14 
DIRECT-CURRENT DYNAMOS AND MOTORS. 
137. 
138. 
139. 
140. 
141. 
142. 
143. 
144. 
145. 
146. 
147. 
Express the armature flux in terms of the field density and 
of the dimensions of the armature. 
The total armature flux of a 6-pole dynamo being 9,000,- 
000 lines, what is the flux per pole? 
Find the armature flux of a bipolar 60 K. W. 130-volt 
generator, having 100 armature inductors and running 
at a speed of 700 revs. per min. 
By the use of formula (22), compute the gap induction 
of the machine given in the preceding example, pro- 
vided that-its armature has a diameter of 15 inches and 
a length of 24 inches. | 
A 300 K. W. 4-pole railway generator gives 550 volts at 
4 0 revs. per min.; its frame is of cast iron, and it has 
a toothed ring armature, 44 inches in diameter and 27 
inches long, which is wound with 360 conductors ar- 
ranged in 4 circuits. Find the armature flux by for- 
mula (21) and check the result by formula (22), 
using Table 16. 
Give formula for radial depth of armature core. 
What is the average practical flux density in the armature. 
core, (a) for ordinary bipolar machines, (b) for ordi- 
nary multipolar dynamos, (e) for are lighting ma- 
chines, (d) for low-voltage machines, and (e) for 
alternators? 
The armature of a bipolar incandescent dynamo is 12 
inches long; the armature flux is 6,000,000 lines. How 
deep should the core be made? 
Compute the proper breadth of cross-section for the ar- 
mature of a 4-pole are lighting machine from the fol- 
lowing data: Diameter, 23 inches; length, 9 inches; 
gap induction, 15,000 lines per square inch. 
Show how to find the radial depth in the preceding exam- 
ple, if the length of the armature is not given. 
Find the radial depth of the armature core of an 8-pole 
