POLYPHASE C1RCV1T* 109 



energy to an unbalanced Y-connected load, the neutral of which is 

 not grounded. The line currents are, /i = 14 1 .4 amperes, 7 2 = 1 00 



amperes and 7 3 = 100 amperes. One wattmeter is used and it is 

 connected with its current coil in line 1 and its potential coil 

 lines 1 and 2. If this wattmeter indicates 70.7 kw. what 

 is the total power supplied to the load? If the power factors 

 of each of the three phases are equal what is the voltage between 

 the neutral of the load and the neutral of the generator? What 

 is the power factor? 



27. An unbalanced lamp load, consisting of 115-volt lamps, is 

 connected in Y across the lines of a balanced 3-phase, 200-volt 

 circuit. The line currents are 70.7 amperes, 50 amperes and 50 

 amperes respectively. What is the power supplied to this load? 

 What is the voltage across each phase of the load? 



28. In problem 27 if the resistances of the lamp load are 

 assumed to be constant, what will be the currents in the lines and 

 neutral when the neutral point of the load is connected to the 

 neutral conductor of the circuit? The voltages between the 

 neutral conductor and the lines are equal. 



29. An unbalanced lamp load is connected in delta across the 

 lines of a balanced 3-phase, 230-volt circuit. The re-i-tance- 

 of these loads between lines 1 and 2, 2 and 3, and 3 and 1 are 10 

 ohms, 8 ohms and 6 ohms respectively, (a) What are the line 

 currents'.' (b) If the power is measured by two wattmeter- which 

 have their current coils in lines 1 and 2 what will each instrument 



indicate? 



30. An unbalanced lamp load, consisting of ll.Vvolt lamp-, is 

 connected between the lines and neutral conductor of a balanced 

 :>-phase, 200-volt circuit. The resistances of the loach ! 



line- 1 . I.', and i* and the neutral conductor are ('). S, and 10 ohm- 

 lively. The line voltages are equal and the voltages from 

 the lines to the neutral conductor are also equal. What would 

 t\v<> wattmeter- indicate which have their current coil- in lines 

 1 and '2 and their potential coils across line- 1 and M and line-'Jand 

 3 respectively? What i- the total power -upplied" What i-the 

 current in the neutral conductor? 



31. Three -ingle-pha-e tran-forinere each of which ha- a rat i 

 of tran-fnrmation of 2.5 to 1 are connected in delta on the high- 



M -ide. The low-ten-ion winding- are not connected but 

 supply three separate single-phasel.,; ad-. The fir-t ,.f tlie-e load- 

 is 90 kilowatts at unit pn tor, the -ecoiid i- (ill kilowatt- 



