US2431189A - Electromagnetic induction apparatus - Google Patents

Description

1 s. D. MORETON ET AL 3 ELECTROMAGNET I C INDUC T ION APPARATUS Filed March" 28, 1946 Inventor s: 1 Stuart D. Mor'etoh, Quinton Shaffer",

Their Attorney.

Patented Nov. 18, 1947 ELECTROMAGNETIC INDUCTION APPARATUS Stuart D. Moreton, Allison Park, and Quinton Shaffer, Philadelphia, Pa., assignors to General Electric Company, a corporation of New York Application March 28, 1946, Serial No. 657,696

3 Claims.

Our invention relates to electro-magnetic induction apparatus and particularly to a structure for mountingsuch apparatus.

Our invention is especially adapted for use in the mounting of a bushing current transformer which usually consists of a heavy magnet core around which is wound an insulated winding in which is induced a current that is proportional to that passing through the conductor of the electrical bushing about which the bushing current transformer is mounted.

Heretofore it has been common practice to mount such a bushing current transformer directly to the supporting wall of the bushing by clamping means that merely hold it compressively in place. It has been found that such clamping methods result in stressing, -disturbing, and possibly damaging the insulated Winding on the core.

It is therefore one object of our invention to provide an improved mounting structure for electromagnetic induction apparatus whereby it may be mounted without hazard of impairment to the winding or its insulation.

It is also an object of our invention to provide an improved mounting structure for electromagnetic induction apparatus that is simple, safe, reliable, and of low cost.

Another object of our invention is to provide mounting structure having members that extend through the electromagnetic induction apparatus, thereby providing additional or auxiliary support for the apparatus.

Another object of our invention is to provide extended mounting structure through electromagnetic induction apparatus that serves to support additional induction apparatus or devices associated therewith.

A further object of our invention is to provide extended mounting structure through electromagnetic induction apparatus that serves to support cover means, or other ancillary gear incidental thereto.

The advantages of our invention will become apparent from the following description and the accompanying drawing and the features of novelty which characterize our invention will be pointed out with particularity in the claim annexed to and forming a part of this specification.

In the drawing, Fig. 1 is a perspective view showing a pair of bushing current transformers mounted and protectively covered by a sheet steel housing in accordance with our invention; Fig. 2 is an end or axial view of one of such bushing current transformers, showing a preferred arrangement of the mounting sup-ports relative to the toroidally shaped transformer body, and Fig. 3 is a cross-sectional view along the lines 33 of Fig. 2, showing one method of attachment of the supports to the transformer core.

In the embodiment depicted in the drawing, instrument current transformers made in accordance with our invention are shown as applying to metal enclosed switchgear, in which the component devices of the apparatus such as the circuit breaker, disconnecting switches, bus conductors, etc., are segregated into separate and grounded sheet metal subcompartments. In this well known type of switchgear it is usual to electrically interconnect the related devices in adjacent compartments by means of conductor bushings which project through the intervening partitions.

Referring to Fig. 1, a conductor bushing IE projects through a suitable aperture in the partition wall H, and may be assumed to proceed from a disconnecting switch (not shown) that is mounted upon and concealed by the partition wall I l. The bushing Hi further may be assumed to be a component part of thedisconnecting switch so that it is supported thereby independently from any of the structure shown on the drawing and may comprise a hollow externally corrugated porcelain cylinder, within which is supported the laminated bars l2 for electrically interconnecting the disconnecting switch with another device such as a circuit breaker (not shown) on the near side of the partition I E.

It is conventional practice to mount toroidal type current transformers (familiarly known as B. C. T.s) concentrically about electrical bushings, where the bushing stud or laininations 12 in this embodiment serve as the transformer primary circuit. In accordance with this practice a pair of B. C. T.s I3 are shown mounted concentrically about and independently of the bushing l0. Independent mounting for transformers and their associated bushings prevent interaction due to possible physical shock stresses that conceivably might be of a damaging nature to either or both.

