POL YPHASE CIRCUITS 1 1 1 



If line 3 is opened what power will the instruments indicate? 

 The terminal voltage of the generator is constant. 



37. In problem 36 if line 3 is opened between the terminal of 

 the generator and the potential coils of the wattmeters what 

 power will each instrument indicate? The terminal voltage of 

 the generator is constant. 



38. Two alternating-current generators, operating in parallel, 

 deliver power to a balanced, 3-phase load. The output of each 

 generator is measured by the two-wattmeter method. The 

 terminal voltage is 2210 volts. The wattmeter readings are: 



First generator Second generator 



TFi = 196kw. TF! = 172kw. 



TP 2 = 312kw. TF 2 = 88kw. 



The similarly numbered instruments are connected in the same 

 lines. What is the total power supplied? What is the power 

 factor of the load? 



39. Two alternating-current generators, operating in parallel, 

 deliver power to a balanced 3-phase load. The output of each 

 generator is measured by the two-wattmeter method. The ter- 

 minal voltage is 6650 volts. The wattmeter readings are: 



First generator Second generator 



TTi = 412kw. TFi 



TF 2 = 626kw. TF 2 



The similarly numbered instruments are connected in the same 

 lines. What is the total power supplied? What is the power 

 factor of the load? 



40. It is desired to transform 200 kw. from 2-phase to 3-phase 

 by Scott-connected transformers. The two-phase line voltage 

 is 2200 volts and the three-phase line voltage is 230 volts. What 

 should be the rum-nt and voltage rating, and tlir ratio of tran- 

 formation of each transform* 



41. It is desired to transform 100 k\\. from 3-phase at 6600 

 volts to 2-phase at 110 volts by the means of Scott-connected 

 transformers, What should be the current and voltage rating, 

 and the ratio of transformation of each transform 



42. Throe single-phase transformers are connected in delta on 

 Ix.th the primary and secondary sides. With a primary volta^- 

 on op. n circuit of 22,000 volts the secondary voltage is 440 volts. 

 The -h<>rt -.-in-Hit cha ic data of each transformer are: 



