US1561270A - Bus bar - Google Patents

Description

D. F. MINER Nov. 10 1925- BUS BAR Filed Sept. 17, 1920 0 Amperes 2 6 Ens.

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ATTORNEY Patented Nov. 10, 1925.

UNITED STATES v restart PATENT @FFHQE.

DOUGLAS F. MINER, OF WILKINSBURG,.IENNSYLVAhf-IA, ASSIGNOR-TO WESTING- HOUSE ELECTRIC & MANUFACTURIN \COMPANY, A CORPORATION OF PENNSYL- VANIA.

ians BAR.

Application filed September 17, 1920. Serial No. 410,896.

To all whom it may concern:

Be it known that I, DOUGLAS F. MINER, a citizen of the United States, and a residentof Wilkinsbur in the county of Allegheny and State of ennsylvania, have invented a new and useful Improvement in Bus Bars, of which the following is a specification.

My invention relates to electrical conductors and particularly to bus-bars for switchboard structures.

The object of my invention is to provide means for attachment to, or for association with, conductors in a manner to compensate for the skin effect thereof to effect, thereby, a more uniform distribution of current therethrough, eliminate'undue heating and utilize the conductor effectively and economically.

When alternating current passes through a conductor, an alternately expanding and contracting magnetic field is created in and around the conductor. This field induces a counter-electromotive force in the conductor which produces what is known as skin effeet. The apparent resistance of a given conductor to alternating current divided by its resistance to direct current, is known as the skin-effect ratio for the particular conditions and the frequency of the alternating current considered. With alternating currents of relatively high values, the skin effect causes the outer portions of a conductor to carry a greater amount of current than the center portion. resulting in undue heating and in an inefiicient and uneconomical use of material. l

In practicing my invention, I provide conductors and magnetizable members associated in parallel relation thereto to so redistribute the magnetic field of the conductor as to compensate for the skin effect thereof, thus eliminating undue heating and permitting the effective and economical use of com ducting material.

In my copending application, Serial No. 412529, filed Sept. 24:, 1920, is disclosed a structure for accomplishing results similar to those herein set forth by forming the conductors in a special manner andwithout the use of 'magnetizable members as herein described. Other devices appertaining. [0 the distribution of current in conductors are set forth in my copending applications, Serial No. 412530, filed-."Sept. 24, 1920, and Serial No. 412531, filed'Sept. 24:, 1920, and in a copending application of C.-F. Wagner, Serial No. 412461, filed Sept. 24,1920. ylllgure 1 of the accompanyin drawings ISFS: cross-sect1onal view of a bus-bar of usual form combined with a diagram showing the distribution of current therein.

Fig. 2 is a sectional perspective view of a portion of a bus-bar embodying myinvention, and

Fig. 3 is a diagram, showing, by dotted and full-line curves, respectively, a com-- parisonbetween the curve of Fig. 1 and a curve representing the, distribution of current in a bus-bar constructed in accordance with the device illustrated in Fig. 2.

In Fig. 1, a bus-bar 1 of usual form is so affected by alternating current as to cause a greater amount of current to flow along the edges of the conductor than along the center portion thereof. The approximate distribution of current is represented by a curve 2 on a diagram 3, the current values of which, as

indicated in the diagram, increase in a diwith magnetizable members 5, preferably of iron or steel and constructed of substantially channel shape, and mounted on, or adjacent to, the conductor in any suitable manner. As shown, the members 5 are disposed on the conductor 4 along the edges 6 thereof and have portions? engaging the sides of the conductor and projecting toward the center of the latter. This construction will so increase the reactance of the outer elements of the conductor as to redistribute the current as indicated by a curve 8 in Fig. '3.

This redistribution of the current is accounted for by the fact that, when iron or magneticsubstanceis placed near a conductor carrying current, it 'redistributes the ma netic field surrounding the conductor, t e flux lines being distorted a; pass through its the iron which affords a path of least resistance. The most concentrated portion of the field is near the iron, and because the iron is disposed adjacent the edges of the conductor, the number of flux lines passing through the conductor adjacent the condnw tor is increased.

The concentration of flux at the outer edges of the conductor induces a countere'lectromotive force in the neighb n-ingelements thereof. The effect is an increase in the apparent resistance Qrreactance of the under the curves 2 and 8 are equal for the same total current but inasmuch as the root mean square value of current in the conduc tor 4 is less than that in the conductor 1, the heating in the conductor 4; Will be less.

l/Vhile the total voltage drop over a given length of a conductor having compensating means thereon is greater than an uncompensated conductor of the same shapeand length, it is apparent from a study of the current curves above referred to that the permissible current may be increased Without increasing the temperature above that of the uncompensated conductor carrying a considerably lower amount of current.

It has been.found in actual practice that considerably more current can be carried by a conductor compensated in the manner described than can be carriedby an uncompensated conductor of equal shape for a given temperature rise. It is apparent, therefore, that a compensated conductor may serve to carry current with the same temperature rise that has heretofore required a conductor of greater proportions. .It Will be seen that, by reason of this fact, considerable saving of copper is accomplished in large installations.

By varying the sizes, shapes, proportions and relation of the conductor 4 and the members 5, substantially any desired distribution of current in the conductor may be obtained.

'lVhile I have shown and described a particular form of my invention, changes may be effected therein without departing from the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention:

1. A conductor having a non-circular cross-section and int-ans for compensating the skin effect thereof comprising inductive means disposed adjacent the points in the conduct-2r normally carrying more current than other points thereof.

2. A conductorhaving a non-circular cross-section and magnetic means disposed adjacent the point in the conductor normally carrying more current than other points thereof for compensating the skin efiect thereof.

' 3. An elongated conductor havlng a noncircnlar cross-section and ,a magnetic metal mation and magnetic metal members em-' bracing the opposite edges thereof to compensate for skin effect in the conductor.

7. A bus-bar and i'i'lagnetizable members of substantially channel-shape embracing the opposite edges thereof.-.

In testimony whereof, I have hereunto subscribed my name this 11th day of September 1920.

' DOUGLAS F. MINER.

member disposed thereon adjacent a point normally C:l1l \'J1lg more current than other

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