In this embodiment of our invention, the inde pendent mounting means for the B. C. T.s i 3 comprise a plurality of formed flat metal support members M which as most clearly shown by Fig. 3 are secured to the heavy laminated toroidal core l5 by means of clamping bands IS. The two extremities of each support member i i extend beyond the transformer body and are provided with upturned mounting feet I! and [8 that radiate outwardly as clearly shown by Fig. 2 so as to form a U-shaped member. Each upturned foot contains a mounting hole. Although four such U-shaped supporting members are shown, thereby providing mounting holes that are equally spaced around a circle concentric with the B. C. T., it will be understood that other variants may best be served by a lesser or greater number of mounting members having holes arranged to suit other mounting conditions. We find it preferable to place the two holes in the feet of each support member I4 in the same axial alignment as indicated by the centerline I9 in Fig. 3, and it is also advantageous that a clearance hole be provided in one leg While providing a tapped hole in the opposite leg. Accordingly, Fig. 3 shows the support members I 4 having a plain hole in what may be termed the main mounting foot I8, and a so-called punch-tapped hole in the corresponding auxiliary mounting foot I 1.

From the description thus far, and as shown best by Fig. 3, it will be understood that a unit B. C. T. made in accordance with our invention comprises the toroidal core I5 having a plurality of double-ended mounting members l4 secured thereto by bands I6, together with the secondary windings and their protective insulation 20 that is coiled and wrapped around the core I5 in a manner well known in the art. The advantages of this unitary construction are best appreciated by reference to Fig. 1 from which it will be observed that a single B. C. T. unit can be readily mounted upon the partition wall II by means of bolts or screws 2| through the main mounting feet I8 and which mounting may be entirely independent of the bushing about which it is mounted. It will be clear that such an arrangement permits the removal or addition of either the B. C. T. or its associated bushing irrespective of the presence of the other. Obviously this type of mounting is superior to some prior methods in which the toroidal transformer constructed with no mounting means was merely clamped directly and compressively to the partition wall, thereby stressing and possibly disturbing or damaging the comparatively sensitive windings and their insulation.

B. C. Ts are used variously for providing a source of current for operating instruments, meters, protective relays or breaker trip coils so that occasionally the provision of more than one transformer per phase is desirable. Fig. 1 illustrates how in such cases transformers with our novel mounting means are readily mountable one upon the other because as already explained the auxiliary mounting feet I! are made to register with the main mounting feet l8. Expeditions mounting of the second transformer on the first is readily accomplished by entering the screws 22 through the clearance holes of the main feet I8 of the second transformer and screwing them into the tapped holes in the auxiliary feet I! of the first transformer without the necessity of providing separate nuts for the screws 22.

In metal enclosed switchgear it is good practice to protect and isolate the secondary devices and wiring from the primary apparatus and its connections. Accordingly, the B. C. Ts of Fig. 1 are provided with a light boxlike sheet metal enclosure 23. By suitably flanging and welding its sides and cover, the enclosure 23 may be prefabricated into a unit structure as shown. Our invention provides a simple, improved, and economic means for supporting the protective enclosure 23, because the use of the projecting auxiliary feet 5! for this purpose obviates any necessity for providing additional or external fastenings, say on the partition I I, for the enclosure 23. We therefore simply employ screws 24 which engage the tapped auxiliary feet I! of the second transformer for mounting the protective enclosure 23 in proper relationship about the B. C. Ts I3. For the more usual applications which employ but a single B. C. T. the outer transformer would be omitted and an enclosure similar to but correspondingly shorter than enclosure 23 would be provided for bolting directly to the auxiliary feet I! of the B. C. T. that is bolted to the partition I I. In such a case a correspondingly shorter bushing than the bushing l0 shown would be substituted.

