DSpace Collection:

Bearing fault detection by a novel condition-monitoring scheme based on statistical-time features and neural networks

Wed, 19 Jun 2013 07:54:17 GMT

Title: Bearing fault detection by a novel condition-monitoring scheme based on statistical-time features and neural networks Authors: Delgado Prieto, Miguel; Cirrincione,, Giansalvo; García Espinosa, Antonio; Ortega Redondo, Juan Antonio; Henao, Humberto Abstract: Bearing degradation is the most common source of faults in electrical machines. In this context, this work presents a novel monitoring scheme applied to diagnose bearing faults. Apart from detecting local defects, i.e., single-point ball and raceway faults, it takes also into account the detection of distributed defects, such as roughness. The development of diagnosis methodologies considering both kinds of bearing faults is, nowadays, subject of concern in fault diagnosis of electrical machines. First, the method analyzes the most significant statistical-time features calculated from vibration signal. Then, it uses a variant of the curvilinear component analysis, a nonlinear manifold learning technique, for compression and visualization of the feature behavior. It allows interpreting the underlying physical phenomenon. This technique has demonstrated to be a very powerful and promising tool in the diagnosis area. Finally, a hierarchical neural network structure is used to perform the classification stage. The effectiveness of this condition-monitoring scheme has been verified by experimental results obtained from different operating conditions.

Dielectric, thermal, and mechanical properties of acrylonitrile butadiene styrene reinforced with used tires

Fri, 07 Jun 2013 10:39:39 GMT

Title: Dielectric, thermal, and mechanical properties of acrylonitrile butadiene styrene reinforced with used tires Authors: Mujal Rosas, Ramón María; Òrrit Prat, Jordi; Ramis Juan, Xavier; Marín Genescá, Marcos; Rahhali, Ahmed Abstract: Mass production of tires as well as their storage or elimination is a real environmental problem. Various methods for recycling of tires are currently used, such as mechanical grinding, which separates vulcanized rubber, steel, and fibers from tires. Rubber is, then, used in several industrial applications such as flooring, insulations, and footwear. This paper focuses on a new application for old used tires (ground tire rubber, GTR). Tire dust and acrylonitrile butadiene styrene (ABS) have been mixed, and the maximum accepted concentration of GTR can be attained while keeping dielectric, thermal, and mechanical properties within acceptable limits, and therefore their possible industrial application will be in manufacturing of, for example, dielectrics for capacitors, low-voltage electric fences or electrical cable pipes, and trays. Actually, tire dust with particle sizes <700 μm has been classified into three different groups depending on the particle sizes (p < 200, 200< p < 500, and p > 500 μm). Afterward, ABS has been mixed with different concentrations of GTR, i.e., 5%, 10%, 20%, 50% and 70%, to establish its properties through thermal, mechanical, and dielectric tests. Finally, the fracture surfaces of the composite samples have been evaluated by using scanning electron microscopy. Description: Cop. 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E399–E415, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21287

A control technique for integration of DG units to the electrical networks

Fri, 31 May 2013 10:26:42 GMT

Title: A control technique for integration of DG units to the electrical networks Authors: Pouresmaeil, Edris; Miguel Espinar, Carlos; Massot Campos, Miquel; Montesinos Miracle, Daniel; Gomis Bellmunt, Oriol Abstract: This paper deals with a multiobjective control technique for integration of distributed generation (DG) resources to the electrical power network. The proposed strategy provides compensation for active, reactive, and harmonic load current components during connection of DG link to the grid. The dynamic model of the proposed system is first elaborated in the stationary reference frame and then transformed into the synchronous orthogonal reference frame. The transformed variables are used in control of the voltage source converter as the heart of the interfacing system between DG resources and utility grid. By setting an appropriate compensation current references from the sensed load currents in control circuit loop of DG, the active, reactive, and harmonic load current components will be compensated with fast dynamic response, thereby achieving sinusoidal grid currents in phase with load voltages, while required power of the load is more than the maximum injected power of the DG to the grid. In addition, the proposed control method of this paper does not need a phase-locked loop in control circuit and has fast dynamic response in providing active and reactive power components of the grid-connected loads. The effectiveness of the proposed control technique in DG application is demonstrated with injection of maximum available power from the DG to the grid, increased power factor of the utility grid, and reduced total harmonic distortion of grid current through simulation and experimental results under steady-state and dynamic operating conditions.

