Fault Detection of VFD-Fed Induction Motor Under Transient Conditions Using Harmonic Wavelet Transform

Among a myriad of techniques in motor current analysis for fault detection in transient regime, the discrete wavelet transform (DWT) was widely implemented in the embedded online condition monitoring system (CMS) of the direct online (DOL)-fed induction motor (IM). However, the use of DWT-based CMS faces practical problems with variable frequency drive (VFD)-fed IM due to the required continuous redefinition of the decomposition tree to cope with the variable spectral content. To overcome this major limitation, an approach based on a novel DWT called multiple-windowed harmonic wavelet packet transform (MWHWPT) is then presented in this article. The originality of the proposed approach lies in the use of drive's data to continuously tune the programmable MWHWPT in order to adapt to the varying spectral content of the motor current. The new approach has been validated experimentally under transient conditions covering both random variations of load and fundamental frequency with broken rotor bar fault on a VFD-fed 3-kW double-cage IM. Fault feature extraction results show the robustness and flexibility of the proposed approach through a clear distinction between healthy and faulty motor conditions for both steady and transient modes.