226 



ELEMENTS OF ELECTRICAL ENGINEERING. 



The principle involved in the transformation of phases may be 

 best brought out by considering the transformation from two 

 phases to any number of phases, say, three ; although any 

 arrangement of transformers which will transform from two-phase 

 to #-phase will serve to transform from ^-phase to two-phase. 



Let A and B, Fig. 193, represent the two electromotive 

 forces of a two-phase alternator, and let E l be any given elec- 

 tromotive force which it is desired to produce. The component 

 of E l parallel to A is E l sin /9, and the component of E l 

 parallel to B is E l cos /S ; and to produce the desired electromo- 





Fig. 194. 



tive force ZT, it is only necessary to produce the components of E l 

 in the respective secondaries of two transformers, of which the 

 primaries are supplied from A and B respectively ', and to con- 

 nect these secondary coils in series. Thus Fig. 194 shows two 

 separate transformers with their primary coils connected to phase 

 A and phase B y respectively, of the two-phase alternator, the 

 secondary coil a has a number of turns sufficient to produce the 

 the electromotive force E l sin /3, the secondary coil b has a 

 number of turns sufficient to produce the electromotive force 

 E l cos /3, and the two coils a and b connected in series give 



