Wavelet Transform Method for Diagnosing Rotor Broken-bar Fault of Asynchronous Motor
Jianwen Zhang · Gao dianya jishu · 2006
Wavelet ridge is a effective and sensitive method for diagnosing rotor broken-bar fault of asynchronous motors, but it has such disadvantages as complex mathematic definition, great calculation quantity of iterative imminent process and so on. In order to avoid above disadvantages of wavelet ridge, a new diagnostic method based on wavelet frequency-band energy is proposed in this paper. Startup current signals of two same model motors whose condition is different were practically measured, above these two motors, one motor's rotor has a broken-bar, another is in good condition. By means of Morlet continuous complex wavelet, these measured current signals are respectively decomposed under multiple different scales, meanwhile intervals of central frequencies corresponding to decomposing scales are uniform. Based on general definition of signal energy, frequency-band energies under different scales are calculated, analyzed and compared, consequently signal energy's difference of above two different condition motors is discovered. The ratio of frequency-band energy (RFBE) is defined and its ration criterion is presented, that is, RFBE of broken-bar fault is more than two times of RFBE of good condition. Analytical Results of measured signals also show that the RFBE is not nearly interfered by noise. Not only has this new RFBE method the such advantages of wavelet ridge as high sensitiveness, no influence from load fluctuation, but also its diagnostic course is greatly predigested, meanwhile is not interfered by noise and has strong practicability.