B. Cornut

Estimation of magnetic loss in an induction motor fed with sinusoidal supply using a finite element software and a new approach to dynamic hysteresis

A method to estimate precise iron loss in an electrical machine is presented. This method implements a 2D finite element simulation of moving structure including the non-linear magnetic behaviour and a new dynamical hysteresis model of the magnetic circuit. The 2D finite element simulation is used to evaluate the induction evolution with time in any point of the motor structure. The time evolution induction signal is then used as the input of the dynamical hysteresis model to estimate the hysteresis cycle and therefore local iron loss. Results on a 4 kW, 4-pole, 3-phase sine fed induction motor show a good agreement between theoretical estimation and measurement. For the first time, it is shown that rotor loss represents 30% of the motor iron loss.

Punching influence on magnetic properties of the stator teeth of an induction motor

In order to study the effects of punching of electrical steel sheets, a suitable geometrical structure able to characterize the stator teeth behavior of an induction motor is proposed and validated. The influence of the punching on a fully processed M330-65A is then characterized. A spectacular degradation of loss and B(H) curves is observed. This leads to a perceptible increase of the no-load machine current.

Numerical computation of the dynamic behavior of magnetic material considering magnetic diffusion and hysteresis

The numerical solution of the diffusion equation in an electrical steel sheet cross section is studied with a time-dependent surface applied field. The study implements a local hysteresis magnetic law. The solutions are compared to both the classical nonlinear anhysteretic resolution and the experiment. The effect of taking into account an hysteretic magnetic law in numerical simulation is studied with different excitation frequencies.

Fe3Si surface coating on SiFe steel

Abstract Fe3Si layers were prepared using chemical vapor deposition of Si on the surface of GO steel and its subsequent heat treatment. The changes in the structure and phase composition after different heat treatment conditions have been analyzed. The coating is characterized by high hardness, good corrosion resistance, high electrical resistivity, and the spin texture which differs from the steel substrate.

Frequency magnetic behaviour of SiFe sheets in a rotational field

Abstract The frequency dependence of losses and the magnetic field has been investigated for different kinds of sheets at 1 T, circular B and in the range 10–400 Hz. The loss behaviour is discussed according to the rotational loss prediction developed by Fiorillo and Bertotti. As the frequency increases, the locus H y ( H x ) rotates exhibiting an increasing area. Analysis of the H modulus and phase shows the anisotropy and hysteresis effects. For thick samples, the contribution of the eddy current is considerable. A homogenization effect is observed which leads to isotropic behaviour.

A two-dimensional Preisach particle for vectorial hysteresis modeling

A new two-dimensional Preisach particle is proposed to describe domain wall motion mechanisms under uniaxial or rotating exciting field. It is coupled to the coherent magnetization rotation Stoner Wohlfarth model adapted to a biaxial particle. The model is tested under uniaxial and rotating excitation and can be applied to both cubic textured or non-oriented materials.

Performance evaluation of a large rotational single sheet tester

Abstract A large Rotational Single Sheet Tester (RSST) designed for the in-plane characterization of a 300 to 500 mm square sample is described in this paper. It is made up of two double vertical yokes and is equipped with B and H search coils. Validation of the RSST and the corresponding measurement equipment has been achieved by a comparison with a 300 mm SST. The need to use a Double H-coil method is also pointed out and justified.

Analysis and comparison of magnetic sheet insulation tests

Abstract Magnetic circuits of electrical machines are divided into coated sheets in order to limit eddy currents. The surface insulation resistance of magnetic sheets is difficult to evaluate because it depends on parameters like pressure and covers a wide range of values. Two methods of measuring insulation resistance are analyzed: the standardized ‘Franklin device’ and a tester developed by British Steel Electrical. Their main drawback is poor local repeatability. The Franklin method allows better quality control of industrial process because it measures only one insulating layer at a time. It also gives more accurate images of the distribution of possible defects. Nevertheless, both methods lead to similar classifications of insulation efficiency.

Influence of low Al content on anomalous growth in 3 % Si-Fe magnetic sheets

Abstract In order to get {100}〈001〉 final texture in electrical 3% Si-Fe sheets, a combination of cross-rolling and inhibition as cube nuclei selection steps before the surface energy effect is attempted to provide a process that draws concurrently on the texture results of each mechanism. The effects of aluminium content and the annealing atmosphere on the final magnetic anisotropy have been studied, and indicate a preferential Al content range and a high sensitivity to the annealing atmosphere. This process leads to significant changes in magnetic properties.

Evaluation of intralaminar losses in magnetic cores

Abstract Laminations of electrical machines are coated to be insulated from each other. However, defects can appear in the insulating layer and losses produced by eddy currents flowing from one sheet to another have to be evaluated. Measurements performed with a standard Franklin device show that the surface insulation resistance of the sheets have a wide range of values. In this paper two models of intralaminar losses calculation are presented but they do not take this scattering into account. The model that we develop is more appropriate to the stochastic aspect of the measurements.