18 



ELECTRICAL MACHINERY 



Magnetization Curves for Iron. By referring to Fig. 1, 

 which gives the magnetization curves for 'cast iron, cast 

 steel, and soft sheet iron, it is seen that for ordinary densities 

 the soft sheet iron is much more permeable than either of 

 the others. The cast iron is so much inferior to cast steel 

 as a magnetic conductor that it is scarcely ever used. It 



Ampere Turns per Centimeter Length 

 FIG. 1. Magnetization Curves, or B-H Curves. 



is seen by the shape of these curves that, after a certain 

 density has been reached, the density does not increase 

 very much even if the m.m.f. is doubled. When a large 

 increase in m.m.f. produces but small increase in the flux 

 density, the iron is said to be saturated; hence the name 

 saturation curve. 