Design of a simpler ampere-hourmeter

Mon, 27 May 2013 17:00:57 GMT

Title: Design of a simpler ampere-hourmeter Authors: Farré, Lluís; Closas Torrente, Lluís; Casals Torrens, Pau Abstract: In any application in which working with batteries is a must, the knowledge of the batteries’ state-of-charge (SOC) is a fundamental parameter for anyone, so it determines the remaining capacity in the battery. There exist several methods for the estimation of this SOC in Lead-acid batteries; however, when the requisites of the measuring method must offer, besides precision and reliability, the possibility to integrate the results into an automatized system, the Coulomb’s counter is the method that prevails. This paper presents, then, the design of a simpler Ampere-hourmeter based lead-acid battery SOC estimating system. Supported by previous studies in the field of SOC estimation in Hybrid Electric Vehicles and by experimental tests carried out by the researchers, the modelling of the simpler measuring system has been parameterized by following Peukert’s Equation, and afterwards it has been integrated into a data acquisition and processing system designed through a CSNX25 current sensor and a low-cost and low-consume 16F877 microcontroller. The fundamental conclusion of this paper is that obtaining an accurate result while estimating the SOC of a lead-acid battery with an simpler Ampere-hourmeter developed through a microcontroller based system is achievable but only if the used microcontroller holds enough memory to include the whole data treatment algorithms.

Electric drives for light e-scooters

Mon, 06 May 2013 17:52:03 GMT

Title: Electric drives for light e-scooters Authors: Andrada Gascón, Pedro; Blanqué Molina, Balduino; Martínez Piera, Eusebio; Torrent Burgués, Marcel; Perat Benavides, Josep Ignasi; Sánchez López, José Antonio Abstract: In the next years is expected an important rise in sales of electrical scooters in the entire world but especially in China. In order to address this challenge the electric scooter industry has to be more competitive in the transportation market and therefore important improvements, in terms of energy density and costs, have to be done in the electric storage system and in the electric propulsion system. In this paper, an analytical and experimental comparison of two different drives for electric scooters is carried out. Both are permanent magnet synchronous outer rotor motor drives but one placed inside the rear wheel and the other connected to the wheel trough a mechanical transmission.

Autonomous photovoltaic lighting system

Tue, 09 Apr 2013 11:31:27 GMT

Title: Autonomous photovoltaic lighting system Authors: Hafez, Ahmed A. A.; Montesinos Miracle, Daniel; Sudrià Andreu, Antoni Abstract: This paper introduces a comparison between the conventional and Photovoltaic (PV) lighting systems. A simple sizing procedure for a PV stand-alone system was advised. The paper also proposes a novel PV lighting system. The proposed system is simple, compact and reliable. The system operation was investigated by thoroughly mathematical and simulation work.

Lightning initiation from a tall structure in the Basque Country

Wed, 13 Mar 2013 15:22:51 GMT

Title: Lightning initiation from a tall structure in the Basque Country Authors: López, Javier; Montañá Puig, Juan; Maruri, M.; De la Vega, D.; Aranda, J.A.; Gaztelumendi, S. Abstract: Lightning detection in the Spanish Basque Country is performed using the LF TOA, VHF interferometer and the VLF lightning detection technologies in which two independent networks are based, providing a better detection quality due to the combination of these different techniques. Total lightning activity related to the tall structure of the weather radar operated by the Basque Meteorology Agency (Euskalmet) is presented. The tall structure is a 50 m tower located on the top of Kapildui Mountain (at about 1169.48 m ASL). Remarkable electrical activity associated to this place has been witnessed in the last two years. Two particular flashes during November 30th 2009 caused damage to the weather radar. Two different lightning detection networks detected five and six cloud-to-ground strokes, respectively. Only nine VHF sources were detected in the first flash without any VLF detection classified as intracloud. But for the second flash non VHF source was detected and two detections were reported by the VLF system. In both cases some intracloud detections were reported before cloud-to-ground strokes and some others during the flash. This paper presents the study of a winter episode with a special impact in the tower, the research carried out for characterizing the lightning events and the measures taken in order to achieve a better protection mechanism for the radar site

