Guillaume Parent

Complete Analytical Calculation of Static Leakage Parameters: A Step Toward HF Transformer Optimization

The predetermination of the leakage inductances of transformers is essential for component designers. Except for special winding disposal, the usual analytical methods of evaluation are ineffective, while the finite-element-method simulation evaluation requires too much time to be suitable for any optimization process. In a previous work, we supplied the analytical expression for vector potential from which we deduced leakage inductance through numerical integration. In this paper, an explicit expression of leakage inductances is given. This expression does not appear as a series, requires shorter computing time, and opens up a lot of future applications relying on optimization software. Moreover, the calculation is not restricted to leakage inductances: It has been extended to all the parameters characterizing the whole leakage behavior of any transformer. The influence of ferrite permeability and thickness is also investigated.

Using a Galerkin Projection Method for Coupled Problems

For coupled problems, two different coupling strategies, either direct or indirect, can be used. One of the advantages of the indirect coupling strategy is its ability to solve each problem separately on dedicated meshes. However, such a technique requires a projection method of each solution obtained on one mesh onto another one. In this paper, a projection method based on a Galerkin technique is presented.

Analysis of the Magnetic Flux Distribution in a New Shifted Non-Segmented Grain Oriented AC Motor Magnetic Circuit

This paper deals with a new AC electric motor magnetic circuit structure made of shifted non-segmented grain oriented steel laminations. The aim of the paper is to understand with a finite element approach the local distribution of the magnetic flux density inside shifted laminations as well as in the air-gaps between them. It is shown that the air-gap flux distribution is not trivial at all and very difficult to appreciate.

Accurate Projection Method of Source Quantities in Coupled Finite-Element Problems

Projecting discrete quantities from one mesh to another one is a critical operation which is usually required in multiphysical problems. The efficiency of a Galerkin projection method is studied for magnetothermal and magnetoelasticity couplings. As examples of application, two electromagnetic (EM) devices are studied: a three-phase busbar system as a magnetothermal problem and an electromagnet as a magnetomechanical problem.

Design of a Coupling Transformer With a Virtual Air Gap for Dynamic Voltage Restorers

Dynamic voltage restorers are devices inserted in transmission and distribution electrical grids to improve efficiently the power quality. The weak point of these series devices is the fault current protection of the voltage source converter (VSC). We propose a new topology of the coupling transformer to protect the VSC, by replacing the usual electromechanical bypass by an embedded magnetic one. In this paper, the design method and the experimental validation of a low-voltage coupling transformer with a magnetic bypass are detailed.

Coupling transformer with a virtual air gap for the protection of dynamic voltage restorers

The dynamic voltage restorers are efficient series compensation devices to improve power quality. Indeed, they are composed of a coupling transformer and power electronics to provide fast voltage sag correction and harmonics compensation. This paper focuses on a new topology of a coupling transformer for the dynamic voltage restorers which improves the protection of the voltage source converter against grid fault including short-circuits, by changing the magnetic state of the transformer core. In this paper, the operating modes in steady state of the proposed coupling transformer equipped with a virtual air gap are studied by both Finite Element simulations and experimental measurements.

On the use of carrier phase jumps to reduce some PWM switching effects

This paper is based on a method recently developed by the authors to characterize analytically, without switching angle determination, the voltage harmonic three-phase systems generated by the switching of PWM inverters. On this basis, it is possible to define control strategies that modify the spectral content of the output signals. The presented developments are focused on the carrier phase jump which aims to act on two harmonics simultaneously by controlling the effects on the other spectral components.

Experimental Model for Study of Electromagnetic Phenomena in Stator Core-End Laminations of Large Generators

This paper describes an experimental model for the characterization of electromagnetic phenomena that occur within the end regions of large turbo-generators. The study is based on a test bench that contains a stack of steel laminations from a 900MW turbo-generator stator and two exciting circuits in order to combine a transverse magnetic ∞ux with the in-plane ∞ux. In order to explain the ∞ux penetration within the magnetic sheet stack, accurate experimental measurements are performed. Results are compared with flnite-element simulations using code Carmel3D. In the same time, theoretical and experimental results are analyzed with a view to examining the in∞uence of transverse ∞ux on additional losses.

Study of stator core-end packets under the action of two incident fluxes — Real scale model

This paper describes an experimental procedure for characterization of electromagnetic phenomena that occur in the end regions of large turbo-generators. The test bench contains a stack of steel laminations from a 900MW turbo-generator stator and two exciting circuits in order to combine a transverse magnetic flux with the in-plane flux. The theoretical and experimental results will be analyzed with a view to examine the influence of transverse flux on losses.

Increasing the energy-efficiency of induction machines by the use of grain oriented magnetic materials and die-casting copper squirrel cage in the rotor

This paper deals with an induction machine whose squirrel cage is made of copper obtained by a die casting process. The major issue of this process is the thermal shock suffered by the laminations, leading to the deterioration of insulation coating as well as the generation of interbar currents, those currents being responsible for addition stray losses. This issue can be counteracted by using grain-oriented (GO) laminations on the rotor. In particular, the paper highlights that due to the specificity of the insulation coating of that kind of electrical steel, it does not suffer from the thermal shock. It is shown that using a squirrel cage made of copper combined to GO laminations in the rotor leads to a decrease of both core losses and stray load losses and an increase of the efficiency of 1.6%.