Research On Diagnosing Stator And Rotor Fault Of Squirrel-cage Induction Motor Fed With Frequency Converter

With the rapid development of science and technology, the integration level ofelectrical equipments is increasing. For speed regulation and energy conservationrequirements, the induction motor is driven by frequency converter in many occasions.The incipient fault characteristic of the induction motor is usually very weak. In addition,the soaring harmonic components in converter and the noises produced by peripheralequipment make it more difficult for the incipient fault detection. Based on thisbackground, this paper focused on the research and analysis on the stator and rotor faultdiagnosis in squirrel-cage induction motor fed with frequency converter.The faults mechanism and characteristic of inter-turn short circuit and broken rotorbar are analysed in squirrel-cage induction motor fed with frequency converter. The paperproposed a method of the fault diagnosis based on the stator current. Since a large numberof harmonics and noise components from the frequency converter seriously affected thediagnosis in the inter-turn short circuit fault diagnosis. In order to solve the aboveproblems, the fundamental component of modulated frequency in the stator current can beextracted accurately by using the advanced correlation algorithm, so that it can avoid theinfluence of the unbalanced supply voltage and higher harmonic produced by converter.And the positive sequence component of modulation frequency is turned into the secondharmonic by using synchronous speed transformation of the inverse modulated frequency,and the negative sequence one is transformed into the DC component. The DC componentcan be separated out by taking the mean algorithm applied to samplings of whole period.A sensitivity factor is defined to characterize of the fault severity; When induction motorhas happened the broken bar fault, the fundamental component of modulated frequency inthe stator current was removed by the advanced correlation algorithm, and the rotorbroken bar fault signal can be emerged in frequency spectrogram by Fourier transform.The system will select the LabVIEW software as the whole analysis platform of the faultdiagnosis, and the block diagram is constructed by combining with the characteristics ofARM and LabVIEW, which will be read and wrote facilitately in the actual production,and provides a friendly man-machine interface.