CIRCUITS 113 



of each transformer are: I 7 = 310 volts, 7 = 9.1 amperes (full-load) 

 P=1000watts. In the case of the open delta the load is connected 

 across one transformer. 



48. In problem 47 compare the regulation in the two cases 

 when a single-phase load of 150 kw. at 0.8 power factor is sup- 

 plied, which in the case of the open delta is connected across the 

 terminals of the two transformers, i.e., across the open side. 



49. Three transformers whose primaries are connected in Y 

 and whose secondaries are connected in delta are in parallel on t he 

 primary sicje with three others whose primaries and secondaries 

 are both connected in Y. If one secondary terminal of the first 



connected to one corresponding terminal of the second set 

 what are the greatest and least voltages that can exist between 

 the other secondary terminals of the two sets? The line voltages 

 o n t he secondary sides are 1 1 00 volts for the two sets of transfon n e rs . 



50. Three transformers whose primaries and secondaries are 

 both connected in delta are in parallel on the primary side with 

 three others whose primaries are connected in delta and who<> 

 secondaries are connected in Y. If one secondary terminal of 

 the first set is connected to a corresponding terminal of the 

 second set, what are the greatest and least voltages that can 

 between the other secondary terminals of the two sets. The line 

 voltages are 1100 volts for the two sets of transformers. 



51. Three transformers whose primaries and secondaries are 

 both connected in delta are in parallel on the primary side with 

 three others whose pri maries are connected in Y and whost > second- 

 aries are connected in delta. If one secondary terminal of the fir-t 

 -t is connected to a corresponding terminal of the second <-t 

 what are the greatest and least \< thai ran exist between 

 the <,ther secondary terminals of the two sets. The line voltages 

 are 1100 volts for the two sets of transformer- 



52. Three auto-transformers are connected as shown in 1 

 eive power fn, m a :*-phase, 11,000-vnlt circuit. The ratio 

 n-fnnnatinn for each trail-former from hi^h ten-ion to low 



ten-inn i- 1> to 1. What i- the -econdary line vnltaire. and what i< 

 the phase relation of the corresponding primary and -emndary 

 line voltages on open circuit '.' 



53. Three auto-tran-fnrmers are connected as shown in I 



. phase. 1 I. ODO-volt circuit. The ratio 



^formation faon hiu'h tension to low ten-inn fa L> to i. What 

 is the secondary line voltage, and what is the phase relation of 



