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An interaction mechanism was proposed to explain the influence of static magnetic fields on electrochemical processes that take place when a ferromagnetic electrode is submerged in a paramagnetic electrolytic solution. The proposed mechanism suggests that the magnetic field effect is strengthened by magnetic flux density and magnetic susceptibility of the solution and is weakened when temperature and stirring rate is decreased. The magnetoconvection phenomena suggested is supported by experimental results.

A study was conducted to investigate the effective areas, current distributions and inductances of slotted, high-temperature dc superconducting quantum interference devise magnetometers. Results indicate that the magnetometers' inductance, flux and field noise are influenced by the number of slots. For instance, SQUID magnetometers with many slots show low flux noise values.

This paper discusses the phenomena of the axially non uniform distribution of magnetic flux densities and losses in a 3-phase squirrel cage induction motor of which the rotor bars are skewed. A 2-dimensional complex finite element method taking account of the effects of the skewed rotor bars is utilized for the analysis of characteristics such as copper and iron losses and the loss distributions are examined. The summing up values of non-uniform losses resulted from the finite element analysis are compared with measurement values. Index Terms - Induction motors, skew effect, finite element methods, losses

A study of flat airgap synchronous couplings uses the analytical formulas of the tangential and radial components of the force between two permanent magnets. These formulas are applied to compare the torque transmitted by three different structures of flat airgap couplings. In the first, the magnets have a radial magnetization direction with respect to the rotation axis. This direction is tangential to the rotation axis in the second structure and parallel to the rotation axis in the third where the force is computed with a semi-analytical method. The torque of the different couplings is studied and compared. The dependence of the torque on various parameters such as the number of pole pairs and the width, length, and depth of the magnets is also investigated. The analytical and semi-analytical methods used afford efficient optimization of the coupling structure with full compliance with practical and economic constraints. Index Terms - Magnetic coupling, permanent magnet.

This paper deals with a complete three-dimensional calculation of the magnetic vector potential and of the magnetic flux density created by disk conductors, in which an assigned current flows. The formulas presented are valid either inside or outside the conductor. The effectiveness and the time-saving possibilities of the expressions derived is shown by comparison with the numerical results obtained by direct integration of the Biot-Savart formulas and with experimental results. Index terms - Magnetic fields, integral equations, algorithms.

An analytical technique has been developed to predict the instantaneous magnetic field distribution in the air gap of a permanent magnet motor. The effect of the stator slotting and rotor eccentricity on the magnetic field has been considered. The slotting effect is explained by a newly redefined boundary value problem in polar coordinates in the annular air gap/magnet region of a multipole permanent magnet motor. A perturbation technique is introduced to describe the effect of rotor eccentricity. The analytical method has been validated by a corresponding finite element model. Two prototype motors are used as examples to show the effectiveness of the analytical technique proposed in the paper. The analytical solutions are in good agreement with those obtained by the finite element method, both in amplitude and wave form. Index Terms - Analytical, eccentricity, motor, noise, permanent magnet, perturbation, slots, vibration.

The purpose of this paper is to determine the mutual inductance between two noncoaxial circular coils. In many cases, such as coil guns or tubular linear motors, one of them is fixed while the other one is moving, and if not supported, its axis may not coincide with that of the fixed coil. This paper presents a method for the calculation of the mutual inductance in the case of noncoaxial coupled coils, the characteristics of this inductance, and experimental results. The computation is based on complete elliptic integrals and on mesh-matrix technique. The method enables one to obtain accurate results from a relatively simple procedure and calculation program. Index Terms - Mutual inductance, noncoaxial coils.

The crystallographic structure of {Fe(ptz)(sub 6)}(PF(sub 6))(sub 2) was characterized through the use of studies of its thermal spin transition curves. It was found that the interaction constant was very close to the critical value above which a hysteresis was expected secondary to the cooperative effects. An external pressure of 1 kilobar accelerated the high-spin -> low-spin relaxation by 1 order of magnitude.

