Third International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Third International Symposium on Magnetic Suspension Technology was held at the Holiday Inn Capital Plaza in Tallahassee, Florida on 13-15 Dec. 1995. The symposium included 19 sessions in which a total of 55 papers were presented. The technical sessions covered the areas of bearings, superconductivity, vibration isolation, maglev, controls, space applications, general applications, bearing/actuator design, modeling, precision applications, electromagnetic launch and hypersonic maglev, applications of superconductivity, and sensors

Mathematical modelling of a vector controlled LIM drive

The linear induction motor is often still considered to be a special-purpose machine that is tailored to meet specific needs, but it is slowly finding more applications with its added advantages over rotary motors. This thesis is concerned with the development of a mathematical model which provides the transient and steady-state performance of a current-regulated inverter-fed linear induction motor system. The linear induction motor is posed as a one-dimensional electromagnetic field problem, to provide a better understanding of the so called 'endeffect' phenomena, which accounts mainly for the difference in performance between the linear induction motor and its rotary counterpart. An equivalent circuit is described that takes into account these end-effect transients for a single-sided linear induction motor. An accurate model for the inverter switching action is developed and the performance of the complete system under various operating conditions is studied, and compared with experimental results obtained from published literature. A closed-loop control system is implemented, using conventional field-oriented control and a newer and simpler method known as Natural Field Orientation is investigated, and compared with both the direct and indirect field orientation methods. In Natural Field Orientation, a decoupled control of torque and flux producing components of current is easily achieved by using the machines inherent properties, to establish a correct field-orientation, and this allows the induction motor to provide a performance that combines the control characteristics of the dc motor with the merits of the induction motor

Fourth International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Fourth International Symposium on Magnetic Suspension Technology was held at The Nagaragawa Convention Center in Gifu, Japan, on October 30 - November 1, 1997. The symposium included 13 sessions in which a total of 35 papers were presented. The technical sessions covered the areas of maglev, controls, high critical temperature (T(sub c)) superconductivity, bearings, magnetic suspension and balance systems (MSBS), levitation, modeling, and applications. A list of attendees is included in the document

Design and fabrication of a long-life Stirling cycle cooler for space application. Phase 3: Prototype model

A second-generation, Stirling-cycle cryocooler (cryogenic refrigerator) for space applications, with a cooling capacity of 5 watts at 65 K, was recently completed. The refrigerator, called the Prototype Model, was designed with a goal of 5 year life with no degradation in cooling performance. The free displacer and free piston of the refrigerator are driven directly by moving-magnet linear motors with the moving elements supported by active magnetic bearings. The use of clearance seals and the absence of outgassing material in the working volume of the refrigerator enable long-life operation with no deterioration in performance. Fiber-optic sensors detect the radial position of the shafts and provide a control signal for the magnetic bearings. The frequency, phase, stroke, and offset of the compressor and expander are controlled by signals from precision linear position sensors (LVDTs). The vibration generated by the compressor and expander is cancelled by an active counter balance which also uses a moving-magnet linear motor and magnetic bearings. The driving signal for the counter balance is derived from the compressor and expander position sensors which have wide bandwidth for suppression of harmonic vibrations. The efficiency of the three active members, which operate in a resonant mode, is enhanced by a magnetic spring in the expander and by gas springs in the compressor and counterbalance. The cooling was achieved with a total motor input power of 139 watts. The magnetic-bearing stiffness was significantly increased from the first-generation cooler to accommodate shuttle launch vibrations

Método de estimación de las pérdidas de los conductores y del núcleo de componentes inductivos asimétricos mediante la técnica de análisis por método de elementos finitos en 3D

