US 2716736 A
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Description (OCR text may contain errors)
Aug. 30, 1955 H. B. REX
SATURABLE REACTOR Filed Deo. 8, 1949 R m W.. In on B. w 0 M H 6) 07C ATTORNEY.;
United States Patent O SATURABLE REACTOR Harold B. Rex, Falls Church, Va.
Application December 8, 1949, Serial No. 131,882
1 Claim. (Cl. 336-155) (Granted under Title 35, U. S. Code (1952), sec. 266) This invention relates to a new and improved variable reactance and particularly to the core construction for toroidal variable reactances.
With the advent of new and improved magnetic materials of high permeability e. g., the ferrites disclosed and claimed in the U. S. patents to Jacob L. Snoek, 2,452,529 and 2,452,530, the toroidal coil has become of N particular advantage as a reactance element. However, it has been impracticable in the past to utilize a toroidal coil in instances where the inductance of the coil must be varied, because the only practicable means for changing the inductance, and the associated inductive reactance of the coil, was to change the actual number of turns in the windings. In complex circuitry such as that associated with fire control equipment, wherein the coil of this invention is particularly well adapted, it is not often feasible to permit a change in the actual number of turns in the windings.
The present invention has for its object therefore the construction of a toroidal inductance unit wherein the inductive reactance may be variable without altering the number of turns. It is also an object of this invention to provide a novel core construction for a saturable reactor.
The features of this invention by means of which the above objects are obtained reside in the use of a circumferentially wound saturating winding positioned within the core interior so that the saturating lines of iiuX flow through the core material in a direction normal to the path of the main flux. Thus by altering the magnitude of the direct current flowing in the saturating Winding the reluctance of the core material is altered thereby altering the magnitude of the magnetic fluX produced by the toroidal coil wound about said core in a direction generally paralleling the direction of the saturating flux.
A better understanding of the invention may be had from the following description together with the accompanying drawing in which:
Fig. l shows an isometric view partially in cross section of the overall toroidal inductance unit of the present invention;
Fig. 2 is a partial sectional view of a modied construction of the coil core of this invention.
Fig. 3 is a partial sectional view of a further modificatlon.
In Fig. l a toroidal coil 1 is shown wound upon a sectionalized hollow core 2 comprised of cooperating portions 3 and 4 which are provided respectively with circumferentially extending recesses S and 6. These recesses are shown as being of substantially equal rectangular crosssection and equally positioned radially from the axis of the toroid so that when the two portions are assembled with the recessed surfaces opposing a totally enclosed space will be provided. As shown in Fig. l the cooperating core portions are provided with slots 7 and 8 configured so as to receive opposite ends 11 and 12 of strip wound coil 10. It will be understood that the windings 10 include suitable insulating material, such as varnish or impregice nated paper between layers of turns. In the event the core portions 3 and 4 are formed of ferrite as is preferred, insulation covering on the inner and outer surfaces of the strip winding 10 are not required for the preferred type ferrites such as disclosed by the above-mentioned patents to Snoek have a specific resistance greater than 1000 ohm-cm. rendering the core substantially nonconducting with respect to coil 10. The ends 11 and 12 are in elfect leads or terminals connecting respective ends of the windingr by means of which a suitable D. C. potential may be applied to give the core 2 and coil 10 the desired degree of transverse saturation with magnetic linx. The strip winding 10 when formed of magnetic and electrically conductive material, such as any one of the numerous ferrous alloys known to the reactor art, as is preferred reduces the overall reluctance of the core structure.
ln the modification illustrated by Fig. 2 wherein like reference numerals refer to like parts in the embodiment illustrated in Figs. l and 2, the strip winding of magnetic and electrically conductive material is replaced by a conventional coil 15 formed of turns of insulated electrically conductive wire. Opposite ends of the wire are brought out through the core to provide terminals to which a D. C. voltage may be applied.
In the modification illustrated in Fig. 3 the toroidal core structure 2 is composed of a plurality of ring-like lamina containing the circumferentially disposed saturating winding 10. This winding may be a conventional preformed coil as in Fig. 2 or as is preferred and illustrated the winding 10 is composed of wound strip or ribbon-like conductor, the windings of which are insulated from each other and from the core structure as by means of the insulation 16. It is of course preferred in this ernbodiment that the ribbon-like conductors be formed of a magnetic material although such material may not possess the optimum in electrical resistance. It is understood that the laminae 2 may be held together in a conventional manner and that slots (not shown) are provided to receive the inner and outer ends of the spirally wound strip coil 10. These slots are preferably formed by slitting the ring-lamina and aligning the slits to form the Slots through which project the ends of the ribbon. It is understood also that the inductance coil 1 is wound about the core so that the ends of the ribbon are accessible through the main inductance coil. Clearly other constructions of the core may be devised, for example the laminated core may be formed of ribbon windings in a manner similar to the inner coil, however, the construction illustrated is preferred. Also the ribbon conductor may be used alone as a core for the inductance winding.
It is apparent from the foregoing that there is provided by this invention an improved toroidal Winding the inducance of which may be varied by altering the saturation of the closed core structure about which the toroid is wound with a ux produced by direct current conductors contained within the core structure and wound in a direction circumferentially of the core so that the saturating ux will be in a direction normal to the main flux.
Obviously many other modifications and variations of the present inventionl are possible in the light of the above teachings. It is therefore to be understood, that, within the scope of the appended claim, this invention may be practiced otherwise than as specifically described.
The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
A variable reactance device comprising a multiturn spiral coil of substantially ribbon-shaped high permeability conducting material, insulating means disposed between adjacent turns of said coil, a high permeability nonconducting ferrite toroidally-shaped core having a substantially continuous outside surface constructed of two symmetrical solid sections with a continuous groove therein forming an annular space Within the core body for receiving a high permeability coil, said spiral coil being enclosed within said core with the conducting material of said ribbon-shaped coil in direct Contact with said core, means penetrating said core for providing electrical con nections to the opposite ends of said spiral coil, and a toroidal coil of nonpermeable conducting material Wound around said score.
References Cited in the le of this patent UNITED STATES PATENTS 743,444 Burgess et al Nov. 10, 1903 1,287,982 Hartley Dec. 17, 1918 1,289,418 Elmen Dec. 31, 1918 1,561,782 Given Nov. 17, 1925 1,606,777 Payne Nov. 16, 1926 1,935,208 Haydon Nov. 14, 1933 2,333,015 Kramer et al Oct. 26, 1943 2,445,813 Walworth July 27, 1948 2,452,529 Snoek Oct. 26, 1948 2,474,988 Sargrove Iuly 5, 1949 OTHER REFERENCES Printed Circuit Techniques National Bureau of Standards Circular 468, issued November 15, 1947. (Par- V ticularly page 18.)