98 
_ 
ALTERNATING GENERATORS AND SYNCHRONOUS MOTCRS. 
” 
For the continuous current dynamo, the factor k is always 
equal to 1, but in alternating current machines, where the 
effective value of the current is different from that of the 
mean current, the form factor varies as above stated. - 
When the wave form of the E.M.F. is sinusoidal, then the 
factor k = 2.22; for a rectangular wave form k = 2; and 
for a wave composed by two inverted quarter sine curves, 
the form factor k = 2.62. 
175. Resultant Wave Form.—The resultant wave form of 
the E. M. F. of a generator depends on the kind of winding 
employed, that is, on the space and distribution of the 
armature coils and on the ratio between the pole are and 
TABLE 14.—-FORM FACTOR “k” FOR DIFFERENT WINDINGS. 
Columns. 1 2 3 4 
Number’ of! Electrically 
slots per} equivalent 
pole and| toa smooth 
phase...... winding.... 3 1 
With  refer- 49, 52. 48. 51 47, 50. 
ence to Fig. 55. 58. 54, 57 53. 56, 
Number of 
phases..... | 1 | 2 | 3 |1land2|1and3/1land2|1land3/ land 2and 3 
Ratio of coil 
breadth to 
‘pole pitch..| 1 4 $ $ 2 + 4 0 
2 4 1.64 | 2.32/2.50| 2.36 2.54 2.45 2.59 2.83 
ad = 
2) 
Sa | # |149/213/2.93| 216 | 2.26 | 218 | 2.30 2.46 
iy a BE 
58! 4  |1.29/1.82]1.96! 1.98 | 2.10 | 2.02 | 212 2 23 
So 
Pes eae ena 
a 1 1116/1 64/176) 1.68 | 1.80 | 1.72 | 182 2 00 
