168 TRANSFORMERS. [Exp. 



former is given below, any errors being less than the usual 

 errors of observation. 



Regulation is to be computed for non-inductive load and for 

 loads of various power factors, with current lagging and lead- 

 ing. (It is suggested that the reader compares the results ob- 

 tained by this method and by other methods with which he may 

 be familiar, and that he also compares the labor required in 

 applying the different methods.) 



Let r be the per cent, resistance drop and x the per cent. 

 reactance drop, as determined by the short-circuit test. Thus, 

 in Fig. 7, r = 2.$? and ^=1.76 (not .0257 and .0176). 



36. Non-inductive Load. The regulation on non-inductive 

 load is computed as follows: 



Per cent, regulation = r + 



1 



For all practical purposes, as a glance at the numerical ex- 

 ample will show, this may be written 



v 2 

 Per cent, regulation = r + . 



For example, when ^ = 2.57 and jr= 1.76; 



In-phase drop r =2.57 per cent. 

 x i 



Effective quadrature drop=: --- = 0.015 per cent. 



^oo 



Regulation = 2. 585 per cent. 



It is seen that the regulation is practically determined by the 

 resistance drop; the effect of reactance drop on non-inductive 

 load is nearly negligible. This is seen in Fig. 9 which is dis- 

 cussed later. In computing the regulation, therefore, the accu- 

 racy of the results depends directly upon the accuracy with 

 which the resistance is determined. Regulation varies with tem- 

 perature and to be definite must be for a specified temperature. 



37. For Lagging Current. When the load has a power 



