34 DIRECT-CURRENT DYNAMOS AND MOTORS. 
tiplying the height of the winding space by the number 
of wires per inch and rounding the result to the next 
smaller whole number. 
In case of but a few layers of heavy wire, if the calculated 
number of layers is a considerable fraction above a whole 
number, it is even advisable to replace the armature con- 
ductor by two or more wires of equivalent total cross- 
section, and to re-design the arrangement of the armature 
winding so that the permissible winding space is made 
use of more economicéally. 
The actual total number of inductors on the armature is 
then the number of armature divisions times the number 
of wires per division, divided by the number of wires em- 
ployed in subdividing the area of the armature conductor. 
28. Arrangement of Wires on Toothed Armature. 
—The number of slots of a toothed armature is governed 
by its size, the usual limits of the slot numbers for various 
sizes of toothed armatures being given in Table 15, for 
reference. 
; TABLE 15. 
NUMBER OF SLOTS IN TOOTHED ARMATOURES. 
Diameter of Armature. Number of Slots. 
5 inches. 25 to 40 
10 ‘s 30 ‘* 60 
1 40 “© 80 
20 sia 60 ‘* 100 
30 ee 80 ** 150 
50 3 100 ‘* 200 
100 i 150 ‘* 300 
150 a 200 ‘* 400 
Dividing the total number of wires, obtained from formula. 
(17%), by the number of slots, taken from Table 15, the 
number of wires per slot is obtained. The latter must be 
such that the slot is evenly filled with the winding; that. 
is to say, the slot must contain a proper number of full 
