Influence of corona charging in cellular polyethlene film

[En] Cellular polymers have recently attracted attention for their property of exhibiting a piezoelectric constant when they are electrically charged. The electrostatic charge generated in the voids by the internal discharges creates and internal macrodipole which is responsible for the piezoelectric effect. Charging by corona discharge is the most used method for cellular polymers. Many works has been published on polypropylene and polyethylene films mainly focused on the required expansion process or on the results obtained for raw cellular materials electrically activated. Our work is based on commercial polyethylene cellular films which have been physically characterized and electrically activated. The effect of thermal treatment, physical uniaxial or biaxial stretching and corona charging was investigated. The new method of corona charging improved the piezoelectric constant under other activation conditions.This work has been developed under the project Intelligent Materials with Mechanical and Electrical Properties interaction (E-MAT)" which has been submitted for funding with reference number IMDEEA/2011/13 to the call of Technological Centers of IMPIVA Network 2011, Strategic development program (action 1, R+D projects) financed by the Generalitat Valenciana through the Instituto de la Mediana y Pequena Empresa Valenciana (IMPIVA) and the European Regional Development Fund (ERDF).Ortega Braña, GE.; Llovera Segovia, P.; Magraner Bella, F.; Quijano Lopez, A. (2011). Influence of corona charging in cellular polyethlene film. Journal of Physics: Conference Series. 301:1-4. doi:10.1088/1742-6596/301/1/012054S14301Fukada, E. (2000). History and recent progress in piezoelectric polymers. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 47(6), 1277-1290. doi:10.1109/58.883516Sessler, G. M., & Hillenbrand, J. (1999). Electromechanical response of cellular electret films. Applied Physics Letters, 75(21), 3405-3407. doi:10.1063/1.125308Hillenbrand, J., & Sessler, G. M. (2000). Piezoelectricity in cellular electret films. IEEE Transactions on Dielectrics and Electrical Insulation, 7(4), 537-542. doi:10.1109/94.868074Paajanen, M., Välimäki, H., & Lekkala, J. (2000). Modelling the electromechanical film (EMFi). Journal of Electrostatics, 48(3-4), 193-204. doi:10.1016/s0304-3886(99)00065-0Gerhard-Multhaupt, R. (2002). Less can be more. Holes in polymers lead to a new paradigm of piezoelectric materials for electret transducers. IEEE Transactions on Dielectrics and Electrical Insulation, 9(5), 850-859. doi:10.1109/tdei.2002.1038668Wegener, M., & Bauer, S. (2005). Microstorms in Cellular Polymers: A Route to Soft Piezoelectric Transducer Materials with Engineered Macroscopic Dipoles. ChemPhysChem, 6(6), 1014-1025. doi:10.1002/cphc.200400517Hillenbrand, J., Behrendt, N., Mohmeyer, N., Altsadt, V., Schmidt, H.-W., & Sessler, G. M. (s. f.). Charge retention in biaxially-oriented polypropylene films containing various additives. 2005 12th International Symposium on Electrets. doi:10.1109/ise.2005.1612375Xiaoqing Zhang, Sessler, G. M., & Hillenbrand, J. (s. f.). Optimization of Piezoelectric Properties of Cellular Polypropylene Films by Repeated Expansion. 2005 12th International Symposium on Electrets. doi:10.1109/ise.2005.161231

Complex bifurcation maps in electroelastic elastomeric plates

[EN] Stress-strain relationships for rubbery materials are highly non-linear. In this work, a particular configuration of electroactive material is considered: an isotropic, incompressible electroelastic squared plate is subjected to equal biaxial homogeneous deformation and a scalar electrical potential is applied on the sides of compliant electrodes. This case is analysed according to two methodologies: the Hessian approach and the use of incremental deformation together with increment in the electric displacement. First, an extended Mooney Rivlin model is considered for the material and then an Ogden model is also analysed. Results, show, that despite of available experimental results, some predictions can be made and the pertinent analysis show complex bifurcation maps. This can help in the future progress in the knowledge of the instabilities and bifurcation phenomena which should appear in these materials. The present paper has been mainly motivated by the work of Ogden and DorfmannDíaz Calleja, R.; Llovera Segovia, P.; Quijano Lopez, A. (2017). Complex bifurcation maps in electroelastic elastomeric plates. International Journal of Solids and Structures. 113:70-84. doi:10.1016/j.ijsolstr.2016.12.021S708411

Smart-Sensor for the Automatic Detection of Electromechanical Faults in Induction Motors Based on the Transient Stray Flux Analysis

This research was funded by ¿GENERALITAT VALENCIANA, Conselleria de Educación, Investigación, Cultura y Deporte, grant number AICO/2019/224¿Zamudio-Ramírez, I.; Osornio-Ríos, RA.; Antonino-Daviu, JA.; Quijano-Lopez, A. (2020). Smart-Sensor for the Automatic Detection of Electromechanical Faults in Induction Motors Based on the Transient Stray Flux Analysis. Sensors. 20(5):1-19. https://doi.org/10.3390/s2005147711920

