Research On Fault Diagnosis Of Permanent Magnet Synchronous Motor For Electric Vehicle

Permanent magnet synchronous motor with high efficiency, high power density, etc.,has become the most advantage of the system power unit in electric cars,with wide range of applications.As a transport, car calss for high security.Motor,the power source of the electic vehicle,is taken its reliability into account.An availabe fault diagnosis system is vital for good operation of motor.This paper takes the permanent magnet synchronous motor in electric vehicle as research object,and focus on the common faults of motor and their diagnosis technologies. Because of work conditions,serious vibration and high temperature,motor fails usually. Winding short-circuited fault, eccentricity and demagnetization are the common faultsBased on the mechanism of motor faults,finite element model for faulted motor is established,and a lumped-parameter model,whose parameter is caculated by finite element model is propsed to save simulation time.Winding short-circuited fault has been researhed,for the characteristic of faults and operation of motor ,a diagnostic strategy is presented with combination of on-line detection and off-line detection.A new caculaiton of negative sequence current using Park transformation is introduced for on-line detction. The fault is diagnosed by amplitude of negative sequence current. A high frequence voltage is applied to diagnose faults when motor stops. The high frequence voltage can increase the induction of motor and makes the fault features easy to observe.Therefore it is a sensitive method.The two methods are simple and fit for electric vehicles.Winding search coils are proposed to detect the eccentricity,which is used to detect the situation of Air-gap magnetic field.When eccentricity happens,. characteristic frequency will apear that is used to diagnose fault.The search coils eliminate the disaavantage of vibration and have good effects on electric vehicles. When permanent magnets demagnetize, the back EMF decreases and the voltage used to drive motor decreases.Quadrature axis voltage is used to diagnose demagnetization in vector control system because it equals the product of permanent magnet flux and motor speed.The ratio between quadrature axis voltage and motor speed is caculated to relfect health of permant magnet.This simple method has advantage in application of electric vehicles.The simulation based on MATLAB and FEA is presented to verify the application proposed method.