T. Waeckerle

Field computation in non linear anisotropic sheets using the coenergy model

To achieve reliable field computation in electromagnetism, the finite element method must be used with accurate magnetization law models. The anisotropic nonlinear behavior of electrical sheets is modeled using the coenergy density. This model leads to a good representation of the magnetization processes in magnetic materials. The uniqueness of the solution given by the finite element method is ensured by modeling materials with the coenergy. The model and its implementation in finite element computation software are presented. >

Magnetic flux and losses computation in electrical laminations

This paper deals with the numerical computation of the average induction over sheet laminations by solving the magnetic diffusion equation. Different models are used to describe the magnetization law: an anhysteretic law and the static and dynamic hysteresis Preisach models. The computed flux and associated losses are then compared to experimental results for wide frequency range and different magnetization levels.

Application of Preisach model to grain oriented steels: comparison of different characterizations for the Preisach function p(/spl alpha/, /spl beta/)

To take into account scalar hysteresis in magnetic calculations, accurate models are required to correctly describe soft magnetic material behavior. The Preisach model makes it possible to do so if its distribution function p(/spl alpha/, /spl beta/) is well determined. This paper presents a comparison of four methods of characterization of the function that uses different peak magnetization level loops of grain oriented sheets. The choice of a lorentzian function with a term of interaction field shows interesting results.

Characterization of SiFe sheet insulation

Magnetic circuits of electric machines are laminated using coated sheets in order to limit eddy currents. The standard Franklin device is widely used to measure the coating surface resistance. Its main drawback is a bad local repeatability. Resistance measurements performed on the same sample reveal a wide range of values. Hence the mean value may not be considered as a sufficient criterion for the insulation quality; a statistical approach is needed. The characterization of several types of coating by different means (Franklin device, scanning electron microscope and thickness tester) has been performed. The measurements have shown that the scattered resistance values can be explained by inhomogeneities in the insulating layers. Interlaminar losses have been modeled taking into account this scattering. Thermal calculation has shown that defects in the coating surface cannot be responsible for significant damage (dangerous overheating) in the magnetic circuit. >

The development of {100} texture in Fe 3% Si electrical sheets

Today, a way to strongly raise the operating flux density in rotating machines is to use (100) cubic textured sheets. The hot rolling texture gradient strongly influences the development of the preferential final texture. This paper presents a process based on a specific heterogeneously strained hot deformation and a subsequent annealing which leads to a final misoriented cubic texture after a normal grain growth.

Analytical computation of average induction in a sheet cross section considering magnetic diffusion and hysteretic features

The analytical solving of diffusion equation in a sheet cross section is studied with a time dependent surface applied field, including hysteretic characteristics in a large frequency range. The local induction is then calculated by the dynamic Preisach model. The resulting average induction is finally compared with experimental and numerical results.

Application of the coenergy model to different electrotechnical devices: comparison of different magnetic sheets

Models taking into account the anisotropy and nonlinearity of doubly oriented, grain oriented and nonoriented electrical sheets, were implemented in finite element CAD software. These models based on the coenergy density have been used to model different electrical power devices and to compare their performance. The doubly oriented sheets proved to be more suitable than the conventional soft magnetic materials. The power devices modelled were: a large generator, a small synchronous motor, a T-joint of three-phase power transformer, and a small punched transformer.

New compact and precise magnetometer

Abstract Torque magnetometer can give a rough evaluation of electrical sheet texture components. A small torque magnetometer for routine measurements is described. The 14xa0mm diameter punched sample is placed in an homogeneous field of 1xa0T created by an Halbach type cylinder. The torque sensitivity is (3.75±0.04)×10 −5 xa0Nm/mA. Result on FeNiCrCo is presented and some relevant uncertainties are discussed.

A metallurgical and magnetic study of {100} textured soft magnetic sheets

Abstract This paper deals with a metallurgical and magnetic study of {100} 〈001〉 textured soft magnetic sheets. The influence of several parameters of an elaborate process based on cross-rolling and inhibition effects on the final magnetic performance has been studied and the main results are presented. A correlation between the microstructure and the magnetic behavior of the produced samples characterized in a rotating field device has been established.

Magentic properties of a new grade of thin grain-oriented 3% silicon-iron

It is pointed out that thin-gauge electrical sheets (thickness less than 0.20 mm) hold a privileged position when equipment operates at medium frequencies and often in nonsinusoidal induction conditions. The magnetic properties of two samples obtained by two different fabrication processes are compared. The first was prepared by rolling standard-gauge GO (grain-oriented) sheets at the required thickness, and the second was obtained by direct recrystallization at the final thicknesses. The latter sample presents better characteristics than the former in sinusoidal as well as in trapezoidal induction. It is concluded that better control of the secondary recrystallization process for the GOSS texture makes it possible to elaborate thin grain-oriented 3% silicon-iron by direct recrystallization at the final thicknesses. >