Abstract :
Formulae are deduced for evaluating the increase in m.m.f. and power due to the presence of overlapping joints in a magnetic core under a.c. magnetization conditions, assuming that the magnetic material is homogeneous, and that its permeability is a constant quantity. The effect of hysteresis is considered, and the formulae appear to be applicable at frequencies in, at least, the power- and audio-frequency ranges. The investigation shows that a certain value of mean flux density exists, under constant-frequency conditions, for which the percentage increase of both the m.m.f. and the power loss attains a maximum value. The maximum value and the values of mean flux density at which it occurs increase as the frequency is reduced. Experimental results for both Mumetal and 4% silicon-steel have been obtained, and they serve to verify the general validity of the formulae which have been derived in the theoretical investigation.
