coefficient of each surface of the motor are determined.The loss and temperature distribution of the motor are analyzed in the no-load state.Considering the structure of the rotor of interior PMSM,sleeve is not necessary and the coating on the surface of permanent magnet is not thick enough,so a thin copper plate is covered on the surface of the permanent mag-net to reduce the eddy current loss of permanent magnet.The rotor stable temperature is reduced by 30.6%.Finally,the experimental platform of the motor no-load temperature rise is set up,the validity of the simulation results is verified by experiments.