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The purpose of this paper is to present a new device (thermoelastic actuator) for accurate control of position whose principle is based on thermal dilatation of its working unit brought about by induction heating.

The device must satisfy the prescribed operation parameters (mainly the above thermal dilatation). The task to find them is a multiply coupled problem (interaction of electromagnetic field, temperature field and field of thermoelastic displacements) that is solved by the finite element method supplemented with a number of other procedures.

The control of position based on the described thermoelastic effect is very accurate and ranges from 1×10⁻⁶ to 1×10⁻³ m.

The device also contains two self‐locking friction clutches of conical shapes whose purpose is to fix the position of the plunger in the prescribed position. Further attention should be paid to their dynamic behaviour during the process of fixing.

The device can be used in various technical domains such as optics and laser or microscope techniques.

The principal part of the device contains no movable element, which is a substantial advantage in comparison to other systems based on mechanical, hydraulic or pneumatic principles working with movable elements or media.

The heating of flat metal products has an increasing importance in different technical applications. One of the most advanatageous heating methods is induction heating. The heat is generated within the workpiece itself. It provides high power densities and high productivity. For induction heating of flat metal products two methods are applied: the longitudinal and the tranverse magnetic flux heating. In our case we have applied tranverse flux heating. This paper presents certain results of electromagnetic field obtained by means of finite element method and transient thermal field obtained by finite difference method. The analysis is made by simulating the heating phenomenon while the sophisticated software has been employed.

The paper seeks to present a methodology of computer simulation of coupled magneto‐thermo‐mechanical processes in various electrical engineering devices. The methodology allows determining their parameters, characteristics and behaviour in various operation regimes.

The mathematical model consisting of three equations describing magnetic field, temperature field and field of mechanical strains and stresses (or thermoelastic displacements) is solved numerically, partially in the hard‐coupled formulation.

The methodology seems to be sufficiently robust, reliable and applicable to a wide spectrum of devices.

At this stage of research, the hard‐coupled formulation of thermo‐mechanical (or thermoelastic) problems is still possible only in 2D.

The methodology can successfully be used for design of numerous machines, apparatus and devices from the area of low‐frequency electrical engineering ranging from small actuators to large synchronous generators.

Complete numerical analysis of coupled magneto‐thermo‐mechanical phenomena in electrical devices.

As far as the authors know, no sufficiently complete model of continual induction hardening was developed and solved so far. The paper presents both mathematical model of the process and algorithm of its solution in the quasi‐coupled formulation.

Computation of electromagnetic and temperature fields is based on the finite element method, while time variable boundary conditions are determined by means of an original theoretically‐empirical procedure.

Substantial are backgrounds for design of the inductor and parameters of the field current as well as parameters of the cooling medium.

The model reached a good level of accuracy validated by suitable experiments. Nevertheless, next work in the field will also have to respect history of the heating before cooling itself (the austenitizing temperature is a function of the velocity of heating). Very important is also appropriate meshing of the investigated region to suppress numerical instabilities appearing during the computation process. Finally, acceleration of numerical schemes is a must, because modelling of one common task (on very fast PCs) takes about 4 h.

The results and conclusions may be used for designing devices for continual induction hardening of axisymmetric bodies.

Complete mathematical and computer model of the process, original methodology for finding the coefficient of convective heat transfer from the cooled part of the heated workpiece to ambient water spray.

The paper deals with the problem of induction hardening of long prismatic ferromagnetic bodies. The body is first heated to the austenitizing temperature typically in a cylindrical inductor fed from a source of harmonic current and then merged into a cooling medium. In specific cases, equalisation of temperatures within the body before its cooling may also be required. The mathematical model of the induction heating consists of two non‐linear second order differential equations of the parabolic type describing the distribution of the electromagnetic and non‐stationary temperature fields while the cooling is described by the heat equation and a theoretically empirical algorithm for mapping the process of hardening. The suggested methodology partially takes into account the temperature dependencies of all material parameters. The theoretical analysis is supplemented with an illustrative example and discussion of the results. Computations have been performed by means of professional codes and single‐purpose user programs developed by the authors.

Introduces the fourth and final chapter of the ISEF 1999 Proceedings by stating electric and magnetic fields are influenced, in a reciprocal way, by thermal and mechanical fields. Looks at the coupling of fields in a device or a system as a prescribed effect. Points out that there are 12 contributions included ‐ covering magnetic levitation or induction heating, superconducting devices and possible effects to the human body due to electric impressed fields.

