70 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
field, and the ratio between them would be unity. The 
value of this ratio is always larger than 1, and for alterna- 
tors with a large leakage coefficient it often reaches a 
value of 2.45. Such a value has been experimentally 
found for the 235 KVA. inductor type three-phase gen- 
erator mentioned in Par. 117. 
For the standard inductor type alternator, this ratio factor 
is on the average equal to 2, and for revolving field 
machines about 1.2. 
The extraordinarily high value in the ease of the 235 KVA. 
generator, reveals its disadvantages in the design, which 
indicates that the ampere turns on the armature are too 
small and the iron body consequently too large, which 
results in an excessive leakage, requiring a strong field 
to keep the voltage drop within small limits. 
From the above it will be seen that too much copper and 
iron has been used for a purpose which could be achieved 
much more cheaply by proper design. 
121. Influence of Stray Field.—tThe influence of the stray 
field on the short cireuit characteristic may be expressed 
as follows: 
Aig ACK Se eae (15) 
where A,, is the amount of the field ampere turns; © 
A,, the ampere turns of the short-circuited arma- 
ture; and 
k, the ratio factor which characterizes the leakage 
conditions. ss 
The method of calculating the ratio factor k, and its effect 
on the voltage drop is shown in Par. 15%. The nearer 
the value of k, is to unity, the better the alternator from 
the standpoint of regulation. 
122. Load Characteristic.—In a loaded alternator, the eur- 
rent may be in phase with, or lagging behind the E.M.F., 
as the case may be. The armature ampere turns have 
