Abstracts of papers for

Previous issue vol. 43, no. 3 (2002)

vol. 43, no. 4 (2002)

Next issue vol. 44, no. 1 (2003)

Contents of issue 4, vol. 43

1. M. Bugeza and R. Fišer : 2D numerical model of electromagnetic structures for educational purposes
2. M. Bugeza, R. Fišer and S. Ferkolj : Calculation of linear induction motor performance using finite element method
3. W. Burlikowski and K. Kluszczyński : An analytical field model of a squirrel cage induction motor: experimental verification
4. K. Ciosk : Calculation of electromagnetic field in a disk-type induction motor using a 3-D reluctance network method
5. H. De Gersem and K. Hameyer : Motional finite element simulation of magnetic brakes and solid rotor induction machines
6. R. Fišer and S. Ferkolj : The application of the finite element method in diagnostics of electrical drives
7. V. Goričan, A. Hamler, B. Hribernik, M. Jesenik and M. Trlep : Measurement set-up for 1-D and 2-D testing of magnetic properties of magnetic steel sheets
8. M. Jesenik, V. Goričan, M. Trlep, A. Hamler and B. Štumberger : Eddy current calculation in the circular sample of the two-phase rotational single sheet tester
9. A. Krawczyk and R. Kotowski : Some introductory remarks on modeling of the electromagnetic phenomena
10. D. Križaj and V. Valenčič : AC current conduction in biological tissues
11. A. Kwiatkowska, A. Krawczyk and J. Sikora : Material derivative technique in optimal design
12. D. Miljavec and S. Knez : Newly re-designed magnetic head for wire rope NDT
13. K. Pawluk : Magneto-static field distribution due to inherent magnetisation of permanent magnets
14. B. Polajžer, D. Dolinar, G. Štumberger and K. Hameyer : Force calculation of the laboratory implementation of a radial active magnetic bearing
15. P. Puternicki and R. Sulima : User-friendly system PROJMAT 2001 for deterministic optimisation of small commutator motors
16. J. Rozman, M. Trlep, B. Zorko and M. Bunc : Stimulation of nerves innervating the pancreas of a dog
17. T.J. Sobczyk : Interaction of saturation of magnetic circuits for the main and leakage fluxes in induction machines
18. Ž. Štih, Z. Haznadar, M. Topolnik and S. Berberović : Modelling of current-limiting circuit breakers
19. B. Štumberger, A. Hamler, M. Jesenik, V. Goričan and M. Trlep : Flux-weakening and output power capability estimation of interior permanent magnet synchronous motor in variable speed drive applications
20. I. Tičar, D. Ružič, K. Preis and O. Bíró : Simulation of a high frequency electromagnetic field using the TEM propagation mode method
21. S. Wiak, P. Drzymała and H. Welfle : Electromagnetic field analysis of 2D-3D structure of switched reluctance motors (disc-type)
22. S. Wiak, P. Drzymała and H. Welfle : Comparative study of shunt reactor structures by field models
23. I. Zagradišnik and B. Slemnik : Rotating field in induction motor under consideration of anisotropy and cutting strains of steel sheets
24. H.K. Lachowicz, K. Závěta and A. Ślawska-Waniewska : Partially devitrified metallic glasses
25. T. Zyss, A. Zięba and A. Krawczyk : Electricity of electroconvulsive therapy

M. Bugeza and R. Fišer : 2D numerical model of electromagnetic structures for educational purposes

The paper presents the development of a software package for static and time-variable magnetic field calculations in 2D electromagnetic structures for educational purposes. It has a simple and clear structure in order to assure students a simple tool for studying electromagnetic fields. It enables the step-by-step insight into the procedure of the pre-processor, structure of the solvers and representation of the results. The computational results are also compared with other FEM packages and have proved to be of a significant practical value in the post-graduate courses.

Contents

M. Bugeza, R. Fišer and S. Ferkolj : Calculation of linear induction motor performance using finite element method

The paper presents the calculation of a linear induction motor steady-state and dynamic characteristics using the finite element method. The 2D nonlinear eddy-current solver was used for magnetic field and force calculations. Quantities like magnetic vector potential, flux density, force components, primary and secondary currents, mutual and leakage inductance, can be determined very precisely. The detailed insight in magnetic field distribution of a linear induction motor forms the basis for evaluation of its operational behaviour. The results obtained by the finite element method are further used in the process of the mathematical modelling and control simulation based on the space vector theory.

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W. Burlikowski and K. Kluszczyński : An analytical field model of a squirrel cage induction motor: experimental verification

The paper presents the results of experimental verification of an analytical field model of a squirrel cage induction motor. Basic properties of the model are presented. Methods employed in the measurement are described. The obtained torque measurement data are compared with the simulation results for a selected machine prototype.

