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The purpose of this paper is the numerical verification of the linearization coefficient ap proposed by Turowski for the calculation of the electromagnetic field distribution and therefore the stray losses inside magnetically saturated solid steel conductors.
The numerical verification is performed on a case study consisting of a simple current conductor sheet parallel to a solid steel plate. Numerical computations are compared with analytical calculations with and without inclusion of the semi-empirical Turowski’s coefficient.
Results confirm a good agreement between numerical values for steel with non-linear permeability and analytical ones applying Turowski’s coefficient. This is particularly powerful in the case of analytical calculation of the magnetic surface impedance (SI) to increase precision when hybrid methods are used. The concept of SI enables the establishment of hybrid approaches for the calculation of stray losses, combining the numerical methods (finite difference method, finite element method (FEM), etc.) together with the analytical formulation, gaining from the advantages of both methods.
Previous numerical analysis was focused on the field dependence on time for several depths inside solid steel. The aim of this paper is to investigate the electromagnetic field distribution inside solid steel on a representative FEM model and verify how the linearization coefficient ap proposed by Turowski works.
Introduction Academic institutions involved in electrical engineering education now realise the importance of students' understanding of the concepts of magnetic fields…
Introduction Academic institutions involved in electrical engineering education now realise the importance of students' understanding of the concepts of magnetic fields and their application in various electromechanical devices and systems. Students find it extremely difficult to comprehend magnetic fields and to grasp the physical phenomena which occur in those devices and systems. Often to be able to consider, and skillfully investigate, the behaviour of such devices and systems, students have not only to demonstrate the knowledge and understanding of difficult physical phenomena, but also show the ability to perform sometimes extremely complex mathematical calculations. Of the many aims and objectives to consider when teaching, two important factors are:
Magnetostaic field analysis of 3‐D nonlinear model problem (No.10 ‐ TEAM Workshop) is carried out by the authors using the Reluctance Network Method. The components and…
Magnetostaic field analysis of 3‐D nonlinear model problem (No.10 ‐ TEAM Workshop) is carried out by the authors using the Reluctance Network Method. The components and resultant flux density are computed and compared with measurements and results obtained by other authors and shaw reasonable convergence and much less CPU time.
This paper presents the numerical solution of the TEAM Workshop Problem 7 obtained by Reluctance Network Method (RNM). The problem represents a three‐dimensional multiply…
This paper presents the numerical solution of the TEAM Workshop Problem 7 obtained by Reluctance Network Method (RNM). The problem represents a three‐dimensional multiply connected eddy current problem with a time — harmonic excitation. The numerical results obtained by RNM in reasonable computing time, agree extremely well with experimental data and other methods results.
The paper presents a historical review, the state of the art and recent advances in the field of computational electromagnetics at leading universities and research institutes in Poland. Contributions made by Polish scientists to the development of fundamental electromagnetism, as well as to computational methods, are emphasized, and some conclusions are drawn regarding expected future developments.
Heavy current bushings passing through steel cover plates and housing walls of power transformers, generators and other large power equipment are thermally hazardous…
Heavy current bushings passing through steel cover plates and housing walls of power transformers, generators and other large power equipment are thermally hazardous elements of construction and a source of additional power losses. Safety and reliability of such expensive objects and safety of power delivery often depend on the proper design of these elements. In the paper a computer analysis, based on Maxwell equations and analytical representation of electromagnetic field was carried out. Non‐linear permeability of solid steel was considered with the help of analytical approximation. Eddy current losses have been calculated and compared using different methods of calculation and experiments. The method of forecasting possible excessive heating and hot spot with the help of electromagnetic criteria was used. Various constructional means of loss and hot spot reduction were proposed and examined.
Recent progress in the development of electromagnetic field theory and sophisticated software for solution of complicated, non‐linear, 3‐D structures is not always…
Recent progress in the development of electromagnetic field theory and sophisticated software for solution of complicated, non‐linear, 3‐D structures is not always accompanied with relatively cheap and simply presented engineering instructions, easy to use for regular industrial design. In the paper some theoretical and practical examples are given as to how one can get over a excessive calculating difficulties to obtain quickly simple design directions and reduce complicated theory to simple practical conclusions. The fast and cheap package RNM‐3D is validated by comparison with industrial test data and with the interactive graphics system is the final illustration of the effectiveness of such an approach. RNM‐3D is used successfully in many transformer works the world over.
The work aims at investigating the law of miniaturization of a linear reluctance motor by expressing the ratio of force to mass as a function of bar position in per unit…
The work aims at investigating the law of miniaturization of a linear reluctance motor by expressing the ratio of force to mass as a function of bar position in per unit, for different scale factors. Corresponding to the same factors, inductance is also computed. Finally the ratio of the bar length to external diameter is changed and the analysis is accordingly repeated.
The recent achievements in electronic control as well as the higher performance of advanced permanent magnets have brought about a change in the general strategy for…
The recent achievements in electronic control as well as the higher performance of advanced permanent magnets have brought about a change in the general strategy for design and development of new types of small electrical machines. A special application of permanent magnets (PM) is represented by hybrid stepping motors (HSM). The latter are a sort of combination of variable reluctance‐motors and permanent magnet‐motors. The influence of various PM inserts into the magnetic circuits of electromechanical converters on field and force distribution has been already investigated by the authors (1996). Promising results for HSM have been reported, especially when rare‐earth PMs are used. The main aim of PM inserting, when they are put into slots of slotted pole shoes with radial N‐S polarization, is to focus magnetic field lines in the corresponding teeth. As a result, the reluctance stepping torque can be increased depending on the material used. Now a further step is made by extending the analysis from the case of linear to that of non‐linear demagnetization curves of permanent magnets.
The purpose of the paper is to compare losses and temperatures in power transformer tanks for different high current lead arrangements.
3D computational tools MagNet and ThermNet based on the finite element method are used to calculate magnetic field distribution in 3D models of power transformers. Eddy current losses in conducting metal parts are induced by the stray magnetic field of transformer windings and high current leads. From loss distribution and appropriate cooling condition temperature values are calculated.
From calculation results it is possible to understand advantages and disadvantages of different lead arrangements. The analysis is finalized with a short presentation of the influence of magnetic shielding height on temperature and loss values.
Results give transformer designer clearer understanding of precautions that should be taken for avoiding high temperatures on the tank wall of a transformer.