HYSTERESIS LOSS IN TRANSFORMER CORES. 105 



S = \dt 



-JLUM J>* 



= 2AN \db 

 J o 



= 2ANB (32) 



where B is the maximum value of the induction, and T is the 

 periodic time. 



If we assume that the hysteresis loss W\ is given by (Stein- 

 metz's formula) 



Wi = knB 



where a and k are constants, and n is the frequency, we get, by 

 substitution 



Again, the eddy- current loss is given by (see p. 102) 



w m I T (dW 



W *=T\ (dt) dt 

 o 



where m is a constant, by (31) 



T being the periodic time. Therefore 



W 2 = -72*f2 x (mean square value of primary counter E.M.F.) 



The total iron losses are therefore given by 

 W= W+W* 



/ /S \ ^ *W7 



= \2AN) "*" A*N 2 X ( mean S( l- va l ue f primary counter E.M.F.) 

 Now, on open secondary circuit, the primary P.D. is almost 



