United States Patent Office.
Nikola Tesla, of New York, N. Y.
Apparatus for Transmission of Electrical Energy.
Specification forming part of Letters Patent, No. 649,621, dated March 20, 1900.
Application filed September 2, 1897. Serial No. 650,343. Divided and this application filed February 19, 1900. Serial No. 6,780. (No model.)To all whom it may concern:
Be it known that I, Nikola Tesla, a citizen of the United States, residing at the borough of Manhattan, in the city of New York, county and State of New York, have invented certain new and useful improvements in Apparatus for the Transmission of Electrical Energy, of which the following is a specification, reference being had to the drawing accompanying and forming a part of the same.
This application is a division of an application filed by me on September 2, 1897, Serial No. 650,848, entitled “Systems of transmissions of electrical energy”, and is based upon new and useful features and combinations of apparatus shown and described in said application for carrying out the method therein disclosed and claimed.
The invention which forms the subject of my present application comprises a transmitting coil or conductor in which electrical currents or oscillations are produced and which is arranged to cause such currents or oscillations to be propagated by conduction through the natural medium from one point to another remote therefrom and a receiving coil or conductor at such distant point adapted to be excited by the oscillations or currents propagated from the transmitter.
This apparatus is shown in the accompanying drawing, which is a diagrammatic illustration of the same.
A is a coil, generally of many turns and of a very large diameter, wound in spiral form either about a magnetic core or not, as may be desired. C is a second coil formed by a conductor of much larger size and smaller length wound around and in proximity to the coil A.
The apparatus at one point is used as a transmitter, the coil A in this case constituting a high-tension, secondary, and the coil C the primary, of much lower tension of a transformer. In the circuit of the primary C is included a suitable source of current G. One terminal of the secondary A is at the center of the spiral coil, and from this terminal the current is led by a conductor B to a terminal D, preferably of large surface, formed or maintained by such means as a balloon at an elevation suitable for the purposes of transmission. The other terminal of the secondary A is connected to earth, and, if desired, to the primary also, in order that the latter may be at substantially the same potential as the adjacent portions of the secondary, thus insuring safety. At the receiving-station a transformer of similar construction is employed; but in this case the longer coil A′ constitutes the primary, and the shorter coil C′ the secondary, of the transformer. In the circuit of the latter are connected lamps L, motors M, or other devices for utilizing the current. The elevated terminal D′ connects with the center of the coil A′, and the other terminal of said coil is connected to earth and preferably, also, to the coil C′ for the reasons above stated.
The length of the thin wire coil in each transformer should be approximately one-quarter of the wave length of the electric disturbance in the circuit, this estimate being based on the velocity of propagation of the disturbance through the coil itself and the circuit with which it is designed to be used. By way of illustration, if the rate at which the current traverses the circuit including the coil be one hundred and eight-five thousand miles per second then a frequency of nine hundred and twenty-five per second would maintain nine hundred and twenty-five stationary moves in a circuit one hundred and eighty-five thousand miles long and each wave would be two hundred miles in length.
For such a low frequency, which would be resorted to only when it is indispensable for the operation of motors of the ordinary kind under the conditions above assumed, I would use a secondary of fifty miles in length. By such an adjustment or proportioning of the length of wire in the secondary coil or coils the points of highest potential are made to coincide with the elevated terminals D D′, and it should be understood that whatever length be given to the wires this requirement should be complied with in order to obtain the best results.
It will be readily understood that when the above-prescribed relations exist the best conditions for resonance between the transmit-