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K. Ciosk : Calculation of electromagnetic field in a disk-type induction motor using a 3-D reluctance network method

The paper presents an analysis of the magnetic field in a disk-type induction motor with double-sided stator and twin rotors. The magnetic flux density was found in a 3-D space using the reluctance network method (RNM). The results were compared with the measurements carried out on the real object.

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H. De Gersem and K. Hameyer : Motional finite element simulation of magnetic brakes and solid rotor induction machines

The torques of a magnetic brake and a solid rotor induction machine, fed by sinusoidal voltage sources, are simulated by a motional finite element method. Oscillatory solutions occurring for motional models with elevated velocities, are prevented by adaptive mesh refinement relying upon intermediate solutions stabilised by upwinded finite element test functions. A relaxed successive approximation deals with the non-linear material properties. The connections of the conductors and windings within the finite element model to external loads, impedances and supplies are represented by an electric circuit and added to the system of equations. The technical examples indicate the advantages of the motional formulation.

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R. Fišer and S. Ferkolj : The application of the finite element method in diagnostics of electrical drives

The paper presents the application of the finite element method for predicting the performance of induction motor having asymmetry of stator and/or rotor winding due to the different combination and propagation of faults gained during heavy-duty operation. Quantities like magnetic vector potential, flux density, force components, rotor and stator currents, mutual and leakage inductance are determined very precisely. The detailed insight in magnetic field distribution of a squirrel cage induction motor, forms the basis for further evaluation of its operational behaviour. Increasing anomaly in magnetic field distribution due to the increasing stage of faults propagation results in a degradation of steady-state and dynamic performance of the induction motor and can be evaluated with computer simulation eliminating expensive and time-consuming laboratory tests.

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V. Goričan, A. Hamler, B. Hribernik, M. Jesenik and M. Trlep : Measurement set-up for 1-D and 2-D testing of magnetic properties of magnetic steel sheets

In electrical machines core loss is caused not only by alternating but also by rotational magnetic fields. Therefore the interest in 2-D measurement of magnetic properties of magnetic steel sheets in rotational magnetic field increases. The round rotational single sheet tester (RRSST) for circular samples is presented. Special attention is paid to achieve a greater measuring region and the equality of field distribution in the sample for all magnetisation directions. The completely automated measuring set-up allows the measurements in alternating, pure rotational, elliptical and also in distorted rotating magnetic field. The field metric measuring technique was used.

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M. Jesenik, V. Goričan, M. Trlep, A. Hamler and B. Štumberger : Eddy current calculation in the circular sample of the two-phase rotational single sheet tester

Round rotational single sheet tester (R.R.S.S.T.) is used for the measurement of magnetic properties in rotational and alternating magnetic fields. The homogeneity of the magnetic field and the influence of eddy currents on the homogeneity of the magnetic field distribution in the circular sample are investigated. Results of the calculation are compared with results of the measurements.

Contents

A. Krawczyk and R. Kotowski : Some introductory remarks on modeling of the electromagnetic phenomena

Cum Deum calculat, fit mundus.
          G.W. Leibniz
Everything should be made as simple as possible but not simpler.
          A. Einstein

Contents

D. Križaj and V. Valenčič : AC current conduction in biological tissues

Electrical properties and structure of biological tissue determine the manner of current conduction through them. Numerical simulation of a cell suspension is performed demonstrating the effect of frequency-dependent effective specific conductivity and permittivity. For AC current conduction, magnetic induction effects can be neglected in a wide frequency range. Displacement current is in general smaller than conductive, however, for proper analysis it cannot be completely neglected.

Contents

A. Kwiatkowska, A. Krawczyk and J. Sikora : Material derivative technique in optimal design

The paper deals with the problem of shape design, and the shape has to ensure the assumed distribution of the function. The concept of material (substantial) derivative has been employed in order to solve the problem. The numerical model was based on the Finite Element Analysis. The quoted results show that the method of optimisation is effective for the problem of shape design.

Contents

D. Miljavec and S. Knez : Newly re-designed magnetic head for wire rope NDT

The aim of the present paper is to analyse a newly re-designed magnetic head. Basic use of this head is in non-destructive testing (NDT) of wire ropes. The magnetic head system is composed of two main areas and three main parts. These areas are: magnetic flux leakage area in central region, and eddy current magnetic field area in outer side region of magnetic head. The analyses were carried out by analytic approach and by the finite element method. The value of induced voltage in flux leakage pick-up coils was calculated by axisymmetric 2D magnetostatic finite element analysis made by ferromagnetic rod to simulate the wire rope. Meanwhile, voltage induced by changes in eddy current magnetic field was calculated by a 2D transient linear motion finite element analysis. All numerically calculated results were compared with the measured ones on a geometrically similar ferromagnetic rod. Also, we have presented the measured results carried out by newly re-designed magnetic head on real steel wire rope with anomalies.