Tesis doctoral con la Mención de "Doctor Internacional"Dentro del campo de la ingeniería eléctrica, los convertidores electrónicos de potencia, que permiten generar una tensión y corriente de unas determinadas características a partir de una fuente de energía, juegan un papel crítico en las energías renovables, vehículos eléctricos o la ingeniería aeroespacial. Los componentes magnéticos constituyen uno de los elementos esenciales en los convertidores de potencia determinando el filtrado de corriente, la operación y la eficiencia del convertidor. Uno de los parámetros más críticos que influyen en la eficiencia de los convertidores son las pérdidas de los componentes magnéticos que dependen de determinados efectos electromagnéticos como el efecto pelicular, de proximidad, de entre-hierros y de borde. Estos efectos son aún más relevantes en rangos de alta frecuencia, a la que suelen operar habitualmente los convertidores electrónicos de potencia. La optimización del convertidor de potencia requiere un análisis detallado de los componentes magnéticos y de los efectos de frecuencia producidos en función de cada aplicación particular, y sus requisitos específicos, principalmente en los rangos de media y alta frecuencia. La trasmisión, almacenamiento y pérdidas de energía eléctrica y magnética son relevantes en este contexto y están determinadas por las ecuaciones de Maxwell, cuya resolución es compleja. Existen tres importantes enfoques para la resolución de estas ecuaciones: métodos analíticos, análisis utilizando herramienta de elementos finitos y por realización de ensayos. El primero de ellos consiste en la resolución analítica de las ecuaciones, con las necesarias simplificaciones, siendo la más habitual el asumir simetrías en las distribuciones de los campos magnéticos para poder resolver las ecuaciones de Maxwell en una o dos dimensiones. Como desventaja, dicha simplificación no permite determinar la distribución del campo magnético dentro de los conductores. El segundo enfoque utiliza un método de elementos finitos, resolviendo las ecuaciones de Maxwell en cada elemento finito, no siendo posible simular algunos componentes magnéticos complejos por precisar un tiempo de simulación sea muy elevado, haciendo que esta solución no resulte práctica para los ingenieros de desarrollo. El tercer enfoque, basado en la realización de ensayos de laboratorio, permite obtener los parámetros eléctrico de cualquier componente magnético. No obstante, el tiempo necesario es también alto y sólo es usado para los ajustes finales. La mayoría de los ingenieros electrónicos y científicos usan los análisis basados en elementos finitos de los componentes magnéticos realizando las posibles simplificaciones teniendo en cuenta la distribución de campo magnético y la simétrica del componente. Cuando el componente magnético no presenta ninguna simetría, deben utilizarse modelos 3D para la determinación de sus parámetros del circuito eléctrico equivalente y la optimización magnética del componente, así como un detallado estudio de los efectos pelicular y de proximidad, que son especialmente relevantes cuando el componente trabaja en alta frecuencia. En este trabajo, se proponer una metodología basada en elementos finitos en 3D con un bajo tiempo de simulación que permite obtener los parámetros que del modelo eléctrico equivalente para componentes magnéticos asimétricos a partir de la estimación de las pérdidas del bobinado y del núcleo.In electrical engineering, power converters, as devices that are able to transform a defined current and voltage from an energy source, have a critical role in different fields as renewable energy, electric vehicles or aerospace engineering. The magnetic components are relevant elements in power converters because determines the current filtering and conversion functions and converter efficiency and performance. One of the critical parameters that influence in the efficiency of converters are the losses in the magnetic components that depends on particular effects as they are the skin, proximity, airgap and edge effects. These effects are more relevant in the high frequency ranges where the power converters are usually operated. The optimization of the power converter requires of the detailed analysis of the magnetic component and the involved frequency effects according to the application when particular requirements are needed, mostly in the medium and high frequency. Transmission, storage and losses of magnetic and electric energy analysis is relevant in this context and are determined by the Maxwell´s equations whose resolution is a complex task. There are three main methods to solve this equation system: analytical method, finite element method analysis and experimental methodology. The first method consists on the analytical resolution of the equations with the necessary simplifications, being the most common approach the assumption of the magnetic field distribution in one or two dimensions to solve the equations system, however this simplification does not allow determining the magnetic field into the conductors. The second approach uses the Finite Element Method, solving the Maxwell equations in very finite element of the component, but is not possible to simulate some complex magnetic components because it requires a high computational time, being not useful for power electronics designers. The third method, based on experimental lab tests, allows to obtain the electrical parameters for any magnetic component. Nevertheless, the time cost is also huge and it is only used for adjustments in the final stage. Most of the power electronics designers and scientists use the analysis of the magnetic components based on Finite Element Method doing the available simplification taking into account the magnetic field distribution and the symmetry of the magnetic component. If the magnetic component has not any symmetric, a 3D model is necessary to determine the electromagnetic or thermal parameters for the electrical equivalent circuit and the magnetic component optimization, as well as a detailed study for skin effect and proximity effect, even more if the magnetic components work at high frequency. In this work, it is proposed a new method based in 3D Finite Element Analysis with a low computational time that allows obtaining the electrical equivalent model parameters for asymmetric magnetic components from the estimation of winding and core power losses

