PRACTICAL OPERATION OF DYNAMOS. 



225 



The additional cost of oil and supplies is about 40 per cent, of 

 the cost of this item for the steam plant alone. 



The ordinates of the curve H in Fig. 140 give the capacity 

 in kilowatts of the electrical equipment corresponding to various 

 horse-power capacities of engine plants. This curve is not exactly 

 a straight line inasmuch as the efficiency of an electrical generator 

 increases with its size. 



The curves in Fig. 141 show an approximate analysis of the 

 cost of electrical power when the station is operated at full-load 

 for 3,080 hours each year. 



Curve / shows the cost of steam power per kilowatt-year of 

 electrical output. 



Curve J shows the fixed charges on the electrical equipment 

 per kilowatt -year. This item is reckoned as 14 per cent, on the 



200 300 400 500 



Kilowatts capacity of generator. 

 Fig. 141. 



700 



cost of the electrical equipment and it includes interest at 6 per 

 cent., depreciation 4 per cent., repairs 2 per cent., insurance I per 

 cent, and taxes I per cent. 

 15 



