Heat Flow Path Planning Of High-Voltage Solid-Rotor Line-Starting Permanent Magnet Synchronous Motor

High Voltage Solid Rotor Line Start Permanent Magnet Synchronous Motor(HVSRLS-PMSM)combines the line start characteristics of industrial induction motors with the high efficiency and high power factor of permanent magnet synchronous motors.The inverter necessary for the permanent magnet synchronous motor is saved.The HVSRLS-PMSM is to replace the industrial induction motor,which can effectively improve the energy utilization rate in the industrial field and save a lot of energy;compared with the permanent magnet synchronous motor,it saves a lot of materials and supporting equipment,and greatly reduces the cost.The HVSRLS-PMSM needs line start by means of the induced eddy current in the solid rotor,but in steady state operation,the eddy current loss caused by the high-order harmonic magnetomotive force in the solid rotor is much larger than that of the ordinary induction motor,resulting in the motor temperature is high,especially the rotor temperature is high.If the heat flow path is improperly designed,it is easy to cause high-temperature demagnetization of the permanent magnet.In severe cases,the inner winding of the motor is thermally aging,and even the motor is burnt.Therefore,the development of heat flow path planning in the motor is of great significance for the safe and stable operation of the HVSRLS-PMSM.In this dissertation,a 315kW,6000V,air-cooled internal and external dual-channel ventilation and cooling system of HVSRLS-PMSM is used as the example object,to establish the equivalent fluid network model of the internal circular single/dual asymmetric ventilation cooling system.The flow rate and flow velocity of different positions in the system change,and the parameters such as inlet flow rate and outlet pressure of the HVSRLS-PMSM ventilation system are determined.The fluid-heat transfer coupling calculation model of the motor and the cooler is established by the fluid-solid coupling method.The circulating air outlet parameters in the cooler are used as the air inlet parameters of the motor inner circulation.This method can effectively improve the complex three-dimensional global fluid.Coupling with heat transfer solves the calculation accuracy of the model,and greatly reduces the calculation of the HVSRLS-PMSM.However,the temperature of the air outlet of the cooler and the temperature of the air inlet of the motor cannot be accurately determined.In order to solve the above problems,a dual-port air temperature multiple iteration method is proposed.The internal magnetic-thermal double convergence iteration and the internal and external temperature iteration between the motor and the cooler are carried out until the given convergence accuracy is satisfied.At this time,the split body fluid-heat transfer coupling calculation model can be equivalent to the overall fluid-heat transfer coupling calculation model.In addition,the method fully considers the comprehensive influence of the temperature inside the motor on the conductivity,permeability,thermal conductivity of each structural member.The accuracy of the method is verified by comparing the experimental results with the calculated results.Finally,the fluid field and temperature field of the single/dual asymmetric ventilation cooling system motor are studied by using the established split body fluid-heat transfer coupling calculation model,revealing the single/dual asymmetric ventilation cooling system to the motor.The air velocity distribution,the temperature distribution of each structural part,and the influential law of the heat flow path are revealed.Aiming at the problem that the maximum temperature of the stator core and stator windings in the dual path asymmetric ventilation cooling system is too high and the axial temperature distribution is uneven that cause the local thermal stress too large,this dissertation proposed a plan:based on the dual-port wind temperature multiple iterative calculation method,a multiple branch channel heat flow path method is proposed.The influence of the number of stator radial ventilation ditch on the maximum temperature and axial temperature difference of stator core and stator winding in the motor are studied,and the reasonable value of stator radial ventilation ditch branch is determined.The influence of the unequal spacing(US)stator radial ventilation groove and the unequal width(UW)stator radial ventilation groove on the heat flow path in the motor are compared and analyzed;on the basis of analyzing the loss distribution and temperature distribution in the motor of different ventilation structures of the stator,the magnetic-thermal comprehensive evaluation coefficient is proposed to comprehensively measure the evaluation results of different ventilation structures on motor starting,running and heat dissipation.Aiming at the problem of excessive rotor temperature in solid rotor permanent magnet motor,the micro-circulation ventilation cooling structure of the rotor surface is proposed.The influence of the radial height of solid cage strip on the rotor surface heat dissipation coefficient and the maximum rotor temperature is studied.The starting ability of the motor,the eddy-current loss distribution of the rotor and the temperature distribution of each structural part of the solid rotor are compared and studied.The influence of the stator-guided magnetic conductive alloy wedge structure and material composition on the magnetic field distribution and starting performance of the motor are gradually worked out.And the influence of the electromagnetic characteristics of the stator wedge on the eddy-current loss distribution of the rotor is revealed,and the reasonable stator wedge structure and material composition which can effectively reduce the eddy current loss on the solid rotor surface are determined.Aiming at the problems such as high temperature rise of the motor,and large axial temperature difference,etc.,a multi-channel air-split supply and ventilation structure is proposed.The effects of split flow of the air supply duct to the radial branch air duct,air-gap duct and rotor of the stator shaft in the motor are studied.Also the influence of the fluid field and temperature field in the radial branching channel of the shaft are revealed by studying the influence of the split air supply ventilation structure on the heat flow path of the motor,and the heat flow path planning that can effectively reduce the temperature rise of the motor is determined.By studying the comprehensive influence of the axial relative position of the rotor radial ventilation groove and the stator radial ventilation groove on the temperature distribution inside the motor,the influential law of the axial relative position of the radial ventilation groove and the stator radial ventilation groove on the heat flow path of the motor is revealed.In order to further reduce the maximum temperature of the rotor,a hybrid ventilation cooling system combining the new rotor auxiliary slot ventilation and the shaft radial ventilation structure is proposed.A three-dimensional all-field fluid-heat transfer coupling calculation model of the new hybrid ventilation cooling system is established.By comparing and studying the air flow law and temperature distribution in the motor of the hybrid cooling system,the optimal heat flow path to reduce the maximum temperature of the stator and rotor of the motor was planned.The experimental research on HVSRLS-PMSM with the new hybrid cooling system is carried out.The heat dissipation effectiveness of the planned heat flow path is verified,which can provide a theoretical basis for the design of the high-voltage solid rotor line start permanent magnet motor cooling system.