United States Patent Office.
Nikola Tesla, of New York, N. Y.
Electrical Transformer.
Specification forming part of Letters Patent, No. 593,138, dated November 2, 1897.
Application filed March 20, 1897. Serial No. 623,453. (No model.)To all whom it may concern:
Be it known that I, Nikola Tesla, a citizen of the United States, residing at New York, in the county and State of New York, 5have invented certain new and useful Improvements in Electrical Transformers, of which the following is a specification, reference being had to the drawings accompanying and forming a part of the same.
10The present application is based upon an apparatus which I have devised and employed for the purpose of developing electrical currents of high potential, which transformers or induction-coils constructed on the 15principles heretofore followed in the manufacture of such instruments are wholly incapable of producing or practically utilizing, at least the apparatus itself and danger to persons 20approaching or handling it.
The improvement involves a novel form of transformer or induction-coil and a system for the transmission of electrical energy by means of the same in which the energy of the 25source is raised to a much higher potential for transmission of the line than has ever been practically employed heretofore, and the apparatus is constructed with reference to the production of such a potential and so as to 30be not only free from the danger of injury from the destruction of insulation, but safe to handle. To this end I construct an induction-coil or transformer in which the primary and secondary coils are wound or arranged 35in such a manner that the convolutions of the conductor of the latter will be farther removed from the primary as the liability of injury from the effects of potential increases, the terminal or point of highest potential being 40the most remote, and so that between adjacent convolutions there shall be the least possible difference of potential.
The type of coil in which the last-named features are present is the flat spiral, and this 45form I generally employ, winding the primary on the outside of the secondary and taking off the current from the latter at the center or inner end of the spiral. I may depart from or vary this form, however, in the particulars 50hereinafter specified.
In constructing my improved transformers I employ a length of secondary which is approximately one-quarter of the wave length of the electrical disturbance in the circuit including the secondary coil, based on the 55velocity of propagation of electrical disturbances through such circuit, or, in general, of such length that the potential at the terminal of the secondary which is the more remote from the primary shall be at its maximum.60 In using these coils I connect one end of the secondary, or that in proximity to the primary, to earth, and in order to more effectually provide against injury to persons or to the apparatus I also connect it with the primary.65
In the accompanying drawings, Figure 1 is a diagram illustrating the plan of winding and connection which I employ in constructing my improved coils and the manner of using them for the transmission of energy over long70 distances. Fig. 2 is a side elevation, and Fig. 3 a side elevation and part section, of modified forms of induction-coil made in accordance with my invention.
A designates a core, which may be magnetic75 when so desired.
B is the secondary coil, wound upon said core in generally spiral form.
C is the primary, which is wound around in proximity to the secondary. One terminal80 of the latter will be at the center of the spiral coil, and from this the current is taken to line or for other purposes. The other terminal of the secondary is connected to earth and preferably also to the primary.85
When the two coils are used in a transmission system in which the currents are raised to a high potential and then reconverted to a lower potential, the receiving-transformer will be constructed and connected in the same 90manner as the first—that is to say, the inner or center end of what corresponds to the secondary of the first will be connected to line and the other end to earth and to the local circuit or that which corresponds to the95 primary of the first. In such case also the line-wire should be supported in such manner as to avoid loss by the current jumping from line to objects in its vicinity and in contact with earth—as, for example, by means of long insulators,100 mounted, preferably, on metal poles, so that in case of leakage from the line it will pass harmlessly to earth. In Fig, 1, where such a system is illustrated, a dynamo G is con-