G. Bertotti et al., CORE LOSS PREDICTION COMBINING PHYSICAL MODELS WITH NUMERICAL FIELD ANALYSIS, Journal of magnetism and magnetic materials, 133(1-3), 1994, pp. 647-650
An improved procedure for calculating iron losses in electrical machin
e cores is presented. It is based on physical models and experiments o
n losses in magnetic laminations, under one- and two-dimensional field
s, and exploits a finite element computation of the flux distribution
in the core. Physical modelling relies on the basic concept of loss se
paration, extended to the case of vectorial magnetic flux with generic
elliptical loci. Starting from a theoretical formulation of power los
ses under unidirectional fields and generic induction waveform and its
extension to the case of elliptical flux, general expressions are der
ived for the hysteresis, excess and classical loss components in two d
imensions. Quasi-static and 50 Hz total losses under alternating sinus
oidal flux and pure rotational flux are the sole experimental data nee
ded for a complete loss prediction. In the present work, two different
types of nonoriented FeSi 3.2% laminations are considered, which are
assumed to be assembled into a model three-phase motor core. By means
of a 2D finite element analysis, the distribution of magnetic field an
d induction in the core is obtained for different values of the supply
current and the loss calculation is carried out. A comparison with st
andard loss calculation methods points to the detrimental role of two-
dimensional fluxes, although this may not be fully appreciated in conv
entional 50 Hz induction motors.