Study On The Internal Fault Analysis And Detecting Method To Induction Motors

Induction motors are widely used in the all kinds of industrial production because of its simple structure, high reliability and low price. The operational status of their direct impact on the normal production process,Owing to the impact of a variety of reasons, induction motor faults have often occurred. Once occured faults, not only the motor itself is damaged, so serious that it led to disruption in the work throughout the production system. Therefore, the analysis and detection on the induction motor appears especially important.Induction motor faults can be divided into: stator faults, rotor faults, bearing failure, as well as air gap breakdown. In this paper, the most common for the induction motor stator winding inter-turn short-circuit fault and rotor broken bars fault detection methods have been studied, mainly to complete the following work:1. After reading a lot of literature at home and abroad, based on the introduced induction motor fault types, detection methods, technological developments and the current status quo.2. From the relationship between basic electromagnetic induction motor starting, the stator winding inter-turn short circuit and rotor broken bars fault characteristics of mechanism is analyzed.3. Based on multi-loop theory, established the induction motor in the normal, stator winding inter-turn short circuit, broken rotor bars three cases of multi-loop mathematical model.4. For the stator winding inter-turn short-circuit fault, this article describes two kinds of detection methods, and make a digital simulation analysis. Based on Parker- change detection methods: Based on the changes in principle Parker, Parker on the stator three-phase current to do the changes, when the stator winding inter-turn short circuit occurs, due to the presence of negative sequence current, making Parker vector trajectory occurs distortion in the coordinate system, from circular into elliptical. Using this method can be based on signal spectral analysis method of fault diagnosis into a planar graph recognition. Based on this proposed model of the square of Parker vector spectral analysis, dq0 according to whether the spectrum contains a 2 f1 component to determine whether there has been the stator winding inter-turn short circuit. Based on spectrum correction and adaptive filtering of the stator negative sequence apparent impedance detection method: Use of spectrum correction and adaptive filtering can remove rotor bar breaking fault of negative sequence component, the stator negative sequence impedance is equal to the stator negative sequence voltage and negative sequence current ratio, the failure of stator negative sequence impedance as the characteristic quantity of stator winding inter short-circuit fault detection, simulation results show that the method has good reliability and sensitivity.5. For rotor broken bars fault, this paper describes two kinds of detection methods, and makes a digital simulation analysis. Based on the stator single-phase instantaneous power detection method: power signals than the current signal is more informative, first of all filtered stator single-phase instantaneous power signal in the DC component, and then to Fourier transform according to the signal frequency spectrum for the presence of frequency components to determine whether the rotor broken bars. This method avoided the current edge detection of the frequency components, there is no low sensitivity and high resolution sampling shortcomings. Based on Hilbert transform and the continuous refinement Fourier transform detection methods: Firstly, the stator current signal obtained for Hilbert transform to reflect characteristics of broken rotor bars in the modulation signal, and then filter out DC components, the final Fourier transform of continuous refinement to whether the spectrum modulation signal frequency components to determine the existence of whether the occurrence of rotor broken bars.