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Variations in the longitudinal drag force on a magnet close to a slowly moving strip sample of electrical steel are shown to provide sensitive, nondestructive indications of local inhomogeneity in the permeability, dimensions, and hysteresis loss of the sample. Measurements of both grain-oriented and nonoriented electrical steels showed drag force variations of unexpectedly large amplitude for movements of just a few millimeters, often with quasiperiodic features. Hysteresis variations were smaller and less drastic. [ABSTRACT FROM AUTHOR]

The aim of the paper is to find the optimal geometry of a passive shield for the reduction of the magnetic stray field of an axisymmetric induction heater. For the optimization, a space mapping algorithm is used that requires two models. The first is an accurate model with a high computational effort as it contains finite element models. The second is less accurate, but it has a low computational effort as it uses an analytical model: the shield is replaced by a number of mutually coupled coils. The currents in the shield are found by solving an electrical circuit. Space mapping combines both models to obtain the optimal passive shield fast and accurately. The presented optimization technique is compared with gradient, simplex, and genetic algorithms. [ABSTRACT FROM AUTHOR]

An optimization of a multilayered material is presented for the shielding of sinusoidal magnetic fields. The shield consists of alternating layers of aluminum and snonlinear hystereticd steel. The optimization variables are the total shield thickness and the fraction of steel. The optimization goals are to obtain the desired shielding factor, to minimize the shield thickness, and to minimize the eddy currents and hysteresis losses. In the objective function, analytical expressions are used for the shielding factor and the electromagnetic losses. Simulation results of a planar shield show that both the optimal shield thickness and the fraction of steel decrease with the frequency. [ABSTRACT FROM AUTHOR]

In this paper, a method is developed to calculate the core loss in a switched reluctance machine. The magnetic circuit of the motor is described as a magnetic network. The electromagnetic behavior of each magnetic network element takes into account the iron loss using the Preisach model and the principle of loss separation. Using the numerical routines, the local core loss in the different motor sections is calculated. The global core loss is compared with the experimentally determined core loss. [ABSTRACT FROM AUTHOR]

Analytical expressions are presented tofind the shielding effectiveness and the losses of a shield consisting of ferromagnetic, isotropic, nonlinear, and hysteretic material, characterized by the Preisach distribution function in the Rayleigh region. The nonlinear shield is divided into a sufficient number of piecewise linear sublayers with a permeability that is constant (space independent) and complex (to model hysteresis). Simulations of an infinitely long cylindrical shield in transverse sinusoidal flux show that the shielding of perfectly linear material is better than the one of nonlinear metal sheets. More hysteresis and nonlinearity deteriorate the shielding factor, as eddy current losses decrease. [ABSTRACT FROM AUTHOR]