Research On Temperature Rise Of Permanent Magnet Canned Motor Based On Thermal Network Method

Canned pump is the combination of pump and motor.The cans play the role of separating the transport medium and motor body,and the quality of the canned motor determines the quality of the canned pump.Because of its special physical structure,the canned motor needs to ensure the airtightness in the working process,which leads to a large eddy current loss at the cans.The eddy current loss of the cans accounts for about 30%-40% of the total loss,which leads to a great decline in the efficiency of the motor.At the same time,because of the canned eddy current loss,the temperature rise of the canned motor is also larger than that of the ordinary motor.Therefore,this paper takes the permanent magnet canned motor as the research object,and takes the research of temperature rise as the goal.It conducts in-depth research from four aspects: the calculation of eddy current loss of the cans,the improvement of the thermal resistance of the cans,the simplification of the thermal resistance of the stator slot,and the coupled calculation method of temperature field and flow field of electric machine based on finite volume method.According to the law of electromagnetic induction,the loss expression of the cans is obtained,and the eddy current loss in the cans is calculated and analyzed by using the finite element method.A calculation method of canned loss considering the influence of temperature is put forward.With the method obtained,the canned loss of different sizes and materials is calculated and analyzed.At the same time,the influencing factors of canned loss are discussed,and the methods to reduce canned loss are proposed.The losses of each part of the permanent magnet canned motor obtained from electromagnetic analysis are taken as the heat source,and the thermal network model of the permanent magnet canned motor is built.On the premise of considering the uneven heat dissipation of the cooling water channel,the calculation formula of the thermal resistance is improved,and the corresponding thermal resistance is corrected according to the heat dissipation of the cooling water channel.Based on the original thermal network model,the optimization and improvement are made.In order to verify the accuracy of the thermal network model and its optimization model of the permanent magnet canned motor,the simulation of the temperature field was carried out.Taking the losses of each part of the permanent magnet canned motor as the heat source,the temperature distribution of each part of the motor in the axial direction is calculated,and the effects of the cooling fluid flow rate,the thickness of the cans,the power factor angle,the core lamination coefficient and the residual magnetic flux density of the permanent magnet on the temperature of each part of the motor are analyzed.The research results have certain significance for the loss calculation and temperature rise optimization of the permanent magnet canned motor.