Induction motor diagnosis by advanced notch FIR filters and the wigner-ville distribution

During the last years, several time-frequency decomposition tools have been applied for the diagnosis of induction motors, for those cases in which the traditional procedures, such as motor current signature analysis, cannot yield the necessary response. Among them, the Cohen distributions have been widely selected to study transient and even stationary operation due to their high-resolution and detailed information provided at all frequencies. Their main drawback, the cross-terms, has been tackled either modifying the distribution, or carrying out a pretreatment of the signal before computing its time-frequency decomposition. In this paper, a filtering process is proposed that uses advanced notch filters in order to remove constant frequency components present in the current of an induction motor, prior to the computation of its distribution, to study rotor asymmetries and mixed eccentricities. In transient operation of machines directly connected to the grid, this procedure effectively eliminates most of the artifacts that have prevented the use of these tools, allowing a wideband analysis and the definition of a precise quantification parameter able to follow the evolution of their state. © 1982-2012 IEEE

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

Rotor-bar breakage mechanism and prognosis in an induction motor

© 1982-2012 IEEE. This paper proposes a condition-based maintenance and prognostics and health management (CBM/PHM) procedure for a rotor bar in an induction motor. The methodology is based on the results of a fatigue test intended to reproduce in the most natural way a bar breakage in order to carry out a comparison between transient and stationary diagnosis methods for incipient fault detection. Newly developed techniques in stator-current transient analysis have allowed tracking the developing fault during the last part of the test, identifying the failure mechanism, and establishing a physical model of the process. This nonlinear failure model is integrated in a particle filtering algorithm to diagnose the defect at an early stage and predict the remaining useful life of the bar. An initial generalization of the results to conditions differing from the ones under which the fatigue test was developed is studied

Results of a university experience, comparing face-toface, online and hybrid teaching in a context of Sarscov19

[EN] The irruption of sarscov19 in the spring of 2020 was a challenge for everyone, particularly university teaching, where solutions had to be improvised urgently. Technological resources and online teaching played a fundamental role, and the involvement of students, teachers and administration led to an acceptable outcome. After the first impact of the pandemic, new alternatives compatible with the protocols of social distancing and health security were proposed in the planning for the academic year 2020-2021. As in many other universities, a synchronous hybrid learning (SHL) model was offered at the Universitat Politècnica de València (UPV), combining online learning and face-to-face (F2F) activities. In the SHL model, some students attended classes in-person (the room capacity limited the number according to the minimum distances between people required) and stream for the rest of the students, who followed the class simultaneously. In addition, the classes were recorded to enable their asynchronous use. SHL was only used when the conditions were favourable. Vulnerable teachers were teaching entirely online in their groups. When the number of students in a group was small enough, teaching was fully F2F, maintaining the online option only for vulnerable or confined students. The laboratory practices followed a similar hybrid scheme. The tutorials were attended by email or videoconference, and the exams were preferably in-person, with ad hoc solutions in the cases of confined or vulnerable students. Between February and June 2021, a pilot experience was carried out in the Electricity course of the degree in Electronic Engineering and Industrial Automation at the UPV. Three groups were taught with a different methodology: online, SHL and F2F teaching. Planning, academic resources, and evaluation were the same in the three groups. All three followed active flipped classroom methods. In this paper, the student's academic outcomes and the results of opinion surveys conducted on the activities are presented. Results are analysed in terms of the three groups/methodologies showing reasonable doubts about the SHL model where, the academic results and the student's opinions are significantly lower than the other two methodologies. These results could help to decide the best methodological solution if we had a similar situation in the future.Authors would like to thank the Institute of Education Sciences of the Universitat Politècnica de València (Spain) for supporting the Teaching Innovation Group e-MACAFI and for the financial support through PIME Project PIME 20-21/220 and PIME Project PIME/2018/B25.Tort-Ausina, I.; Gómez-Tejedor, J.; Molina Mateo, J.; Riera Guasp, J.; Meseguer Dueñas, JM.; Martín-Cabezuelo, R.; Vidaurre, A. (2022). Results of a university experience, comparing face-toface, online and hybrid teaching in a context of Sarscov19. IATED. 896-905. https://doi.org/10.21125/edulearn.2022.025889690

Effect of the use of videos in the pre-class preparation of laboratory sessions taught by flip teaching

[EN] Nowadays, it is well stablished the effectiveness of flip teaching in different areas. Video is widely used as a pre-class learning material and it is progressively replacing text-document materials. The students, 70 in total, are enrolled in the laboratory practice of the subject of Physics (Bachelor¿s Degree: Industrial Electronics and Automation Engineering) at the Universitat Politècnica de València. Student¿s perception data were collected from the results of a survey. Students were asked about the usefulness of the videos and the in-class work, paying special attention to the roll of the instructor in relation to the flip teaching methodology and the pre-class material. The students were divided into two groups. In one of them, the videos were recorded by the same instructor present at the lab session, whereas the other group, the videos used were recorded by instructors different from the instructor present at the lab. The results indicate that students feel that the videos are very useful, rather than the written documents. They attribute a high value to the instructor in the lab session as they feel more confident with their work and they can ask for help when needed. They value positively the possibility of work autonomously. Small differences have been found in the opinion of both groups being the higher in the question that concerns the preference of the videos respect to the text.This work has been supported by the Universitat Politècnica de València through the Project of Innovation and Educational Improvement Program (Projects PIME/2018/B26 and PIME/2018/B25 Convocatoria de Proyectos de Innovación y Convergencia).Meseguer Dueñas, JM.; Quiles Casado, SDLS.; Sabater I Serra, R.; Serrano, M.; Gómez-Tejedor, J.; García-Sánchez, TM.; Tort-Ausina, I.... (2020). Effect of the use of videos in the pre-class preparation of laboratory sessions taught by flip teaching. Iated. 6107-6112. https://doi.org/10.21125/inted.2020.1654S6107611

