Rotational Single Sheet Tester Research Articles

Accurate field strength measurement in rotational single sheet testers

The accuracy of the field strength measurement in rotational single sheet testers (RSST) has been investigated by means of both finite element calculations and measurements on the built set-up. Shielding laminations should be used above and underneath the actual sample in order to obtain a two-dimensional and homogeneous magnetization and to measure the field strength accurately.

Application of neural networks for the prediction of multidirectional magnetostriction

This paper describes attempts to use artificial neural networks (ANNs) for the prediction of magnetostriction (MS) characteristics of transformer core materials. In this first approach, the ANNs were trained with data from a rotational single-sheet tester to predict MS in rolling direction (r.d.) as a function of material grade, amplitude and shape of multidirectional magnetisation as well as the level of additional mechanical stress. It is shown that ANNs are able to forecast the corresponding relative MS changes in an approximate way.

Waveform control algorithm for rotational single sheet testers using system identification techniques

In rotational single sheet testers (RSST), the magnetic properties of electrical steel sheet are measured for well-defined one- or two-dimensional induction waveforms over a large frequency range (1–200 Hz). For this task, a new iterative waveform control algorithm is presented. It is based on the recursive least squares system identification technique. The modeling of the setup as well as the principles and implementation details of the algorithm are discussed. Simulation and measurement results for alternating sinusoidal magnetization of the sample are presented. The main advantage of the proposed method is that it does not require preliminary information concerning the properties of the tested material or the measurement setup. The method is therefore ideally suited for use in a fully automated measurement system. Furthermore, especially for low frequencies (1–10 Hz) the proposed algorithm exhibits faster convergence compared to previously described methods.

Field homogeneity in a two-phase rotational single sheet tester with square samples

Finite element method (FEM) calculations have been used to determine the geometry and field homogeneity in a two-phase rotational field single sheet tester with square samples. Mounting shielding laminations above and underneath the actual sample improves the field homogeneity. Chamfering the yoke also enhances field distribution, but this effect turns out to be less important than shielding the sample.

Field distributions in rotational single sheet testers

This paper concerns rotational single sheet testers (RSST) as applied for investigations of laminated soft magnetic materials. Most RSSTs use a square 64 cm 2 sample with rather small sensor elements. They yield effective average loss values for fine-grained SiFe rotationally magnetized up to 1,2 T. For highly grain oriented (h.g.o.) SiFe sheets, characterized by large grain size and high crystallographic order, we have developed a 3-phase exited RSST which uses a hexagonal sample of 166 cm 2 area. It allows for increased induction values and for the application of large, well averaging sensors, the degree of flux homogeneity however being questionable. The aim of this study was a numerical estimation of the actual conditions of homogeneity for the two set-ups. Calculation was performed for the whole apparatuses by means of 2-dimensional FEM. The material was assumed to show uniaxial anisotropy with orthogonal principal directions for the permeability tensor. For both RSSTs, the results indicate good homogeneity of the induction vector B for the entire sample area. Effects of air gaps between sample and yokes prove to be less critical in the hexagonal case. In a second step, a heterogeneous model was used to simulate the magnetically hardest 55°-direction of Goss-textured material. With respect to the areally averaged vector interdependence between B and H, a comparison with measured results shows good qualitative agreement.

Numerical waveform control for rotational single sheet testers

Rotational single sheet testers are imposed as measuring systems for a complete, in plane. characterisation of magnetic materials. The numerical waveform control that drives the RSST is, despite its slow speed. more precise and versatile than the analogic version. Its adaptability to almost every induction waveform in a large frequency range makes it suitable for completely automated test procedures. The actual hardware implementations is reported. The existence of a variable coupling between the two principal axes imposes a simultaneous correction with respect to the flux waveform of the perpendicular axis. The magnetic circuit with airgaps hinders a-simple direct relation between circuit and field equations. whence the difficulty of estimating the first correction steps. The electromagnetic model and the electrical equations are discussed in order to determine solutions that improve numerical convergence.

Experimental analysis of the field distribution in a large RSST

In this paper, the distribution of the magnetic field in a 300 mm RSST (rotational single sheet tester) is determined. Measurements have been carried out on GO and NO samples, using Hall probes, for three excitation axes: rolling, transverse and 45°. The influence of the material anisotropy and the yoke-sample air gap is reported. Variation of the field perpendicular to the sample plane justifies using the double H-coil method.

Performance evaluation of a large rotational single sheet tester

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.

2D analysis of rotational loss tester

In this study a rotational single sheet tester is simulated using a 2D finite element software Flux2D. Its main goal is to find the best geometrical structure of the device which reaches the largest homogeneity of the magnetic field in the sheet plane. This imposes the size of the sheet area in which the measurements have to be achieved. The simulations have been performed using the magnetic vector potential A formulation and have been limited to a magnetostatic case. The results point out that the square shaped specimen is the best one. The influence of the yokes width is also shown and discussed.

Macroscopic anisotropy characterization of SiFe using a rotational single sheet tester

Macroscopic magnetic anisotropy of two electrical steel samples of GO and NO SiFe materials are characterized thanks to a rotational single sheet tester. This nonstandard set up allows us to perform magnetic measurements under both a rotating excitation field and an alternating one applied along any direction of the sheet plane. The anisotropy of the magnetic losses and of the exciting field of each material quality is discussed. As expected, the GOSS texture of the GO SiFe is well pointed out with its very easy magnetization rolling direction. The hard magnetization axis at 55/spl deg/ emerges as the induction increases and replaces the transverse direction. The NO SiFe shows closely similar magnetic characteristics but remains anisotropic. The vectorial aspect of B(H) law is also highlighted. Such characteristics will be useful in many fields, e.g. material elaboration, magnetic law behaviour modelling and construction of electrical machines.