ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 81 
field ampere turns the source of the exciting magneto- 
motive force. The lines of useful magnetomotive force 
cut, so to speak, the armature winding and generate an 
E.M.F., which produces a current when the armature 
winding is closed. 
The current carrying armature coils represent the source of 
another magnetomotive force in the magnetic circuit of 
the machine. 
138. Treatment of Magnetic Circuit.—The treatment of 
the magnetic circuit in a manner similar to that of an 
electric circuit, is the simplest method to explain the 
somewhat complicated origin of the inherent’ regulation. 
Fig. 41, indicates the magnetic circuit of one pole of the 
machine illustrated in Fig. 40. 
Ly 
VE 
a z 
od tid a4 
% a 
Ley 
Fie. 41.—HyporHeTicAL REPRES2\ TATION OF THE MAGNETIC 
CrecuItTs OF A GENERATOR. 
The symbols used in Fig. 41, are as follows: 
A,, the ampere turns or magnetomotive force of the 
exciting field ; 
A,, ampere turns or magnetomotive force of the armature 
winding ; 
r,, Yeluctance of the field system consisting of the paths 
in the wheel rim, pole cores and pole shoes: 
F,, flux in the field system, that is, the number of lines of 
