Towards absolute measurements of magnetic losses by the rotational single sheet tester (RSST): an interlaboratory comparison

A comparison of the magnetic energy loss measurement in non-oriented Fe–Si sheets under alternating and rotational polarization has been accomplished by four European laboratories using different Rotational Single-Sheet Tester (RSST) setups and different sample shapes. The measurements, performed in the frequency and polarization intervals 5 Hz ≤ f ≤ 200 Hz, 1.0 T ≤ J p ≤ 1.5 T, aimed at providing a benchmark test for these special measurements, looking for a connection between the RSST outcomes and absolute loss values, obtained by a combination of IEC 60404-2 Epstein data and precise local measurements. The laboratory-averaged RSST alternating loss values are found to range in a ±5% interval around the reference values, with the lab-to-lab discrepancies chiefly descending from the heterogeneous variety of the employed magnetic circuits. Numerical analysis highlights the critical role of the effective field and its uniformity across the RSST sensing area. The statistical assessment of the laboratories' best estimates provides the empirical standard deviations s = 4.5% and s = 3.6% for the alternating and rotational loss figures, respectively, thereby showing a significantly reduced dispersion of the results compared with a previous international comparison launched in the ‘90s. It additionally points to the circular geometry for both sample and magnetizer as best suited for the prospective standardization of 2D measurements.