82 SYNCHRONOUS MOTORS 



and, with compensation, it would be 



The saving in cost of generators, in the second case, would, there- 

 fore, be 



p E I w { -7 i ). 



\cos 9 / 



Let e equal the counter E.M.F. of synchronous motors operating with 

 a magnetizing current - tan </> which is lagging. Let ej equal their 



counter E.M.F. with the same magnetizing current leading in phase. 

 The values of e and e\ are deduced from formula (26) which gives 



ZI\ 2 2Z 



) + (ysin0-* cos 9), 

 / Cj \ 



in which E\ is the potential difference applied at the terminals of the 

 motor and / the resultant current. 



The nominal power of the motors and, consequently, their cost, 



e\ 



would be increased, in the second case, in the ratio , and the increase 



e 



in purchase-price of the synchronous motors, resulting from the intro- 

 duction of compensation, and on the assumption that the price per 

 k.w. of the synchronous motors and induction-motors is equal, would 

 be 



A i IW IW \ 



p\(ei - -r-e - T ). 

 \ 2 cos 9 2 cos 9/ 



Let us see, now, what would be the saving in annual operating expenses: 

 The saving in interest and depreciation, for copper, is 



~ COS 



The saving in interest and depreciation, for the machines, is 



[poEoIwi -- T i ) pile! - ^r e - ^ r ) (0.10 + 0.05). 

 r \cos / \ 2 cos <f> 2 cos 9/ J 



