RECTIFIERS: THE SYNCHRONOUS CONVERTER 347 



the individual inductor electromotive forces, as shown in Fig. 

 318. In (a), the several conductors upon the surface of the 

 armature are shown. In (6) are the vector electromotive 

 < generated in the various conductors, together with their 

 vector sum (also see page 121, Par. 58). The total single- 



Single'Fh. Slip- 

 Ring Taps > 



O O 



o e 



O 



O 



Single.Ph. Slip--}" 

 Ring Taps 



Fio. 318. Relation of induced emfs. to belt span, in a closed armature winding 



phase voltage is the diameter of a circle drawn to the proper 

 scale, as shown in Fig. 318(6). The three-phase electromotive 

 force is the vector sum of the individual electromotive forces 

 included within a 120 arc, Fig. 318(6). The four-phase electro- 

 motive force is the vector sum of the electromotive forces in- 

 cluded within a 90 arc, and the six-phase electromotive force is 

 the vector sum included within a 60 arc. 



This gives a simple method for obtaining the various electro- 

 motive force relations in a con- 

 r armature. Draw a circle. 

 Fig. Xl\), whose diameter is 100 

 units. Let this represent a single- 

 phase electromotive force of 100 

 \ <>lt s effective. The direct-current 

 electromotive force will then be 

 V2 X 100 = 141.4 volts, which is 

 shown by extending the diameter. 

 The three-phase electromotive force 



is th. length of a chord subtending 



an arc of | Ji ) , OF 86.6 Volt*. The four-phase elect romot iv 



i> th- l.-niitli of a chord subtending 90, or 70.7 volts. The six- 



pha>- el.-rtroinotivc force is the length of a chord subtending 



60, or o() volts. 



^D.C.- 141 Volte 



Fio. 319. Relations e\ 

 aiiiotiK voltages in a synchronous- 



: t<-r at in.'iturc. 



