AVALVSIS OF PriJ; AXD MAGXKTIZ ATIOX MKASTHF.MKXTS 



93 



As both (Rc/iSi' and 0\c/6{' arc small, substitution of JF 

 proceding expression gives as an approximation: 



(ft" = (R' + V^ftc^i' , 



from which: 



{(R" - (R'Y' 



(il (f in the 



(Re = 



(R' 



(11) 



Thus, as indicated in Fig. 9, the value of (R' may be read from any 

 one of the rekictance curves, and the corresponding value of <p"6{' com- 

 puted. The value of (R corresponding to ^ = (R'(p'' is read from the curve, 

 and taken as (R". The values of (R" and (R' are then substituted in (11) 

 to determine (Re. This procedure may be followed for all the reluctance 

 curves, and a mean value of (Re computed. (Re is then taken as 



/(Re/C*^" - ^'). 



Evaluation of External Reluctance Constants 



The procedures described above provide for the determination (a) of 

 the equivalent constants of Fig. 4, (b) of the minimum value (Re of 6{c 

 in Fig. 5. The remaining constants of Fig. 5 can then be computed by 

 means of the equivalence equations (7). Table I lists, for the measure- 

 ments of Figs. 1 and 8, the values of the ec^uivalent constants deter- 



3^ = <f>" (R' 

 J^ = 47rNl — »- 

 Fig. 9 — Alternative method of evaluating core reluctance. 



