Analysis And Simulation Of Insulation Damage Strength Of AC Motor Stator With Initial Defects

The AC traction motor was identified as one of the key components of the electric locomotive drive system.As locomotive speed and traction capacity continued to increase,the operating environment of the motor became more complex and harsh,with dynamic load changes and complex electromagnetic force excitations.The winding of the traction motor was subjected to mechanical and electromagnetic vibrations for extended periods,resulting in dynamic mechanical stress in the insulation layer of the winding.The insulation structure was prone to damage,accelerating the aging and breakdown of insulation materials.Currently,winding short circuit faults were identified as one of the main causes of traction motor accidents,whether directly or indirectly.A lot of research work has been carried out by domestic and foreign scholars on the electromagnetic and vibration problems of the motor end winding.However,most of them focused on the force of the winding conductor and rarely considered the mechanical stress state of the insulation layer.In practice,the mechanical stress state of stator insulation of the traction motor had an important influence on the expansion of insulation damage,operation life,and reliability of the motor.Hence,it was necessary to study the stress and damage propagation law of the winding insulation layer.This paper took the traction motor winding as the research object and used the three-dimensional finite element method to simulate and calculate the multi-physical field modeling.The insulation damage strength was analyzed through crack damage simulation,and the characteristic parameters of insulation mechanical damage under complex conditions were extracted.The expansion law and influencing factors of insulation damage were studied.The specific research contents were as follows:Firstly,a three-dimensional finite element analysis model of the end winding of the traction motor is established by magnetic-solid coupling analysis.The distribution characteristics of the end leakage magnetic field and electromagnetic force of the winding under three-phase current excitation are analyzed.The stress state of the winding conductor and the insulation layer is obtained,and the stress and strain concentration distribution of the winding insulation layer is determined,which lays a foundation for the study of the winding insulation damage strength.Secondly,based on the theory of fracture analysis,the crack damage of winding insulation layer is analyzed.The crack damage element is used to simulate the initial defects of insulation.The stress and strain states near the crack are obtained by fracture analysis.The stress intensity factor is introduced to study the influence of different initial crack states on the strength and propagation degree of insulation damage.The results show that the crack damage at the stator outlet is easier to expand than that at the nose end,and the transverse crack is easier to expand than the longitudinal crack.The deeper the crack depth,the greater the degree of expansion.Finally,the influence of winding dynamic stability on insulation damage strength was studied by considering the local support failure of the end hoop caused by the loosening of the end winding.The structural modal and forced vibration responses under different failure states were calculated,and the stress and displacement responses of the end winding were obtained.It was found that the maximum stress value and the stress concentration position changed after the local support failure.At the same time,the stress intensity factor of crack damage under local support failure was calculated and compared.The local support failure has a significant effect on the damage and expansion degree of the insulation layer,which may be expanded by more than 10 times.The results of this paper can provide important theoretical reference for the study of motor insulation damage mechanism,insulation state diagnosis and life prediction.