POLYPHASE SYSTEMS 



81 



J behind E oa . Also, <* is numerically equal to \/3 E* = 

 73 Eob. In a similar manner $ bc = $ bo + $ 0f and $ CQ = # co +# oa . 



/hese three line voltnL -hown in Kiir. 80. 



/? /s to 6e noted that in a balanced Y-system, the three line voltages 



are all equal and are 120 apart. Each line voltage is 30 out of 



FIG. 78. Y-connection of generator coils. 



phase with one of its respective coil voltages. The three tine volt- 

 ages are each \/3, or 1.73, times the coil voltage. 



It is obvious from Fig. 79 (a) that the three coil currents 

 I oa, lob and loc are respectively equal to the three line currents 

 I aa ', IN>' and 7 CC /, as the coil and line are in series. 



(a) (6) 



Fio. 79. Y- \ oltae vector diagram. 



Therefore, in // Y- Cistern the Inn currents and the respective coil 



f <(/U<ll. Moreover, as tile tlll'er rojK meet ill a C'OIll- 



iiion point, tip -inn <t" the thivr eui-rent^ must l>e /rn by 



Kirehhoti : aw, provided there is no neutral- i and 



current. Tli 



I 



