ANALYSIS OI' IM 1,1; AM) M A(i N lOTlZ Al'IoX MlvVSl UllMKNTS *.)!) 



Ifi(lh l)( Hsili/ Pull — Anuaturc Sdliodlion 



A similar licalnicnt is applical)!^ in the case of arnialui'c satiii'at ion, 

 \vli(M-(> /■" F is ('([ual to ipa^ ip'a as before. In this case, however, it is if(:,\pA 

 rather than ipa/^p that is constant, so that the expression corresponding 

 to (14) is: 



^' = feY, (16) 



where (Rf is the reluctance JF£/<P--i of Fig. 6(a), and (Sip is its minimum 

 x'alue. The limiting expression for (Rp is ^E/<f>A , and the approximation 

 corresponding to (15) is therefore: 



In general, there is no simple expression for J^ ;7, and (17) is of Httle 

 interest as a general expression. When saturation is wholly confined to 

 the armature, however, (Re is a constant and usually a minor term, and 

 ^E is then nearly ec^ual to 3^. In this case, the high density pull is given 

 by the approximation: 



F = 



(17A) 



The application of this approximation may be simplified by develop- 

 ing an approximate expression for (R/r in terms of the e([ui^'alent mag- 

 netic circuit constants. The expression for (S{p can be read from Fig. 

 6(b), where 6^/.? is usually large compared with (sX^i + x/ Ai , so that the 

 latter term is an approximate expression for (s\f ■ As (17A) applies only 

 for (Re small, and as Fig. 6(b) is then of nearly the same form as the 

 ecjuivalent circuit of Fig. 4, the ecjuivalent constants (Rn and .4 are in 

 this case approximately equal to(J^n2 and A2 , respectively. Hence in the 

 case of saturation confined wholly to the armature, to wiii(4i (17A) 

 applies, Up can be taken as given by (Ro + x! A, and (17A) then iiu'olves 

 only (/7.4 , ^pa , and the e([ui\'alent magnetic circuit constants (ii,, and ,1. 



5 AXALY.SLS OF PILL MEASUKKMEXTS 



The following discussion relates primarily to the use of jxill measure- 

 ments in analytical studies as a means of evaluating the magnetic 



cii'cuit constants. 



