ANALYSIS OF PL LL AND MAGNETIZATION .MEASlKKMENTa 105 



termined: the latter in this case are those corresponding (o the e(iui\aleiit 

 schematic of Fig. ^(b). 



For the high (IcMisity pull, \ahu\s t)t' F'/F may be tletermincd and 

 plotted against 5 as before. The resulting plot is similar to Fig. 13 in 

 showing linear relations for each value of ;r, radiating from a common 

 intercept. For the presentation of pull results, therefore, this method of 

 plotting is applicable for both core and armature saturation, and for the 

 case where saturation is approached concurrently in both. 



When the slopes y are determined, however, and y{\ + ii) plotted 

 against ti as in Fig. 14, a straight line is not usually obtained unless 

 saturation is confined to the core. The observed relation for armature 

 saturation is usually a curve which is concave upward, and approaches 

 the horizontal at small values of u (travel x small). This result can be 

 interpreted from the expression (17) for F'/F in the case of saturation 

 confined to the armature. The corresponding expression for?/ is \/{(S{'f'p"a). 

 It was shown above that in this case (Rp is approximately equal to 

 (Ro + x/A or (Ro(l + u). The corresponding expression for y{\ + u) is 

 therefore the constant term (1/((Ro^a)- Thus for saturation confined to 

 the armature, the plot of y{\ + w) versus u is simply a horizontal line, 

 from whose value ipA. can be determined. In the more usual case of con- 

 current saturation, this relation is approached at small values of u, 

 where (f)A/<p is relatively large, while at larger values of w, where ^.i/^ is 

 smaller, the relation approaches that for core saturation. 



6 DISCUSSION 



The procedures for the analysis of pull and magnetization measure- 

 ments descril)ed in this article are primarily intended for the evaluation 

 of the magnetic circuit constants in development studies. They also have 

 some related applications, and the choice of procedure varies ^^^th the 

 application and with the measurements available. The following discus- 

 sion of the applications of this analysis indicates the most convenient 

 procedures for each case. 



Presentation of Pull Measurements 



Pull measurements are used not only for the guidance of development 

 studies, V)ut as engineering data in the a|)})licatioii of i-clays and other 

 electromagnets. A coii\'enient form of presentation is that used in Fig. 

 11, where the pull is plotted against ampere turns on logarithmic paper. 

 In j^reparing such data, iiitcMpolat ion of the measurements and the 



