THE POLYPHASE CIRCUIT. 309 



The readings of the three wattmeters must then be added 

 together to give the total power of the circuit. 



The following experiment illustrates Method II. given 

 above. 



EXPEEIMENT XLV. DETERMINATION OF POWER AND POWER- 

 FACTOR IN A BALANCED THREE-PHASE LINE. 



DIAGRAM OF CONNECTIONS. 



-o 



Ms 7n s 



M 1} M 2 ,M 3 Source of three-phase alternating current. 

 m i , w 2 ,m 3 Points connected to a balanced partly- 

 inductive load. 

 W Wattmeter. 



A Ammeter for measuring line current. 

 V Voltmeter for measuring line voltage. 



Instructions. Connect three conductors from the source 

 of three -phase alternating current to a partially loaded 

 transformer, induction motor, or other inductive resistance. 



Insert in one line wire the current coil of the watt- 

 meter and an ammeter. Connect a voltmeter between 

 one pair of wires, and connect the free end of the volt coil 

 of the wattmeter alternately to the two wires not containing 

 its current coil, i.e., alternately to M 2 m.^ and M 3 m s 

 in the diagram above. 



Make sure that the voltage between each pair of line 

 wires is the same, and then take readings on the ammeter, 

 voltmeter, and two readings with alternative connections 

 of the wattmeter for several values of the load on the 

 circuit. 



