Pole-face losses in alternators. An investigation of eddy-current losses in laminated pole shoes

A recent re-examination of the phenomenon of tooth-ripple flux pulsations at laminated pole-faces in alternators resulted in a new theoretical analysis by means of which the pole-face eddy-current loss can be calculated. The primary purpose of the present investigation has been to make measurements of tooth-ripple losses which could be compared with values calculated from the new formulae. In order to make these measurements an experimental homopolar machine was built and values of eddy-current losses were determined over a fairly wide range of flux density and frequency for four different thicknesses of lamination. It is found that there is moderately good agreement between calculation and experiment for the thicker laminations and in general the agreement is markedly better with the new formulae than with those previously developed.