Design And Analysis Of High Speed Permanent Magnet Synchronous Motor For Flywheel Energy Storage System

Flywheel energy storage system is a kind of mechanical energy storage device.It has the advantages of high energy storage density,high efficiency,fast response,long service life,maintenance-free and other significant advantages.It has been used in transportation,new energy power generation,aerospace,uninterruptible power supply and other fields,the development prospect is good.Motor is the core of energy conversion in flywheel energy storage system,which has a great influence in system performance.Since the 1990 s,with the great breakthrough in flywheel rotor materials,bearings and power conversion devices,the flywheel energy storage system begins to develop towards the high speed flywheel energy storage system.However,the unique vacuum operating environment and working mode of the flywheel energy storage system put forward some special requirements for the motor,and there are also some key problems in the high speed motor itself.In this paper,a 250 k W,12000r/min high speed permanent magnet synchronous motor for flywheel energy storage system is taken as the research object,and the electromagnetic design,loss and temperature field calculation,rotor strength and other aspects are studied and analyzed.The main research contents of this paper are as follows:Firstly,according to the design requirements of the motor for flywheel energy storage system and the design method of the high speed permanent magnet synchronous motor,the motor scheme is designed,including the choice of stator inner and outer diameter,the choice of air gap length,the choice of the number of rotor poles,the choice of the pole slot match,the stator slot design,the design of stator winding,the choice of the rotor structure,the choice of materials,and so on.The design of 250 k W and 12000r/min high speed permanent magnet synchronous motor is completed,then,the electromagnetic characteristics of the motor are simulated and analyzed with ANSYS finite element analysis software to verify the rationality of the motor design scheme.Then,the loss of motor for flywheel energy storage system is analyzed.The magnetic flux frequency of high speed motor is high.And the flywheel energy storage system operates in maintenance mode most of the time.The loss is mainly concentrated in the core loss of the stator.The orthogonal decomposition iron loss model is used to analyze and calculate the iron loss.At the same time,the iron loss,copper loss and rotor eddy current loss are analyzed and calculated by ANSYS finite element analysis software.Because the motor runs in a vacuum environment and adopts magnetic suspension bearings,the wind friction loss and mechanical friction loss of the motor can be ignored.In order to verify whether the efficiency of the designed motor reaches the design index,the changes of various motor losses when the motor completes a complete working cycle with rated power are analyzed.In order to verify whether the temperature rise of the designed motor is within a reasonable range,the calculated loss is taken as the heat source to further analyze the temperature field of the motor.Finally,high rotor speed of high speed motor leads to large centrifugal force.And the permanent magnet has a poor ability to bear the tensile stress.In order to verify the reliability of mechanical performance of motor rotor,the strength of motor rotor was analyzed by ANSYS finite element analysis software.In addition,because the motor is connected with the flywheel coaxially,the common flywheel rotors are analyzed,and the rotor dynamics of flywheel shafting is discussed.