ALTERNATE-CURRENT MACHINERY. 



By Gisbert Kapp, Assoc. M. Inst. C. E. 



Alternators. 

 The theory of alternate-current ma- 

 chines, as given in modern text books, is 

 based upon the assumption that the cur- 

 rents are generated in wire coils, the 

 magnetic induction through which under- 

 goes periodical changes according to a 

 simple sine-function. A machine of this 

 character would be represented, in its 

 most elementary form, by a coil of in- 

 sulated wire revolving round an axis in 

 its own plane, with uniform velocity in a 

 uniform magnetic field, the axis of rota- 

 tion being at right angles to the lines of 

 the field. Fig. 1 represents such a ma- 

 chine ; a rectangular coil A B is placed 

 in the field produced by the polar sur- 

 faces N S, and if these surfaces extend 



