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Publication numberUS433702 A
Publication typeGrant
Publication dateAug 5, 1890
Filing dateMar 26, 1890
Publication numberUS 433702 A, US 433702A, US-A-433702, US433702 A, US433702A
InventorsNikola Tesla
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Nikola tesla
US 433702 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

[No Model.)


7 No. 433,702. Patented Aug. 5, 1890.

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SPECIFICATION forming part of Letters Patent No. 433,702, dated. August 5, 1890.

' Apnlicat ion filed March 26. 1890. Serial No. 345,390. (No model.)

To all whom it may concern;

Be it known that I, NIKOLA TESLA, a subj ect of the Emperor of Austria-Ilungary, from Smiljan, Lika, border country of Austria- Hungary, residing at New York, in the county and State of New York, have invented certain new and useful Improvements in Electrical Transformers orlnduction Devices, of which the following is a specification, reference beinghad to the drawings accompanying and forming a part of the same.

This invention is an improvement in electrical transformers or converters, and has for its main objects the provision of means for securing, first, a phase difference between the primary and secondary currents adapted to the operation of my alternating-current motors and other like purposes, and, second, a constant current for all loads imposed upon the secondary.

In transformers as constructed now and heretofore it will be found that the electromotive force of the secondary very nearly coincides with that of the primary, being, however, of opposite sign. At the same time the currents, both primary and secondary, lag behind their respective electro-motive forces; but as this lag is practically or nearly the same in the case of each it follows that the maximum and minimum of the primary and secondary currents will nearly coincide, but differ in sign or direction, provided the secondary be not loaded or if it contain devices having the property of self-induction. On the other hand, the lag of the primarybehind the impressed electro-niotive force may be diminished by loading the secondary with a noninductive or dead resistance-such as incandescent lam ps-whereby the time interval between the maximum or the minimum periods of the primary and secondary currents is increased. This time interval, however, is limited, and the results obtained by phase difference in the operation of such devices as my alternating-current motors can only be approximately realized by such means of producing or securing this difference, as above indicated, for it is desirable in such cases that there should exist between the primary and secondary currents, or those which, however cuits of a transformer into the closest possi- 6o ble relations, as has hitherto been done, I protect in a measure the secondary from the inductive action or effect of the primary bysurrounding either the primary or the secondary with a comparatively-thin magnetic shield or screen. Under these conditions or circumstances, as long as the primary current has a small value, the shield protects the secondary; but as soon as the primary current has reached a certain strength, which is arbitrarily deter- 7o mined, th eprotectingmagnetic shield becomes saturated and the inductive action upon the secondary begins. Itresults, therefore, that the secondary current begins to flow at a certain fraction of a period later than it would without the interposed shield, and since this retardation may be obtained without necessarily. retarding the primary current also, an additional lag is secured, and the time interval between the maximum or minimum periods of the primary and secondary currents is increased. I have further discovered that such a transformer may, by properly proportioning its several elements and determining in a manner well understood the proper relations between the primary and secondary windings, the thickness of the magnetic shield, and other conditions, be constructed to yield a constant current at all loads. N o precise rules can be given for the specific construction and proportions for securing the best results, as this is a matter determined by experiment and calculation in particular cases; but the general plan of construction which I have described will be foundunder all conditions to conduce to the attainment of this result.

In the accompanying drawings I have illus trated the construction above set forth.

Figure 1 is a cr0ss-section of a transformer embodying my improvement. Fig. 2 is a simi- I0 To more perfectly 5 5 lar view of a modified form of transformer, showing diagrammatically the manner of using the same.

