DIRECT-CURRENT DYNAMOS AND MOTORS, 69 
ditions being the same. In case the machine is designed 
for low speed, its armature will be proportionately larger, 
and its leakage, therefore, is reduced to that for a cor- 
respondingly. larger output. In machines of small ca- 
pacity, the employment of a ring instead of a drum 
armature likewise increases the size of the armature and 
reduces the leakage. . 
~The fact that the leakage factor decreases with the size of 
the machine is due to the difficulty, or ratherimpossibility, 
of advantageously dimensioning the magnetic circuit in 
small machines. In these the length of the air gaps is 
comparatively much larger, and the distance of the leak- 
TABLE 24. 
LEAKAGE FACTORS FOR VARIOUS TYPES AND SIZES OF 
DYNAMOS. . 
Ordi ted ¥e la¢ | Multipola 
Capacity Horseshoe pee, Bet ees upc : 
of “Type. Type. Type. Type. Type. 
Dynamo, 
in 
Kilowatts. 
Fae 
al 1.50 fo 2.00] 1.40 fo 1.75 1.25 I 1.50 
25 W45 - 180/135 « 160]145 200) 1.22» 140 
5 H.40 «© 1:70) 130 » L500] 1L40 « 190] 120+ 135 
i 1.35 « 1651 1.25 + 145])135 6 180) 118 « 30 
2.5 1.30 » 160) 1.20 + +40) 130 + 1.70) 116 « 128] 1.35 61.75] 1.20 1 1.50 
5 1.25 + L55/ 618 * 1351125 « 160] Li4 « 125/132. 165/418 , 140 
10 122 . LSOL LNG © 130] 120 + 55] 112. 122) 130. L6O] LG . 135 
25 1.20 + 145/114 © 125/118 +» LS5O] 110 . 120) 128 + L555] 415 - 132 
50 LIS « L40}Li2 « £22) 116 + 1451109 - 1181 126- 150/114 « 130 
100 L1G « LBSPINO + L201) 415 + 140] 1.08 - LIS | L246 L45] 113 » 128 
200 hi ¢ f30l. ——— gees janes 122. 1.40] bi2 . 625 
300 1.12 +125) —- — —— |{120- 135) 401 + 122 
500 aoe prasad ae — — 110 + £20 
1000 — —— —— Sees — | 109.118 
2000 ee a ition pene aes | [08 - 115 
age surfaces much smaller, than in large dynamos; the 
reluctance of the air gaps, therefore, is relatively much 
larger, while the reluctances of the leakage paths are con- 
siderably smaller, comparatively, than in large machines. 
Since'each of these causes will individually effect a greater 
leakage, it is evident that their combined result will pro- 
duce a high value of the leakage factor for asmall dynamo, 
