The physical assumptions underlying the static and dynamic Jiles-Atherton (JA) hysteresis models are critically analyzed. It is shown that the energy-balance method used in deriving these models is actually closer to a balance of coenergies, thereby depriving the resulting JA phenomenology of physical meaning. The non-physical basis of its dynamic extension is demonstrated by a sharp contrast between hysteresis loops predicted by the model and those measured for grain-oriented steel under conditions of controlled sinusoidal flux density at frequencies of 50, 100, and 200 Hz.

No abstract

No abstract

We have studied the ability of two one-dimensional (1-D) time-stepping models, both based on the concept of magnetic viscosity, to reproduce dynamic loops and losses in grain-oriented (GO) electrical steels under arbitrary magnetization regimes. We found that GO steels (0.3 mm thick) can be modeled quite accurately at magnetizing frequencies up to 200 Hz by a thin sheet representation, which is applied to a bulk material. At higher frequencies, acceptable results can be obtained through a finite-difference solver of a 1-D penetration equation whose applicability to GO steels can be explained in terms of domain wall bowing. Because of the inertial effect introduced by the magnetic viscosity, the average error in the loss prediction is reduced from 40% for the conventional classical method to 5% for the methods we studied. We demonstrated the accuracy of the models using two GO steels whose losses and -characteristics were measured by computer-controlled Epstein and single-sheet testers.

No abstract

A method is proposed to account for the influence of the tank walls in the topological transient model of a three-phase, three-limb core-type transformer. The influence of the trans- former tank walls as a distributed-parameter hysteretic element is reproduced by solving a diffusion equation that describes the penetration of the plane electromagnetic wave into the depth of the wall. The reliability of the model is validated by comparing its zero-sequence impedances to those measured on a 25-MVA transformer, in the presence and absence of a tertiary stabilizing winding. An Electromagnetic Transients Program–Alternate Transients Program implementation of the model is outlined

A topology-correct transformer model, which covers core operation under heavy saturation conditions, is presented. A method of accounting for magnetic fluxes outside the core and windings is proposed. Representation of the magnetization curve at high flux densities is considered. The equivalent air gap in the core is taken into account. The model is capable of reproducing inrush currents accurately regardless of which transformer winding (LV or HV) is energized. The model is illustrated by calculating inrush currents produced by subsequent energizations of a single-phase transformer

No abstract