CHAPTER VI 

 POLYPHASE CIRCUITS 



1. Three equal impedance units, each of which has an equiva- 

 lent resistance of 2.0 ohms and a reactance of 1.25 ohms are 

 connected in delta across a three-phase 220-volt circuit. What 

 current does each unit take? What is the line current? What is 

 the total power supplied? 



2. The three impedance units described in problem 1 are con- 

 nected in Y across a three-phase, 220-volt circuit. What cur- 

 rent does each unit take What is the total power supplied? 



3. Six equal impedance units each of which has an equivalent 

 re-ivtance of 2.5 ohms and a reactance of 1.5 ohms are connected 

 across a three-phase, 220-volt circuit three in delta and t hree in Y. 

 What is the line current? What is the total power supplied? 



4. Three equal impedance units each of which has an equivalent 

 resistance of 2 ohms and a condensive reactance of 1 ohm are 

 connected in delta across a three-phase, 220-volt circuit. At the 

 same point three other equal impedance units, each of which has 

 an equivalent resistance of 1.5 ohms and an inductive reactance 

 of 1 ohm, are connected in Y across the circuit. What is the line 

 current? What is the total power supplied? 



5. Three equal resistances are connected in delta across a tin < - 

 phase circuit. What should be the relative value of three other 

 equal resistances which will take the same power when connected 

 in Y across the circuit? 



6. Three equal impedance units, each of which has an equiva- 

 lent resistance of 2.0 ohms and a reactance of 1.0 ohm are con- 

 nected in delta across a three-phase, 220-volt circuit. Three 

 other equal impedance units are connected in Y acr<>-< the -..,,,. 

 circuit. What -hould be their equivalent resistance and i 

 RUM in order that they will take the same line current and the 

 same total power? 



7. Three equal impedance unit- each .t" which has an equiva- 

 lent resistance of 2.0 ohms and an inductive reactance of 1.0 

 ohm are connected in delta at the end of a tran-mi inn line. 

 conductor of which has a resistance of 0.2 ohm and an induct ive 



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