ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 105 
RELUCTANCE OF WHEEL Rim: ‘Take for example the case 
where the useful flux is equal to 1.34 x 10° lines; then 
2.04 * 10° 
2x X 160 
lines per square inch, because the sectional area is equal 
to 160 square inches for which the induction is 6,400, 
provided that the rim material is ordinary cast iron; then 
the ampere turns required to overcome the resistance of 
one inch length is equal to 10. 
As the total length of the rim path e, belonging to one pole 
is 6 inches, the total ampere turns for the rim are equal 
to 10 x 6 = 60 per pole. 
the magnetic density in the wheel rim will be 
RELUCTANCE OF PoLE CorE: The section of the pole core is 
5.4 X 3.95 x 0.96 = 20.5 square inches, and so the magnetie 
; 10° X 
density : : ret = 100,000 lines per square inch 
(approx.). 
The material being sheet iron, the necessary ampere turns 
per one inch length of path — 90, according to the data of 
Fig. 46. 
As the height d, of the pole core = 7.37 inches, the total 
ampere turns belonging to this part of the magnetie circuit. 
=o <°7387 = 663. 
RELUCTANCE OF TEETH: The teeth opposite to one pole shoe 
face offer a section of - STK EX 04 = 2s < L33-xX 
5.5 X 0.9 = 17.5 square inches, for the flow of the useful 
flux of 1.34 x 10° lines; therefore the magnetic density is 
1.34 x 10° 
17.5 
the ampere turns per unit length of path are equal to 30. 
The height 7 of a tooth being 2.16 inches, the toothed path 
requires a M.M. F. of 2.16 X 30 = 65 ampere turns. 
It may be pointed out at this stage, that in the case of a 
small armature bore where the height of the teeth is a large 
= 77,000; and as the material is of sheet iron, 
