Fundamental-frequency eddy-current loss due to rotating magnetic field. Part 2: Eddy-current loss in hollow rotors

A nonlinear analysis is given for the flux penetration in hollow ferromagnetic cores. The fundamental magnetisation curve is represented by the equation B1 = KH1¿2/n. Graphical correlations are given to eliminate lengthy numerical calculations. For a given core of finite depth subjected to a surface magnetising force of known frequency, the total current, flux, eddy-current loss etc. can be readily obtained by a reference to these graphs. The theory is applied to induction motors with hollow rotors, and the results of experimental work on such a motor are presented.