Rotor broken bars fault diagnosis for induction machines based on the wavelet ridge energy spectrum

A new method for rotor broken bars fault diagnosis for induction machines based on the startup electromagnetic torque signal is presented. The fault characteristic torque frequency variation during the startup can be extracted using the wavelet ridge, which can be used to identify rotor broken bars fault. The wavelet coefficients modulus indicate the signal energy of the corresponding scale, so the wavelet coefficients modulus of the fault characteristic ridge will give us the magnitude variation law of the fault characteristic torque. According to these, the wavelet ridge energy spectrum is defined. Using the wavelet ridge energy spectrum of the fault characteristic torque as the fault severity index, the number of adjacent broken rotor bars can thus be given. Experimental results verify the feasibility of the proposed fault diagnosis method.