Calculation And Analysis Of Electromagnetic And Temperature Fields Of Servo Permanent Magnet Synchronous Motor

Servo permanent magnet synchronous motor has simple structure,reliableoperation, high efficiency, high power factor, fast response speed, high overloadcapacity, etc, it conforms to the development direction of high efficiency andenergy saving motor and is being widely used in CNC machine, robot industries.It is necessary that a controller supplies electric power for servo permanentmagnet synchronous motor, but the controller will increase current harmoniccontent. The harmonic current will cause loss increase, and reduce the efficiencyfor the motor, which makes the temperature of the motor rise accordingly. Toohigh temperature will bring the performance of the permanent magnet down, andeven could lead to permanent magnet demagnetization and motor will be not ableto work properly, reduce the running performance of the motor, shorten theservice life of the motor, so it is very important for study of electromagnetic fieldand temperature field of the servo permanent magnet synchronous motor.In this thesis, electromagnetic field and temperature field of servopermanent magnet synchronous motor used for injection molding machine isstudied. This paper take a12.5kW,8servo permanent magnet synchronousmotor as an example for analysis. Firstly, the structure of the machine is simplyexpounded. Temperature of winding and armature current were simply testedwhen the prototype was at rated load, on the basis, the harmonic content of theexperimental current is analyzed. Second,2D transient electromagnetic fieldmodel is established by the structure and dimensions of the motor. Two-dimensional transient electromagnetic field model was solved through the finiteelement method. Eddy current loss brought by different harmonic currents in thesheath are analyzed, and the eddy current loss effect of the sheath resulted in the measured harmonic current is got. And then the cogging torque is analyzedfor the different rotor structures. In order to accurately calculate the eddy currentloss in the sheath, when the sheath the prototype use sectional type, three-dimensional transient electromagnetic field was calculated, and the results areanalyzed. Finally, the sheath structure is improved.Too high temperature rise influence the performance of the motor, so aimingat the possible problem of higher permanent magnet temperature rise, twodimensional temperature field of permanent magnet motor was calculated andanalyzed. Under considering eddy current loss produced by the harmonic currentin the sheath, temperature field distribution of the motor were analyzed when thesheath use different segmented structure, especially the temperature fielddistribution of permanent magnet, in order to illustrate the rationality of thedesign of the motor. The simulation results compared with the experimentalresults, which proved the loss calculation result is reliable. Through calculationand analysis of electromagnetic field and temperature field, the conclusion givean important reference to the servo motor designers.