QUESTIONS AND I'liniu.KMS 485 



nee of this machine and its regulation at unity and at 0.8 power- 

 factor, lagging current. 



94. Two similar 1.000 kw. alternators operate in parallel. The speed- 

 load characteristic of the first alternator is such that its frequency drops from 



from no load to full kilowatt load. The frequency of the 



. alternator drops from 64 to 58 cycles under the same conditions. 



When the combined load on the two alternators is 1,500 kw. how much load 



ach alternator supply? 



95. The ten-ion in the governor spring of the second alternator of problem 

 94 is so adjusted that both alternators have the same frequency when the 

 load on each is 1,000 kw. This change in the speed-load character; 



ond machine raises its speed-load characteristic two cycles at every 

 point. How much power does each alternator deliver when there is n<> 

 load on the system ? 



96. Two alternators are operating; in parallel supplying single-phase 

 power at 2,300 volts to a load of 400 kw. whose power-factor is unity. 

 No.- 1 alternator supplies 109 amp. at 0.8 power-factor, lagging current. 

 What power and what current does alternator No. 2 supply? 



97. Two three-phase alternators are operating in parallel to supply a 

 2,000 kw. load at 6,600 volts, this load having unity power-factor. The 

 current delivered by alternator No. 1 is 83 amp. at 0.85 power-factor, 

 leading current. What power and what current is alternator No. 2 de- 

 livering? What is its power-factor? 



QUESTIONS ON CHAPTER VII 



1. Define a transformer. What distinct advantages do transformers 

 possess over most other types of electrical machiii 



2. By what means is energy transferred from one circuit to the other? 

 Which winding is called the primary? The secondary? 



3. Show that the induced electromotive force of a transformer winding 

 is proportional to the number of turns. To what three factors is the induced 

 electron! otive force in any transformer winding proportional'.' 



4. What current flows into a trail-former primary when the secondary i- 

 open? What is its order of magnitude? What is the relation of the 

 direction of primary current to the direction of flux in the core? Of the 

 secondary current? Explain. 



5. Kxplain the sequence of reactions which cause the primary to take more 



from the line when load is applied to the secon.: 



6. Why i- the mutual flux in a transformer nearly constant from n 

 to rated load? What is the magnitude of the variation of the magi 

 current under these conditions? 



7. What relation exists between primary amjM-re-turns and secoi 

 am|H>re-turn-? What relation exists between primary current and 

 ary current? 



8. D ii between primary leakage flux, secondary leakap 



and mutual flux Whid .regoing depend upon the voltage and 



which depend upon the run-- 



