114 PROBLEMS IN ALTERNATING CURRENT MACHINERY 



the corresponding primary and secondary line voltages on open 

 circuit? 



54. Three auto-transformers are connected as shown in Fig. 5 

 to receive power from a 3-phase, 11,000-volt circuit. The ratio 

 of transformation for each transformer from high tension to low 

 tension is 2 to 1. What is the secondary line voltage, and what 



L.T. 



/ 



H.T. 



FIG. 4. 



is the phase relation of the corresponding primary and secondary 

 line voltages on open circuit? 



55. A 1500-kw., 5500-volt, 3-phase generator delivers power 

 to a transmission line through three single-phase transformers 

 which have their low-tension windings connected in delta and their 

 high-tension windi ngs connected in Y. The following data on this 

 generator and the transformers are given: 



GENERATOR 



The core loss at the rated voltage is 20.2 kw. and the friction 

 and windage is 8.4 kw. Both of these losses may be assumed 

 constant. The effective resistance of the armature is 0.362 ohm 

 per phase. The resistance of the field winding is 0.376 ohm. 

 The armature windings are connected in Y. 



TRANSFORMER 



Full-load current. 



