DIRECT-CURRENT DYNAMOS AND MOTORS. 11L 
The total EK. M. F. at normal load, according to formula 
(55), if we assume the armature resistance to be .0125 
ohm, is: 
EH = 1.05 X 125 + 1.25 X 240 X .0125 = 135 volts. 
Inserting this value instead of the no-load voltage into 
(21), the flux required for excitation at normal load is 
found: 
® = 5,000,000 x +5? = 5,4.00,000 lines. 
The flux densities and specific magnetizing forces for 
_ normal load, consequently, are: 
135 
B," = 45,000 x [== 48,600; H,” = .313 x 48,600; 
135 
B, = 120,000 x 75~ = 130,000; Hy’ = 1,100; 
E 135 ; ; 
B,’ = 80,000 x 55. = 86,400; HH,” = 43; 
B,."= 90,000 x = = 97,200; H,," = 78; 
and the magnetizing forces at normal load are obtained 
as follows: 
at, = .313 xX 48,600 X 4= 3,800 ampere-turns. 
at, = 1100x2 = 2,200 “ 
Gia 43 x 5 = ' 240 oe 
At, = 78 X 26 = 2,030 ¢< 
at, (from Par. 69) = 630 * 
Total: AT = 8,900 ee 
As shown in Par. 74, the series winding must supply the 
difference between the ampere-turns on normal load and 
on open circuit, or, by (53): 
ATs. = 8,900 — 6,420 = 2,480 ampere-turns. 
The series winding is, therefore, calculated .as’ follows: 
