US2922834A - Multiple conductor for large currents - Google Patents

Description

Jan. 26, 1960 D. A. CAVANAGH 2,922,334

MULTIPLE coynucwoa FOR LARGE CURRENTS.

Filed Nov. 50,1956

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FIG. I 2

In ven tor DANIEL A. CA VANA GH Mud-W51 United States Patent MULTIPLE CONDUCTOR FOR LARGE CURRENTS This invention relates to a multiple conductor for alternating currents.

The design of heavy current industrial apparatus in cluding the design of electric melting furnaces and the like has been limited in prior practice due to the magnetic field pattern which exists about the conductors used for carrying a heavy electrical current thereto and the low power factor of the conductors. It is accordingly the main object of the present invention to provide a multiple conductor adapted to carry heavy electrical currents of the order of 20,000 amps. and larger at current densities of the order of up to about 10,000 amps. per square inch while confining the magnetic field effects of said conductor substantially to the structure of said conductor and with improved power factor.

It is another object of the invention to provide a heavy current multiple conductor construction in which a cancellation of a substantial portion of the mechanical forces efifected by passage of electrical current therethrough, is accomplished.

A still further object of the invention is to provide a heavy current multiple conductor which may be connected to relatively moving points in utilizing apparatus and wherein such apparatus is not affected by magnetic fields generated by the passage of heavy electrical currents through the conductor.

Other objects of the invention will be appreciated by a study of the following specification taken in conjunction with the accompanying drawings.

In the drawings:

Figure 1 as an elevation of a preferred form of conductor according to the invention having a flexible portion extending betweentwo rigid portions thereof.

Figure 2 is a view of Figure 1 looking in the direction Figure 3 is a of Figure 2; and

Figure 4 is a sectional view on the line 4-4 of Figure 2.

In Figure 1, the rigid conductor portion comprises the inner conductor 11 for one voltage line spaced by insulating means 12 and 13 from the outer conductors 14 and 15 which latter together serve as the other voltage line. By way of example, the multiple conductor construction of the invention may be adapted to operate at a current density of 1,660 amps. per square inch at a total current carrying capacity of 20,000 amps. The inner conductor may be comprised of a copper bar one inch thick and twelve inches wide as is designated by the numeral 11. The outer conductors 14 and 15 being electrically in parallel together carry the current for one partial sectional view on the line 3-3 'side of the line supply and thus, according to the invention, are each equal to one-half the sectional area of the bar or conductor 11 so that they will each be twelve inches wide and one-half inch thick.

The rigid conductors 11, 1'4 and 15 continue in the form of structure shown for electrical connection to conductors or about 2,922,834 Patented Jan. 26, .1960

suitable utilizing apparatus. Because the outer conductors 14 and 15 carry current passing opposite in direction to the current flow in the conductor 11 at any one instant, the magnetic field generated by current flow in the central conductor 11 will be cancelled by the magnetic field generated by current flow in the outer conductors except at the side edges of the construction. However, by reason of the relatively shallow depth of the construction as compared with its width, the magnetic field pattern does not extend significantly beyond the side edges of the construction.

It should be appreciated that the mechanical forces involved may be substantial. Thus, in the example considered, the central conductor may repel the outer conductors with a force of about eight pounds per inch of length of the central conductor. It will therefore be understood that the mechanical problems associated with the design of single heavy current conductors of the prior art have been substantial.

In the construction of the. present invention, however, the outer conductors attract one another with a force of about three pounds per inch of length. Accordingly, the net outward repulsive force for the total construction is reduced to about one-half that between a lone pair of four pounds per inch of length of the multiple conductor construction herein. By this means, therefore, the mechanical design of the conductors is materially assisted by adoption of a construction of the invention as described.

The multiple conductor construction of the invention may be provided in a flexible form as is also shown in Figure 1, wherein the heavy current transformer 16 is supported on stationary arms 17 fixed to a machine bed 18 and has projecting therefrom the fixed single phase terminals 19 and 20, It is to ;be assumed that the con ductor 10 is adapted to be moved on a path Y parallel to the terminals 19, 20, 21 and 22. While separate single flexible conductors have been provided heretofore formed of a plurality of sheets of metal to permit relative movement between connecting points, the present invention contemplates the provision of such flexible leads in the special magnetic flux cancelling arrangement shown.

