[LM111382], Letter from Arthur Edwin Kennelly to Caspar Frederick Goodrich, April 22nd, 1889
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Title
[LM111382], Letter from Arthur Edwin Kennelly to Caspar Frederick Goodrich, April 22nd, 1889
Editor's Notes
.####[page 189]####23rd April 89####W.J. Jensk Esq####Director Standardizing Bureau####Dear Sir####With references to your letter of the 20th on the most important practical question of the carrying capacity of wires, there is unfortunately at the present time a deplorable uncertainty as to [fixed?] data at convention. The common english rule used to be 1000 ampere to the square inch meter reduced by the Board of trade I think to 800 per sq. inch or as capacity varying as this squares of the diameter or directly with the circular millage. This plan is uneconomical for small wire and purely empirical having no sound natural basis.####The german plans are based on theoretical considerations connected with the radiation of base wires in air, an error in the opposite direction inconsistency with practice, The tables of the Edison Electric Light Engineering Department for underground conductors are based on almost exactly the same data -- the capacity varying as the cube of the square ---- of the diameter.####The latest circulars from schenectady employ quite a new rule based let us hope on experiment for underground or the sixth power of the fifth rest. I think that is more rational.####[page 190]####(21)####There ought really to be different tables for different kinds of services ones for underground mains another for overhead wires and a third for house works.####The matter is so important that I do not like to advise any precise formulas. I think that experiments should be made with specimens of covered wire in [woodwork? woolwool?] to represent actual practice and the limiting safer temperature found by a measured current from the known coefficient of resistance and now observed rise in resistance. If Mr Edison desired it we could probably make all the necessary measurements in one day. As it is, unless you fall back o the precedent of your small wire too cool and your large ones too hot, you run the risk of being unnecessarily severe on continuation on the one hand, or of -nc---ing cons--- from electric light critics on the other.####Yours very truly####A.E. Kennelly####
Author
Recipient
Mentioned
Date
1889-04-22
Type
Folder/Volume ID
LM111-F
Microfilm ID
109:294
Document ID
LM111382
Publisher
Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University