Many electric circuits feature some type of non-linearity of their used devices. Non-linear resistors or inductors could be typical examples. Also, all semiconductor devices are in their nature non-linear ones. The simulation models are very important parts of the design of the devices in various fields of industry. Multiply (multiple) simulation, verified by the measurement on the physical sample, help to improve the converter design by understanding the current and voltage behavior of non-linear elements. The paper aims to discuss these issues.

Mathematical model of LCTLC inverter was made. Fictitious exciting function was applied on LCTLC inverter model. The non-linear inductance with the real core EFD model has been created and consequentially used for MatLab simulation experiments. MatLab and OrCAD/PSpice simulation results were compared with experimental measurements carried out on physical sample.

The authors have found how to simulate non-linear resonant circuits within mathematical apparatus using fictitious exciting function method. The authors provided comparisons between proposed simulation mathematical model and relevant physical sample. Multiply simulations can help to improve the converter design by understanding the current and voltage behavior of non-linear elements.

The proposed method is applicable for simulation purposes. The only limitation is that MatLab model does not include hysteresis curve of the core, therefore it has to be modeled.

The design of power supplies (switched mode power supplies, UPS and resonant inverter).

Research in the area of behaviors of non-linear components in resonant circuits.

The analysis of the magnetic field and computation of the leakage magnetic flux is important for optimum design of the motor, especially for the small machines on low voltage loaded from the accumulator battery. In our contribution we analyzed the computation of the leakage magnetic field and flux by means of analytical, respective numerical methods (Finite Elements Method — FEM).

High-voltage overhead lines produce low-frequency electromagnetic fields around them. These fields are easy to compute wherever the line route is straight, as opposed to places where its direction is changed. The purpose of this paper is to perform a numerical analysis of an electromagnetic field occurring along a high-voltage overhead line at the places of the changed direction and to compare the results with the exposure limits for low-frequency electromagnetic fields in order to assess their effects on living organisms.

The computation was conducted in the MATLAB SW by means of a combination of integral and differential methods in a three-dimensional (3D) arrangement, taking into account the location and shape of the tower. Special procedures within the MATLAB software had to be coded.

Within the research, the following electromagnetic field quantities were computed: the distribution of electric field strength, magnetic flux density, Poynting vector, electric potential and surface charge density. The results obtained indicate the influence of both the line route changing its direction and the deviation tower location on the electromagnetic field around the tower.

In order to shorten the computation time, it was necessary to achieve a minimum number of degrees of freedom by adjusting the real shape of both the cross-section of the deviation tower beam and the conductors. In some further research, attempts could be made to further optimize the results by using the real shapes of the cross-section of the deviation tower beam and the conductors. Furthermore, it could be beneficial to shorten the set distance between two adjacent nodes in order to obtain a finer mesh while still achieving an optimal ratio between the number of nodes and the computation time.

The Czech Regulation no. 1/2008 Coll., concerning protection of health against non-ionized radiation, stipulates 100 μT to be the maximum safe value of magnetic flux density in case of an uninterrupted exposure and frequency of 50 Hz. The investigated area did not exhibit values exceeding this limit. The same was true for the maximum permissible level of electric field strength being specified at 5,000 V/m.

Similar problems are often solved by means of FEM in 2D arrangements. However, when applying this method for conductors passing through a large 3D area, it is difficult to model an optimal 3D mesh within the conductors and the tower beams. This research shows that the application of integral methods reduces the complexity of the generated mesh. Unlike FEM, requiring the generation of a 3D mesh, the integral method only requires a surface mesh on the conductors and tower beams, thus significantly reducing the number of degrees of freedom. FEM only remains necessary for areas adjacent to the tower beams and conductors.

This paper aims to create mathematical models and control algorithms allowing the authors to study and form effective modes of operation of multi-inductor system of electrical heating of moving hollow cylindrical blanks.

The developed mathematical models were based on the finite-difference method, the control volume method and their combination. The reliability of the results obtained was verified by comparing the calculated results with the experimental ones. The temperature control system was synthesized using methods of the object management theory with distributed parameters.

A set of mathematical instruments has been created that allow modelling the operation modes of installation for induction heating of moving hollow cylindrical blanks. Recommendations were given on the formation of an automatic control system that provides heating of a moving hollow cylindrical billet to the required temperature with simultaneous equalization of temperature along the length of the billet in case of highly uneven initial temperature along the length of the billet.

Part of the paper will be used by the industrial plant for the purpose of heat treatment of iron alloys workpiece. Particularly, a control system will be basically formed based on the models.

The scientific novelty of the paper is to create control algorithms and mathematical models for the induction heating system of tubular workpieces allowing to explore interrelated electromagnetic and thermal processes taking into account nonlinearities and design features of the system, as well as to form effective modes of its operation based on transfer functions and methods of the object management theory with distributed parameters.