La comprensión de la aproximación a un número en el acceso al significado de límite de una función en un punto

Esta investigación estudia la influencia de la comprensión de la aproximación a un número y de los modos de representación en la construcción de la concepción dinámica del límite en estudiantes de Bachillerato. El análisis de realizó usando el análisis implicativo (Gras, Suzuki, Guillet y Spagnolo, 2008). Los resultados indican que la construcción paulatina de la concepción dinámica del límite se realiza mediante procesos diferenciados de aproximación en el dominio y en el rango, y, dentro de estos últimos, aquellos en los que las aproximaciones laterales coinciden de las que no coinciden. Además, nuestros resultados indican que el modo numérico o el modo algebraico-numérico desempeñan un papel relevante en el desarrollo de la comprensión de la concepción dinámica de límite

A Precise, General, Non-Invasive and Automatic Speed Estimation Method for MCSA Diagnosis and Efficiency Estimation of Induction Motors

[EN] Efficiency estimation and diagnosis via MCSA require precise knowledge of speed. In an industrial environment, speed must be obtained with a non-invasive, automatic and general method. Recent studies have shown that Sensorless Speed Estimation techniques based on detecting Rotational Frequency Sideband Harmonics (RFSHs) or Rotor Slot Harmonics (RSHs) are best suited to these purposes. RFSHs-based methods are easier to apply as they only depend on the number of poles. RSHs-based are much more accurate due to their wider bandwidth. Yet, their use is not trivial as they require to identify the RSHs family, assign to each RSH its order of the current harmonic (¿) and determine the number of rotor slots (R), a rarely known parameter. This paper ends with this trade-off between accuracy and applicability by proposing a novel RSHs-based technique that, for the first time in technical literature, eliminates the need to estimate the number of rotor slots and provides a reliable and automatic procedure to locate the RSHs family and determine their ¿ indices. Finally, the method is validated under all types of conditions and motor designs, by simulations, lab tests and with 105 industrial motors, highlighting its high accuracy (errors below 0.05 rpm), and applicability.This work was supported by the Universitat Politecnica de Valencia and the Spanish Ministry of Science, Innovation and Universities [FPU19/02698]Bonet-Jara, J.; Pons Llinares, J. (2023). A Precise, General, Non-Invasive and Automatic Speed Estimation Method for MCSA Diagnosis and Efficiency Estimation of Induction Motors. IEEE Transactions on Energy Conversion. 38(2):1257-1267. https://doi.org/10.1109/TEC.2022.32208531257126738

Advanced Rotor Fault Diagnosis for Medium-Voltage Induction Motors Via Continuous Transforms

[EN] Anumber of field case studies for rotor fault diagnosis on medium-voltage induction motors operating in a petrochemical plant are presented in this paper. The methodology employed is based on analyzing the induction motor startup current with advanced signal processing tools (continuous transforms) that enable a capture of a complete picture of the rotor condition. Indeed, unlike the classical tools that often rely on the detection of few fault frequencies, these new tools allow extraction of the evolution of a wide range of fault components during the startup transient and steady-state evolutions, which enables improved reliability. This is crucial in medium-high-voltage motors, where a false diagnosis may result in significant expense due to inspection, repair, or forced outage. An additional contribution of the study is its immunity to external voltage supply disturbances, which introduce components that are not related to the failure and which are difficult to detect with classical tools. The results of this study prove how the advanced continuous tools enable an improved visualization of the fault components, distinguishing them from the other components that are not linked to the failure.This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology under Grant NRF-2013R1A1A2010370, and in part by the Human Resources Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) funded by the Korea Government Ministry of Trade, Industry, and Energy under Grant 20134030200340Antonino-Daviu, J.; Pons Llinares, J.; Lee, SB. (2016). Advanced Rotor Fault Diagnosis for Medium-Voltage Induction Motors Via Continuous Transforms. IEEE Transactions on Industry Applications. 52(5):4503-4509. https://doi.org/10.1109/TIA.2016.2582720S4503450952

Computer based learning and comprehension of power generation cycles using a model programmed in Engineering Equation Solver (EES): Analysis of a Gas- Turbine Brayton cycle

[EN] The comprehension of the influence of each design and operation parameter in a power generation cycle requires a complex analysis mainly due to coupled effects existing in these cycles and which is too hard to be assessed manually by the students during a practical session. Therefore, the use of a software tool specially developed for this purpose becomes essential. The present work presents a model of a Gas-Turbine Brayton cycle developed in EES (Engineering Equation Solver), which enables the student to make simulations in the software and easily determine the optimal design parameters that would maximize the electric energy production in this kind of cycle. In order to evaluate the usefulness of this tool, two questionnaires with the same questions were prepared and were provided to the students before and after the practical session. After analyzing the results of the questionnaires, and taking into account the comments provided by the students, it was concluded that using this methodology helps to stimulate the student’s understanding during the session, and enables to verify that students put into practice their theoretical knowledge, being able to make a better transfer to more complicated and real applications in the future.Montagud, C.; Pons Llinares, J.; Rodríguez Monzonis, MC. (2015). Computer based learning and comprehension of power generation cycles using a model programmed in Engineering Equation Solver (EES): Analysis of a Gas- Turbine Brayton cycle. En 1ST INTERNATIONAL CONFERENCE ON HIGHER EDUCATION ADVANCES (HEAD' 15). Editorial Universitat Politècnica de València. 467-474. https://doi.org/10.4995/HEAD15.2015.283OCS46747