Porównanie filtrowania tradycyjnego i falkowego w diagnostyce niesymetrii klatki maszyn indukcyjnych

The paper deals with the diagnosis of squirrel cage asymmetries in induction machines. The results of practical measurements and analyses for two different cases are included. The first case refers to a 400 kW industrial induction machine and the second one to a 1.1 kW laboratory induction motor. In both cases the rotor cages are concluded to possess broken bars. Two different diagnostic approaches are employed. The first or traditional one is the digital low pass filtering. The other or more modern one is the wavelet decomposition. Both approaches were found to be viable, although the latter one shows some potential advantages over the previous one, especially if in future more diagnostic harmonics should be accounted for.Artykuł dotyczy diagnozowania stanu klatek silników indukcyjnych klatkowych. Podano wyniki pomiarów i analiz dwóch rzeczywistych maszyn. Przypadek pierwszy dotyczy maszyny o mocy 400 kW a drugi o mocy 1,1 kW. W obu przypadkach wyniki analiz diagnostycznych wskazują na obecność przerwanych prętów w klatkach ich wirników. Analizy diagnostyczne wykonano dwoma metodami. Pierwsza polegała na zastosowaniu tradycyjnego cyfrowego filtrowania dolnoprzepustowego. Druga, nowoczesna, polegała na zastosowaniu dekompozycji falkowej. Stwierdzono, że choć obydwa podejścia były skuteczne, to jednak analiza diagnostyka bazująca na analizie falkowej wnosi perspektywicznie większe możliwości, zwłaszcza jeśli w przyszłości diagnostyka bazować będzie na kilku a nie, jak dotychczas, jednej harmonicznej

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

Simulation of skin effect via separated representations

[EN] Purpose - The purpose of this paper is to apply the method of separation of variables to obtain the current distribution in the slot of an electrical machine, taking into account the skin effect. Design/methodology/approach - A slot in an electrical machine, filled with a solid conductor, and fed with an externally imposed density current, presents a current distribution that depends on the skin effect. The magnetic potential vector is formulated and solved using a separate representation as a finite sum of unidimensional (space and time) functions, taking into account the boundary conditions. The proposed method obtains the transient and permanent distribution of the current in the interior of the slot, both in transient and steady regime, and the results at the end of the transient are compared with the analytic ones in permanent regime. Findings - The magnetic potential vector in the interior of a slot filled with a solid conductor can be expressed as a finite sum of just 16 modes, which capture the evolution of the field during the transient and permanent regime. These modes are expressed as the product of space and time functions, which have been obtained automatically by the separation of variables algorithm. Instead of solving multiple field problems, one for each time instant, the proposed method just solves two single-variable differential equations, one in the time domain and other in the spatial one. Research limitations/implications - The application of the proposed method to non-sinusoidal currents, such as those generated by variable speed-drives, would allow to compute the field taking into account both the very small time scale of the pulse width modulation pulses, in the range of kiloHz, and the wide time scale of the currents envelope, in the range of 0-100 Hz. Extension to 2D and 3D spatial configurations is also under consideration. Originality/value - Using the method of separation of variables to solve electromagnetic problems provides a new method which can simplify and speed up the computation of transient fields in multidimensional time and space domains.This work was supported by the Spanish “Ministerio de Educación y Ciencia” in the framework of the “Programa Nacional de Proyectos de Investigación Fundamental”, project reference DPI2008‐06583/DPI.Pineda-Sanchez, M.; Chinesta, F.; Roger-Folch, J.; Riera-Guasp, M.; Pérez-Cruz, J.; Daim, F. (2010). Simulation of skin effect via separated representations. COMPEL The International Journal for Computation and Mathematics in Electrical and Electronic Engineering. 29(4):919-929. https://doi.org/10.1108/03321641011044334S919929294Ammar, A., Mokdad, B., Chinesta, F., & Keunings, R. (2006). A new family of solvers for some classes of multidimensional partial differential equations encountered in kinetic theory modeling of complex fluids. Journal of Non-Newtonian Fluid Mechanics, 139(3), 153-176. doi:10.1016/j.jnnfm.2006.07.007Ammar, A., Mokdad, B., Chinesta, F., & Keunings, R. (2007). A new family of solvers for some classes of multidimensional partial differential equations encountered in kinetic theory modelling of complex fluids. Journal of Non-Newtonian Fluid Mechanics, 144(2-3), 98-121. doi:10.1016/j.jnnfm.2007.03.009Ammar, A., Normandin, M., Daim, F., Gonzalez, D., Cueto, E. and Chinesta, F. (n.d.), “Non‐incremental strategies based on separated representations: applications in computational rheology”,Communications in Mathematical Sciences(in press).Chinesta, F., Ammar, A., Lemarchand, F., Beauchene, P., & Boust, F. (2008). Alleviating mesh constraints: Model reduction, parallel time integration and high resolution homogenization. Computer Methods in Applied Mechanics and Engineering, 197(5), 400-413. doi:10.1016/j.cma.2007.07.022Gonzalez, D., Ammar, A., Chinesta, F. and Cueto, E. (2010), “Recent advances in the use of separated representations”,International Journal for Numerical Methods in Engineering, Vol. 81 No. 5, pp. 637‐59.Rvachev, V. L., & Sheiko, T. I. (1995). R-Functions in Boundary Value Problems in Mechanics. Applied Mechanics Reviews, 48(4), 151-188. doi:10.1115/1.300509