Contents

K. Pawluk : Magneto-static field distribution due to inherent magnetisation of permanent magnets

A boundary-integral model of the static magnetic field due to cylindrical permanent magnets that is put in free space is considered. Magnetic scalar potential quantities created by a virtual quantity "surface magnetic charge density" is expressed by means of Lipschitz-Hankel integrals that for the considered case are reducible (by the way of hypergeometric series) to some algebraic expressions, in which elliptic integrals of various kinds occur. This approach seems to be more effective than that can be reached by the use of a typical professional software for the field problems in which numerical integration, being not quite conform to the considered case, is common. The magnet subjected to the analysis has to be virtually subdivided in some number of elementary pieces, inside of which the uniform distribution of the inherent magnetization is supposed.

Contents

B. Polajžer, D. Dolinar, G. Štumberger and K. Hameyer : Force calculation of the laboratory implementation of a radial active magnetic bearing

Performances of the controlled active magnetic bearings can be sufficiently improved with the exact knowledge of the bearing force in the entire operating range. Therefore the magnetic force calculation of the laboratory implementation of a radial magnetic bearing, using 2D finite element method, is presented in the paper. Two methods for the force calculation are used, where both, i.e. the Maxwell stress tensor method and the virtual work method, give very close results. The verification of the bearing force calculation is performed by their comparison with measurements. The obtained results make it possible to perform a robust control design in the entire operating range.

Contents

P. Puternicki and R. Sulima : User-friendly system PROJMAT 2001 for deterministic optimisation of small commutator motors

System PROJMAT 2001 is used for designing small commutator motors. The software in the Matlab 5.0 and the Toolbox Optimisation is used for multicriterial optimisation. The software has an interface which is constructed of elements and functions in the Uitools package of the Matlab. The interface is build on the basis of a series of windows which enables the data segregation and communication with the user. It gives a possibility of an easy and comprehensible preparation of all input technical data and constraints. The main parts of the system are: the optimisation block, the postprocessor block and controlling over them the interface block. The example of small motor design is given in this paper.

Contents

J. Rozman, M. Trlep, B. Zorko and M. Bunc : Stimulation of nerves innervating the pancreas of a dog

The purpose of the study was to evaluate the influence of electrical stimulation of nerves innervating the pancreas on the function of the cardiovascular system, lungs and urinary tract, measured as an ECG, blood pressure and pressure in the bladder of a dog. Spiral cuffs with 33 electrodes (1.0×2.0mm) within a silicone sheet were manufactured and implanted in a Beagle dog in the vagus nerve, in the splanchnic nerve and in the pancreatic nerve. Each nerve was stimulated individually with biphasic, rectangular and current pulses (10mA, 200μs, 20Hz). When stimuli were 10mA or higher, measurable changes were observed during stimulation of both the vagus and the splanchnic nerves. In the splanchnic nerve, they were expressed as an increase in pressure in the bladder and as a tremor of the whole stomach. In the vagus nerve, they were expressed as a drastic decrease of arterial blood pressure and as abnormalities in the heart rate. In a further increase of stimuli to about 18mA, the heart rate was slowed until it ceased as fatal brachicardia, asystolia and consequently hypotensia was occured.

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T.J. Sobczyk : Interaction of saturation of magnetic circuits for the main and leakage fluxes in induction machines

The paper presents a model of induction machines, in which saturation for both the main and leakage fluxes of individual windings is represented. The model operates with the real winding currents what gives a chance to model saturation of leakage magnetic circuits separately for each winding. The saturation of the main magnetic circuit is modelled by introducing a magnetising current defined analytically by all machine currents. Such a model allows to study the interaction of saturation of separately treated magnetic circuits of the main and leakage fluxes. Remarkable results of simulations are shown in the paper.

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Ž. Štih, Z. Haznadar, M. Topolnik and S. Berberović : Modelling of current-limiting circuit breakers

A circuit model of current-limiting circuit breakers that enables the simulation of the limiting process as well as the analysis of the parameters of transient phenomena is described. The model consists of a system of non-linear time-dependent differential equations that has to be coupled to the numerical solution of the magnetic field in the contact space. Reliability of such breakers highly depends upon the actuator in the tripping system. The modelling of the dynamic response of the actuator is based on the response surface methodology and on the lumped parameter time domain simulation of response of actuator to a voltage pulse. The results of the simulations are compared with measurements.

