SPECIAI, METHODS OF DISTRIBUTION. 85 
so called ““booster’’ system and the Edison three-wire sys- 
tem worked 500 volts on a side. We will first consider the 
former. Fig. 49 gives a general idea of its character. AB 
is the line which it is desired to feed, C the main generator 
connected to the track and ground return at E, and D the 
boosting generator for raising the voltage on AB, 
This booster is a relatively small dynamo connected in 
series with the main one. Its voltage is proportioned to 
the extra voltage desired on A B, and its capacity in cur- 
rent is equal to the demands of AB. Its function is to 
supply the energy which must be lost in the line in order 
to reduce the cross section of the line copper while preserv- 
ing the proper voltage and output at B. It is driven by 
any convenient motive power, sometimes when small by an 
  
  
A B 
c ity -8 
L'% D 
n 
| 
Y 
E 3 
F16. 49. 
electric motor. In Fig. 49 the booster voltage is taken at 
200, while we will assume that 500 amperes are to be 
delivered as in the case just discussed. The capacity of 
the booster would then have to be 100 k. w., while that of 
the main generator might be anything that local conditions 
on the system should demand. The effect of the boosting 
system is quite obvious. The initial combined voltage 
would be 750, of which 300 volts might be lost in the line. 
The result would then be to reduce the copper needed in 
the line to one-half of its former amount. The cost of the 
booster and its equipment including motive power would 
be $3000 to $4000, so that there would be a net gain of 
nearly $20,000 in first cost of equipment. Reckoning, as 
in our previous example, interest and depreciation on this 
at ten per cent, there is a gross saving of about $2000 per 
year to offset the cost of the extra power lost in transmis-