Study On The Diagnosis Of Demagnetization Fault Of PMSM Based On The Induced Voltage Decomposition

Permanent magnet synchronous motor(PMSM)uses permanent magnet to replace exciting winding,has no commutator and brush that has advantage of light weight,small volume,compact structure,low loss,high efficiency and good reliability,so it has been widely used in military field,industrial and living fields.However,compared with the traditional electric excitation motor,the risk of demagnetization of the permanent magnetic material of permanent magnet synchronous motor is an objective existence.Under high temperature,humidity,vibration or winding under short-circuit fault,the permanent magnet will be likely irreversible demagnetization,and will lead to the motor performance degradation.If failed to timely find excitation-loss fault and continue to use the motor,it will cause serious damage of the motor.So,studying on the demagnetizition fault diagnosis research for permanent magnet synchronous motor is of great significance.As for permanent magnet synchronous motor demagnetizition fault diagnosis,how to quickly and directly find simple and effective and significant fault characteristic from a number of operation signal of the motor is the key problem to the motor demagnetizition fault diagnosis research.In this paper,the embedded permanent magnet synchronous motor is used as the research object.According to the calculation and analysis of stator tooth magnetic flux,it is found that the magnetic faults have obvious influence on the rotor component of stator tooth in its range.Using this feature,this paper uses the way of buring detecting coil in motor stator tooth to directly obtain the stator flux,and by the way this paper proposes a demagnetizition fault diagnosis method based on the decomposition of induction electric potential.The method can obtain accurate magnetic fault component,and using the fault component radar map can furher determine the fault location and the fault characteristic of the permanent magnet synchronous motor.First of all,the basic structure and working principle of the permanent magnet synchronous motor are introduced in this paper,and the characteristics of permanent magnet and the mechanism of permanent magnet demagnetization are described.Then calculating and analysing stator tooth magnetic flux,and the phase calculation method of tooth flux rotor is derived,which is the phase calculation method of tooth flux stator component generated by stator current and permanent magnet.Then the phasecalculation method is used to decompose the induced voltage of the stator tooth flux in the state of demagnetizition of permanent magnet synchronous motor.It lays the theoretical foundation for the proposed diagnostic method.Then,the finite element model of permanent magnet synchronous motor is build by ANSYS Maxwell,and the ANSYS Simplorer,ANSYS Maxwell and Matlab Simulink joint simulation scheme is put forward,so the uniform demagnetization model and the local demagnetization model of the permanent magnet synchronous motor are established based on speed running control and the finite element model.By analysing the fault characteristic features under the different levels of demagnetizition fault,it is concluded that there is a corresponding relationship between the degree of demagnetizition and the fault characteristic feature.And then eliminated the influence of diagnosis methods caused by the torque and rotational speed,so it improves the adaptability of the diagnosis method.Finally,useing simulation results of permanent magnet synchronous motor's permanent magnet field loss situation caused by several common winding short-circuit fault compared with diagnosis results of diagnostic methods,the correctness and effectiveness of the diagnosis method is verified.