异步电机断条故障的启动电流小波诊断法

Wavelet Transform Method for Diagnosing Rotor Broken-bar Fault of Asynchronous Motor

为克服小波脊线在诊断异步电机断条故障过程中存在的数学定义复杂、迭代逼近运算量大等缺点,应用Morlet连续复值小波,多尺度地、中心频率等间隔地分解了实测的同型正常电机和有一根断条的故障电机启动电流信号,分析和比较了对应尺度下的频带能量后,找出了上述电机两种状态的信号能量差异;定义了频带能量比(RFBE)的概念,得出断条故障电机的RFBE比良好状态的至少大2倍的定量判据,并据此提出了基于RFBE的电机断条故障诊断新方法。研究表明:该法不仅具有小波脊线方法的高灵敏度、不受负载波动影响,且诊断过程大为简化、不受噪声干扰影响、实用性更强。

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.