Overview
IEC TR 62981:2017 is an IEC Technical Report that documents international studies and comparisons of magnetic measurements on grain-oriented electrical steelsheet using the Single Sheet Tester (SST) method and the Epstein test method. The report presents results from inter‑laboratory exercises that characterize the statistical performance of SST measurements on high‑permeability (P‑grade) grain‑oriented (g.-o.) electrical steel and compares these with up‑to‑date Epstein test data. It also investigates systematic error sources in SSTs, notably the effect of yoke lamination insulation on measured losses.
Key topics
- Statistical performance of SST measurements - analysis of inter‑laboratory dispersion and reference value derivation for power loss and apparent power (many comparisons referenced at 50 Hz and at common induction levels).
- Establishing SST reference values for P‑grades - methodology to specify obligatory SST‑measured reference values for grading high‑permeability g.-o. materials independently from traditional Epstein classification.
- Epstein vs. SST comparisons - parallel measurements to update statistical characteristics of the Epstein method and enable direct comparison with SST results.
- Systematic error studies - experiments linking SST yoke insulation/lamination resistance to measured magnetic losses, illustrating how yoke construction affects SST accuracy.
- Inter‑laboratory circulation and analysis - protocols for sample circulation, measurement procedures, and statistical analysis of laboratories’ “best estimates.”
Applications
- Material grading and specification - use IEC TR 62981 results to support SST‑based grading of P‑type grain‑oriented electrical steelsheet when specifying material performance for transformers and other magnetic components.
- Test laboratory quality assurance - benchmark SST performance, identify sources of systematic error (for example, yoke insulation quality) and improve calibration and test repeatability.
- Manufacturer production control - compare in‑house SST measurements against reference values and inter‑laboratory statistics to monitor product consistency.
- Metrology and standardization - inform national metrology institutes and standards committees when harmonizing SST and Epstein measurement practices.
Who should use this report
- Electrical steel manufacturers and quality engineers
- Independent and national testing laboratories
- Transformer and electrical machine designers specifying core materials
- Metrology institutes and standards developers
Related standards
- IEC 60050‑121 (Electromagnetism) and IEC 60050‑221 (Magnetic materials and components) - normative references cited in the report.
- IEC 60404 series - classification and specification context for electrical steels (referenced conceptually in the report).
Keywords: IEC TR 62981:2017, single sheet tester, SST, Epstein test, grain‑oriented electrical steel, P grades, magnetic measurements, power loss, yoke insulation, inter‑laboratory comparison.