Francis Piriou

Finite element analysis in electromagnetic systems-accounting for electric circuits

Two approaches for the numerical simulation of electromagnetic systems, accounting for electric circuit equations, are presented. First, the indirect coupled model, which permits the simulation of synchronous machines fed by controlled inverters with moderate calculation time is considered. Second, a direct coupled model where the magnetic and electric circuit equations (2-D or 3-D) are solved simultaneously is developed. This approach takes more calculation time but gives more precision. Applications concerning several electromagnetic systems are treated, and numerical results are compared with experimental ones to verify the validity of the models. >

Comparison of Preisach and Jiles–Atherton models to take into account hysteresis phenomenon for finite element analysis

Abstract In electrical engineering, study and design of electromagnetic systems require more and more accurate models. To improve the accuracy of field calculation code, hysteresis phenomenon has to be taken into account to model ferromagnetic material. This material model has to be accurate and fast. In that context, two macroscopic models are often used: the Preisach and the Jiles–Atherton (J–A) models. In this paper, both models are presented. Field calculation requires a model giving the magnetization M versus either the magnetic field H or the magnetic flux density B . Consequently, from the classical Preisach and J–A, two sub-models M ( H ) and M ( B ) are deduced. Then, we aim at comparing these models in terms of identification procedure facilities, accuracy, numerical implementation and computational effort. This study is carried out for three kinds of materials, which have different magnetic features: ferrites, FeSi sheets and a soft magnetic composite material. Then, the implementation of these models in a finite element code is presented. As example of application, a high-frequency transformer supplied by a rectangular voltage is studied.

A model for coupled magnetic-electric circuits in electric machines with skewed slots

A model permitting the simulation of skewed-slot saturated machines associated with nonlinear external circuits is proposed. To take the slot effects into account, the magnetic circuit is modeled through the combined two-dimensional calculations along the machine axis. In this simulation the electric circuit equation is directly coupled with the magnetic one. The solution of the resulting nonlinear time-dependent equation is obtained using step-by-step numerical integration and the Newton-Raphson iterative procedure. The model is used for the simulation of a 4.6-N-m permanent-magnet synchronous machine in various modes of operation. >

Determination and utilization of the source field in 3D magnetostatic problems

In this paper we study different approaches to introduce the source terms due to the inductors crossed by a uniform current density J/sub 0/ in 3D FEM. Two equivalent methods are developed to decompose the current density J in the facet element space with divergence free close to J/sub 0/. This decomposition is used in the a-formulation without gauge condition. Moreover, from the flux facet the source field H/sub s/ can be calculated in the edge element space and introduced into the /spl phi/-formulation. As examples of applications we have studied a coil with a complex geometry and a iron core coil.

A non-linear coupled 3D model for magnetic field and electric circuit equations

The authors propose a 3-D numerical model in which the magnetic field and electric circuit equations in the absence of eddy currents are solved simultaneously. To consider the magnetic equations, use is made of a magnetic vector potential formulation with the gauge condition (A.w=0) which makes it possible to reduce the number of unknowns. To take into account the magnetic and electric nonlinearities, the Newton-Raphson algorithm has been used. Two applications have been considered: an iron core coil fed by sinusoidal voltage through a diode and a current transformer. For the latter example the results obtained from the simulation are compared with experimental ones. >

Comparison between two approaches to model induction machines with skewed slots

To study electric machines with skewed slots, it is necessary to use 3D models. However, to limit computation time, some approaches based on 2D or 2D-3D models are proposed. In this paper, we compare both approaches. The first one is based on a 2D sliced model and the second one, on a 3D using the 2D-invariant hypothesis. In both models, we take into account the coupling with the electric circuit, the magnetic nonlinearity and the mechanical motion. The results obtained are compared to experimental ones.

Modeling of A Linear and Rotary Permanent Magnet Actuator

In this paper, we propose to study an electromagnetic actuator which involves linear and/or rotary movements. The studied device is constituted of permanent magnets, iron teethed armature and concentrated coils with a simplified design. The aim of this paper is to study the main electromagnetic features of the actuator using 3D finite element method (FEM). First, the actuator is described and the design choices are given and discussed. Then, the electric and magnetic behaviors (fluxes, forces, etc.) are studied thanks to 3D-FEM analyses. Results are given and compared to measurements.

Design and study of a multiphase axial-flux machine

In this paper, a 7-phase axial-flux double-rotor permanent magnet synchronous machine is studied using analytical and finite element methods. This type of machine shows a higher sensitivity to the inductance harmonics and electromotive force (emf) compared with the 3-phase machines. So, the conventional analytical modeling method, in which only the first harmonic is taken into account, leads to significant errors in the determination of the control parameters, e.g., the frequency of pulse width modulation voltage source inverter. A multimachine model explains the reasons for this sensitivity and a more sophisticated analytical method is used. Results are compared with those obtained by the 3-D FEM

Study of a Stator Current Excited Vernier Reluctance Machine

This paper deals with the study of a stator current excited Vernier reluctance machine. This structure is well known for operating at low speed and high torque. In the first part of this paper, we introduce an energetic model which yields the conditions on teeth and polarity numbers necessary for the smooth running of such a structure. Then, we give the procedure used to design a prototype. The second part is devoted to a brief look at the two-dimensional numerical approach used to model the machine. Finally, we present, and study, the constructed prototype. Different tests are performed, and the experimental values are compared to the calculated ones. We validate the operating principle of the current excited Vernier reluctance machine, and show its potential for low speed direct driven applications

Numerical model to discretize source fields in the 3D finite element method

This communication presents a method to discretize electromagnetic source fields in the Whitney element spaces for static electromagnetic potential formulations. This method requires no finite element solution to calculate this source fields. It is based on the use of a facet or an edge tree. We will test it on electrokinetic, electrostatic and magnetostatic examples.