Cooling System Design And Thermal Analysis Of New Hybrid Excitation Synchronous Motor

Compared with traditional permanent magnet motor,the excitation magnetic source of hybrid excitation motor consists of permanent magnet and electric excitation winding.It has the advantages of uniform and adjustable electromagnetism,wide adjustable speed range and high power density.It has a broad application prospect in new energy electric vehicles,wind power generation and other fields.The armature winding and excitation winding of the hybrid excitation synchronous motor studied in this thesis are set in the stator slot.The amorphous alloy modular stator teeth and yoke are modular spliced with dovetail slots.In order to provide axial magnetic flux path,the stator teeth are stacked in the axial direction and the stator yoke is wound in the radial direction.It is difficult for the stator and rotor to dissipate heat,because the thermal conductivity of the amorphous alloy is small in the stacking or winding direction,Therefore,it is very important to design a cooling system with high heat dissipation efficiency to reduce the temperature rise of the motor and improve the reliability of the motor.Firstly,this thesis introduces the structure and operation principle of the new hybrid excitation synchronous motor,designs a 100 k W hybrid excitation synchronous motor,analyzes its electromagnetic field,and obtains the three-dimensional empty load air gap magnetic density distribution under the rated operation,maximum magnetization and maximum demagnetization conditions.The stator iron loss and permanent magnet eddy current loss of the motor are calculated by the finite element method,and the variation curves of stator yoke iron loss,stator tooth iron loss and ferromagnetic pole iron loss with time under the rated operation state are obtained.The influence of axial segmentation of permanent magnet on eddy current loss of permanent magnet is analyzed.The stator iron loss,permanent magnet eddy current loss,ferromagnetic pole loss,armature winding copper loss and excitation winding copper loss under three operating conditions are calculated.Then,the AC and DC windings in the stator slots of the motor are equivalent,and the three-dimensional temperature field calculation model of the motor is established.The temperature field under the natural heat dissipation condition of the motor is calculated by using the computational fluid dynamics（CFD）method,and the heat transfer characteristics of the motor are analyzed.According to the heat transfer characteristics of the new motor,the water-cooled plate cooling system is designed,the structure of the water-cooled plate cooling system is introduced,and the influence of different water-cooled plate thickness and the number of water channels on the heat dissipation capacity is analyzed.The influence of different inlet flow velocity on the maximum temperature rise of each part of the motor is calculated when the water-cooled plate thickness is 15 mm and 20 mm,and the optimal water flow under different water-cooled plate thickness is obtained.The maximum temperature rise of each part of the motor under the same water flow is compared and analyzed between the water-cooled plate cooling structure and the traditional shell spiral water jacket cooling structure,it is proved that the water-cooled plate cooling can effectively reduce the temperature rise of each part of the motor.In order to further reduce the temperature rise of the rotor,an air-water composite cooling structure is designed based on the water-cooled plate cooling structure.The internal air path and internal fan of the air-cooled structure are analyzed respectively,and the maximum temperature rise of each component under the air-water composite cooling structure and the water-cooled plate cooling structure is compared and analyzed.Finally,according to the heat source distribution and structural characteristics of the motor,the equivalent thermal network model of the motor under air-water composite cooling is established.The convection heat dissipation coefficient required for calculating the thermal resistance is analyzed by CFD method.The temperature rise of each component of the motor is calculated by programming.The calculation results are compared with those of CFD method,which proves the accuracy of the calculation results of equivalent thermal network method.