Edison, His Life and Inventions [165]
first great central- station system in New York on the multiple arc system covered by his feeder and main invention, which resulted in a notable saving in the cost of conductors as against a straight two-wire system throughout of the "tree" kind. He soon foresaw that still greater economy would be necessary for commercial success not alone for the larger territory opening, but for the compact districts of large cities. Being firmly convinced that there was a way out, he pushed aside a mass of other work, and settled down to this problem, with the result that on November 20, 1882, only two months after current had been sent out from Pearl Street, he executed an application for a patent covering what is now known as the "three-wire system." It has been universally recognized as one of the most valuable inventions in the history of the lighting art.[13] Its use resulted in a saving of over 60 per cent. of copper in conductors, figured on the most favorable basis previously known, inclusive of those calculated under his own feeder and main system. Such economy of outlay being effected in one of the heaviest items of expense in central-station construction, it was now made possible to establish plants in towns where the large investment would otherwise have been quite prohibitive. The invention is in universal use today, alike for direct and for alternating current, and as well in the equipment of large buildings as in the distribution system of the most extensive central-station networks. One cannot imagine the art without it.
[13] For technical description and illustration of this invention, see Appendix.
The strong position held by the Edison system, under the strenuous competition that was already springing up, was enormously improved by the introduction of the three-wire system; and it gave an immediate impetus to incandescent lighting. Desiring to put this new system into practical use promptly, and receiving applications for licenses from all over the country, Edison selected Brockton, Massachusetts, and Sunbury, Pennsylvania, as the two towns for the trial. Of these two Brockton required the larger plant, but with the conductors placed underground. It was the first to complete its arrangements and close its contract. Mr. Henry Villard, it will be remembered, had married the daughter of Garrison, the famous abolitionist, and it was through his relationship with the Garrison family that Brockton came to have the honor of exemplifying so soon the principles of an entirely new art. Sunbury, however, was a much smaller installation, employed overhead conductors, and hence was the first to "cross the tape." It was specially suited for a trial plant also, in the early days when a yield of six or eight lamps to the horse-power was considered subject for congratulation. The town being situated in the coal region of Pennsylvania, good coal could then be obtained there at seventy-five cents a ton.
The Sunbury generating plant consisted of an Armington & Sims engine driving two small Edison dynamos having a total capacity of about four hundred lamps of 16 c.p. The indicating instruments were of the crudest construction, consisting of two voltmeters connected by "pressure wires" to the centre of electrical distribution. One ammeter, for measuring the quantity of current output, was interpolated in the "neutral bus" or third-wire return circuit to indicate when the load on the two machines was out of balance. The circuits were opened and closed by means of about half a dozen roughly made plug-switches.[14] The "bus-bars" to receive the current from the dynamos were made of No. 000 copper line wire, straightened out and fastened to the wooden sheathing of the station by iron staples without any presence to insulation. Commenting upon this Mr. W. S. Andrews, detailed from the central staff, says: "The interior winding of the Sunbury station, including the running of two three-wire feeders the entire length of the building from back to front, the wiring up of the dynamos and switchboard and all instruments, together with
[13] For technical description and illustration of this invention, see Appendix.
The strong position held by the Edison system, under the strenuous competition that was already springing up, was enormously improved by the introduction of the three-wire system; and it gave an immediate impetus to incandescent lighting. Desiring to put this new system into practical use promptly, and receiving applications for licenses from all over the country, Edison selected Brockton, Massachusetts, and Sunbury, Pennsylvania, as the two towns for the trial. Of these two Brockton required the larger plant, but with the conductors placed underground. It was the first to complete its arrangements and close its contract. Mr. Henry Villard, it will be remembered, had married the daughter of Garrison, the famous abolitionist, and it was through his relationship with the Garrison family that Brockton came to have the honor of exemplifying so soon the principles of an entirely new art. Sunbury, however, was a much smaller installation, employed overhead conductors, and hence was the first to "cross the tape." It was specially suited for a trial plant also, in the early days when a yield of six or eight lamps to the horse-power was considered subject for congratulation. The town being situated in the coal region of Pennsylvania, good coal could then be obtained there at seventy-five cents a ton.
The Sunbury generating plant consisted of an Armington & Sims engine driving two small Edison dynamos having a total capacity of about four hundred lamps of 16 c.p. The indicating instruments were of the crudest construction, consisting of two voltmeters connected by "pressure wires" to the centre of electrical distribution. One ammeter, for measuring the quantity of current output, was interpolated in the "neutral bus" or third-wire return circuit to indicate when the load on the two machines was out of balance. The circuits were opened and closed by means of about half a dozen roughly made plug-switches.[14] The "bus-bars" to receive the current from the dynamos were made of No. 000 copper line wire, straightened out and fastened to the wooden sheathing of the station by iron staples without any presence to insulation. Commenting upon this Mr. W. S. Andrews, detailed from the central staff, says: "The interior winding of the Sunbury station, including the running of two three-wire feeders the entire length of the building from back to front, the wiring up of the dynamos and switchboard and all instruments, together with