Study On Rotor Fault Diagnosis Method Of Induction Motor

Induction motors are widely used in the industrial and agricultural production because of its simple structure, low price, high reliability and convenient maintenance. With the rapid development of the modem industrial system, the capacity of a single motor is keeping in creasing and the load is also becoming more complicated now. A motor failure not only can result in damage to the motor, but also can result in unscheduled machine downtime and the shutdown of a production line, which will cause heavy financial losses and catastrophic failure. This paper analyzed several methods to diagnose rotor broken bar fault based on the electromagnetic torque and the instantaneous active and reactive power, which are highly sensitive to any asymmetrical operating condition. By comparison, there is no efficiency single diagnosis method can pick up induction motor broken bar fault.The floating threshold filter technique based on the frequency band decomposition of the wavelet packet transformation, which is superior to the Fourier spectrum analyze method for non-stationary signal denoising is presented. An arbitrary signal and its Hilbert transformation constitute an orthonormal pair. Based on this idea, the principle of DC elimination, which is available for an arbitrary signal with random non-integral periods is proposed by the double Hilbert transformation. The Hilbert-Huang transformation which combines the empirical mode decomposition and the associated Hilbert spectral analysis are presented. The variable amplitude and frequency of the intrinsic mode function, is a breakthrough of the constant amplitude and fixed frequency Fourier series expansion. The Hilbert-Huang transformation is auto adaptive for the non-stationary signal analyzing. Efforts are also focused on others diagnose methods. By using correct wavelet package functions, the broken-bar fault can be picked up in small load and slight broken-bar fault.About the online diagnose of three-phase cage induction motor, lot of research work is made. In this paper, a review of the most recent developments in the field of On-line fault diagnosis of three-phase Induction Motors is pretended, and a new FE model of induction motor with bars faulted is created, the simulation result between the motor with good bar and the motor with three faulted bar are compared. Wavelet package analysis based diagnosis system of induction motor with bar faulted is made.Three-phase induction motor broken bar fault diagnose method based on wavelet method is proposed. A real diagnose system is constructed which includes hardware test module, data acquisition module, frequency analysis module, plot module, auxiliary module etc. The frequency analysis module including FFT, wavelet, and wavelet package analysis functions. Base on this system, FE computer method is used and experiment is made in real bar broken condition. Data of normal bar, three broken bars and end ring broken are delivered to diagnose program. The analyze result shows that the system can pick up motor bar fault correctly in small load and slight broken-bar.To diagnosis the fault degree of rotor broken bars, the change of bar current and characteristic signal magnitude are discussed, the motor broken bar diagnosis method based on fuzzy mathematics is improved. The fuzzy relationship matrix is determined by simulations to show the degree of dependence between fault symptoms and fault modes. The simulation experiments are made in conditions of normal bar, one bar broken and four bars broken. The simulation results show that the fuzzy relationship matrix is correct, and the motor broken bar diagnosis method based on fuzzy mathematics is effective.