nowadays, it is familiar to designers to use a numerical method for design, optimization or verification of technical device parameters. The well-known software resources are built on principles of finite or boundary elements (or finite differences several years ago). These methods (especially the Finite Element Method -FEM) have been built on common basic principles; the most important is the Principle of Minimal Energy (described eg by R. P. Feynman in 1966).The basic ideas of the Principle of Minimal Energy will be presented in the paper, followed by practical examples. The reader will be able to follow the principle and build an understandable theory on professional numerical methods basics, theirs possible advantages and disadvantages and shortcomings. The main idea presented in the paper is based on very simple example -motion in the gravitational field of the earth.
A prototype of a special electrical machine ‐ double statored switched reluctance motor ‐ has been developed which produces a very high static and dynamic torque. Possible ways of measuring the machine are presented. The basic parameters of the model are described. Results are compared to those obtained by computer design. A difference between computed and measured results is discussed.
The efficient utilization of energy sources seems to be one of the most challenging problems for designers and scientists alike. This challenge particularly applies to power electronics, where the increasing value of energy density leads to demands for optimization processes and better exploitation (and distribution) of available power sources. As a result, the implementation of frequency-controlled systems is more often in the spotlight. The systems with doubly fed induction machines and a frequency converter in the rotor circuit are typical representatives of these demands. In a wide spectrum of power electronic systems, frequency converters are often used that have a constant current, a diode rectifier, and a thyristor inverter. This article provides a novel approach to modeling methodology, and presents a unique comparison of four different frequency converter schemes that are connected to a doubly fed induction machine. This article presents the modeling methodology itself, as well as the results based on an asynchronous generator motor fed by different frequency converters, a spectral analysis of the output voltage of the used frequency converters, and a comparison of the different technologies. Based on the above, this paper recommends the use of a multistage-multilevel frequency converter scheme.
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