In this paper, the authors propose a method for the diagnosis of rotor bar failures in induction machines, based on the analysis of the stator current during the startup using the Discrete Wavelet Transform (DWT). Unlike other approaches, the study of the high-order wavelet signals resulting from the decomposition is the core of the proposed method. After an introduction of the physical and mathematical basis of the method, a description of the proposed approach is given; for this purpose, a numerical model of induction machine is used, in such a way that the effects of a bar breakage can clearly be shown, avoiding the influence of other phenomena not related with the fault. Afterwards, the new diagnosis method is validated using a set of commercial induction motors. Several experiments are developed under different machine conditions (healthy machine and machine with different levels of failure) and operating conditions (no load, full-load, pulsating load and fluctuating voltage). In each case, the results are compared with those obtained using the classical approach, based on the analysis of the steady-state current using the Fourier Transform. Finally, the results are discussed and some considerations about the influence of the DWT parameters (type of mother wavelet, order of the mother wavelet, sampling rate or number of levels of the decomposition) over the diagnosis are done.

Virtual Instruments offer new possibilities for the electrical machines students to visualize and understand facts and correlations that otherwise often require more or less difficult calculations to be performed beforehand. The recent trend on the introduction of Data Acquisition systems (manipulated, accessed and controlled by means of VIs), either as new laboratory instruments or to substitute classic ones, opens a door to a new and very wide range of applications. This contribution shows the experience in this regard achieved in one of the electrical machines and drives laboratories of the