Jorge Marcos Acevedo

E-Learning Tool for dc Choppers

This work presents a software tool in order to facilitate the learning of the dc choppers. This tool consists of an integrated web-access set of multimedia animation-clips which present, in an interactive way, how the different dc choppers topologies work. The different topologies are classified depending on their quadrant operation and then the user can realize the circuits performance from the simplest class-A to the four quadrant operation class-E converter. To do this, all circuit parameters including load values, duty ratio, and frequency may be selected by the user. Moreover, the load includes an electromotive force (EMF) that allows understanding the energy flow between the source and the load and then, the quadrant operation. Other useful characteristic of the tool is the way in which the circuits are drawn because they can be shown as a bridge or in their simplest form in the case of only the essentials devices being shown. The information about the currents and voltages paths is dynamically presented with sliding rules over the graphs during simulations indicating the state of semiconductor switches by means of changing colours. The multimedia system includes documentation on all the subjects, showing basic concepts and equations, in pdf format and links to industrial manufacturers.

Density measurement in automotive batteries by means of optoelectronic sensors

Lead-acid batteries are an energy storage system used in automotive sector, electric traction, communication remote control, etc. In all of this applications, and specially in remote control, is interested to know ,among other variables, the electrolyte density. This measurement allow us to manage a battery or a set of batteries. In this work we present an optoelectronic sensor developed for the measurement ofthe lead-acid electrolyte density. The sensor has an optical emitter-receiver pair, two plastic optical fibers and the electronic circuit. One fiber is used like a reference in order to minimize the possible common mode errors, due temperature, power supplies, etc. The other fiber is the sensitive fiber and the measurements are taken with it, the functioning principle is an U bend configuration which allows losses due the refraction to the surrounding liquid, this losses depends on the liquid density (electrolyte density). Several tests were done with different conditions and different charging and discharging strategies, the results demonstrate the validity of this technique for the lead-acid electrolyte density measurement with a good stability in the time.Lead-acid batteries are an energy storage system used in automotive sector, electric traction, communication remote control, etc. In all of this applications, and specially in remote control, is interested to know, among other variables, the electrolyte density. This measurement allow us to manage a battery or a set of batteries. In this work we present an optoelectronic sensor developed for the measurement of the lead-acid electrolyte density. The sensor has an optical emitter-receiver pair, two plastic optical fibers and the electronic circuit. One fiber is used like a reference in order to minimize the possible common mode errors, due temperature, power supplies, etc. The other fiber is the sensitive fiber and the measurements are taken with it, the functioning principle is an U bend configuration which allows losses due the refraction to the surrounding liquid, this losses depends on the liquid density (electrolyte density). Several tests were done with different conditions and different charging and discharging strategies, the results demonstrate the validity of this technique for the lead-acid electrolyte density measurement with a good stability in the time.

Lifetime Estimation for Plastic Optical Fibers in Harsh Acid Environments

The work described in this paper explores the suitability of using plastic optical fibers (POFs) as sensors for the development of fast battery chargers. Lead-acid batteries, widely used in the automotive industry, contain an electrolyte formed by a high concentration of sulfuric acid (35% ), an acid environment that can maintain an elevated temperature during the charge and discharge processes. This presents a challenge for the selection of sensors that can withstand such harsh conditions over extended periods of time, in order to monitor the charge cycle and state of health of the battery. POFs can be used as density sensors immersed in the electrolyte at different places within the battery-density varies with location. The accuracy of the density readout must be maintained throughout the useful life of the battery, up to 15 years. In this paper, we present results of over 9000 h of lifetime tests of POFs used as sensing elements for electrolyte density, as well as a procedure to estimate their lifetime for the target application.

Improved interface for a power electronics remote test learning system

A new b-learning environment was set up by means of joining lectures and tutoring sessions, an e-learning moodle platform and an improved interface for an existing remote test learning setup.

Methodology to Obtain the Voltage-Dependent Parameters of a Fourth-Order Supercapacitor Model With the Transient Response to Current Pulses

In order to design power circuits including supercapacitors, a model that responds as closely as possible to results in actual tests, in both fast and slow transients, is required. The network of the parallel RC branches model is widely used to justify the electrical behavior of supercapacitors. In that model, in order to achieve a good fitting between simulation and actual transient responses, the interdependence among the parameters, as well as their voltage dependence, must be considered. This study presents a method to deduce the parameters of the RC network model through the transient response of the supercapacitor including theirs voltage dependence. The methodology considers that the electrical charge provided to the device in the current pulses is not only injected in the fastest branch, but also is simultaneously distributed toward the slower branches. A set of tests have been carried out through the whole voltage range of the device in such a way that in each one the parameters can be considered constant. Then, with the obtained series of values for each parameter, their voltage dependence has been deduced through linear regression. Practical results of a fourth-order model with voltage-dependent parameters are presented and compared with simulations.

A learning methodology oriented towards flyback converter design

The flyback converter is one of the most used topologies, in domestic and industrial environments. The topology combines simplicity and low cost as winning factors. It is also a circuit of a switch-mode power supply (SMPS) adequate for students to learn how to design the power and control stages. A methodology oriented to teach and learn is described in this paper, oriented to the flexibility of access to laboratory and full comprehension of the converter behavior.

Tutorized writing of technical reports as a learning tool for electronic equipment on EMC, Reliability And Safety

In order to develop the communication competencies of the mechanical engineering students, a written technical report consisting of three documents (a report, a set of slides and a script for the slides) is used. Complex aspects of electronics equipments related to EMC, reliability and safety are learned not only by reading information, but also by creating a report. This tutorized task also helps students to learn and understand how information can be classified, to later provide the right kind of presentation to different technical skilled audiences.

Life testing of plastic optical fibers for lead-acid battery fast charge equipment

Our research has been focused in the past years on the development of efficient fast battery chargers of application to electrical vehicles. One of the challenges that we are facing is selecting adequate sensing components to accurately monitor the charging process, due to the harsh environment in the batteries that use an electrolyte with sulfuric acid (H2SO4) at an elevated temperature during the charge process. The sensor must be able to measure the electrolyte density at different places within the battery -density varies with location. The accuracy of the density readout must be maintained through the useful life of the vehicle. In this paper we review our current line of research in fast battery charges as it pertains to their reliability. We present our results on accelerated tests using plastic fiber optics as sensing elements for electrolyte density. The test duration was over one calendar year (9,552 hours) using a sensor with four optical fibers. Three of the optical fibers are used to measure density, and the fourth one as a reference to account for common-mode variation. The charge level of the battery can be derived from this density measurement, as well as the overall health of the battery. For the test, the electrolyte acid density was set to 35%, and the temperature to 70 degrees Celsius. An electronic system for emission and detection of light collected data periodically to assess the transmission loss in the fibers as they aged.