106 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



reactance of 0.3 ohm. If the line voltages at the generating 

 station are each 2200 volts what is the line current? (b) What 

 is the voltage at the load? (c) What is the efficiency of trans- 

 mission? 



8. In problem 7 if the reactance of the impedance units had been 

 condensive instead of inductive what would have been (a) the 

 line current, (b) the voltage at the load, and (c) the efficiency of 

 transmission? 



9. Two equal resistances of 100 ohms each are connected in 

 series across two mains of a three-phase 220-volt circuit and 

 from their junction a resistance of 50 ohms is connected to the 

 neutral conductor of the system. The line voltages are balanced 

 and the voltages from the lines to the neutral conductor are 

 equal, (a) What are the line currents? (b) What is the neutral 

 current? (c) What is the total power absorbed? 



10. Two equal impedances, each of which has an equivalent 

 resistance of 2.0 ohms and an inductive reactance of 1.0 ohm 

 are connected in series across two mains of a three-phase, 220-volt 

 circuit, and from their j unction another unit which has a resist- 

 ance of 1.0 ohm and a condensive reactance of 1.0 ohm is connected 

 to the neutral conductor of the system. The line voltages are 

 balanced and the voltages from the lines to the neutral are equal. 

 (a) What are the line currents? (b) What is the neutral current? 

 (c) What is the total power absorbed? 



11. Three non-inductive resistances of 5, 10 and 15 ohms are 

 connected in delta across the lines of a three-phase, 220-volt 

 circuit, (a) What is the total power absorbed? (b) What are 

 the line currents? 



12. Three impedance units which are represented by the 

 expressions, Zi = 5+j'5, 22 = 5+jlO, 3 = 5 z/10, are connected in 

 delta across the lines 1-2, 2-3, 3-1 respectively of a three-phase, 

 220-volt circuit. If Viz leads 7 23 by 120 degrees (a) what is 

 the total power absorbed? (b) What are the line currents? 



If Viz lags ^23 by 120 degrees, (c) what is the total power 

 absorbed? (d) What are the line currents? 



13. Three non-inductive resistances of 5, 10 and 15 ohms are 

 connected in Y across the lines of a three-phase, 220-volt circuit, 

 (a) What is the total power absorbed? (b) What are the line 

 currents? 



14. Three impedance units which are represented by the ex- 

 pressions, zi = 5 -hj5, z 2 = 5 + jlO, z 3 = 5 .; 10, are connected in Y 



