Alternate Current Transformer. 35 



36. To detemnine n^ the number of secondary turns, so that 

 at full load the secondary e.m.f. shall be 220 volts. 

 From >^ 13, 



37. The sectional area of the conductors to be used being 



^'^and£^^ 



for the primary and secondary respectively, we find (see § § 31, 

 33), 



Sect, area of primary conductor=0.0662^;;/^. 



Sect, area of secondary conductor=0.6218f///^. 



The mean length of a turn of either coil being 



=8(/^ + /5) = 119.3 

 and as /3=1800, 

 the resistances of the coils (warm) are 



Primary, 2.77 ohms. 



Secondary, 0.0308 ohms. 



38. The terminal voltage at no load being (see § 13) 

 fh El 



«i , ^ ^ SinS 

 ' 1+a:iCos8+ 



is =229.5 volts, 

 and as it is 220 volts at full inductive load the drop will be 



4.14 per cent. 



If the same transformer operated a non-inductive load it would 

 be rated as of 



— -= 12.5 K.W. capacity, 



and its voltage drop from no load to a non-inductive load of 

 12.5 K.W. would be 1.5 per cent. 



39. By means of the formulae obtained in Section I. the 

 curves shown in Fis. 3 and Fie;. 4 were constructed for the 