A A is the main core of the transformer, composed of a ring of soft annealed and insulated or oxidized iron Wire. Upon this core is wound the secondary circuit or. coil B B. This latter is then covered with a layer or layers of annealed and insulated iron wires O O, wound in a direction at right angles to said secondary coil. Over the whole is then wound the primary coil or wire D D. From the nature of this construction it will soon be obvious that as long as the shield formed by the wires 0 is below magnetic saturation the secondary coil or circuit is effectually protected or shielded from the inductive influence of the primary, although I would state that on open circuit it may exhibit some electro-motive force. Vhen the strength of the primary reaches a certain value, the shield O, becoming saturated, ceases to protect the secondary from inductive action, and current is in consequence developed, therein. For similar reasons, when the primary current weakens, the weakening of the secondary is retarded to the same or approximately the same extent.

The specific construction of the transformer is largely immaterial. In Fig. 2, for example, the core A is built up of thin insulated iron plates or disks. The primary circuit D is wound next thecore A. Over this is applied the shield O, which in this case is made up of thin strips or plates of iron properly insulated and surrounding the primary, forming a closed magnetic circuit. The secondary B is wound over the shield O. In Fig. 2, also, E is a source of alternating or rapidly changing currents. The primary of the transformer is connected with the circuit of the generator.

.F is a two-circuit alternating-current n10- tor, one of the circuits being connected with the main circuit from the source E, and the other being supplied with currents from the secondary of the transformer.

Having now described my i I claim is 1. In an electrical transformer or induction device, the combination, with the main magnetic core and the primary and secondary coils or circuits, of a magnetic shield or screen interposed between said coils, as herein set forth.

2. In an electrical transformer or inductive device, the combination, with the magnetic core and the primary and secondary coils or circuits, of a magnetic shield or screen surrounding one of said coils only, as set forth.

3. In an electrical transformer or induction device, the combination, with the magnetic core and the primary and secondary coils wound thereon,of a magnetic shield or screen wound on or built up around one only of said coils, as described.

4. In an electrical transformer or induction device, the combination, with a main laminated magnetic core and primary and secondary coils thereon, of a subdivided or laminated magnetic shield or screen interposed between the coils, as set forth.

5. I11 an electrical transformer, the combination, with a magnetic core and primary and secondary coils wound thereon, of a magnetic shield or screen interposed between said coils and surrounding one of them and adapted to be or capable of being magnetically saturated by a predetermined current strength below the maximum in the primary, as set forth.

nvention, what NIKOLA TESLA.

- Witnesses:


Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2519224 *May 28, 1947Aug 15, 1950Westinghouse Electric CorpElectrical transformer
US2722097 *Mar 18, 1952Nov 1, 1955Conservatoire Nat Des Arts EtConical pendulum, alternating current clock
US2776417 *Nov 4, 1952Jan 1, 1957Harris Transducer CorpCompensated winding
US2779907 *Sep 9, 1953Jan 29, 1957Hutchins Electric Company IncElectric motor
US3026491 *Sep 23, 1958Mar 20, 1962Vyzk A Zkusebni Letecky UstavIndirectly excited electromagnetic feeler
US3525964 *Aug 15, 1968Aug 25, 1970Federal Pacific Electric CoZero-phase-sequence transformer
US3683302 *Dec 15, 1970Aug 8, 1972Fred C ButlerSensor for ground fault interrupter apparatus
US6583698Sep 18, 2001Jun 24, 2003Harrie R. BuswellWire core inductive devices
US7053576Oct 15, 2002May 30, 2006Correa Paulo NEnergy conversion systems
US7235945Dec 12, 2005Jun 26, 2007Correa Paulo NEnergy conversion systems
US7382072Sep 26, 2003Jun 3, 2008Erfurt & CompanyGenerator
US9649952Dec 29, 2014May 16, 2017Curtis E. GraberElectromagnetic field generator
US20040232792 *Sep 26, 2003Nov 25, 2004Erfourth Eric J.Generator
US20060082334 *Oct 15, 2002Apr 20, 2006Correa Paulo NEnergy conversion systems
US20060238148 *Dec 12, 2005Oct 26, 2006Correa Paulo NEnergy conversion systems
Cooperative ClassificationH01F38/10