24 
DIRECT-CURRENT DYNAMOS AND MOTORS. 
23%. 
238. 
239. 
240. 
241. 
242. 
2453. 
244. 
245. 
246. 
24%. 
What is the approximate leakage factor of a high-speed 
5 K. W. inverted horseshoe type machine, having a 
smooth armature and cast iron field frame? 
State the approximate leakage factor of a low-speed — 
25 K. W. dynamo of the multipolar ring type, having — 
a toothed armature and a cast steel frame. 
Why is the leakage factor for one and the same magnet 
frame smaller with a toothed than with a smooth 
armature? 
Give reason why a wrought iron or cast steel magnet 
frame for a given armature results in a machine of 
smaller leakage than a cast iron frame. 
If two machines of the same type and construction are 
designed to have equal output at different speeds, which 
one will have the greater factor of magnetic leakage, 
and why? 
Why is the leakage factor of small machines greater than 
in large dynamos of the same type? 
Give rules for the length of the magnet cores in bipolar 
machines having toothed armatures. 
State rules similar to those of the preceding question for 
the length of field cores of bipolar smooth-armature 
machines. 
How should the magnet cores of smooth-armature multi- 
polar machines be proportioned ? 
Give the ratios of length to diameter of magnet cores for 
large, medium, and small multipolar machines with 
toothed armatures. 
Why is it necessary to make the magnet cores longer for 
smooth-armature machines than for those having 
toothed armatures? ern © 