Características de la tematización del esquema de límite de una función

Esta investigación estudia las diferentes estructuras subyacentes en el esquema de límite de una función observadas en 23 estudiantes de Bachillerato situados en el nivel Trans del desarrollo del esquema de límite de una función. El esquema de límite de una función se caracterizó en términos de la habilidad que los estudiantes manifestaron en la construcción de la concepción dinámica del límite mediante la coordinación de los procesos de aproximación en el dominio y en el rango, diferenciando aquellas en las que las aproximaciones laterales coinciden de las que no coinciden. Nuestros resultados sugieren que los estudiantes construyen diferentes estructuras subyacentes al esquema debido a las relaciones que establecen entre el límite de una función en un punto y su representación gráfica que permiten identificar características del esquema tematizado del límite de una función

A comparison of techniques for fault detection in inverter-fed induction motors in transient regime

"(c) 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works."[EN] Fault detection in induction motors operating in non-stationary regimes has become a need in today's industry. Most of the works published deal with line-fed motors. Nevertheless, the number of inverterfed induction motors has significantly increased in recent years. Therefore, several fault detection techniques have been proposed lately for this type of motors, based mainly on an adequate input signal processing to obtain fault signatures in the time-frequency domain. In this paper, a comparison of time-frequency techniques applied to fault detection in inverter-fed induction motors in a transient state is presented. For that purpose, the techniques are applied to two current signals acquired from two induction motors with two types of faults: bar breakage and mixed eccentricity. The paper shows the particularities and special difficulties of diagnosing under this type of feeding, reviewing the works related to each technique. The strengths and weaknesses of these techniques are discussed with the goal of providing a criterion for its application in an industrial environment and guidance for future developments in this field.This work was supported in part by the Spanish Ministerio de Economia y Competitividad and in part by the FEDER program in the framework of the Proyectos I+D del Subprograma de Generacion de Conocimiento, Programa Estatal de Fomento de la Investigacion Cientifica y Tecnica de Excelencia under Grant DPI2014-52842-P.Fernandez-Cavero, V.; Morinigo-Sotelo, D.; Duque-Perez, O.; Pons Llinares, J. (2017). A comparison of techniques for fault detection in inverter-fed induction motors in transient regime. IEEE Access. 5:8048-8063. https://doi.org/10.1109/ACCESS.2017.2702643S80488063

Detection of Broken Rotor Bars in Nonlinear Startups of Inverter-Fed Induction Motors

[EN] Fault detection in induction motors powered by inverters operating in nonstationary regimes remains a challenge. The trajectory in the time-frequency plane of harmonics related to broken rotor bar develops very in proximity to the path described by the fundamental component. In addition, their energy is much lower than the amplitude of the first harmonic. These two characteristics make it challenging to observe them. The Dragon Transform (DT), here presented, is developed to overcome the described problem. In this article, the DT is assessed with nonlinear inverter-fed startups, where its high time and frequency resolutions facilitate the monitoring of fault harmonics even with highly adjacent trajectories to the first harmonic path.Fernández-Cavero, V.; Pons Llinares, J.; Duque-Perez, O.; Morinigo-Sotelo, D. (2021). Detection of Broken Rotor Bars in Nonlinear Startups of Inverter-Fed Induction Motors. IEEE Transactions on Industry Applications. 57(3):2559-2568. https://doi.org/10.1109/TIA.2021.30663172559256857

A virtual laboratory for an enhanced and safe understanding of the electric transformers operation

