Affiliations: [a] Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce, Torino, Italy | [b] SATIE, ENS Cachan, CNRS, UniverSud, Président Wilson, Cachan, France | [c] Dipartimento Energia, Politecnico di Torino, Duca degli Abruzzi, Torino, Italy
Correspondence:
[*]
Corresponding author: O. de la Barrière, SATIE, ENS Cachan, CNRS, UniverSud, 61 av. du Président Wilson, F-94230 Cachan, France. Tel./Fax: +33 147402125; E-mail:[email protected]
Abstract: By means of a newly developed broadband measuring setup we have overcome the
usual upper limit for the test frequency, around a few hundred Hz, which is
encountered in the two-dimensional characterization of magnetic steel sheets
at technical inductions and we have measured the rotational losses in
low-carbon steels up to 1 kHz and peak induction 1.7 T. An important piece
of information is thus retrieved upon a frequency range useful to predict
the performance of high-speed electrical machines. Our experiments,
performed on thick (0.640 mm) laminations, have brought to light the
emergence of the skin effect under rotational fields. This is revealed by an
abrupt deviation of the excess loss component, calculated under the
conventional loss separation procedure, from its well-known linear
dependence on the square root of the frequency. A simple magnetic
constitutive law under rotating induction is proposed and introduced into
the electromagnetic diffusion equation, which is solved by finite elements
coupled to a non-linear algorithm. The classical rotational eddy current
loss, largely prevalent with respect to the hysteresis and excess loss
components on approaching the kHz frequencies in low-carbon steels, is then
calculated in the presence of skin effect, permitting one to achieve full
analysis of the rotational losses and good predicting capability upon a
broad range of frequencies and peak inductions.
Keywords: Magnetic loss, circular induction, non-oriented magnetic steel, skin effect
