302 THE POLYPHASE CIRCUIT. 



Heiice, for a mesh-connected alternator the terminal 

 voltage = voltage of one phase. 



The relation between the currents in the transmission 

 line and in the armature windings is in this case not so 

 simple as in the case of the star-connected generator, 

 since each line is connected to two phase windings, and will 

 receive current from both. The relation between the two 

 currents supplied to each conductor may be represented 

 by an exactly similar diagram to Fig. 150, used to show 

 the voltages in the case of the star-connected armature. By 

 similar calculation the resultant current is seen to be \/3 * 

 current in either phase winding, since the same relations 

 hold in the case of currents in mesh connection as 

 previously were found to exist for the voltage of a 

 star-connected system. 



The results of the preceding paragraph may be sum- 

 marised as follows : 



Let C, E be respectively the current in the line and 

 the voltage between each pair of con- 

 ductors, and 



c, e the current and voltage of each phase 

 winding in the generator armature. 



For star-connected armatures 



C = c, 



E = ^W e, 

 For mesh-connected armatures 



C = V3X 

 E = t. 



The formulae just given also apply to the case of 

 motor armatures supplied from the line, c and e repre- 

 senting the current and pressure in each phase winding 

 of the motor. Similarly, for any resistance or other form 

 of load circuit supplied from the line, the above rule 

 applies if c and e are taken as the current and voltage of 

 each branch, when the branches are connected either in 

 star or mesh connection, and C and E are the current and 

 voltage in the main circuit. 



Power of 3 -phase Circuit. Still employing the symbols 

 just given, it is easy to see what the power transmitted 

 by the 3-phase circuit is. 



First, take the case of non-inductive load. 



