Meniscus of a Magnetic Fluid in the Field of a Current-Carrying Wire: Three-Dimensional Numerical Simulations

Three-dimensional calculations of the meniscus of a magnetic fluid placed around a current carrying vertical and cylindrical wire are presented. Based on the material properties of experimentally used magnetic fluids, the numerically determined menisci are compared with the experimentally measured ones reported by May. The comparison is made for a linear law of magnetisation as well as for the experimentally measured nonlinear magnetisation curve. Up to moderate strengths of the applied current ( I < = 45 A), i.e., up to moderate strengths of the magnetic field close to the wire, the calculated profiles agree satisfyingly with the experimentally measured ones for a linear as well as for a nonlinear law of magnetisation. At a great strength of the applied current ( I = 70 A), i.e., at a large strength of the magnetic field close to the wire, the agreement is less good than in the range up to moderate strengths. Our analysis revealed that the numerically assumed isothermal conditions are not present in the experiment, particularly at the great strength of the applied current. A control of the temperature in the experiment and the implementation of a coupled thermal model in the numerics are considered the most relevant future steps for an improved agreement.

Rotor Resistance Estimator based on Virtual Current Sensor Algorithm for Induction Motor Drives

In this article, model reference adaptive system (MRAS)-based estimator of a rotor resistance of an induction motor (IM) is presented. In contrast to the solutions known from the literature, the reference model of this estimator uses the measured values of the phase current and the adaptive part is a virtual current sensor. The article presents an accurate description of the algorithm taking into account the discrete equations for possible practical implementation in the microprocessor system. In the first step, the impact of motor parameters to stator current estimation quality in the adaptive model was checked. Subsequently, simulation tests of the proposed rotor resistance estimator were carried out for the field-oriented control of the induction motor drive system with a model of an induction motor with fixed parameters and an induction motor with a changing main inductance according to a magnetisation curve. The analysis of the estimator’s work showed its high efficiency and insensitivity to changes in the IM main inductance.

Influence of Annealing on the Microstructure and Magnetic Properties in Amorphous Alloys

The influence of isothermal annealing on the magnetisation process in strong magnetic fields of the amorphous Fe61Co10Y8Ni1B20 alloy ribbons was investigated. Samples in the form of ribbons were produced by rapid quenching of liquid alloy on a rotating copper wheel. In order to study the relaxation process, the investigated Fe61Co10Y8Ni1B20 samples were subjected to annealing below the crystallisation temperature at 700 K for 1 h and then at 770 K for 3.5 h. The structure of the samples was examined by X-ray diffraction measurements (XRD). It was found, that all of measured samples in the as-cast state and after thermal treatment, were amorphous. On the basis of virgin magnetisation curve analysis, the type, size and density of structural defects occurring in the investigated samples were determined. It was found that after the first stage of annealing, decay of linear defects (pseudo-dislocation dipoles) into smaller, more thermodynamically stable, point defects occurs. The presence of point like defects was also confirmed after the second stage of annealing.

Arrangement of Fe/Cr/Fe Film Magnetisation Curve outside the Hysteresis Loop as the Manifestation of Spin Density Wave in Cr Layer

Conditions of coexistence of Fe/Cr/Fe film states with parallel and antiparallel Fe layer magnetisations orientation are established. The transition from antiparallel to parallel orientation in external magnetic field is caused with Cr layer spin density wave phase change when wave node in the centre of Cr layer is substituted with wave antinode. The coexistence of these two states means that Fe/Cr/Fe film ferromagnetic state created with external magnetic field retains after the switching this field off. This phenomenon will manifest itself in the fact that magnetisation curve of initially antiferromagnetic Fe/Cr/Fe film will go outside the hysteresis loop of it's remagnetisation in ferromagnetic state created by external field.

A modified elliptic model of anisotropy in nonlinear magnetic materials

PurposeGrain‐oriented steel has a distinctly anisotropic and nonlinear behaviour. Only in rare cases is the magnetisation curve known for directions other than the principal ones. The paper aims at providing a model to obtain these curves for any direction if those in the easy and hard directions are only given.Design/methodology/approachThe well‐known elliptic model is modified in order to correctly mimic the typical behaviour of grain‐oriented steel which is not described correctly by the original elliptic model. An additional condition is introduced to fix the angle between the flux density and magnetic field intensity.FindingsThe model is found to yield good agreement with measurements in case of a special material for which measured curves for intermediate angles are available.Research limitations/implicationsFurther research is necessary to establish whether the model is applicable to other materials.Originality/valueThe new model can be used in numerical analyses of devices comprising saturated grain‐oriented steel material if the magnetisation curves are given in the principal directions.

Representation of Magnetisation Curves over a Wide Region Using a Non-Integer Power Series

An accurate representation of the magnetisation curve including the incremental permeability curve, is presented. It is based on selected powers of B (not generally integer) with positive coefficients giving a power series. The fit is shown to be superior to those obtained with polynomial and rational fraction polynomial representations.