In double B. C. T. arrangements, as shown in Fig. l, where the transformers are comparatively light in weight, or where they are mounted vertically, as for example around a roof entrance bushing, the screws 24 in the auxiliary feet I! will constitute the sole mounting means for the enclosure 23. However, where heavy double B. C. Ts are arranged in cantilever relationship to the partition II as shown in Fig. 1, it will be obvious that it may become desirable to afford auxiliary means for supporting the overhung weight of the transformers. For this purpose it becomes convenient to furnish external supporting means for the enclosure 23 which may be accomplished in a number of different ways. For example, the side sheets of enclosure 23 can be flanged and bolted to the partition I I or, alternatively, the front end of the enclosure 23 can be suspended from the structure above or supported from the floor of the compartment below. Assuming therefore the enclosure 23 to be externally and satisfactorily supported, the auxiliary feet I! secured by screws 24 to the front cover of enclosure 23 now serve as additional supporting means for the B. C. Ts I3. It will now be evident that-the auxiliary feet I! which are extensions of the supporting members I4 may serve either as additional supporting means for the transformer itself or conversely may serve as the sole or main supporting means for the associated enclosure 23.

Referring to Fig. 3, the supporting members I4 are securely and permanently bound to the tightly wound clock-springlike low-loss silicon steel core I 5 by means of metallic clamping bands It which encircle the core I5 and which may be likened to large diameter hose clamps. A suitable jig is conveniently used for locating the core I5 and the several support members I4 in their interrelated positions prior to the application tensioning and making fast of the clamping bands I6. After the bands are clamped, a hole is handpunched through the bands I 6 in way of each predrilled hole 25 in the support members I4, after which a brass tubular rivet 26 is driven into and heads up permanently within each hole 25. The rivets 25 serve as dowels whereby the relative positions of the supports I4 and bands I6 are ensured. Other means, such as tack-welding the bands and supports together, would serve the same purpose. Conceivably, for light B. C. T.s and where mass production is contemplated, it may be desirable to combine both the supports I4 and their clamping bands I6 into an integral structure, as by stamping from a single metal sheet or by welding together prior to clamping about the core, thereby eliminating any necessity for the above described doweling operation. Preferably, the bands I8 are located as shown, that is with their outer edges flush or in alignment with the flat end faces of the core I5 as at 21. As a con- 2 sequence, and in addition to the supports l4 being held frictionally to the core 15 by the tensioned bands l6, endwise movement of the doweled supports M with respect to the core I5 is further restricted due to the abutting relationship of the bands at 21 to the end insulation washers 28, which are tightly and insulatingly taped to the core [5 before the first layer of the secondary winding is coiled around the toroidal core. The application of successive layers of insulation and secondary windings with the usual tap connections and their terminals as required (not shown) and as is well understood in the art, complete the entire construction of the B. C. T. unit.

Although we have shown and described a particular embodiment of our invention, we do not desire to be limited to the particular embodiment disclosed and we intend in the appended claims to cover all modifications which do not depart from the spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. A supporting structure for a bushing current transformer having a toroidal core and an insulated winding thereon comprising a plurality of supporting arms positioned about the outer periphery of said core and projecting axially therefrom, a plurality of clamping bands secured to said supporting arms and disposed about the outer periphery of said core to hold said supporting arms in position, and means for securing said arms to a supporting base member.

2. A supporting structure for an electromag- I netic device having a toroidal core and an insulated winding thereon comprising a plurality of supporting arms interposed between said core and said winding and extending axially therefrom, a clamping band interposed between said winding and said supporting arms and extending around the periphery of said core for securing said supporting arms in position and means for securing said arms to a supporting base member.

3. A structure for supporting a plurality of similarly constructed electromagnetic devices on a common axis, each device having a core and an insulated winding thereon, said structure comprising a plurality of supporting arms interposed between the core and winding of each device and extending in opposite directions therefrom and disposed in substantially parallel relationship to the common axis, said arms of each device being so disposed with respect thereto as to coincide with and engage the corresponding arms of the adjacent device, means for connecting the engaging portions of the arms of adjacent devices together, clamping means afiixed to said arms for securing said arms in position between the core and winding of each device, a housing for said devices and means for securing the supporting arms extending from each end device to said housing,

STUART D. MORETON. QUINTON SHAFFER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 667,121 Fleming Jan. 29, 1901 755,800 Schmidt Mar. 29, 1904 1,212,755 Fondiller Jan. 16, 1917 1,569,723 Dickinson Jan. 12, 1926 1,830,541 Harris Nov, 3, 1931

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