74 ELECTRICAL ENGINEERING 



and the work done during a complete cycle is 



/Al f* 

 du = -r I 3-C d%& ergs. 

 4 TTiJ 



Al is the volume of the ring in cubic centimeters and therefore 

 the hysteresis loss in ergs per cycle per cubic centimeter is 



d%& (108) 



and is thus proportional to the area of the hysteresis loop. 



The area of the hysteresis loop and thus the hysteresis loss per 

 cycle increases faster than the maximum induction density. 

 Steinmetz gives the following equation for the loss per cycle per 

 cubic centimeter in terms of the maximum induction, 



CO A = T]^ 1 - 6 ergs, ...... (109) 



whese Y] is called the hysteretic constant of the material. For 

 average armature iron the constant has a value about 0.003. 



