ALTERNATING GENERATORS. AND SYNCHRONOUS MOTORS. 103 
In this particular case the number of slots per. pole is 4 and 
the number of slot pitches between the coils of one side is 
1. Consequently the coil breadth ratio is 4; the pole 
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HF i ; 
Fic. 60.—POLE PIECE AND SLOT OF THE 375 KVA., 90% REvs., 
2-PHASE ALTERNATOR. 
are is equal to 5; and the pole pitch to 8.3 inches; so that 
the pole are ratio is 0.6 and from the third column of 
Table 14, a form factor of k = 2.34 is obtained by inter- 
polation. 
Substituting these values in Formula (33), we have: 
10° x 3,000 = 2.34 x 50 x 1,920 x F,, 
because the frequency is 50 and the number of conductors 
per phase, 128 x 15 = 1,920. 
UseruL ARMATURE FLUX: With the above data it is found, 
that for the generation of the different E. M. F.’s a useful 
armature flux, F,, is required, as follows: 
F, = 1.56 x 10® lines for 3,500 volts, 
F, = 1.34 x 10° lines for 3,000 volts, 
F, = 1.12 x 10° lines for 2,500 volts and 
F, = 09 xX 10° lines for 2,000 volts. 
Leakace Factor: In order to complete the required data 
it is necessary to ecaleulate the’ leakage factor. 
