326 



ALTERNATING CURRENTS 



The quadrature current of the synchronous motor 



I 2s = I 2 - I 2 ' = 257 - 93.3 = 163.7 amp. 

 The energy current of the synchronous motor 



80,000 



V= 34C Volti 



FIG. 299. Vector diagram for synchronous motor which raises power-factor to 

 cos 6' and at same time supplies power. 



The total synchronous-motor current 



I = V(I 28 ) 2 + (Ii) 2 = V(163.7) 2 + (77.0) 2 = V32JOO = 181 amp. 

 The synchronous motor will then be rated at 600 volts, 181 amperes, 

 or will have a rating of 188 kilo volt-amperes. .4ns. 



133. The Synchronous Motor as a Regulator of Voltage. 

 Figure 300 shows one phase of a power system, which may be 



either a single-phase or a 

 polyphase system. A con- 

 stant voltage V g is supplied 



/ f~\ Synchronous 

 m ( J Motor 



^r 



to the system by a generator 



FIG. 300. Synchronous motor taking power or by a power plant. At the 

 through resistance and reactance in series. i r j.u i 



receiving end or the line is 



a synchronous motor whose terminal voltage is V m . Between 

 V g and V m are both resistance and reactance in series. These 

 may be the usual resistance and reactance of a transmission line, 

 or they may exist in an impedance coil, having a resistance R 



