Repeatability and reproducibility of physically consistent single sheet testing with H-coil

Abstract

Measurements of magnetic losses of electric steel are usually performed by International Electrotechnical Commission standardized Epstein testers or Single Sheet Testers (SSTs). According to round robin tests, the corresponding levels of repeatability are of the order of 0.1%, and those of reproducibility are of the order of 1%. However, orders of absolute accuracy are unknown due to the applied “current method.” Here, we report corresponding tests for the so-called “physically consistent SST.” Consistency is achieved by a “giant” tangential field coil on a 50 cm long and 17 cm wide soft magnetic sample, using a thin amorphous yoke for magnetization. Tests were made in two labs with very different working conditions (sea levels of 200 and 1100 m, respectively), with very similarly built-up testers. Measurements were made for peak inductions between 1 and 1.9 T. For two distributed samples, the repeatability errors were lower than 0.3%, and the reproducibility errors were lower than 1%. This indicates that SSTs with an H-coil are not less reliable than current based ones. However, the absolute accuracy can be estimated to be much better, being close to 2%.