5-C] CIRCLE DIAGRAM. *93 



APPENDIX I. 

 NOTE ON REGULATION. 



27. Definition of Terms. Regulation is defined by the Institute 

 as follows: 



In constant-potential transformers, the regulation is the ratio of the rise 

 of secondary terminal voltage from rated non-inductive load to no load 

 (at constant primary impressed terminal voltage) to the secondary ter- 

 minal voltage at rated load. (Compare 34, Exp. 5-B.) 



If the secondary terminal voltage is at no load and E 2 at full 

 load, the regulation is, 



Regulation == (E 2 ) -5- 2 



The drop on which regulation depends is E E z , which we may 

 term the regulation drop. This drop, expressed as per cent, of E v 

 gives the regulation. 



28. The total voltage drop, in terms of a I : I transformer, is 

 E^ E 2 and is a little more than the regulation drop, because E^ is 

 a little more than E on account of the drop due to exciting current 

 in the primary winding. 



The per cent, voltage drop is (E t 2 ) -^- 2 , taking E 2 as 100 per 

 cent; or, (E 1 ,) -+- taking E l as 100 per cent. 



29. Numerically, the difference between " regulation " and " per 

 cent, voltage drop " is small. In earlier usage,* the term regulation 

 was commonly employed to designate " per cent, voltage drop." This 

 confusion is one cause for the differences between various methods 

 which have been used (and still are used) for determining regulation. 

 A difference arises, also, according to whether E^ or E 2 is taken as 

 100 per cent. 



*(2ga). See the following articles, in the Elec. World, on the pre- 

 determination of transformer regulation : Bedell, Chandler and Sherwood, 

 August 14, 1897; A. R. Everest, June 4, 1898; F. Bedell, October 8, 1898. 

 See also Foster's Electrical Eng. Pocket Book, p. 492, fifth edition, 1908. 



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