74 



SYNCHRONOUS MOTORS 



(2) Saving in Annual Operating Cost. The annual operating 

 expenses include depreciation and interest on the capital invested, 

 and the cost of the extra energy expended in the generators and syn- 

 chronous motors. 



The energy expended in the line is supposed to be the same with 

 or without compensation. 



Let us assume the following figures: 



Depreciation of copper 3 per cent; 



of machines 10 per cent; 



Interest on capital 5 per cent; 



Price of one k.w.-hour of energy 10 centimes (2 cents). 



Let I' equal the resultant current at the generators when there is 

 compensation; and let us assume that the resistance-loss in the gen- 

 erators, at full load, amounts to 4 per cent of the normal effective 

 output. 



Under these conditions, the saving in resistance-loss in the generators 

 when there is compensation, will be (in francs) 



i, (30) 



wherein h is the total number of hours of operation of the installation. 

 The saving in interest and depreciation, for the 'machines, will 

 be given by the sum 



E\I W 



COS 



COS 



X (0.03 + 0.05) + 



tan <- 



__ 



COS (f) 



io+o.05). 