High-speed video of lightning and x-ray pulses during the 2009–2010 observation campaigns in northeastern Spain

Wed, 13 Mar 2013 14:47:48 GMT

Title: High-speed video of lightning and x-ray pulses during the 2009–2010 observation campaigns in northeastern Spain Authors: Montañá Puig, Juan; Van der Velde, Oscar Arnoud; March Nomen, Víctor; Romero Durán, David; Solà de Las Fuentes, Gloria; Pineda Ruegg, Nicolau Abstract: This paper summarizes results obtained by the 2009–2010 field campaigns conducted in northeastern Spain using a high speed camera, VHF interferometer, VLF lightning location system and scintillation detectors for energetic radiation. The main purpose was to obtain new insight into the lightning processes which emit x/γ radiation. For just one (very close) lightning strike, 99 x-ray pulses were emittedwithin 0.86 ms and had an energy higher that 10 keV. This burst was associated with the final stages of a downward negative leader. The high-speed camera data also allowed to identify various previously unreported features in different types of cloud-to-ground lightning flashes. At video frame rates of 10,000 fps, some branches of negative leaders of cloud-to-ground flashes were illuminated for the duration of only one frame. During positive cloud-to-ground flashes, the high speed videos showed an intense activity of recoil leaders. In the case of intra-cloud lightning, the VHF interferometer network did not present a clear relation between detections and visible leader. Instead, bursts of VHF detections corresponded visually to a long-lasting bright channel under the cloud base

Pareto optimal reconfiguration of power distribution systems using a genetic algorithm based on NSGA-II

Wed, 13 Mar 2013 12:54:14 GMT

Title: Pareto optimal reconfiguration of power distribution systems using a genetic algorithm based on NSGA-II Authors: Tomoiaga, Bogdan; Chindris, Mircea; Sumper, Andreas; Sudrià Andreu, Antoni; Villafafila Robles, Roberto Abstract: Reconfiguration, by exchanging the functional links between the elements of the system, represents one of the most important measures which can improve the operational performance of a distribution system. The authors propose an original method, aiming at achieving such optimization through the reconfiguration of distribution systems taking into account various criteria in a flexible and robust approach. The novelty of the method consists in: the criteria for optimization are evaluated on active power distribution systems (containing distributed generators connected directly to the main distribution system and microgrids operated in grid-connected mode); the original formulation (Pareto optimality) of the optimization problem and an original genetic algorithm (based on NSGA-II) to solve the problem in a non-prohibitive execution time. The comparative tests performed on test systems have demonstrated the accuracy and promptness of the proposed algorithm.

Dielectric, mechanical, and thermal characterization of high-density polyethylene composites with ground tire rubber

Tue, 05 Mar 2013 10:41:14 GMT

Title: Dielectric, mechanical, and thermal characterization of high-density polyethylene composites with ground tire rubber Authors: Mujal Rosas, Ramón María; Marín Genescá, Marcos; Orrit Prat, Jordi; Rahhali, Ahmed; Colom Fajula, Xavier Abstract: The mass manufacture of tires and the difficulty in storing or disposing them constitute a serious environmental problem. At present, various recycling methods for tires are used, such as grinding, which separates the steel and fibers from the vulcanized rubber, then using the rubber in numerous industrial applications such as pavements, insulators, footwear, etc. The aim of this article focuses on finding a new application for the ground tire rubber (GTR). This would allow including GTR in industrial applications of recycled high-density polythene (HDPE). Tire dust and HDPE thermoplastic have been mixed, and the maximum accepted values of GTR concentration that can be admitted while keeping dielectric, mechanical, and thermal properties within acceptable values, as well as initial polymer microstructure, have been checked. In addition, the suitability of the compounds for antistatic applications is studied. The recycled tire dust which results from the industrial milling processes has been divided by sieve in three different categories according to the size of the particles (<200, 200–500, and >500 mm). This has then been mixed with HDPE in different GTR concentrations (0%, 5%, 10%, 20%, 40%, 50%, and 70%) in order to establish its conduct through electrical, mechanical, thermal, and microstructure tests, which will be held in a temperature range 30–120_C, and with a frequency range 1 _ 10_2 and 3 _ 106 Hz. The thermal tests determined the enthalpies and fusion temperatures which allow for the observation of changes in crystalline and microstructure of the matrix, and finally, the fracture surfaces of the compound samples have been evaluated using scanning electron microscopy

