The production of electric steel sheet of various qualities is not far from 1M tonnes. The prices vary considerably with the power losses in the material. For that reason an intercomparison was organised in the previous BCR programme. It had shown that the accuracy required by the commercial classifications are hardly achievable by the best laboratories. The measurements were done by the usual Espstein frame method. This method is time consuming and therefore expensive. The IEC has proposed a new method called the Single Sheet tester which is capable of accommodating sheets of 500 x 500 mm. Most producers and some metrology laboratories are already equipped for this kind of measurement. The project was designed for measurements to be done on six different materials available in sheet of two or three thicknesses.
The participating laboratories measured for 7 sheets of grain oriented material and 13 sheets of non-oriented materials the specific power Loss (Ps), the specific apparent power (Pa), and the relative magnetic permeability (pr).
In the case of Ps for oriented sheets, 3 laboratories agreed to within +/- 1%, 4 to within 3% and on sheets 4-6, 5 laboratories agreed to within 3%; while for non-oriented sheets, 4 laboratories agreed to within +/- 1%, except for sheet 17 which was particularly wavy and, in some cases, at higher field (1.5 T).
In the case of Pa for oriented sheets, 4 laboratories agreed to within 1% for many measurements and to within +/- 5% for the majority of the remainder, while for non-oriented sheets, 5 laboratories agreed to within +/- 1% at J=1 and 1.3 T, and within +/- 5% at different values of J with the exception of sheet 17.
All measured values of Pr have always been found to agree within +/- 1% at any value of J.
Funding SchemeCSC - Cost-sharing contracts
TW11 0LW Teddington