The flexible portion of the multiple conductor 23 of the invention comprises the inner flexible conductor 24 formed of a plurality of sheets of copper. Adhering to the foregoing example, a plurality of plies of flexible copper sheet twelve inches wide may be provided to supply a total current carrying sectional area for the conductor 24 corresponding to that of the conductor 11. The outer conductors 25 and 26 are similarly constructed but again embody one-half the number of plies of sheet copper or other flexible conductor material, so that each comprises one-half of the current carrying sectional area of the conductor 24. In the construction shown, the transformer terminals 19 and 20 supply one side of a current source and the terminals 21 and 22 provide another side of current supply source to define a single phase output for the transformer 16. Thus, terminals 19 and 20 are mutually connected by a copper bar 27 and carry connecting plates 28 and 29 adapted to be clamped to the fixed ends 30 and 31 of the outer flexible conductors 26 and 25 respectively, the latter being held firmly in place by means of the clamping plates 32 and 33 adapted to carry the insulated clamping bolts 34 and 35. By this means, a circuit connection is made from the terminals 19 and 20, to the outer flexible conductors 25 and 26.

The terminals 21 and 22 have placed therebetween, the supporting plate 36 and are separated from the outer conductors by insulation 37 and 38 maintained in clamped assembly by the clamping bars 39 and 40 by means of and 61 and suitable clamping bolts portion 65.

some types of apparatus.

a any flexible form, may carry 7 formed, for example, of rubber tubing, which extends for sealed connection at the bolts 57 and at the'bolts 51 at insulated bolts 41 transformer terminals 19 and 20 be grounded to the machine frame, then clamping plates 33 and 40 may provide electrical connection to the frame through the supporting bracket 41 fixed to the stationary frames 17 by bolts 44. It will be observed that the bracket 43 and the various connecting bars and clam-ping plates efiect a rigid anchoring of the fixed end 45 of the multiple conductor construction of the invention.

A connection is now made from the fixed end 45 to the inner flexible conductor 24 by means of connecting plates 46 and 47 held by inner clamping plates 48 and 49 and outer clamping plates 50 fixed by insulated bolts 51 and 52. The movable end 53 of the flexible multiple conductor 23 is connected to the movable rigid conductor in somewhat similar fashion. Thus, the inner flexible conductor 24 connects by conducting plates 54 to the .inner conductor 11 and is separated by insulation 55 from the outer flexible conductors 26 and 25 which project therefrom under the clamping plates'56 held with insulatedbolts 57 to make connection through conducting plates 58 and 59 to the rigid-outer conductors .14 and being held in assembly therewith by clamping plates 60 62. It will be observed that the flexible multiple conductor portion em bodies the arm portions 63 and 64 adapted to change in length as the movable end 53 is moved relative to the fixed end 45. The arm portions are joined by curved The juncture of the armed portion and the curved portion may be represented by tangency lines 66 and 67 which emerge from a'center of curvature 68. In a single conductor flexible conductor construction of the prior art, a free spacing is plies or sheets making up the juncture in the region .of curvature. Thus, for example, where the juncture was accomplishing a 'mean curvature of say three inches radius, the radius center for theinnermost ply would be located at say the'point'68 whereas the rradiuscenter of the outermost ply of the juncture would be displaced outwardly about one-eighth of'an inch or more to the radius center 68a. It has been found that this method of insuring freedom of actionbetween the plies of metal making .up the flexible lead or conductor permits undue distortionin the curved portion to such a degree that parallelismof action may be difiicult to maintain between one end of a moving conductor and the fixed end thereof,

- again leading to. undue fatigue conditions in the plies of.

the flexible lead. .Thiscondition is aggravated where the flexible lead is required to carryvery large currents and in some applications, has rendered the use of flexible leads impractical, thus obviating the practical design of According to the invention, while radius displacement is contemplated between the innermost and outermost ply of any one of the conductors, it has been found essential in heavy current-applications, to restrict the displacement to less than about one-twentieth of the radius of curvature.

For very heavycurrent applications, the invention contemplates the lubrication of'the plies-of metal making up each of the conductors on the interfaces thereof by suitable lubricant such as petroleum jelly, by means of which the radius displacement may be kept to lessthan one-fiftieth'of the radius of curvature whereby thecurvature of the flexible multiple conductor of the invention is of smooth contour obviating bulgingand adapted fo t-normal elastic behaviour of the metal thereof.

The conductor of the invention, particularly in the a flexible. coolant casing 69 the movable and anchored ends respectively of the conductor. As shown, the inlet tube 70 imay pr'ovide for the introduction of inlet air, water, oil oriother suita'ble coolant and the outlet fitting 71 may provide for an o lfiand 42. Where it is desired that the p maintained between the metal intended to cover herein all such changes let of the coolant after passage over surfaces of the flexible conductor. I

in order to provide extrasupport, separating bars or spacers, preferably in the form of the rubber tubes 72 may be placed between the outer and inner conductors as shown in Figure 1. The distance between the spacers may be maintained by textile cords or other suitable means (not shown).

While the invention has been'disclosed in a single-phase connection by way of example, the application of the teachings herein to multi-phase conductor connections will be appreciated by skilled persons.

