(No Model.)

N. TESLA. GOIL FOR ELECTRO MAGNETS.

No.. 512,340. Patented Jen. 9,1894.

aumento/6 UNITED STATES .PATENT OFFICE.

NIKOLA TELA, 0F NEW YORK, N. Y.

COIL FOR ELECTRO-MAGNETS.

SPECIFICATION forming part of Letters Patent No. 512,340, dated January 9, 1894. Application filed July 7.1893. Serial No. 479.804. (No model.)

To all whom it may concern.-

Beit known that I, NIKOLA TESLA, a`citizen of the United States, residing at New York, in the county and State of New York, have invented certain new and usefullmprovements in Coils for Electro-Magnets and other Apparatus, of which the following is a specification, reference being had to the drawings accompanying and forming a part of the same.

In electric apparatus or systems in which alternating currents are employed the selfinduction of the coils or conductors may, and, in fact, in many cases does operate disadvantageously by giving rise to false currents which often reduce what is known as the commercial eciency of the apparatus'composing the system or operate detrimentally in other respects. The effects of self-induction, above referred to, are known to be neutralized by proportioning to a proper degree the capacity of the circuit with relation to the self-inducv tion and frequency of the currents. This has been accomplished heretofore bythe use of condensers constructed and applied as separate instruments.

M present invention has for its object to avoi the employment of condensers which are expensive, cumbersome and dithcult to maintain in perfect condition, and to so construct the coils themselves as to accomplish the same ultimate object.

I would here state that by the terni coils I desire to include generally helices, solenoids, or, in fact, any conductor the diierent parts of which by the requirements of its application or use are brought into such relations with each otheras to materially increase the self-induction.

l have found that in every coil there exists a certain relation between its self-induction and capacity that permits a current of given frequency and potential to pass through it with no other opposition than that of ohmic resistance, or, in other words, as though itpossessed no self-induction. This is due to the mutual relations existing between the special character of the current and the self-induction and capacity of the coil, the latter quantity being just capable of neutralizing the self-induction for that frequency. It is wellknown that the higher the frequency or potential diierence of the current the smaller the capacity required to counteract the selfinduction; hence, in any coil, however small the capacity', it may be sufficient for the purpose stated if the proper conditions in other respects be secured. In the ordinary coils the difference of potential between adjacent turns ror spires is ,very small, so that while they are in a sense condensers, they possess but very small capacity and the relations between the two quantities, self-induction and capacity, are not such as under any ordinary conditions satisfy the requirements herein contemplated, because the capacity relatively to the self-induction is very small.

In order to attain my object and ,to properly increase the capacity of any given coil, I wind it in such way as to secure a greater difference of potential between its adjacent turns or convoiutions, and since the energy stored in the coil-considering the' latter as a condenser, is proportionate to the square of the potential difference between its adjacent convolutions, it is evident that I mayin this way secure by a proper disposition of these convolutions a greatly increased capacity for a given increase in potential dilerence'between the turns. V

I have illustrated diagrammatically in the accompanying drawings the general nature of the plan which I adopt for carrying out this invention.

`Figure l is a diagram of a coil wound in the ordinary manner. Fig. 2 is a diagram of a winding designed to secure the objects of my invention.

Let A, Fig. 1, designate any given coil the spires or convolutions of which arewound upon and insulated from each other. Let it be assumed that the terminals of this coil show a potential difference of one hundred volts, and that there are one thousand convolutions; their considering any two contiguous points on adjacent convolutions let it be assumed that there will exist between them 'a p ptential difference of one-tenth of a volt. If now, as shown in Fig. 2, a conductor B be wound parallel with the conductor A and insulated from it, and the end of A be connected with the starting point of B, the aggregate length of the two conductors being such that the assumed number of convolutions or turns is the same, viz., one thousand, then the po- IOO tential diterencebetween any two adjacent lpoints in Aand B will be fifty volts, and as the capacity effect is proportionate to the square of this difference, the energy stored 5 in the coil asja whole-will now be two hunred and fifty thousand as' 'greatl' Following out this principle, I may wind any'given coil either in Whole or in part, not only in the specic manner herein` illustrated, but 1o in a great variety of ways,well known `in the art, so as to secure between adjacent convolutions such potential dicrence as .will give the proper capacity to neutralize the self-induction for any given current that may be r 5, employed. Capacity secured in this particular way possesses an additional advantage in that it is evenly distributed, a consideration of the greatest importance in many cases, and the results, both as to-eiiiciency and economy, zo are the more readily and easily obtained as the size of the coils, the potential difference,

6r frequency of t'ne currents are increased.

Coils composed of independent strands or l conductors wound side byside and connected 25l in series' are not in themselves new, and I do not regard a more detailed description ofthe same as necessary. l3nt heretofore, so far as I am aware, the objects in view have been essentially diterent from mine, and the results which I obtain even if an incident to such 3o forms of winding have not been appreciated or taken advantage of.

In carrying outmy invention it is to be observed that certain facts are well under-- stood by those skilled in the art, viz: the re lations ot' capacity, self-induction, and the frequency and potential dierence of the current.- What capacity, therefore, in any given case it is desirable to obtain and what special winding will secure it, are readily determinable from the other factors which are known.

What I claim as my invention isn l. A coil for electric apparatus the adjaent convolutions o'f which form parts of the circuit between which there exists a potential difference sufficient to secure in the coil a capacity capable ot neutralizing its self-induction, as hereinbefore described.

2. A coil composed'of contiguous or adjacent insulated conductors electrically con; nected in seriesand having a potential ditference of such value as to give to the coil as a whole, a capacity sufficient to neutralize its self-induction, as set forth.

NIKOLA TESLA.

` Witnesses: v

ROBT. F. GAYLORD, PARKER W. PAGE.