A simple theory is proposed using Faraday's law and the Lorentz force to analyze the effect of magnetic damping on an aluminum plate moving on a horizontal air track as it passes between the poles of a horseshoe magnet. The position, velocity, and acceleration of the nonmagnetic conducting plate are measured as a function of time using a motion detector. Using some simplifying assumptions, a theoretical model is obtained in which a single free parameter is used to fit the experimental data. This parameter corresponds to an effective length ([L.sub.R]) in which the eddy current encounters resistance as it moves around a closed path in the conductor. This leads to some interesting, but unexpected, results about the shape and magnitude of induced eddy currents.

A new transformer model based on core topology is developed. The model simulates the transformer as a set of coupled inductances. Winding flux linkages are chosen as state variables and currents are computed from the flux linkages using the directly-formed inverse inductance matrix, the [Gamma]-matrix. Due to the strong magnetic coupling among the windings, the inductance matrix of a transformer is ill-conditioned. Directly forming the [Gamma]-matrix will not only speed up the computation but also make it more stable. Transformer core saturation is represented by its anhysteretic magnetization curve. Eddy current and hysteresis losses of the core, and stray losses of the transformer are accounted for by a resistive load on the secondary. Winding capacitances are lumped to the terminals, the model is thus accurate up to 5 kHz. A supporting routine is written to generate [Lambda]-i curve data for each segment of the core and the other input data for EMTP. The model has been incorporated into the Alternative Transients Program (ATP), the BPA EMTP, for evaluation, and has passed the benchmark test of the GPU line energization test of 1973.

Experiments are performed to analyze the magnetic flux coupling phenomenon between a superconducting quantum interference device (SQUID) and the wires of an integrated circuit (IC). Results show that the effective mutual inductance between a SQUID and the wires of the IC decreases as the distance between them increases. The data also suggest that mutual inductance between the SQUID and the wires can be reduced by using a wire with a stripline-structure.

The magnetic properties, including ac core loss, dc hysteresis loss, eddy current loss, ac and dc permeability at 10 kG and 15 kG, and magnetic flux density at field strength 2500 A/m, of 17 heats of fully processed, continuous-annealed low-carbon electrical steels with grain diameter from 8.98 [[micro]meter] to 23.25 [[micro]meter] have been measured. Regression analysis is applied to find the relationships among magnetic properties, grain size, texture, and impurity. Grain size is the predominant factor to influence ac core loss, hysteresis loss, ac and dc permeability, and magnetic flux density. In addition, carbon is deleterious to ac core loss and hysteresis loss at both inductions and dc permeability at 10 kG. Sulfur increases ac core loss and hysteresis loss at 15 kG. Nitrogen and oxygen decrease ac permeability at 10 kG and 15 kG, respectively. Soluble aluminum is detrimental to hysteresis loss and ac permeability at 15 kG. Texture component of [(I/[I.sub.R]).sub.222] is deleterious to hysteresis loss at 10 kG and magnetic flux density.

A method to calculate the Lorentz force on an electrically conducting sphere placed in an arbitrary sinusoidally varying magnetic field is developed. The crux of this method lies in expressing the external magnetic field and the eddy current density in the sphere in terms of a 'source function' of the current sources and a 'skin depth dependent function.' The general formula for the Lorentz force is used to derive the special case of a sphere in an axisymmetric stack of circular current loops. Numerical results for this case are presented as a function of the stack geometry. Approximations of the skin depth functions for practical situations are presented. Finally, a procedure to determine the magnetic pressure distribution on the surface of a levitated liquid metal droplet is given.

A highly efficient (99.5%) transformer and resonant inductor with very high power density (1500 W/[in.sup.3]) and low profile (height 40) of small gaps to reduce the effect of fringing fields. The high-frequency loss measurements for such highly efficient inductors requires a special ring down measurement set-up which is also described.