Reliable Detection of Rotor Winding Asymmetries in Wound Rotor Induction Motors via Integral Current Analysis

(c) 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, 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 component of this work in other works[EN] Current analysis has been widely employed in academy and industry for the diagnosis of rotor damages in cage induction motors. The conventional approach based on the FFT analysis of steady-state current (MCSA) has been recently complemented with the development of alternative techniques that rely on the time-frequency analysis of transient quantities of the machine. These techniques may bring important advantages that are related to the avoidance of eventual false indications provided by the classical MCSA. Moreover, their application is also suitable for variable speed conditions. However, the application of current-based methodologies to wound rotor induction motors (WRIM) has been much less studied and, hence, their validation in field WRIM is scarce. The present work proposes the application of an integral methodology based on the analysis of both stationary and transient currents for the diagnosis of winding asymmetries in WRIM. The method, based on up to five different fault evidences, is validated in laboratory motors and it is subsequently applied to a large field motor (1,500 kW) that was showing signs of abnormal rotor functioning. The results prove that the method is of interest for the field since it helps to ratify without ambiguity the existence of eventual asymmetries in the rotor windings, with no interference with the machine operation. However, due to the complex constructive nature of the rotor winding as well as the presence of auxiliary systems (slip rings, brushes, contactors, etc ), once the fault presence is detected, it may be interesting the utilization of complementary tools to accurately locate the root cause of the asymmetry.This work was supported in part by the Spanish Ministerio de Economia y Competitividad and in part by the Fondo Europeo de Desarrollo Regional 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.Antonino-Daviu, J.; Quijano Lopez, A.; Climente Alarcón, V.; Garín-Abellán, C. (2017). Reliable Detection of Rotor Winding Asymmetries in Wound Rotor Induction Motors via Integral Current Analysis. IEEE Transactions on Industry Applications. 53(3):2040-2048. https://doi.org/10.1109/TIA.2017.2672524S2040204853

Electrostatics comfort in buildings and offices: Some experiences and basic rules

[EN] Electrostatic charges may cause several damages to electronic devices, sensible products or processes. They may also lead to electric discharges which represent a hazard for explosive atmospheres or may cause serious problems in equipment in hospitals. For these well-known situations there are standards that give rules and solutions to users and designers. However, there is still a large field of possible electrostatic problems which cannot be classified into damages or dangers but that represent rather a problem of discomfort to users. Some examples are electrostatic discharges in homes, offices, shops, supermarkets, public areas or public car parks. The general solutions proposed in the standards for electrostatic charges in industrial environments, may not be applicable or cost-effective for these situations. These cases represent an original technical problem aimed at solving the troubles caused by electrostatic charges to users. Solutions may be inexpensive, definitive (i.e. without maintenance or requiring very long periods for maintenance) and, in some situations, they may reduce at a maximum their visual impact for esthetical reasons (e.g. the use of coating with conductive black painting are seldom acceptable).This paper will describe some representative examples of electrostatic discomfort in non-standardized environments, gathered after 15 years of experience. Some practical solutions will be proposed.Llovera Segovia, P.; Domínguez-Lagunilla, M.; Fuster Roig, VL.; Quijano-Lopez, A. (2022). Electrostatics comfort in buildings and offices: Some experiences and basic rules. Journal of Electrostatics. 115:1-6. https://doi.org/10.1016/j.elstat.2021.1036501611

Dynamic clustering segmentation applied to load profiles of energy consumption from Spanish customers

[EN] The following article describes the work of dynamic segmentation of daily load profiles throughout years 2008 and 2009, of a representative sample of Spanish residential customers. The technique applied is classification of the energy consumption time series of load profiles by means of dynamic clustering algorithms. The techniques used and analysis performed prove adequate as a fast tool to classify clients according to their energy consumption patterns, as well as to evaluate their overall energy consumption trends at a glance. The segmentation of the energy consumption load profiles is performed, and the results are analyzed and discussed.The works developed in this document have been possible thanks to Iberdrola Distribucion Electrica S.A.U. and the development of the GAD project. The GAD or "Active Demand Management" (in Spanish) project was a project supported by the Spanish Government, and participated by 14 different companies and 14 research centers. It was sponsored by the CDTI (Technological Development Centre of the Ministry of Science and Innovation of Spain), and financed by the INGENIO 2010 program.Benítez Sánchez, IJ.; Quijano-Lopez, A.; Diez, J.; Delgado Espinos, I. (2014). Dynamic clustering segmentation applied to load profiles of energy consumption from Spanish customers. International Journal of Electrical Power & Energy Systems. 55:437-448. https://doi.org/10.1016/j.ijepes.2013.09.022S4374485

Charging of Piezoelectric Cellular Polypropylene Film by Means of a Series Dielectric Layer

