This document, which is a Technical Report, provides the results of international exercises and comparisons focusing on achieving the knowledge of the statistical performance of single sheet tester (SST) measurements made on grain-oriented electrical steel. These experiments aim at specifying obligatory reference values, measured by the single sheet test method, for the grading of high permeability (P grades) grain-oriented (g.-o.) materials, independently from the Epstein classification as it is practiced today. Besides this, Epstein test measurements have been made in order to gain more up-to-date statistical performance for comparison with the SST statistical characteristics. A few experiments were carried out aiming at improved knowledge on the systematic error performance of the SST, i.e. they were to determine the correlation between the quality of insulation separating laminations in the SST yokes and the measured loss.

There are various designations for “non-oriented electrical sheet steel” and for “grain-oriented electrical sheet steel” in use, for example in the IEC 60404 classification and specification standards, and there are also abbreviations like CGOS (for conventional grain-oriented steel) often used in industry. In this report, the following designations and abbreviations are used:

electrical steel as generic term;
n.-o- electrical steel and g.-o. electrical steel as generic terms for these two types;
S-type electrical streel or c. g.-o. electrical steel for “conventional grain-oriented electrical steel”;
P-type g.-o. electrical steel or high-permeability g.-o. electrical steel;
DR g.-o. electrical steel for “domain refined grain-oriented electrical steel”;
where two terms are used, it can depend on the context;
“electrical steel” can be replaced with “material”, depending on the context.

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2	undefined
6	CONTENTS
8	FOREWORD
10	1 Scope 2 Normative references 3 Terms and definitions
11	4 Background 4.1 Historical background and former concepts of the SST-Epstein relationship Figures Figure 1 – Epstein frame and single sheet tester, schematic view, windings partly omitted
12	4.2 Establishing reference values for grain-oriented electrical steels determined by independent SSTs – A new approach to the purpose
13	5 Preliminary comparisons and experiments 5.1 General
14	5.2 Comparison of the relative difference δPSE = (PSST – Peps)/PEps measured by steel manufacturers on their own products using own set-ups Figure 2 – Relative difference δPSE = 100 (PSST – PEP) / PEP versus peak magnetic polarization J measured by six contributors on samples of their own products
15	5.3 Preliminary comparisons and experiments made by four Chinese laboratories using six SSTs with stacked yokes Figure 3 – Contact pattern for the measurement of lamination resistance in the air gap of SST yokes
16	Figure 4 – Ratio of the power loss PSST to that of the SST with the best yokes, PSSTopt, versus lamination conductivity factor CY of the yokes
17	5.4 Necessity of comparing independent SST results Figure 5 – Ratio of the power loss at 100 Hz to that at 40 Hz, P100/P40, at 1,7 T, versus lamination conductivity factor CY of the yokes
18	Figure 6 – Relative difference δPSE = 100(PSST – PEP) / PEP versus magnetic polarization Figure 7 – Relative difference δPSE = 100(PSST – PEP) / PEP at 1,7 T determined by three standard laboratories, IEN, NPL and PTB, on S- and P-type g.-o. sample pairs
19	6 International comparison of SST measurements on grain-oriented electrical steel and accompanying Epstein measurements 6.1 General conditions, samples, participants Figure 8 – Dispersion of manufacturer’s grain-oriented material production in form of Epstein samples (PTB 1999)
20	6.2 Circulation of the samples and measurement procedure Tables Table 1 – Participating laboratories
21	6.3 Results and analysis of the measured quantities Table 2 – Circulated grain-oriented electrical steel test samples
22	Figure 9 – Example of scattering of the laboratories’ best estimates around the reference value (CGO sample No. 2, unweighted average, dash-dotted line)
23	Figure 10 – Example of scattering of the laboratories’ best estimates around the reference value (HGO sample No. 4, unweighted average, dash-dotted line) Figure 11 – Example of scattering of the laboratories’ best estimates around the reference value (HGO sample No. 5, unweighted average, dash-dotted line)
24	Figure 12 – Samples No. 1 to No. 5: ratio of SST to Epstein power loss reference values δPSE(Jp) = ( – ) / at 50 Hz versus peak polarization
25	Table 3 – Reference values at 50 Hz for the power loss P and the apparent power S
26	Table 4 – Standard deviations associated with the reference values at 50 Hzfor the power loss P and the apparent power S (Table 3) Table 5 – Reference values at 50 Hz of the polarization at H = 800 A/m J800 and standard deviation of the distribution of the laboratories’ best estimates
27	Figure 13 – Overall dispersion (all labs, Jp values, and samples) of the laboratories’ best estimates Pi of the power loss at 50 Hz around their reference values
28	Figure 14 – Overall dispersion (all labs, Jp values, and samples)of the laboratories’ best estimates Si of the apparent power at 50 Hzaround their reference values, with and without outliers
29	Figure 15 – Dispersion around the reference value of the laboratories’ best values of the power loss P measured at 50 Hz by the Epstein and the SST methods at 1,7 T
30	Figure 16 – Dispersion around the reference value of the laboratories’ best values of the apparent power S measured at 50 Hz by the Epstein and the SST methods at 1,7 T
31	Figure 17 – Overall dispersion (European metrological laboratories only, all Jp values and samples) of the laboratories’ best estimates Pi of the power loss at 50 Hz around their reference values, with and without outliers Table 6 – Relative standard deviations of 50 Hz power loss P and apparentpower S distributions around their reference values
32	Figure 18 – Dispersion of the laboratories’ best estimatesof SST (a) and Epstein (b) power loss at 50 Hz
33	Figure 19 – Dispersion of the laboratories’ best estimates of SST (a)and Epstein (b) power loss at 50 Hz
34	6.4 Conclusions of the international comparison Figure 20 – Dispersion of the laboratories’ best estimates, represented by the standard deviation σ of SST (red) and Epstein (blue) power loss (a) and apparent power (b) at 50 Hz, versus the peak value of the polarization, JP, summarizing Figures 18 and 19
35	7 Summary and conclusions
36	Bibliography

Published By	Publication Date	Number of Pages
BSI	2017	42


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Status	Definitive
Pages	42
Publication Date	2017-08-18
ISBN	978 0 580 89689 7
Standard Number	PD IEC/TR 62981:2017
Title	Studies and comparisons of magnetic measurements on grain-oriented electrical steelsheet determined by the single sheet test method and Epstein test method
Identical National Standard Of	IEC TR 62981:2017
Descriptors	Quality, Performance, Statistics, Test methods, Magnetic measurement
Publisher	BSI
Committee	ISE/108
ICS Codes	29.030 - Magnetic materials

BSI PD IEC/TR 62981:2017

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