THE SYNCHRONOUS MOTOR. 



159 



the current, and the negative reactance of an over-excited synchro- 

 nous motor in operation is equal to the wattless component of the 

 supply voltage divided by the current flowing through the machine. 

 Thus, Fig. 133 is a clock diagram exactly similar to Fig. 129 



\ 



\ 





Fig. 133. 



except that the motor voltage B is greater than the supply voltage 

 A t and the point P is shown in the position corresponding to 

 zero motor load. The resultant voltage E and the current / 

 are shown, and it may be seen that / is far ahead of the supply 

 voltage A in phase. The negative reactance of the machine is 

 equal to the component of A at right angles to / divided by 

 the value of /. 



77. The operation of alternating-current generators in parallel. - 



Consider an alternator A, Fig. 1-34, driven by an engine and 

 delivering current to a receiving circuit, and consider what must 

 be done to start up another alternator B and connect it in 

 parallel with A so that the receiving circuit may be supplied 

 from both generators. The procedure is exactly the same as would 