Model of discharge lamps with magnetic ballast

Fri, 15 Feb 2013 10:49:21 GMT

Title: Model of discharge lamps with magnetic ballast Authors: Molina, Julio; Sainz Sapera, Luis; Mesas García, Juan José; Bergas Jané, Joan Gabriel Abstract: Magnetic ballast discharge lamp modeling has been extensively studied because these lamps can be an important source of harmonics. Discharge lamp models usually represent the arc voltage by a square waveform. However, this waveform can be far from actual arc voltages, which affects the accuracy of the lamp models. This paper investigates the actual arc voltage behavior of discharge lamps from laboratory measurements and proposes a novel characterization of these voltages to reformulate the conventional models. The accuracy of the new model is validated with experimental measurements.

Saturation effects on torque- and current–slip curves of squirrel-cage induction motors

Thu, 14 Feb 2013 10:08:24 GMT

Title: Saturation effects on torque- and current–slip curves of squirrel-cage induction motors Authors: Monjo Mur, Lluís; Córcoles López, Felipe; Pedra Durán, Joaquim Abstract: This paper measures and analyzes the saturation effects on torque- and current–slip curves of three squirrel-cage induction motors.Motor saturation is illustrated by three sets of measurements: I) torque and current for each slip measured at three voltage levels; II) short-circuit impedance measured at different current levels; and III) no-load impedance measured at different voltage levels. In test I, torque and current measured at reduced voltage are prorated to full voltage for comparison purposes. A double-cage model is used to model the motors, and the nonlinearity of their reactances is examined. In order to evaluate the individual weight of every nonlinear reactance on the observed saturated behavior, we try to fit the measurements considering that only one reactance of the double-cage model is nonlinear. Good agreement is obtained only when the stator leakage reactance is considered nonlinear. On the contrary, when magnetizing or remaining leakage reactances are considered nonlinear, they predict machine behaviors inconsistent with measurements. In otherwords, the saturation of the stator leakage reactance is the main contributor to torque and current behavior, while the saturation of the remaining reactances has a negligible influence. Consequently, when all voltage levels are considered, the squirrel-cage induction motors can be accurately modeled (with reasonable accuracy) with a double-cage modelwhere only the stator leakage reactance is considered nonlinear. When only a constant voltage level is considered, the paper also proves that a linear double-cage model (all reactances are linear) accurately predicts machine behavior at such voltage level.

Study on dielectric, mechanical and thermal properties of polypropylene (PP) composites with ground tyre rubber (GTR)

Mon, 11 Feb 2013 14:57:40 GMT

Title: Study on dielectric, mechanical and thermal properties of polypropylene (PP) composites with ground tyre rubber (GTR) Authors: Mujal Rosas, Ramón María; Orrit Prat, Jordi; Ramis Juan, Xavier; Marín Genescá, Marcos; Rahhali, Ahmed

Design and control of a modular multilevel DC/DC converter for regenerative applications

Mon, 11 Feb 2013 10:25:07 GMT

Title: Design and control of a modular multilevel DC/DC converter for regenerative applications Authors: Montesinos Miracle, Daniel; Massot Campos, Miquel; Bergas Jané, Joan Gabriel; Galcerán Arellano, Samuel; Rufer, Alfred Abstract: This paper compares different cascaded and multilevel topologies to interface supercapacitors to a dc bus in regenerative braking applications. It is shown that the modular multilevel dc/dc converter (MMC) can benefit from both reduced voltage and increased frequency across the inductor to reduce its weight and volume when using phase shifting modulation. The proposed controlmethod is able to balance supercapacitor voltage while providing precise output current control. The converter topology and control method are validated with simulations and experimental results.

Aplicaciones eléctricas del acrilonitrilo butadieno estireno (ABS) reforzado con neumáticos fuera de uso (GTR)

Fri, 08 Feb 2013 13:57:52 GMT

Title: Aplicaciones eléctricas del acrilonitrilo butadieno estireno (ABS) reforzado con neumáticos fuera de uso (GTR) Authors: Mujal Rosas, Ramón María; Orrit Prat, Jordi; Ramis Juan, Xavier; Marín Genescá, Marcos