THE ARMATURE REACTIONS OF ALTERNATORS 269 



their armature surface is less utilized for e.m.f., but also their arma- 

 ture reaction gives rise to a hurtful, parasitic self-induction which 

 does not exist in polyphase alternators and which reduces their good 

 regulation. This parasitic inductance can only be partially suppressed 

 at a cost of the expenditure of energy equivalent to a considerable 

 augmentation of the apparent resistance of the armature. 



RESUME AND CONCLUSION 



To sum up, it has been established in this paper that the theory 

 of two reactions of the armature admits of analyzing the phenomena 

 of alternators with greater precision than the old theories, besides 

 having the advantage of referring them to conditions similar to those 

 of direct-current machines. Simple diagrams are given applicable to 

 alternators of saturated field magnets and unsaturated armatures 

 (Fig. 4) and even to saturated armatures (Fig. 7) without involving 

 a complicated correction. 



It has been indicated how to calculate the coefficients of reaction, 

 not only theoretical, but also actual values, by means of curves of 

 magnetic potential in the air-gap. Interesting relations have been 

 established between these coefficients and those of the induced e.m.f. 



Comparisons have been established between the different types of 

 winding, and the advantages possible for a special winding with short 

 bobbins have been made evident. 



It has been shown that single-phase alternators may be treated 

 by the same methods, adding, however, to the inductance of the stray 

 field a parasitic inductance which does not exist in polyphase machines. 



Finally the consideration of the transverse reaction has permitted 

 the discussion of a construction in view of good regulation, showing 

 the interest which attaches to reducing the coefficient of distortion 

 in alternators, and indicating the means of such reduction. 



The author hopes that, thanks to simplicity of application, much 

 greater than is often believed, and by its relations with the theory 

 of direct-current machines, this method of calculation (in which he 

 has had practical experience for several years) may be of service to 

 designers and satisfy the need of rational precision in this work. 



