Laurent Bernard

Effect of Stress on Magnetic Hysteresis Losses in a Switched Reluctance Motor: Application to Stator and Rotor Shrink Fitting

A magnetic hysteresis model is developed based on the vector generalization of Jiles-Atherton (JA) model combined with a simplified multiscale approach to take into account the effect of mechanical stress on the magnetic behavior. The model aims at representing electrical steel behavior under any loading configuration considering the magnetic field vector and the mechanical stress second-order tensor. Mechanical stress is introduced in the JA hysteresis model through the anhysteretic magnetization and a modified pinning parameter. The main properties of the model are shown under alternating and rotating applied induction, especially in terms of hysteresis losses. The differential magnetic susceptibility is derived from the model, and the implementation into a time-stepping finite-element method is detailed. Finally, a quasi-statically rotating switched reluctance motor is studied: considering different shrink-fitting conditions, the resulting stress is shown to have a significant effect on both distribution and global value of hysteresis losses.

Inductive Charger for Electric Vehicle: Advanced Modeling and Interoperability Analysis

This paper focuses on the interoperability analysis of a resonating contactless charging system for electric vehicles (EVs). The design uses different inductive loops realized by industrial partners. It highlights an advanced electromagnetic modeling (EM) concerning the geometrical characteristics, the resonant topologies, and the control loop. It is shown that the EV chassis plays a major role in the calculation of the electrical parameters and the radiation of the interoperable system. Furthermore, the position of the interoperable magnetic couplers with respect to the EV (middle or backend) has an important effect on the values of the coupling factor and also for the radiation of the system. Finally, an efficiency of 90% is realized in the experimental test with the interoperability which gives flexibility for the driver to use charging stations with different technologies.

Modeling of magnetic induced deformation using computer code chaining and source tensor projection

Equivalent stress projections are developed for the numerical resolution of magneto-elastic coupled problems when magnetostriction induced deformation, material anisotropy and multi-layer inhomogeneity are considered. A comparison with classical force density projection is carried out to show the better performance in the application of a multi-layer transformer core.

Modeling of Magnetic Field Perturbations on the Balance Spring of a Mechanical Watch

A magnetic field is a major enemy of a mechanical watch. Such field modifies the structure of the balance spring that gives rhythm to the watch and thus changes its resonance frequency. Consequently, the watch loses its accuracy. The aim of this paper is to quantify the impact of the magnetic field on the structure and the resonance of the balance spring using a finite-element approach. This coupled magnetomechanical problem implies magnetic force computation, including both magnetostatic forces and magnetostriction effect, while accounting for a large rotation of the spring. An algorithm, including a dynamic mechanical time-stepping scheme, is proposed to quantify the change of the resonance frequency.