A new approach to control the speed and rotor flux of an induction motor using the theory of the sliding-mode is presented. Sabanovic's equations for an induction motor are first modified to a state space form suitable for the present design of the algorithm. For controlling the speed and rotor flux of the drive, a simple control algorithm is proposed based on the existence of a certain positive definite matrix. Lyapunov direct method is used to ensure the reaching and sustaining of sliding-mode. Obviation of flux measurement is achieved through manipulation of Stanley's equations. Simulation studies are conducted. The control algorithm exhibits excellent drive performance in the presence of load disturbances and stator and rotor resistances changes up to 100% of the nominal values.

Estimations of current-voltage (I-V) characteristics of externally shunted Josephson tunnel junctions, which have a nonzero inductance for external shunts show that standard I-V curves are present at temperatures below 6.6k. An increase in this temperature causes anomaly in the I-V curves due to nonzero inductance in the shunt loop. Subharmonic relaxation oscillations control the I-V curve dynamics in this anomalous region.

Numerical simulations of the white noise characteristics in a high-Tc dc superconducting quantum interference device show that the thermal noise at 77 K influences the noise characteristics resulting in a difference in the inductance-dependence of noise characteristics from the conventional results. The voltage noise is weakly inductance-dependent while inductance degrades the transfer functions and hence the flux noise at 4.2 K. The simulations thus indicate that enhancement of noise characteristics requires an enhancement in the transfer functions.

The use of the coherent Foucault imaging method facilitates imaging of the magnetic domain structures in thin films. The resultant images of the structures are magnetic interferograms that display the arrangement of magnetic induction in thin films. A field-emission gun system is essential for the Foucault imaging and a simple analytical theory, when combined with experimental results and computer simulations, validates the imaging method.

Reduction of the permeance variations due to slot openings can be achieved through the use of closed or semi-closed slots or magnetic slot wedges. A complete transient finite element model analyzes the effects of slot closure in an induction motor. The analysis of the air gap flux density and magnetic force waves determined by the finite element model reveals two effects of stator slot closure: (a) a reduction of those flux density and force waves generated by stator slotting, which was expected, and (b) an increase in the amplitude of th flux density and force waves originating from saturation.

In this paper, on the basis of theoretical analysis of hierarchical element structure, an adaptive finite element computation of h-p version for magnetic field problems is presented. Through detailed investigation of three typical problems in electrical engineering with both h-p and h version, two new kinds o efficient adaptive schemes of h-p version are obtained.

To optimize the production of high-efficiency induction skull melting furnace, we analyzed magnetic flux density, eddy current and electromagnetic force distributions using the 3D edge-based finite element method excited from a voltage source. Changing the number of copper rods and, therefore, the distance between them, we analyzed both the intensity and direction of the electromagnetic forces and the amount of power consumed by the molten alloy and the rods. In this paper, we present our analysis method, the obtained results and conclusions.

Computer simulation of the magnetizing process has been carried out by applying a numerical model to the theory of the rotation magnetization for magnetic materials. This model has been made in order to adjust to the two-dimensional magnetic property. This numerical model is combined with the finite element method in which the magnetic scalar potential and the magnetization are regarde as unknown quantities. It is possible to calculate that the magnetic materials with single domain structure are magnetized in the mode of rotation or of reverse of the magnetization vector.

The method for analyzing flux distributions in transformer cores made of grain-oriented silicon steel is improved in order to reduce error in calculatio due to anisotropy in magnetic materials. A model to verify the improved method is proposed, and the calculated results are compared with measured ones.

In the conventional magnetic field analyses that are applied to such things as rotating machines, the magnetic properties of the arbitrary direction have been modeled by using the magnetic properties of the easy axis and its perpendicular direction. Such kind of numerical modeling can not exactly show the phase difference between the magnetic flux density B and the magnetic field strength in the case of a rotating magnetic flux excitation. In this paper, the B- and H-values are measured as vector quantities under the rotating magnetic flux excitation. The magnetic properties of the material are expressed by the magnetic reluctivity tensor based on the measured results. This new expression is applied to the rotating magnetic field problem. As a result, it is shown tha our new method is applicable to the problem in the case of the rotating magneti flux excitation.