[EN] Piezoelectric polymer cellular films have been developed and improved in the past decades. These piezoelectric materials are based on the polarization of the internal cells by means of induced discharges in the gas inside the cells. Internal discharges are driven by an external applied electric field. With this polarization method, cellular polypropylene (PP) polymers exhibit a high piezoelectric coefficient d(33) and have been investigated because of their low dielectric polarization, high resistivity, and flexibility. Charging polymers foams is normally obtained by applying a corona discharge to the surface with a single tip electrode-plane arrangement or a triode electrode, which consists of a tip electrode-plane structure with a controlled potential intermediate mesh. Corona charging allows the surface potential of the sample to rise without breakdown or surface flashover. A charging method has been developed without corona discharge, and this has provided good results. In our work, a method has been developed to polarize polypropylene foams by applying an insulated high-voltage electrode on the surface of the sample. The dielectric layer in series with the sample allows for a high internal electric field to be reached in the sample but avoids dielectric breakdown of the sample. The distribution of the electric field between the sample and the dielectric barrier has been calculated. Experimental results with three different electrodes present good outcome in agreement with the calculations. High d(33) constants of about 880 pC/N have been obtained. Mapping of the d(33) constant on the surface has also been carried out showing good homogeneity on the area under the electrode.Llovera Segovia, P.; Ortega-Braña, G.; Fuster Roig, VL.; Quijano-Lopez, A. (2021). Charging of Piezoelectric Cellular Polypropylene Film by Means of a Series Dielectric Layer. Polymers. 13(3):1-12. https://doi.org/10.3390/polym13030333S11213

Relationship between surface potential and d33 constant in cellular piezoelectric polymers

[EN] The development of cellular piezoelectric polymers has shown very promising results thanks to their high d33 piezoelectric constants which make them candidates for many applications. Cellular piezoelectric polymers, known as ferroelectrets, are obtained by means of an activation process which consists in generating an internal dipole with electrostatic charges produced by internal electric discharges. The most common system for this activation process is the application of a corona discharge on the surface of the sample in order to produce a high internal electric field. The theoretical electrostatic model of the process which is widely used is the Sessler model which relates the internal surface charge density, the air and polymer layers thickness, the dielectric permittivity of the polymer and the Young's Modulus of the cellular material to the d33 piezoelectric constant. In our work, we relate the internal charges of the material with the d33 piezoelectric constant by means of a surface potential scanning of cellular polypropylene biaxially stretched samples. Samples were charged by a corona discharge controlled with a triode electrode. Surface potentials were high enough to generate internal discharges and obtain measurable d33 piezoelectric constants but low enough to be measured with spatial resolution by means of a 3 kV electrostatic probe. Surface potential profiles showed some deviations from the expected bellshape profile due to the internal electric field generated by the internal static charge. These deviations can be numerically related to the measured d33 piezoelectric constant with the electrostatic Sessler model.Ortega Braña, GE.; Llovera Segovia, P.; Domínguez-Lagunilla, M.; Quijano Lopez, A. (2017). Relationship between surface potential and d33 constant in cellular piezoelectric polymers. Journal of Electrostatics. 88:94-99. doi:10.1016/j.elstat.2016.12.014S94998

Joining together theory and practice in the classroom for electrical engineering undergraduates: The large-scale portable laboratory

[EN] Teaching electrical engineering requires a combination of theoretical and practical lessons to acquire knowledge and develop skills. However, in general, laboratory sessions are conducted separately from theoretical lessons for practical reasons. We shall describe a proposal to bridge the gap between theoretical explanation or exercises and practical application in a laboratory: the large-scale portable laboratory. This temporary laboratory can be set up and then collected again in a conventional classroom in just a few minutes. By using safe voltages and currents it allows us to illustrate and mmediately apply theoretical concepts or to discover some phenomena, which can then be explained theoretically. It is a tool to connect experimental observations and theoretical explanations during student learning. This laboratory has some physical limitations and does not replace practical sessions in an electrical engineering laboratory. A full session with this laboratory will be described and the results obtained will subsequently be presented. As a result, student involvement dramatically increases. It provided good results in learning and helped the electric laboratory sessions. Some difficulties such as preparation time and time spent during the session are also discussed.Llovera Segovia, P.; Fuster Roig, VL.; Quijano-Lopez, A.; Vilaplana Cerda, RI. (2019). Joining together theory and practice in the classroom for electrical engineering undergraduates: The large-scale portable laboratory. International Journal of Electrical Engineering Education. 1-11. https://doi.org/10.1177/0020720919833030S11

Modelization of earth electrode excited by atmospheric discharges based on FEM

[EN] The aim of this paper is to obtain the distribution of tensions in the land excited by currents type ray using different types of electrodes: the goad electrodes and the deep goad electrodes, and as an exceptional case an electrode type drags was used. In this work, the program ANSYS® that is based on the finite elements method (FEM) was used. After the simulation of the distribution of tensions, different parameters were obtained, such as the tensions of step (Vp) and of contact (Vc) which determine the security of the installation of put in the earth (PE) protection.Bueno Barrachina, JM.; Cañas Peñuelas, CS.; Catalán Izquierdo, S.; Quijano Lopez, A. (2008). Modelization of earth electrode excited by atmospheric discharges based on FEM. Renewable Energy and Power Quality Journal. 1(6):727-732. http://hdl.handle.net/10251/92551S7277321