| The external rotor permanent magnet hub motor has been widely used because of its many advantages,such as environmental protection,high efficiency and flexible driving mode.however,the heating problem of the motor caused by its high power density,large working current,narrow workspace and poor heat dissipation conditions is a difficult problem that it must face.This dissertation takes a 75 k W external rotor permanent magnet hub motor as the research object,and its electromagnetic loss and heating are studied in detail in three parts.Firstly,the solution of multi-mode loss and the suppression of eddy current loss of permanent magnet.First of all,different analysis methods are used to calculate the electromagnetic loss of the motor under rated operating conditions,and the calculation results of different methods are compared and verified,which provides more accurate heat source data for hub motor temperature field simulation.At the same time,combined with the actual operating conditions of the hub motor,three typical driving conditions of the hub motor are selected for research,and the loss value and its growth of the heat source components of the motor are analyzed.It is found that the electromagnetic loss increases significantly during climbing and high-speed operating conditions,which are two extreme operating conditions that need to be paid attention to.Then,in order to restrain the eddy current loss of permanent magnet to reduce the temperature rise of permanent magnet,to explore the law of magnetic density fluctuation and eddy current density distribution in permanent magnet,two kinds of non-uniform segmentation schemes of permanent magnet to restrain eddy current loss are put forward.it is found that the suppression effects of the two schemes are similar,which should be considered comprehensively and selected reasonably.Secondly,the establishment and analysis of the solution model of fluid-solid coupling temperature field of hub motor under rated working conditions.First of all,it is determined that the axial "Z" cooling waterway is more suitable for the limited space and compact structure of the hub motor,and then the motor cooling waterway is optimized according to the water cooling heat dissipation mechanism.the superiority of the optimized waterway structure is verified by fluid dynamics simulation.Then,according to the simplified model of each component of the hub motor and its equivalent physical parameters,the finite element model of the fluid-solid coupling temperature field of the unit hub motor is established,the temperature distribution law of the hub motor is revealed,and the transient temperature rise curve of the key components is given.the correctness of electromagnetic field and temperature field analysis is verified by setting up an experimental platform for temperature rise of end windings of hub motor.Thirdly,the influence factors of temperature rise of key components of hub motor under climbing and high-speed conditions are studied.First of all,the steady-state temperature rise of windings and permanent magnets under these two working conditions is studied.In order to solve the problem that the temperature rise of the winding exceeds the limit under the condition of high overload,the allowable time limit for the stable operation of the hub motor is given,and the circumferential uneven segmentation scheme of the permanent magnet is adopted to restrain the temperature rise of the permanent magnet.Finally,the variation of the temperature rise of hub motor windings with different coolant temperature and inlet velocity under these two working conditions is explored,and the suggestion of the best inlet velocity of coolant is given. |
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