US2994845A - Adjustably mountable current transformer and apparatus employing same - Google Patents

Description

Aug. l, 1961 J. w. ALBRIGHT ET AL 2,994,845

ADJUSTABLY MCUNTABLE CURRENT TRANSFORMER AND APPARATUS EMPLOYING SAME Filed May 25, 1960 4 Sheets-Sheet l Aug. 1, 1961 J. w. ALBRIGHT ErAL 2,994,845 ADJUSTABLY MCUNTABLE CURRENT TRANSFORMER y AND APPARATUS EMPLOYING SAME Filed May 25, 1960 4 Sheets-Sheet 2 Aug. l, 1961 J. w. ALBRIGHT ETAL 2,994,845

ADJUSTABLY MCUNTABLE CURRENT TRANSFORMER AND APPARATUS EMPLOYING SAME Filed May 25, 1960 4 Sheets-Sheet 3 Meir Aug.. l, 1961 .1.w. ALBRIGHT ET AL 2,994,845

ADJUSTABLY MOUNTABLE CURRENT TRANsFoRMER AND APPARATUS EMPLOYING SAME Filed May 25, 1960 4 sheets-Sheet 4 :www

United States Patent O 2,994,845 ADJUSTABLY MUNTABLE CURRENT TRANS- FORMER AND APPARATUS EMPLOYING SAME John W. Albright, Pittsfield, and Ernest E. Bianco, North Adams, Mass., assignors to General Electric Company,

a corporation of New York y Filed May 25, 1960, Ser. No. 31,710 17 Claims. (Cl. 336-68) This invention relates to electrical devices and more in particular to current transformers and the apparatus with which they are associated.

In many situations, electrical apparatus, such as transformers and the like, have current transformers associated therewith for the purpose of measuring or controlling the output of the apparatus. Current transformers associated with high voltage transformers may be heavy and over a foot in height because of the size and large number of turns in their secondary windings. Such current transformers may be mounted on the exterior of high voltage power transformers so that when a lead or bushing is employed as their primary winding the height of the tank surrounding the transformer need not be increased. But, because of height limitations placed onequipment transported over highways or railroads, current transformers of any significant height cannot remain on the outside of large electrical equipment when the equipment is being moved from one place to another, as for example, when the equipment is 4being shipped from its manufacturer to the ultimate user. Consequently, in the past, externally mounted current transformers have been packed and shipped separately from the apparatus with which they are to be used. This has increased the cost of the apparatus because, in addition to the cost of packaging and shipping the current transformers separately, the current transformers must be connected to the apparatus by the manufacturer for test purposes, then disconnected for shipment, and then reconnected by the purchaser at the point of use of the apparatus. Another disadvantage of this procedure is that the ultimate user of the apparatus is not nearly so well equipped in terms of trained personnel and specialized equipment to install the current transformer as is its manufacturer. Furthermore, high voltage electrical apparatus and the current transformers associated therewith are conventionally dried to remove moisture and then hermetically sealed in a tank or enclosure containing an insulating medium. Once a pre-dried, insulated enclosure containing electrical apparatus has been sealed, it is undesirable to expose it to the atmosphere by breaking the seal for any length of time. The installation of a current transformer at the point of use requires the connection of numerous leads and thus requires that the sealed enclosure be opened for a considerable time. This increases the danger of contaminating substances entering the enclosure and reducing the insulation strength. Also the previously dried current transformers are likely to absorb moisture or other contaminating substances if they are removed from the sealed enclosure for shipment.

In apparatus constructed in accordance with our invention, these disadvantages are eliminated by providing a current transformer with means at either end thereof for supporting same in a non-operating position below the top of the apparatus it is used with, and in an operating position above such apparatus. This permits the current transformer to be attached by its manufacturer to the apparatus upon which it is to be ultimately used with all leads connected, without the necessity for separate packing and shipping of the current transformer. By lowering the current transformer below the surface of the apparatus with which it is associated, the problem of road clearance caused by its additional height is eliminated.

Accordingly, it is an object of our invention to provide Patented Aug. l, 1961 ICC a movable current transformer which can be attached to other electrical apparatus without the necessity for removing the current transformer when the electrical apparatus must be transported on public ways.

Another object of our invention is the provision of electrical apparatus with a current transformer attached thereto, said current transformer being movable from a nonoperating position to an operating position.

Another object of our invention is to provide an improved method of reducing the height of electrical apparatus.

Other objects and advantages of our invention will become apparent from a reading of the following specification and claims and an examination of the accompanying drawings.

In the drawing:

FIG. l is a partially broken away side elevation of an embodiment of our invention.

FIG. 2 is an enlarged, perspective partially cross-sectional view of the current transformer illustrated in FIG. l.

FIG. 3 is a plan view of the current transformer of FIG. 2 with portions of the structure broken away.

FIG. 4 is a cross-sectional view taken along the lines 4 4 in FIG. 3 with the current transformer in the operating position.

FIG. 5 is a cross-sectional partly broken away view corresponding to FIG. 4, except that the current transformer is in the non-operating position.

FIG. 6 is a cross-sectional view of another embodiment of our invention with the current transformer in the operating position.

FIG. 7 is a plan view of a mounting plate for the embodiment illustrated in FIG. 6.

FIG. 8 is a perspective partially cross-sectional view of one mounting bracket of the embodiment illustrated in FIG. 6.

FIG. 9 is a perspective partially cross-sectional view of another mounting bracket of the embodiment illustrated in FIG. 6.

