376 



ELECTRICAL MACHINERY 



factor different than cos 4> = 1, that coil having the greatest 

 current will be close to the a-c. tap but on one side of the 

 tap only; the adjacent coil, connected on the other side of 

 the a-c. tap will be much cooler. 



115. Heating of Coils. The heating of the different 

 coils will evidently be different because the heating depends 

 upon the magnitude of the current; it follows that some 



Kesultani curre^il; in dotted lines 



FIG. 246. Actual Current in any One Coil Must be the Resultant 

 of the Rectangular Curves of Current Output and the Sine Wave 

 of Current Input. 



coils will be hot when the converter is operating and others 

 will be comparatively cool. In those coils which run coolest 

 the alternating current flowing into the coil and the continuous 

 current flowing out of the coil nearly neutralize each other; 

 the more completely this neutralization takes place the 

 cooler the coil will be. 



Neutralization of Currents in Various Coils. In a poly- 

 phase synchronous converter, this neutralization of currents 



