84 



ALTERNATING CURRENTS 



Fig. 83 (a) shows vectorially the three voltages E a b, Eb c , and 

 E ca , acting from a to 6, b to c, and c to a, respectively. 



At first sight Fig. 82 looks like a short-circuit, the three coils, 

 each containing a source of voltage, being short-circuited on 



FIG. 82. The delta-connection of alternator coils. 



themselves. The actual conditions existing in this closed cir- 

 cuit may be demonstrated by the use of the subscript notation. 

 Assume that the coil be is broken at c 1 ', Fig. 84 (a). The voltage 

 E^ = $ba + E ac . The vector sum of these two voltages, shown in 

 Fig. 84 (b), lies along voltage Ehs, and is equal to it. Therefore, 



fee' 



FIG. 83. Relation of line to coil voltages and currents in a delta-system, unity 



power-factor. 



the voltage E c > r . = and points c and c' can be connected without 

 any resulting flow of current. This is the same condition which 

 exists when two direct-current generators having equal voltages 

 are connected in parallel. No current flows between the two if 

 the proper polarity is observed. 