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B. Štumberger, A. Hamler, M. Jesenik, V. Goričan and M. Trlep : Flux-weakening and output power capability estimation of interior permanent magnet synchronous motor in variable speed drive applications

Flux-weakening and output power capability estimation of the four-pole interior permanent magnet synchronous motor (IPMSM) determined from the finite element method (FEM) analysis of magnetic conditions is presented. The influence of the iron loss on the output power capability (OPC) and the constant-power speed range (CPSR) of the tested IPMSM is included in the analysis by the posterior iron loss calculation. Results of the calculations are partially verified by the measurements.

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I. Tičar, D. Ružič, K. Preis and O. Bíró : Simulation of a high frequency electromagnetic field using the TEM propagation mode method

Much has been written about the possible health hazards of electromagnetic fields (EMFs). Consumers are bombarded with quasi-scientific reports, many of which are more confusing than accurate. This paper presents a project undertaken to evaluate high frequency electromagnetic fields using a TEM mode, the propagation mode calculation method followed by confirmation of any doubts about field levels using on-site measurements. An electromagnetic field can be monitored through all stages from the design to the operational state of the radiation source because of the use of both possible evaluation methods (calculation and measurements).

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S. Wiak, P. Drzymała and H. Welfle : Electromagnetic field analysis of 2D-3D structure of switched reluctance motors (disc-type)

In the paper comparative studies of 2D-3D disc-type Switched Reluctance Motor (SRM) structures are performed. The calculation of magnetic field distributions and the static torque characteristics have been computed by means of Finite Element Method (FEM) for 2D and 3D motor structures. It has been emphasized that the calculations of the model structure (thanks to axial symmetry) have been done for a half of the volume while the boundary conditions are predefined. 3D structure of the model motor is built up, then the mesh is generated for number of elements exceeding 100000. The results of 3D calculations are presented in the form of the static torque characteristics and magnetic flux curves versus rotor angular positions and current densities in the stator winding as well. Disc-type SR motors thanks to their specific structures are commonly used in automotive system, servo-drives, etc. The motor structure consists of the stator core toroidally shaped in which slots are placed on both sides of the active surface; moreover stator windings are wounded as Gramma type (made of identical coils surrounding the stator core). SRM are proposed to be mounted at the wheel of gearless electric vehicles (small cars, wheelchair, scooters, etc.).

Contents

S. Wiak, P. Drzymała and H. Welfle : Comparative study of shunt reactor structures by field models

The paper presents the results of field analysis of the shunt reactor 3D structure based on a field method. The magnetic field computations have been carried out for the shell-type and two-limb structure of a one-phase shunt reactor, then to be assembled as a 3-phase unit. The field calculations are performed for 3-D model reactor structures with different number of core slices (different number of air gaps, but with constant intermediate - slice air gap length). The 3D structure of the model reactor is built up, then the mesh is generated for a number of elements exceeding 200000. The optimal value of the ratio d/g (height of the intermediate-slice air gap/height of the limb slice) and the ratio d/g (height of the intermediate-slice air gap/diameter of the limb) are evaluated leading to minimum values of the weight and capitalized cost of the device.

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I. Zagradišnik and B. Slemnik : Rotating field in induction motor under consideration of anisotropy and cutting strains of steel sheets

The rotating magnetic field in a symmetrical induction machine supplied with a sine-shaped and balanced system shows an asymmetrical shape if the magnetic medium is anisotropic. The shape of the air gap magnetic flux distribution is repeated twice per one revolution of the rotating field in a two-pole machine. The harmonic analyses show that all components rotate with variable magnitudes and non-uniform speeds. The variations are greater if the order of the component is higher. Only odd harmonics occur. Due to the spatial dependence of reluctance and the electric voltage balance in an induction machine, the magnetizing current also shows a spatial dependence.

Contents

H.K. Lachowicz, K. Závěta and A. Ślawska-Waniewska : Partially devitrified metallic glasses

Ábiit non óbiit.
The paper presents a review of selected experiments which have been carried out using partially devitrified Fe- and Co-based metallic glasses as the research objects. It is shown that by a suitable choice of the composition of the metallic glass and also by the conditions of annealing, a variety of magnetic phases can be created in these systems. It is also shown that by controlled processes of annealing, the coercivity of metallic glass can be altered by several orders of magnitude, giving a possibility to produce materials with the extremely soft magnetic properties, up to the magnetically semi-hard ones. The magnetostriction of nanocrystalline materials of the FINEMET-type is discussed as well, showing that the size-dependent phenomena and the symmetry restriction at the particle boundaries create the surface contribution to the effective magnetostriction. Finally, the magnetic interactions between particles in partially devitrified samples are considered and the observed effects of temperature and hydrostatic pressure discussed.

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T. Zyss, A. Zięba and A. Krawczyk : Electricity of electroconvulsive therapy

This paper describes physiological phenomena of a electrical stimulation of nerve cell and presents technical issues of electroconvulsive therapy used by psychiatrists.

Contents