While there has been described what is at present considered a preferred embodiment of the present invention, it will be appreciated-by those skilled in'the art that various changes and modifications can be made therein without departing from the essence of the invention and it is and modifications as come Within the true spirit and scope pended claims.

What'I 'claim as my invention is: v

l. A multiple conductor for carrying large singlephase electrical currents from a current source having a voltage between two output terminals thereof to a' utilizing system having corresponding input terminals and comprising, in combination: an inner conductor of predetermined sectional area'formed of a plurality of stacked'flexible conconductors having a corresponding exterior major surface overlying an exterior major surface of said inner conductor inparallel spaced relationthereto, said outer conducsaid predetermined sectional area;-means-for connecting tors being of a total sectional area substantially equal to said inner conductor electrically between one output terminal and one input terminal; means: for electrically connectingallofsaid outer conductors electrically in parallel between the other output terminal and the other input terminal; means supporting the ends of said multiple conductor for relative motion and defining a curved portion in said multiple conductor between said ends; andmeans for maintaining-the spacingbetween said inner conductor.

and said outer conductors between said ends.

2. A multiple conductor for carrying large electrical currents from a current source having a voltage between two output terminalsthereof to a'utilizing system having corresponding input terminals and comprising, in combination: aninner conductor of predetermined sectional areaformed of a plurality of-stacked flexible conducting sheets and of a width between the edges of said sheets substantially greater than the total thickness of said sheets between the'major surfaces thereof; an outer conductor formed ofa plurality of stacked conductingsheets of substantially saidjwidth for each of the exterior major surfaces of said inner conductor, each of said outer conductors having a corresponding exterior major surface overlying an exterior major surface of said inner conductor in parallel spaced relation thereto, said outer conductors being ofa total sectional-area substantially equal to said predetermined sectional area; means for connecting said inner conductor electrically between one output terminal and one input terminal; means forelectrically connecting all of said outer conductors electrically in parallel between the other, output terminal and .the other input terminal; means supporting the ends of said multiple conductor for relativemotion and defining a curved portion between said ends; means for and means for said outerconductors between said ends;

1 communicating a cooling medium about said conductor.

3, A multiple conductor for carrying large electrical of the apcurrents from a current source having a voltage between two output terminals thereof to a utilizing system having corresponding input terminals and comprising, in combination: an inner conductor of predetermined sectional area formed of a plurality of stacked flexible conducting sheets and of a width between the edges of said sheets substantially greater than the total thickness of said sheets between the major surfaces thereof; an outer conductor formed of a plurality of stacked conducting sheets of substantially said width for each of the exterior major surfaces of said inner conductor, each of said outer conductors having a corresponding exterior major surface overlying an exterior major surface parallel spaced relation thereto, said outer conductors being of a total sectional area substantially equal to said predetermined sectional area; means for connecting said inner conductor electrically between one output terminal and one input terminal; means for electrically connecting all of said outer conductors electrically in parallel between the other output terminal and the other input terminal; means supporting the ends of said multiple conductor for relative motion and defining a curved portion in said multiple conductor between said ends; means for maintaining the spacing between said inner conductor and said outer conductors between said ends; and a transformer support carrying said end supporting means at one end of said multiple conductor.

4. A multiple conductor for carrying large electrical currents from a current source having a voltage between two output terminals thereof to a utilizing system having corresponding input terminals and comprising, in combination: an inner conductor of predetermined sectional area formed of a plurality of stacked flexible conducting sheets and of a width between the edges of said sheets substantially greater than the total thickness of said of said inner conductor in sheets between the major surfaces thereof; an outer conductor formed of a plurality of stacked conducting sheets of substantially said width for each of the exterior major surfaces of said inner conductor, each of said outer conductors having a corresponding exterior major surface overlying an exterior major surface of said inner conductor in parallel spaced relation thereto, said outer conductors being of a total sectional area substantially equal to said predetermined sectional area; means for connecting said inner conductor electrically between one output terminal and one input terminal; means for electrically conmeeting all of said outer conductors electrically in parallel between the other output terminal and the other input terminal; means supporting the ends of said multiple conductor for relative motion and defining a curved portion in said multiple conductor between said ends; means for maintaining the spacing between said inner conductor and said outer conductors between said ends; means for communicating a cooling medium about said conductor; and a transformer support carrying said end supporting means at one end of said multiple conductor.

References Cited in the file of this patent UNITED STATES PATENTS 2,318,859 Huguelet May 11, 1943 2,341,841 Carlson -2 Feb. 15, 1944 2,462,887 Muller Mar. 1, 1949 2,483,301 Roberds Sept. 27, 1949 2,676,309 Armstrong Apr. 20, 1954 2,702,311 Botterill et al. Feb. 15, 1955 2,797,255 Wreford June 25, 1957 OTHER REFERENCES Electronic and Radio Engineering (Terman), published by McGraw-Hill (New York), 1955, pages 21-23.

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