Tooth-ripple losses in electrical machines. Some basic measurements

An experimental investigation has been carried out of the eddy-current loss generated at the face of a stack of ferromagnetic laminations by a travelling wave produced by permeance variations, the conditions reproducing those which may exist at the pole face of an alternator. Measurements cover a range of values of lamination thickness, slot pitch, flux density and frequencies up to 3kHz. Experimental results are compared with calculated values based on linear theory. Certain of the phenomena of flux penetration are studied experimentally, and qualitative explanations are offered.