[EN] The paper presents an educational software designed to simulate the behaviour of an electric transformer under no-load, shortcircuit and load test, measuring its input and output magnitudes through network analysers, and enabling the supply voltage and load regulations. This virtual laboratory allows to achieve several objectives. First, the student becomes familiar with the system to be operated in the real laboratory, reducing the subsequent electrical risk and optimizing the time required for carrying out the practice. Second, it enhances the understanding of transformers behaviour, its modelling through the equivalent electrical circuit, and the calculation of its two most characteristic parameters during its operation (performance and internal voltage drop). Finally, the application auto evaluates the transformer characterization performed by the student. The simulator reproduces schematically, but precisely, the assembly that the student faces during the lab lesson: an autotransformer to regulate the supply voltage, a transformer, two input and output network analysers, and different types of loads. The tool is structured in three panels. In the first panel, the student selects a transformer from 24 options, and performs its shortcircuit and no-load tests to characterize it through its electric equivalent circuit. Panels 2 and 3 enable load tests and its main characteristics calculation (performance and internal voltage drop). The student results are introduced in the app to perform auto-evaluation. To measure the performance and usefulness of the application, it has been implemented in the lab lessons of the subject ¿Electrical Technology¿, belonging to the Bachelor¿s Degree in Industrial Electronics and Automation Engineering, taught at the Polytechnic University of Valencia (Spain). The sample size is 96 students and the methodology used is as follows. The 96 students are subdivided into four groups. The practice lessons follow this sequence: a refreshment of the transformer concepts needed + explanation of the practice lesson to be performed + explanation and use of the app solving an example (only for groups 1 and 2) + real laboratory experience + final test on transformers. Finally, the performances between groups 1-2 and 3-4 are compared. It is observed that the students of groups 1 and 2 obtain better results in the final tests than those of groups 3 and 4, reaching higher levels of learning thanks to the previous use of the simulator. On the other hand, it is also observed that the time of completion of the real laboratory practice decreases substantially in groups 1 and 2. As a conclusion, there is a great benefit in using this application specifically designed to obtain very specific learning results, since the application is fully adapted to the needs of the degree and therefore to the level of knowledge that the students need to acquire according to the perception and experience of the teaching staff. Finally, based on the results, the application is permanently implemented in the laboratory lessons of Electrical Technology.This project is supported by Universitat Politècnica de València through the Project of Innovation and Educational Improvement Program (PIME 2018-2019/B26).Bonet-Jara, J.; Pons Llinares, J.; Bernal-Perez, S.; Sabater I Serra, R. (2019). A virtual laboratory for an enhanced and safe understanding of the electric transformers operation. IATED. 9177-9186. https://doi.org/10.21125/inted.2019.2277S9177918

Enhanced Simulink Induction Motor Model for Education and Maintenance Training

[EN] The training of technicians in maintenance requires the use of signals produced by faulty machines in different operating conditions, which are difficult to obtain either from the industry or through destructive testing. Some tasks in electricity and control courses can also be complemented by an interactive induction machine model having a wider internal parameter configuration. This paper presents a new analytical model of induction machine under fault, which is able to simulate induction machines with rotor asymmetries and eccentricity in different load conditions, both stationary and transient states and yielding magnitudes such as currents, speed and torque. This model is faster computationally than the traditional method of simulating induction machine faults based on the Finite Element Method and also than other analytical models due to the rapid calculation of the inductances. The model is presented in Simulink by Matlab for the comprehension and interactivity with the students or lecturers and also to allow the easy combination of the effect of the fault with external influences, studying their consequences on a determined load or control system. An associated diagnosis tool is also presented.This work was supported by the Spanish Ministerio de Ciencia e Innovación under the framework of the Programa Nacional de Proyectos de Investigación Fundamental, Project Reference DPI2011-23740Pineda-Sanchez, M.; Climente Alarcón, V.; Riera-Guasp, M.; Puche-Panadero, R.; Pons Llinares, J. (2012). Enhanced Simulink Induction Motor Model for Education and Maintenance Training. Journal of Systemics, Cybernetics and Informatics. 10(2):92-97. http://hdl.handle.net/10251/105282S929710

Recent Educational Experiences in Electric Machine Maintenance Teaching

[EN] Maintenance of electric machines and installations is a particularly important area; eventual faults in these devices may lead to significant losses in terms of time and money. The investment and concern in developing proper maintenance protocols have been gradually increasing over recent decades. As a consequence, there is a need to instruct future engineers in the electric machines and installations maintenance area. The subject ¿Maintenance of Electric Machines and Installations¿ has been designed under this idea. It is taught within an official master degree in Maintenance Engineering. This work describes the educational experiences reached during the initial years of the teaching of the subject. Aspects such as student profiles, subject approaches, design of the syllabus, methodology and structure of the laboratory sessions are remarked in the work. In addition, the paper discusses other educational strategies which are being introduced to increase the interest in the subject, such as integration of Information and Communication Technologies (ICT), promotion of the collaborative work, inclusion of the possibility of remote learning or development of new assessment systems.This work was supported by the Conselleria d’Educació, Formació i Ocupació of the Generalitat Valenciana, in the framework of the ‘‘Ayudas para la Realización de Proyectos de I+D para Grupos de Investigación Emergentes’’, project reference GV/2012/020.Antonino Daviu, JA.; Pons Llinares, J.; Climente Alarcón, V. (2013). Recent Educational Experiences in Electric Machine Maintenance Teaching. International Journal of Engineering Pedagogy. 3(3):21-26. https://doi.org/10.3991/ijep.v3iS3.2742S21263