70 SYNCHRONOUS MOTORS 



The reactive current will be, at full load, approximately 



124 

 = -- = 42 amperes. 



It can be assumed that the corresponding active current, at no load, 

 is 10 per cent of the total, or 12 amperes. 



Since the synchronous motors, in this case, run without load, it 

 would be necessary, in order to compensate absolutely for the phase- 

 lag, to make them produce also a reactive current 



^=42 amperes; 

 and since their active current attains, at most, 



0.20X100000 



i= = 10 amperes, 



2000 



these motors will take a maximum current equal to 

 7=V / (io) 2 +(42) 2 =42.i amperes, 

 while their normal-load current might attain 



100000 



=62.1; amperes. 

 0.80X2000 



The E.M.F. is given by the approximate formula 

 EZ = 2000 +(i 5X42) = 2630 volts. 

 The line-current, which, without compensation, would be 



\/(io+ 12) 2 + (42)2= 50.5 amperes 



(or at least 42.1 amperes, if the synchronous motors were not operating) 

 would thus be reduced, by the compensation, to 



10+12=22 amperes. 



It might even l)e reduced to 19 amperes, if only two-thirds of the 

 synchronous motors were being operated. 



