110 DIRECT-CURRENT DYNAMCS AND MOTORS. 
The weight of the magnet winding is: 
Wlm = 45 X 28 x a x .0128 = 37 Ibs. per core, 
or 37 <X 4 = 148 pounds, total. 
80. Determination of Compound Winding for Four- 
Pole Toothed-Armature Generator.—The ma- 
chine considered in the preceding paragraph is to be 
compound wound for 5 per cent. over compounding; 
the temperature increase to be 35° C. The four series 
coils are to be connected in parallel, and the four shunt 
coils in two groups of two coils each, 
We must first determine the respective numbers of shunt 
and series ampere turns. We assume the number of 
armature turns to be 250, and 125 to be the voltage on open 
circuit. Proceeding as indicated in Par. %4, we then 
obtain the flux required on open circuit: 
6K IO" SOR eS. 
Eo be 250 X 1,200 
which is the number, upon which the calculations in the — 
previous paragraphs are based. The flux densities on 
open circuit are, therefore, the same as in Par. 69, and 
in this case we have: 
For air-gaps: B,” = 45,000; i," =.313 X 45,000 
“ armatureteeth: B,’ = 120,000; H,! = 700 
° 
‘*< armaturecore: B,” = 80,000; H,” = 31 
° 
‘* magnet frame: B,," = 90,000; H,,” = 51. 
© = 5,000,000 lines, 
Hence, the excitation on open circuit, or the shunt 
excttation: 
at, = .313 xX 45,000 x 4 = 3,520 ampere-turns; 
at, = 00x 2 = 1,400 “ 
at,’ = 31X5 = 12 « 
at, = 51X26 = 1,330 ce 
Total: AT= 6,420 “ 
