The Thomas A. Edison Papers Digital Edition

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Title

[LB007871], Letter from Thomas Alva Edison to Charles Batchelor, August 10th, 1882

Editor's Notes

I do not know whether have called your attention to the importance of preventing a fall of pressure in your Isolated Installations as well as in the general Distribution business. If with an Isolated plant the main wires are run out from the Dynamo all through the [Bristling] there will be as you know a gradual drop and there will be a difference between the first lamp and the last lamp of five or six volts which will bring the lamps up near the Dynamo to from twenty to twenty five candles provided a point is made of keeping these at the extreme distance from the Dynamo at sixteen candles A difference of a few volts when [add--] [duplex] are made to run at a given number of volts will make a [variable] difference in the life of the lamps.##The proper way to do it never have a loss of more than two and at most three per cent upon the wires and mains upon which the lamps are st----]. This will cause a greater resistance in copper but by not connecting the Dynamo to one end of the system but by running from the dynamo out to the centre of your system you can have a loss of what you please on these feeder wires say of five or ten or any per cent you may wish without [affecting] the loss on the mains [carry]ing the lamps and [this] you can bring the copper down so that it would not be more than the amount [---] in the present [me-] [---] and at the same time you can have the great advantage of only having a difference of two per cent between any two lamps on your circuit In the installations with large steam Dynamos your calculations should be [----] to taking advantage of this as it is of great importance not to have more than two or at most three volts difference between the nearest and next distant lamps and this can only be done by the feeder plan as above detailed. Johnsons [enstat---] at [Holborn] Viaduct should have been put down on these lines. He should have run two mains the whole length of the Viaduct and then run out in cash direction a feeder cutting into the mains half way on each side. This they will have to do when they increase their installation for if they attempt to load up the circuit they will find their volts will be irregularand if the lamps at the station are sixteen candle the lamps at the extremity of the circuit will not be more than seven or eight candles it does not require very much more copper for the reason that you can calculate for the loss even as high as ten per cent on your feeders thus diminishing the supply invested in feeders an calculate the loss on your mains at 2% The great drop on your feeders will not affect the lamps at all as you can readily see. The feeders whhere they will have to run out on the Viaduct may be the same size as the mains the loss on the [lathe] being but 2% while on the feeders it may be 8% or 10%. You will see how important this matters is if you think the matter over.##You know in our First District in New York we find by calculating that the copper tubes would Cost $125,000 with a loss of 10% which means about ten volts fall [---] volts fall would cause the lamps to be all kinds of candle power in different parts of the district if the loss were upon the mains [---]. Hence the necessity for [adopting] the plan of [filters] so as to [lesson] the greater loss upon the leaders & the lesser loss upon the mains or in other words the drop in volts that the drop in candle power is upon the feeders & not upon the mains and so we maintain uniformity of candle power. The cost was increased but very little by so doing because we make the mains all alike with a loss upon them of 2% and [made] practicable all our loss upon the feeders increasing the loss from 10% to 15% when all the lights are on so that when our District is in full play there will not be in any part of our District a difference of more than two volts between the lamps.

Author

Edison, Thomas Alva

Recipient

Batchelor, Charles

Mentioned

Johnson, Edward Hibberd

Date

1882-08-10

Type

Letter

Subject

Isolated stations

Central stations

Electrical distribution system

Folder ID

[LB007-F] Letterbook Series -- General Letterbooks

Microfilm ID

80:797

Document ID

LB007871

URL

https://edisondigital.rutgers.edu/document/LB007871

Rights

Thomas Edison National Historical Park

Publisher

Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University

License

CC0 1.0 Universal

Has Version

Archive.org Viewer, Microfilm Series Reel 80

Item sets

[LB007-F] LB-007 (1881-1882)