Application of the Wigner-Ville distribution for the detection of rotor asymmetries and eccentricity through high-order harmonics

The diagnosis of induction machines through the use of methods based on the study of the startup current has become an issue of special interest. These techniques may provide, in certain situations (unbalanced supply voltages, load torque oscillations, variable load, etc.) and for certain faults (broken bars, eccentricity, stator short circuit, etc.) substantial advantages in comparison with the classical method, based on the Fourier spectrum of the steady-state current. Nevertheless, in the case of rotor asymmetries, these transient-based techniques have been mainly focused on the tracing of the lower sideband harmonic (LSH). In this paper, a wideband diagnosis method is proposed, in which the Wigner-Ville distribution is applied to the detection of eccentricity and other high-order components also introduced by the rotor asymmetry. It is shown that the proposed wide band analysis might help to reach a more reliable diagnosis conclusion in cases in which the tracing of commonly used harmonics may be difficult (inter-bar currents, load torque oscillations, non stationary regimes, etc.). An evaluation of the method is carried out through simulations and laboratory tests. The results show the potential of the tool for the detection and quantification of these components as a basis to diagnose such faults. © 2012 Elsevier B.V

Fault Diagnosis in Induction Motors using the Hilbert-Huang Transform

[EN] The work carried out by the authors consists of applying a modern time-frequency decomposition (TFD) tool, the Hilbert-Huang Transform (HHT), to the diagnosis and the evaluation of electromechanical faults in induction machines. These machines are widely spread nowadays, being involved in many industrial processes as well as in power generation installations such as nuclear plants. The core of the proposed methodology is the analysis of the current demanded by the stator winding of the machine during its connection process known as startup transient. Once the current is analyzed, characteristic patterns caused by the evolution of certain components created by the corresponding faults are identified; this evolution is due to the dependence of these fault-related components on the slip s, a quantity varying during a direct startup transient from 1 to near 0. In the present paper, the HHT is applied to the diagnosis of two different faults: rotor bar breakages and mixed eccentricities. In comparison with other TFD tools, the HHT provides certain advantages that are discussed in the work. The validity of the approach is proven through several experimental tests on real machines with different sizes and characteristics. The results show the potential of the methodology for reliable fault diagnosis and for correct discrimination between the different electromechanical failures.Antonino Daviu, J.; Riera-Guasp, M.; Pineda Sánchez, M.; Puche Panadero, R.; Pérez, RB.; Jover-Rodriguez, P.; Arkkio, A. (2011). Fault Diagnosis in Induction Motors using the Hilbert-Huang Transform. Nuclear Technology. 173(1):26-34. doi:10.13182/NT11-A11481S2634173

Detection of rotor broken bar and eccentricity faults in induction motors via second order sliding mode observer

This paper provides a novel approach for detecting certain abnormal operating conditions in squirrel cage induction motors (SCIMs). A mathematical model of the faulty operating mode is derived with the rotor broken bars and the rotor eccentricity being the faults of interest. To detect the fault occurrence, an appropriate FDI observer, based on second order sliding modes, is presented and analyzed by Lyapunov methods. The ability of the suggested FDI observer to produce suitable residual signals which allow a reliable threshold-based fault detection is shown. Once the fault is detected, dedicated FFT analysis of the residuals allows the classification of the fault. The proposed scheme has been verified by real implementation tests using measurements taken from certain commercial three-phase SCIMs intentionally damaged in order to reproduce the fault scenarios of concern. Experimental results confirm the reliability of the suggested framework

Fault Detection in Induction Motors

This chapter introduces recent developments in fault diagnostics of induction motors (IMs), by providing theoretical, simulative, and experimental results along with a number of implementation-related practical considerations and guidelines. The first section of the chapter is a short introduction in which the more common faults of IM are concisely described as well as their causes, consequences, and symptoms. The second section introduces an example of model-based approach for fault detection and isolation (FDI) in IMs based on dynamical observers. The remaining sections deal with diagnostic techniques based on signal analysis approaches. The techniques include classical motor current signature analysis (MCSA) based on the fast Fourier transform (FFT), Hilbert-transform (HT), discrete wavelet transform (DWT), continuous wavelet transform (CWT), Wigner-Ville distribution (WVD) approach, and instantaneous frequency (IF) approach