The modelling methods developed so far for grain-oriented electrical steels can not account for the true properties of materials. When these models were developed, more consideration was given to obtain fast convergence speed for numerical iterations than the accuracy of models themselves. For magnetic materials, the small changes in flux density B can cause dramatic change in permeability, so for the purpose of modelling devices, material modelling has t be as accurate as possible to reflect the true magnetic characteristics.

The analytical expression of the time behaviour of the current density due to a electric discharge on a three dimensional conducting slab has been obtained by means of an analytical method. The electric discharge is modeled by a current pulse injected in the slab. The current injection point can be arbitrarily positioned on the surface of the slab. The diffusion equation was solved in the s domain using the technique of the separation of variables. The time behaviour of the current density was determined applying the inverse Laplace transform to the solution. The analytical results were compared with results obtained with two numerical methods, the first based on an equivalent network formulation and the second based on a Finite Difference Time Domain method. The electromagnetic field in space has been simply determined from the knowledg of the current density distribution.

The improved T-[Omega] method is applied to the computation of the three dimensional eddy current field in a 360MVA/500kV large power transformer, the structure of which is complicated. The different cases of tank wall with magnetic shunt, aluminium screen or without any shield are analyzed. The relations between eddy current losses and the materials, structure and size of the tank shield are presented. Compared with a parallel magnetic shunt arrangement, the vertical magnetic shunt reduces stray losses by 63.8%. The optimal thickness of the vertical magnetic shunt is 10mm. The magnetic shunt should be spread over 0.5mm at both ends of windings in the 360MVA/500kV large power transformer.

In spite of extensive optimizations of transformer core designs, investigations of full sized cores showed distinct inhomogeneities of flux density B. Limbs showed discontinuous variations of B in peripheral packages and minima of B in thick central ones. The latter are not caused by global eddy currents but rathe by localized flux components [[Phi].sub.z] normal to the sheet plane. Attempts to determine the respective effective ac-permeability [[Mu].sub.z] yielded values below 100, i.e., almost three orders below [[Mu].sub.x] of the rolling direction. For given B, (planar) eddy current losses [P.sub.z] proved to exceed the respective values [P.sub.x] by two orders, a ratio which increases with increasing length L of the magnetized sheet region. The low ratio [[Mu].sub.z]/[[Mu].sub.x] yields a tendency of constant package flux throughout the whole core. A key criterium for [[Phi].sub.z]-components between packages proved to be the overlap regions which were studied in a comparative way for several step-lap configurations. Distinct differences of respective values of lap-region excitation [V.sub.L] were observed as a function of air gap lengths and the step number N, respectively. Variations of [V.sub.l] - and especially overlaps of high [V.sub.L] in connection with shifted overlap regions - proved to yield [[Phi].sub.z]-components including flux transfer between packages. In complex way, shifts yielded decreasing excitation power, but increased core losses due to planar eddy currents. In addition, package shifts cause both the discontinuities of B of thin peripheral packages and the minima of local B in thick central ones. With respect to core design, it can be assumed that small shifts favor take over of flux without causing significant planar eddy current losses (due to small L), while large shifts increase total losses in a disadvantageous way. With increasing N, these effects become less significant.

This paper first illustrates the basic dependencies of induction machine parameters on flux and current and describes them by simple equations. Differences of the magnetizing currents at single-phase and three-phase excitation are considered. A novel identification technique determines accurately all parameters and their dependencies on saturation from a few easy-to-perform off-line measurements. It has been designed for use at traction drives with Direct Self Control during system startup. The proposed method has been automated and is well suited for application in the field. Optimal operating points for quasi-stationary operation are derived from identified parameter dependencies and compared to practical measurements.

