Journal of Magnetism and Magnetic Materials 160 (1996) 115-118 ~ l ~ Journal of magnetism JR and magnetic materials ELSEVIER Invited paper European intercomparison of measurements of rotational power loss in electrical sheet steel J. Sievert a.*, H. Ahlers a, M. Birkfeld b, B. Cornut c, F. Fiorillo d, K.A. Hempel b T. Kochmann e, A. Kedous-Lebouc c, T. Meydan f, A. Moses f, A.M. Rietto d Phys.-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany b Inst. fi~r Werkst. der Elektrotechn., RWTH (IWE), Aachen, Germany c Lab. d'Electr, de Grenoble (LEG), Saint Martin-d'Hbres, France d lstituto Elettrotecnico Nazionale G. Ferraris (IEN), Torino, Italy e EBG Gesellschaftf~r Elektromagn. WerkstofJe (EBG), Bochum, Germany t Wolfson Centre for Magn. Technology (WCM), Cardiff, UK Abstract This paper presents the results of a European intercomparison of measurements of the magnetic properties, mainly the power loss, of electrical sheet steel under the conditions of rotating and alternating flux. In the latter case, different directions of the flux in the sample's plane were considered. Two grades of grain-oriented and six grades of non-oriented material were included in the exercise. The six participating laboratories applied different, but partly similar, measurement methods. With non-oriented (NO) materials, the results are in fairly good agreement. For grain-oriented materials the results differ considerably. This can be explained by the large fluctuations of the differential phase angle due to anisotropy, a small measurement area of the sample compared with grain size, and incomplete flux-vector control. The situation appears to require further investigations before a standard can be defined. Keywords: Electrical steel; Rotational power loss intercomparison Progress in the design of electrical machines is consid- ered to depend on the comprehensive knowledge of mag- netic material properties under standard and non-standard excitation conditions. In this respect, special importance is attached to the availability of reliable data describing the performance of the material under rotating flux conditions. However, an agreed standardized method does not exist, and the reproducibilities of the different methods used in a few laboratories in a more or less experimental stage, are in fact unknown. This report presents the conditions and parameters of the intercomparison, the results of the mea- surements, and the conclusions for the improvement of the present situation. Most of the participants used the field sensing method (FS) applied to square-shaped samples. Only IEN exclu- sively applied the thermal method on circular samples, and WCM used the thermal method with thermistors on one of the samples as a supplement to their field sensing method * Corresponding author. Fax: +49-531-592-2405. (for details and original references, see Ref. [1]). EBG and IWE control the polarization J, the other laboratories (except IEN) the flux density B. The field strength values are in such a range that we can consider B and J to be identical. The temperature was to be kept at (23 _+ 3)°C. The characteristics of the setups and sample sizes used by the participants are summarized in Table 1. Two grain-oriented and five non-oriented grades of material were selected for inclusion in this intercompari- son. The selection was made in such a way that a wide range of grain size, silicon content, thickness and loss characteristics was covered. The properties of the selected grades are shown in Table 2. Except for IEN, each partici- pant received two sets of five samples cut from different parts of two parent sheets of grades ORSI 100 and 270-35A in order to evaluate the local scatter of the materials. Before cutting the samples from the 500 mm × 500 mm parent sheets, the sheets were subjected to characterization in the single sheet tester (SST) at the PTB. The main quantity of the intercomparison is the mag- netic power loss measured for a circular rotation of the flux and under the condition of alternating flux, directed at 0304-8853/96/$15.00 Copyright © 1996 Elsevier Science B.V. All rights reserved. PH S0304-8853(96)001 29- 1