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Rotational magnetizations of an Ni-Fe alloy are simulated using two different computer modeling approaches, physical and phenomenological. The first one is a model defined using a single hysteron operator based on the Stoner and Wohlfarth theory and the second one is a model based on a suitable system of neural networks. The models are identified and validated using experimental data, and, finally, an example of their application for a finite-element analysis is given.

This work discusses the vector measurement of the effective magnetic field inside a not oriented grain SiFe steel sample, taking into account the effect of the demagnetizing field. We propose an array of biaxial Hall sensors, placed up to the sample surface. The calibration of the system and a suitable extrapolation data strongly reduce the uncertainties of the direct measurement and provide an accurate evaluation of the magnetic field inside the material sample. Although the approach proposed can be also used for industrial frequencies, 50–60 Hz or more, the analysis is limited here to the static case, because we are mainly interested in static magnetic measurements. These measurements are especially useful for the vector characterization of soft magnetic materials and, in particular, for the identification and the experimental validation of vector hysteresis models. The experimental analysis presented in the paper deals with commercial not oriented grain SiFe steels. Experimental data about hysteresis loops and static power losses are given.

In this paper, we present a benchmark problem for the validation of numerical models of vector magnetic hysteresis. The problem geometry and the measurement system are described. The materials considered are both oriented grain (OG) and not OG Si-Fe steels. A series of experimental data about magnetic field and magnetic induction loci under rotational magnetization are presented with the corresponding magnetic losses. The measured data can be useful as a reference for the numerical models testing, comparison, and development. In addition, we propose here a comparison of the experimental data with the numerical results computed using a vector hysteresis model based on the extension of the Preisach model in 2-D.

This paper deals with a particular magnetic nondestructive technique applied to the control of the position of the steel blades in rotating parts of turbines and engines. The working principle is based on a bridge of four identical magneto-resistive sensors. One sensor is placed near the blades, and the change in magnetic field produced by a permanent magnet and deviated by the change in position of the blade is detected by the sensor bridge. The position of the sensor is indicated, via dedicated FEM simulations, in order to have high sensitivity to the position change and high output signal. The accuracy and effectiveness of the proposed method are shown by experimental tests carried out in our laboratories. In particular, the tests indicate that the proposed magnetic nondestructive technique can be used in an almost large velocity range, and for quite different values of blade tip. The method seems also promising for the detection of blade vibrations.

This paper deals with a neural network approach to model magnetic hysteresis at macro-magnetic scale. Such approach to the problem seems promising in order to couple the numerical treatment of magnetic hysteresis to FEM numerical solvers of the Maxwell's equations in time domain, as in case of the non-linear dynamic analysis of electrical machines, and other similar devices, making possible a full computer simulation in a reasonable time. The neural system proposed consists of four inputs representing the magnetic field and the magnetic inductions components at each time step and it is trained by 2-d measurements performed on the magnetic material to be modeled. The magnetic induction B is assumed as entry point and the output of the neural system returns the predicted value of the field H at the same time step. A suitable partitioning of the neural system, described in the paper, makes the computing process rather fast. Validations with experimental tests and simulations for non-symmetric and minor loops are presented.

In this paper, using suitable three-dimensional finite element method (FEM) approaches, either in frequency or in time domain, we will analyze the real magnetic behavior of a commercial Epstein machine, prescribed as standard magnetic measurement system. The analysis of magnetic field and eddy currents explains some facts that can affect the accuracy of Epstein frames as measuring systems for the magnetic characterization of laminated Si-Fe steels. The same FEM approaches shall be applied here to outline and define quantitatively some advantages in accuracy can be obtained using single sheet testers instead of Epstein frames.

In this work we discuss some procedures to increase the accuracy in the measurement of the magnetic field strength using Round Rotational Single Sheet Tester RRSST frames. The procedures are discussed jointly with the use of different magnetic field probes, such as flat coils and Hall sensors, and with a suitable shielding geometry. Experimental comparison between different methods and a discussion about the results is presented.

This paper deals with the mathematical definition of a general vector hysteresis operator in 3-D, as an extension of previous papers where the theory has been limited to the 2-D case. Although the paper is mainly focused on magnetic hysteresis, the definitions and the results reported can be applied to any general physical phenomenon that exhibits hysteresis. We show here the main general properties of the general hysteresis operator in 3-D.

Some analytical expressions for the calculation of the magnetic induction and the vector potential in iron-free media due to conductors in annular arc shape with regular cross section are reported. The algorithms derived, together with analogous algorithms reported previously for the calculation of the magnetic fields due to conductors in slab shape, can be used to calculate the magnetic fields in more complicated geometries and may be used to evaluate the self- and the mutual-inductance coefficients in systems with massive conductors.

In this paper we present a single disk tester (SDT) developed for vector hysteresis measurements of magnetic steels. The measurement system deals with a stator of a 3-phase induction motor and some suitable magnetic field and magnetic induction probes. Numerical calculations based to a FEM approach in time domain and experimental tests are shown in order to describe both accuracy and efficiency of this measurement system.

The behavior of the electromagnetic and thermal quantities in a plasma arc placed between two conducting rails is analyzed. The plasma hydrogen drives the hydrogen pellets for the refueling of magnetic fusion reactors. Considering the general equations of electromagnetism and of plasma fluid dynamics and assuming steady-state conditions in a frame which is moving at the same rate as the plasma arc armature, a one-dimensional model is deduced. The effects of an applied magnetic field on the behavior of all flow variables are investigated. Results indicate that the adverse effects of plasma arc heating can be reduced by the application of a magnetic-induction field normal to the current path in the armature. At the maximum acceleration pressure (30 bar) applicable to the hydrogen pellet in the proposed one-dimensional model, the arc temperature at the pellet backend falls from 20000 to 14000 K when a magnetic induction of about 5 T is applied. >