98 '  DIRECT-CURRENT. DYNAMOS AND MOTORS. 
nearest diameter in the respective one of the two last. 
columns. For instance, if the diameter of the core is 62 
inches, the ratios for the 6-inch core are taken and the 
mean turn is found: 
Ll,” = 68 X 3.93 = 26 inches, 
if the machine is of a bipolar type; and 
lL,” = 68 X 4.382 = 28.6 inches, 
in case of a multipolar type. 
TABLE 27. 
HEIGHT OF WINDING SPACE FOR DYNAMO MAGNETS. 
Height of Winding Space, inches. Ratio of Mean Turn to 
Size of Magnet Core. Diameter of 
Circular Cores. patel | ol 2 ising Circular Cores, 
Diameter, dention B:polar. |Multipolar.| Bipol Iti Bipol Multi 
inches: 7 ion : s : polar. |Multipolar. ipolar. ultipolar. } 
1 .8 4 2 ant ae 4.71 5.50 
2 3.1 3 14 1 Ss 4.32 | 5.11 
3 "fee Mae 13 14 Q 4.19 | 4.97 
4 12.6 14 2 14 24 4.12 4,71 
6 28.3 14 24 2 23 3.93 4.32 
8 50.3 12 24 24 3 3.83 4.12 
10 78.5 1g 23 23 3} 3.73 4.01 
12 113.1 2 3 3 34 3.66 3.93 
15 176.7 24 34 34 ‘BF 3.59 3.82 
18 254.5 24 34 34 4 3.54 3.75 
R21 346 28 32 3¢ 44 3.50 5.70 
24 452 24 4 4 ae, 3.47 3.67 
27 =| 573 28 44 44 54 3.45 3.64 
NBO UL IOT 23 44 44 6 3 43 3.62 
- 83 | 855 Qh 43 5 64 3.41 | 3.60 
36 |1018 3 5 54 v4 3.40 | 3.58 
74. Calculation of Compound Winding.—In a com- 
pound dynamo the series winding supplies the excitation 