Third International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Third International Symposium on Magnetic Suspension Technology was held at the Holiday Inn Capital Plaza in Tallahassee, Florida on 13-15 Dec. 1995. The symposium included 19 sessions in which a total of 55 papers were presented. The technical sessions covered the areas of bearings, superconductivity, vibration isolation, maglev, controls, space applications, general applications, bearing/actuator design, modeling, precision applications, electromagnetic launch and hypersonic maglev, applications of superconductivity, and sensors

Mathematical Models for the Design of Electrical Machines

This book is a comprehensive set of articles reflecting the latest advances and developments in mathematical modeling and the design of electrical machines for different applications. The main models discussed are based on the: i) Maxwell–Fourier method (i.e., the formal resolution of Maxwell’s equations by using the separation of variables method and the Fourier’s series in 2-D or 3-D with a quasi-Cartesian or polar coordinate system); ii) electrical, thermal and magnetic equivalent circuit; iii) hybrid model. In these different papers, the numerical method and the experimental tests have been used as comparisons or validations

Performance of Induction Machines

Induction machines are one of the most important technical applications for both the industrial world and private use. Since their invention (achievements of Galileo Ferraris, Nikola Tesla, and Michal Doliwo-Dobrowolski), they have been widely used in different electrical drives and as generators, thanks to their features such as reliability, durability, low price, high efficiency, and resistance to failure. The methods for designing and using induction machines are similar to the methods used in other electric machines but have their own specificity. Many issues discussed here are based on the fundamental achievements of authors such as Nasar, Boldea, Yamamura, Tegopoulos, and Kriezis, who laid the foundations for the development of induction machines, which are still relevant today. The control algorithms are based on the achievements of Blaschke (field vector-oriented control) and Depenbrock or Takahashi (direct torque control), who created standards for the control of induction machines. Today’s induction machines must meet very stringent requirements of reliability, high efficiency, and performance. Thanks to the application of highly efficient numerical algorithms, it is possible to design induction machines faster and at a lower cost. At the same time, progress in materials science and technology enables the development of new machine topologies. The main objective of this book is to contribute to the development of induction machines in all areas of their applications

Non-Destructive Techniques Based on Eddy Current Testing

Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future

Second International Symposium on Magnetic Suspension Technology, part 2

In order to examine the state of technology of all areas of magnetic suspension and to review related recent developments in sensors and controls approaches, superconducting magnet technology, and design/implementation practices, the 2nd International Symposium on Magnetic Suspension Technology was held at the Westin Hotel in Seattle, WA, on 11-13 Aug. 1993. The symposium included 18 technical sessions in which 44 papers were presented. The technical sessions covered the areas of bearings, bearing modelling, controls, vibration isolation, micromachines, superconductivity, wind tunnel magnetic suspension systems, magnetically levitated trains (MAGLEV), rotating machinery and energy storage, and applications. A list of attendees appears at the end of the document