N. Sadowski

Inverse Jiles-Atherton vector hysteresis model

In this paper, we present a new vector hysteresis model, which is derived from the original Jiles-Atherton scalar one. The model presents the magnetic vector induction as the independent variable. A modified Langevin equation is used to represent the anhysteretic vector magnetization, and some model aspects are discussed. A comparison between measured and calculated curves for an anisotropic soft magnetic material is performed to validate the model.

A 3-D magnetic vector potential formulation taking eddy currents in lamination stacks into account

A method is developed to take the eddy currents in lamination stacks into account with the finite-element method using the three-dimensional (3-D) magnetic vector potential magnetodynamic formulation. It consists in converting the stacked laminations into continuums with which terms are associated for considering the eddy-current loops produced by both parallel and perpendicular fluxes. Two levels of accuracy are proposed. The best one is based on an accurate analytical expression of the eddy currents and makes the method adapted to a wide-frequency range, i.e., even for low skin depths in the laminations.

Analysis and Test Results of a Brushless Doubly Fed Induction Machine With Rotary Transformer

This paper analyzes a 90-kW brushless doubly fed three-phase induction machine in which a wound rotor circuit is connected to a rotary transformer. It presents the advantages of substituting brushes and slip rings by a rotary transformer. In addition, it shows the rotary transformer design and presents the doubly fed induction machine operation. The steady-state model considers electrical circuit techniques to provide information about current, power factor, and efficiency on load. Equivalent circuit parameters are obtained through laboratory tests under a prototype. Comparisons between simulation and measurement results attest the good performance of the adopted model.

A thermal analysis of induction motors using a weak coupled modeling

Thermal analysis is an important step in designing induction motors. Its principles require the calculation of induced currents in the rotors and obviously this phenomenon is connected to heating. Currents circulating in the stator coil also heats the machine. In this work, in order to evaluate the thermal behaviour of the machine, a weak coupled modeling between electrical and thermal phenomena is proposed, taking into account the transient states. Also, in this work we introduce a new approach to take into account the airgap zone for thermal analysis. Experimental results are presented and compared with calculations.

A general method for coupling static converters with electromagnetic structures

A method allowing coupling of static converters with electromagnetic devices represented by finite elements analysis is presented. Special attention is paid to the fact that the state-variable equations of the static converter are calculated automatically. These equations are then solved simultaneously with those of the electromagnetic structure, step by step with respect to time.

Dual magnetodynamic formulations and their source fields associated with massive and stranded inductors

The treatment of massive and stranded inductors is studied in the frame of dual magnetodynamic finite element h- and /spl alpha/-formulations. On both sides, edge finite elements are used and source fields are defined when needed as mathematical tools to be used directly in each formulation to lead to circuit relations for inductors. Simplified expressions of source fields are proposed. The accuracy obtained on local solutions and circuit parameters is pointed out.

Incorporation of a Jiles-Atherton vector hysteresis model in 2D FE magnetic field computations: Application of the Newton-Raphson method

This paper deals with the incorporation of a vector hysteresis model in 2D finite‐element (FE) magnetic field calculations. A previously proposed vector extension of the well‐known scalar Jiles‐Atherton model is considered. The vectorised hysteresis model is shown to have the same advantages as the scalar one: a limited number of parameters (which have the same value in both models) and ease of implementation. The classical magnetic vector potential FE formulation is adopted. Particular attention is paid to the resolution of the nonlinear equations by means of the Newton‐Raphson method. It is shown that the application of the latter method naturally leads to the use of the differential reluctivity tensor, i.e. the derivative of the magnetic field vector with respect to the magnetic induction vector. This second rank tensor can be straightforwardly calculated for the considered hysteresis model. By way of example, the vector Jiles‐Atherton is applied to two simple 2D FE models exhibiting rotational flux. The excellent convergence of the Newton‐Raphson method is demonstrated.

Electrical machine analysis considering field – circuit – movement and skewing effects

This paper presents a method to analyse electrical machines considering simultaneously the electromagnetic field, electric circuit, control loop, movement and skewing effects. The major contribution of this work leans on its generality, i.e. it can be applied to electrical machines connected to static converters submitted to any control laws, avoiding an a priori analysis. Simulation results of a three‐phase Brushless AC (BLAC) motor fed by a PWM converter is presented as well as a comparison of simulation and experimental results obtained using a two‐phase‐on converter were also presented.

A modified Jiles method for hysteresis computation including minor loops

Abstract This work presents a new methodology for determination of hysteresis curves based on the Jiles–Atherton method. The magnetic induction is adopted as an independent variable which is available in the vector potential magnetic field formulation. The presented method can be directly incorporated in a finite element software.

Study of Static and Dynamic Eccentricities of a Synchronous Generator Using 3-D FEM

This paper deals with the study of static and dynamic rotor eccentricities of a synchronous generator using 3-D FEM. First, both eccentricity cases are introduced, as well as the used approach. Then the models of the structure, based on the magnetic scalar potential formulation and on the magnetic vector potential formulation, are presented. Two eccentricity modeling methods are introduced, the 2-D eccentricity and the 3-D eccentricity. Results obtained for magnetostatic and magnetodynamic cases related to both defects and their combination are presented and discussed.