Search

A procedure is described for identifying a mathematical model of core losses in ferromagnetic steel based on a minimal amount of experimental data. The new model has a hysteresis loss multiplicative coefficient variable only with frequency, a hysteresis loss power coefficient variable both with frequency and induction and a combined coefficient for eddy-current and excess losses that is, within a set frequency range, variable only with induction. Validation was successfully performed on a large number of different samples of nongrain oriented fully and semiprocessed steel alloys. Over a wide range of frequencies between 20 Hz and 2.1 kHz and inductions from 0.05 up to 2 T, the errors of the proposed model are substantially lower than those of a conventional model with fixed value coefficients. Index Terms--Core loss, eddy-current loss, electrical machine, Epstein test, ferromagnetic steel, hysteresis loss, iron loss.

Finite element analysis is used to obtain the non-linear variation of axis and cross-axis flux-linkages for a dq model of an interior magnet, brush-less DC motor (BLDC). The model is used to compare competing designs of the conventional form of BLDC with designs of a novel type that has q-axis flux barriers. It is shown that the flux-barrier motor will give (i) equal rated performance, and (ii) better over-rating performance.