Affiliations: [a] Institute of Electrodynamics, Microwave and Circuit
Engineering, University of Technology, Vienna, Austria | Institute of Electrodynamics, Microwave and Circuit
Engineering, University of Technology, Vienna, Austria
Correspondence:
[*]
Corresponding author: Helmut Pfützner, Institute of
Electrodynamics, Microwave and Circuit Engineering (EMCE), University of
Technology, Vienna, Austria. Tel.: +43 664 39 02 103; E-mail:
[email protected]
Abstract: In principle, single sheet testers (SSTs) or Epstein testers (ETs)
determine iron losses p through the time integral over the field H and the time
derivative of the induction B. Both quantities should be determined in
equivalent ways, i.e. considering an identical quasi-homogeneously magnetized
sample section. Partly, this condition is fulfilled by H-coil methods. However,
the so far used very small coils do not meet the demand of equivalence. At
least outside of Japan, most labs prefer apparatuses where H is assumed to be
proportional to the magnetization current i. But exact proportionality does not
exist due to the periphery – the yoke of SST and the corners of ET,
respectively. Usually, the periphery is considered through a constant effective
magnetic path length l_M based on the peak induction
B_p. But in fact, l_M varies during the
period, i.e. it is a function of B(t) and thus also of time. Our novel "PLC
method" is characterized by path length consideration. We consider dynamics of
length through a "path length function" Λ (B) which is determined for
each grade of material in a calibration process by means of a large, rigid
H-coil. Considering Λ [B(t)] by software, routine measurements on
similar materials can be based on the "corrected" current i(t)/Λ (t).
First results are presented for HGO SiFe investigated in an ET. Here, Λ
proves to be above 1 for low B and below 1 for very high B. As a final target,
application of the method for both ETs and SSTs should yield almost identical
loss values that are close to "true" ones.
Keywords: Iron loss measurements, Epstein tester, single sheet tester
