E. Laloya

Use of an AC self-excited switched reluctance generator as a battery charger

We analyzed an AC self-excited switched reluctance generator used as a battery charger, using a second- order nonlinear oscillator model. Generator capacity can be maintained under variable rotor speed by adapting the external capacitance. The AC voltage generated is rectified and adapted with a DC-DC converter to battery voltage. To keep the flux machine under control, the rectified bus voltage should be changed according to oscillating frequency, following a constant voltage/frequency ratio. The simplicity of the system makes it an adequate wind generator for battery charging in isolated locations.

A Link-Layer Slave Device Design of the MVB-TCN Bus (IEC 61375 and IEEE 1473-T)

The train communication network standard was approved in 1999 by the International Electrotechnical Commission (IEC) and the IEEE to warrant train and equipment interoperability. However, we have not found any published work presenting a top-down device design that is compliant with this standard. None of the found publications deals with the real-time protocols of the design nor resolves the many open points left in it. The link-layer design that is presented here implements the full set of specifications of the IEC 61375-1 standard (also named the IEEE 1473-T standard) that is related to the slave devices for the multifunction vehicle bus (MVB), including all of its real-time protocols, procedures, and free options. It is the first step to obtaining a true system-on-chip, including all the layers of any MVB device, as stated by the standard. Our proposal is based on a concurrent, easily parameterized and reconfigurable, top-down design procedure that is implemented in a single field-programmable gate array plus a very simple embedded application processor. The performance of our design is only limited by the standard constraints themselves, which is restricted neither by its proposed implementation nor by our design criteria.

Test bench for switched reluctance motor drives

After a switched reluctance motor (SRM) has been designed and built a set of tests are performed to verify its main design parameters and characteristics. This paper shows a test bench and the instrumentation that allows coping with this task. Although the test rig has been sized for a 300 W SRM to be used in a domestic washing machine the scheme can easily be adapted for higher power drives

Heat Management in Power Converters: From State of the Art to Future Ultrahigh Efficiency Systems

Thermal management is a key design aspect of power converters since it determines their reliability as well as their final performance and power density. Cooling technologies have been a research area in electronics since the 1940s and, in the last 15 years, the number of articles related to this field has grown significantly. At present, thermal management is essential in new disciplines and it is a critical enabling technology in the development of power electronic systems. This paper aims at presenting a review of the state-of-the-art technology and provides future design guidelines for high efficiency power electronic converters. The main design trends are focused on the need to develop cooling systems able to manage high local density heat fluxes due to two converging trends: higher power dissipation and smaller module size. Considering the latest advances in thermal management, as well as the huge improvement in power electronics in the last decades, a review and classification of the main thermal management techniques is presented. Besides, they are compared considering important parameters such as peak power dissipation, efficiency, cost/complexity, power density or technical maturity, and a design example for an ultrahigh efficiency converter is presented.

3D FEM characterization of a switched reluctance motor from direct experimental determination of the material magnetization curve

Analytical characterization of a switched reluctance motor (SRM) by means of magnetic circuit theory can be a tedious task. Specific software based on the finite elements method (FEM) for solving non linear magneto-static problems has proved very useful for this characterization. However, to solve the Maxwell equations it is necessary first to know the magnetization curve of the material used for building the motor, which may not be available in the program materials library. A simple and low cost method for a direct determination of the first magnetization curve of a magnetic material is presented in this communication. Through one single test of short duration, (which allows to reach high values of the magnetic field strength while keeping the material temperature practically constant), we obtain a B-H curve that fits correctly to the samples obtained by a traditional method requiring the identification of multiple hysteresis loops. This B-H curve has been included in a FEM program to determine the flux linkage-current-position characteristic of a SRM prototype. The results again fit those obtained experimentally, confirming the validity of the proposed method.

Steady-state behaviour of an ac autonomous switched reluctance generator

The switched reluctance motor can be used in generation mode by selecting the firing angles of the phases. This implies the use of the asymmetrical half bridge Miller converter and position sensors or position estimators. In this paper an alternative current (AC) switched reluctance generator is studied. Generation is obtained by doing resonate each phase inductance with an external AC capacitor. Although the machine only generates periodically in the negative slope of the inductance profile, the set formed with the machine and a resonating capacitor behaves like an AC generator. The energy periodically generated in the negative slope is stored in the capacitor smoothing the pulsed generating process and spread on an AC cycle. So, the set generates when the inductance profile is either positive or negative. Further, position sensors are not used, the magnetic circuit is used in two quadrants and the current profile does not have switching harmonics. The system simplicity suits to battery charge in isolated locations.

Line redundancy in MVB-TCN devices: a control unit design

TCN (Train Communication Network) standard was approved in 1999 by the IEC (IEC 61375-1) and IEEE (IEEE 1473-T) organizations to warrant a reliable train and equipment interoperability. TCN defines two serial buses: WTB (wire train bus) and MVB (multifunction vehicle bus), permitting double line attachments in both of them. Each attached device must take one of the lines as its trusted line and commute to the other, its observed line, if necessary. Its line redundancy control unit is responsible for these tasks. The MVB line redundancy control unit design here presented is, to our knowledge, the first one to be published. It is but one bit of the top-down full compliant MVB device design (class 1 to class 5) being developed by the authors to get a true reconfigurable system on chip. Our proposal, based on concurrent and parametrical techniques, owns both a high speed performance and an easy reconfigurability. Moreover, the performance of our design is only limited by the standard constraints themselves, being not restricted by our design criteria or our proposed implementation

Simulation Model of an AC Autonomous Switched Reluctance Generator

Switched Reluctance Machine (SRM) has a nonlinear behavior which difficults its understanding. The electric model shows this nonlinear behavior and it is difficult to derive conclusions but for the linear case. Simulators appear as the ideal tools for studying the machine. Although some papers report simulation models for this machine working in motoring and generating modes, the generating mode is only used for braking but not for generating electricity. In this paper the machine is used for generation purpose and the generated voltage and current are alternative instead of DC as usual. This difference enforces relevant changes demanding a new simulation model. The model has been implemented in Matlab/Simulink and allows analysis of linear and nonlinear cases. It has been used to study the working zones and its steady and transitory state behavior.

Experimental equivalent circuit parameters identification of a switched reluctance motor

The paper describes an experimental method to identify the equivalent circuit parameters of a switched reluctance motor including non ideal effects associated with the magnetic core. The proposed method avoids the use of large capacitors or batteries to reach values of current that guarantee the saturation of the magnetic core, and minimizes the number of power electronic devices. The experimental parameters identification for the proposed equivalent circuit involves the capture of current and voltage over one phase and one auxiliary winding as well as the later processing of those variables to obtain the magnetic characteristics of the motor. The model has been simulated with the experimentally identified parameters, confirming the effectiveness of the method and the model.

Inductance characterization of a SRM using finite element simulation data

FE simulation data provides information about magnetic properties corresponding to a range of foreseen current excitation and rotor positions. This information needs further processing to derive other electric parameters, among which, inductance plays an important role for simulation and modeling purposes. This paper describes this process looking for analytical expressions and evaluating the incidence of simplicity against accuracy. Although searching for analytical expressions is usually justified by time saving, in this case it is because analytical expressions are necessary to model the machine as a second order nonlinear system using analytical equations. This representation provides a better insight in the understanding of the behavior of autonomous self-excited AC switched reluctance generators.