A new type of inductive thin film head has been developed which doubles the effective number of turns by weaving the yoke through the coil twice. The process for producing the head is identical to that of a conventional thin film head with the same number of actual coil layers. This novel approach results in a head that achieves a large number of effective turns with low resistance, inductance, and process complexity. The large number of turns is beneficial to small diameter drives with low velocity. The low inductance per effective turn squared is a benefit in high frequency applications that are resonance limited. The low resistance per effective turn squared produces low noise in all applications. A version of this head with 23 actual turns on a two layer spiral coil has been produced in volume. Its signal to noise exceeds that of the equivalent two and three coil layer conventional thin film heads that were tested for comparison.

A new family of isolated, zero-voltage-switched converters which utilizes the magnetizing inductance of the transformer to achieve zero voltage turn-on of the primary switches is proposed. By employing saturable inductor(s) on the secondary side, soft turn-off of the output rectifier(s) is obtained with a minimum circulating energy flowing through the converter. The proposed converters can operate either with a variable or constant switching frequency. A complete dc analysis and design guidelines for the half-bridge topology are described, and the performance of a 100 W experimental converter is presented.

Akashi and Levy's model of the electric bell was criticized by Criminale and Mar for its failure to account for magnetic hysteresis. Based on Criminale and Mar's improvement of the Akash and Levy model, a solution in a joint limit function is found where the coefficient of restitution for the bell impact and the measure of hysteretic work tend to a member of the one-parameter family. The inclusion of weak, linear damping is discussed.

This paper studies the relationship between the magnetizing inductances of a transformer and of a choke coil in high-voltage power supplies. This analysis defines the conditions for high switching frequency and stable operation of high-voltage power supplies without the power loss increase. This approach is confirmed by the implementation of a high-voltage power supply operating at 200 kHz with a high efficiency of 86%.

The circumstances involved in the occurrence of magnetic induction changes and the primary qualitative characteristics of this phenomena were studied. Experiments were carried out in a uniaxial field and stress rig and involved the application of magnetic field and tensile or compressive stresses to the samples. The non-dependence of the principal anhysteric in a ferromagnet to specific material patrameters was demonstrated.

The paper describes the way of computation for the calculation of the magnetic and fluid flow field in induction melting apparatus. The Finite Element Method will be used for the determination of the magnetic field. On the other hand the calculation of the fluid flow field is done using the Finite Difference Method. Also of importance is the precalculation of the surface shape for which a method will be presented because it influences on the induced melting power.

In order to reduce computer resources for the analysis of eddy current distribution of cold crucible models, the authors employed a current sheet approximation for eddy current distribution because penetration depth of the eddy current is relatively small in comparison with the dimension of the conducting bodies. The eddy current distributions approximated by current sheets are solved for by an integro-differential method using an electric vector potential. Furthermore, magnetic flux density, power loss, Lorentz force and lifting force of the molten metals are obtained from the solved eddy current distribution.

Transient Finite Element Method solvers generally require extensive computation time, especially when the area of interest is at steady-state. By using a frequency domain solution as the starting point for the transient solver, the computation time to reach steady-state can be significantly reduced. In this paper, a frequency domain solution method is presented. The computation time required for a transient solver is investigated for two cases (i) with the frequency domain solution and (ii) without the frequency domain solution. The frequency domain solution can also be applied to the computation of machine parameters. The paper suggests a method for the calculation of equivalent circuit parameters based on simulated locked rotor tests.

Magnetic Barkhausen noise (MBN) measurements were made on a sample of pipeline steel as functions of magnetizing frequency and ac flux density in the sample. The observed MBN responses suggest a strong dependence on these magnetizing parameters. With increasing flux density in the sample, the MBN activity initially increases but finally begins to decrease at higher magnitudes of flux density. The MBN activity also increases with increasing magnetizing frequency. Pulse-height distribution analysis of the MBN waveforms suggests that the dependence of MBN activity on these magnetization parameters is more complex than appears from the rms voltage measurements.