| Permanent magnet synchronous motors are favored by industry and academia due to their small size,light weight,and high efficiency,and have become a current research focus.At present,with the development of high speed and high power density of permanent magnet synchronous motors,the electromagnetic load and thermal load of the motor are gradually increasing,which often leads to a substantial increase in the operating temperature rise of the motor.Excessive temperature rise effects range from bad operating performance to safety issues.This problem has become a key factor restricting the better performance and broader application for such motors.Therefore,it is necessary to study the motor the internal loss distribution characteristics and explore the heat and mass transfer laws of the components inside the motor,analyze the influence of the structural size changes of the components on the loss and temperature rise,and give a reference to motor cooling design.This thesis takes a 50 k W permanent magnet synchronous motor as an example to analyze the influence of stator auxiliary slot size on loss and temperature rise:Firstly,this thesis takes a 50 k W permanent magnet synchronous motor as the research object.According to the original structure parameters of the motor,combined with the assembly relationship of the motor components,some simplified assumptions are made for some components while retaining the overall structural characteristics of the components.On the issue of equivalent stator windings,a layered equivalent model is established.According to the slot size,the equivalent size parameters are obtained after the establishment of computational equations.Based on these assumptions,a computational model of the original motor structure is established to offer physical support the temperature field analysis,making it easier to modify the stator auxiliary slot size.Secondly,according to the symmetry of the magnetic circuit of the motor,a 1/4two-dimensional solution model of the original structure of the motor is established through Boolean operation,reducing the computing time.Based on this,according to the slot size variation,the solution models under slot size variation are established,after performing Boolean operation on the stator teeth.The time-stepping finite element method is applied to calculate the electromagnetic field in models under each size.Analysis of loss distribution characteristic in the motor is performed considering independent effect of slot width and depth.The change laws of stator iron loss,permanent magnet eddy current loss and copper loss are studied.The influence of slot width and depth on different components' loss is clarified,laying the foundation for thermal field calculation.Finally,according to the three-dimensional solution model of the original structure,combined with the symmetry of the magnetic circuit and ventilation structure,the Boolean operation is utilized to establish a half-domain model of full axial length and 1/2 circumferential area.The corresponding solution models for different size schemes are established according to the slot size.In the light of calculation results of the electromagnetic field,heat generation rate in heat-generating parts of the motor are applied as the heat source of the temperature field.The finite volume method is applied to compute the thermal field under each size.The temperature rise distribution law of internal components in the motors with variant slot sizes is revealed,by comparing the temperature rise of the entire motor,stator core,windings,end air cavity,and rotor under slot width and depth variation separately.The impact extent of slot size on temperature rise distribution of each component is clarified.By evaluating the highest and average temperature rise of the components in each scheme,the best heat dissipation scheme was obtained. |
PDF Full Text Request