On Line Fault Diagnosis Strategy Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor has the advantages of high power density,high efficiency and high moment to inertia ratio.In aerospace,ships,CNC machine tools,robots,industrial automation and other aspects of a wide range of applications.Due to these complex operating conditions,the permanent magnet motor may have short-circuit faults,demagnetization faults,eccentricity faults,mechanical faults and other problems during operation.Failure will not only seriously affect the performance,bearing capacity and life of the motor,but also seriously affect the running state of the whole system.So motor drive system with fault diagnosis function,the formation of driving-diagnosis integration system is particularly important.In the initial stage of motor failure,fault diagnosis and measures taken to ensure the normal operation of the original system,reduce the corresponding human and material losses.In this paper,three common faults of the permanent magnet synchronous motor(PMSM)with surface sticking as the research object,namely,inter-turn short circuit,demagnetization and eccentricity,are studied,corresponding fault diagnosis algorithms are analyzed,and comprehensive fault diagnosis research is conducted.Interturn short circuit fault,through the establishment of the stator interturn short circuit fault cases of table type permanent magnet synchronous motor mathematical model,so as to derive the closed-loop control when the input voltage fault characteristics of instruction,then the downtime is deduced when the fault characteristic value of high frequency injection current response,respectively designed to extract the way online and offline fault diagnosis fault,then the algorithm simulation results,the motor simulation tests under different degree of fault,to extract the fault characteristic and observe its change rule.Simulation results show that the fault features selected can effectively represent the severity of inter-turn short circuit fault.This method can realize the monitoring of inter-turn short circuit fault without adding additional sensors and improve the safety of the driving system.Aiming at the permanent magnet demagnetization fault,the variation of motor parameters during uniform demagnetization is studied,the flux chain is selected as the fault characteristics to determine the fault,and then the variation of air-gap flux density and current of the tier-type permanent magnet synchronous motor during local demagnetization is carried out,and the current specific fraction harmonic is selected as the fault characteristics.The fault extraction methods were designed respectively for fault diagnosis of uniform and local demagnetization.Then the algorithm was simulated and tested for uniform and local demagnetization motors respectively to extract fault characteristics and observe their variation rules.The simulation results show that the estimated magnetic flux value can monitor the motor flux value in real time and the diagnosis effect of uniform demagnetization is good.The extracted local demagnetization fault eigenvalues can effectively represent the severity of the fault.Aiming at the permanent magnet eccentric fault,the variation of air gap flux density,current and inductance is studied by analyzing the air gap during the eccentric fault.Specific fractional current harmonics and inductance difference are selected as fault features,and fault features are extracted online and offline,respectively.Then,simulation research is carried out on the algorithm.Under the conditions of shutdown and online,simulation tests are conducted on motors with different degrees of eccentricity to extract fault features and observe their variation rules.The simulation results show that both fault eigenvalues can respond to the occurrence of fault and effectively represent the severity of inter-turn short circuit fault.Combined with the above three fault diagnosis algorithms,the comprehensive fault diagnosis algorithm is designed,and the simulation research is carried out.According to the response of different fault markers under the three fault cases,the fault determination logic is designed.Then it simulates the composite fault,designs the comprehensive judgment logic,and realizes the comprehensive fault diagnosis.