FIG. 1G is a plan view of the embodiment of FIG. 6 in the non-operating position with portions of the structure broken away.

FIG. 1l is a cross-sectional view taken along the lines 11-11 of FIG. l0. n

FIG. l2 is a plan view of another mounting plate for the embodiment of FIG. ll.

Referring now to the drawing, in FIG. l is illustrated an embodiment of electrical apparatus in accordance with the principles of our invention. An electrical transformer 10 comprising a core 11` and a plurality of winding coils 12 is housed in a fluid-tight enclosure 13` in the conventional manner. The enclosure 13` may contain an insulating and cooling lluid, such as transformer oil or a dielectric gas, and may be provided with conventional accessories, such as external heat exchangers or fluid expansion reservoirs. However, such accessories have not been illustrated, since they form no part of the present invention. Bushings 14 may be applied to the transformer 10 to provide external connections for leads 15 from the windings 12.. In order to provide means for indicating or controlling the output of the transformer 10, current transformers 20 may be applied to the exterior thereof around the bushings 14. The bushings 14 are removably mounted on the transformer to reduce its height when necessary.

In FIG. 2, a current transformer according to our invention is shown raised above the upper surface of the housing 13 in its operating position. A bushing 14 passes through the current transformer 20 and is connected to the lead 15 from a Winding of the transformer. Thus, the current conducting element 16 of the bushing 14 acts as an extension of the lead from the transformer winding and passes axially through the current transformer 20 so as to become the primary winding thereof. The bushing 14 may be attached to a housing 35 around the current transformer by means of bolts 17. When it is necessary to remove the bushing 14, the bolts 17 are unthreaded and the bushing lifted upwardly. The lead 15 may be removably connected to the conducting element 16 in any conventional manner, such as by means of threads on the lower end of the conducting element I6. Access to the interior of the tank for connecting or disconnecting the lead may be attained in any conventional manner, such as a removable plate closing a hand hole. It is to be understood, however, that the specific manner in which the lead 15 is connected to the bushing 14 and the specific manner in which access to the interior of the tank is obtained form no part of our invention. The current transformer 20 comprises one or more annular secondary windings 21 which have an axial bore 22 for receiving the primary winding 16. A plurality of leads 23 from the secondary windings of the current transformer may be attached to terminals 24 extending through a side of the enclosure 13 to provide external connections for the current induced in the current transformer 20. The terminals 24 may be connected to indicating or regulating apparatus as desired.

In the operating position, as shown in FIGS. 1-4, the secondary windings 21 of the current transformer are supported by means at one end, such as a plate 31 which rests on lugs 32. The lugs 32 may be attached to one or more annular rings 33 which are welded to the housing 13 around an opening 29. The support plate 31 may be attached to the lugs 32 by means of nuts threaded onto bolts 34, which are welded to the lugs 32. The current transformer may be protected by a housing 35 which is removably attached to the rings 33 by upstanding bolts 36 secured thereto. The housing 35 yis provided with an opening 28 for reception of a bushing 14. The other end of the secondary winding 21 may be provided with a support plate 37 that is identical to the plate 31. The plates 31 and 37 may be coupled together by insulated tie rods 38., and thus form a clamping assembly for holding a plurality of winding coils 21 together. The individual winding coils k21 may be separated by insulating spacers 39 in the conventional manner. The plates 31 and 37 are each provided with an opening Z7 to permit passage of a bushing 14 through the bore 22.

In FIG. 5, the secondary windings 21 arey shown supported by the plate 37, which is resting on the lugs 32. The plate 37 is attached to the lugs 3-2 by the same nuts and bolts 34 that are employed for the plate 31, thus reducing the number of parts that must be handled. This is the non-operating position of the current transformer 20 in which the apparatus 10 may be moved or transported to its ultimate user. The housing 35 has been removed by unthreading the nuts from the bolts 36 and lifting the housing upwardly. The housing 35 is then replaced with a cover plate 40 to reduce the height of the apparatus to an acceptable dimension. The cover plate 40 is attached by means of same bolts 36 that hold the housing 35.

An examination of FIG. 3 will reveal how the secondary winding assembly of the current transformer 20 can be lowered from operating position to the non-operating position. In FIG. 3 the full lines illustrate the supporting plate 31 resting on the lugs 32 in a first angular position. To lower the secondary winding to the nonoperating position, the nuts are unthreaded from the bolts 34 and the plate 31 is raised above the bolts 34. The entire assembly is then rotated to a second angular position, illustrated in dotted lines, so that the corners of the plate 31 will clear the lugs 32. This permits the secondary winding to be lowered until the plate 37 is just above the lugs 32. With the apparatus in this position, the assembly is rotated back to the full line position so that the corners of the plate 37 can rest upon the lugs 32 in identically the safme manner as the corners of the plate 31 rested thereon when the assembly is in the operating position. The secondary winding is secured in its lower position by threading the nuts back on the bolts 34, as shown in FIG. 5. To return the current transformer 20 to the operating position, the above sequence of steps is repeated in reverse. Lifting lugs 41 may be secured to the plate 37 to facilitate the raising and lowering of the secondary winding assembly.

Sufficient slack is provided in the leads 23 so that they will not restrict the movement of the secondary winding. (see FIG. 2.) It is thus apparent that once the leads 23- have been connected to the terminals 24, they need not be disconnected when the transformer 10 is in transit from one location to another because the overall height of the transformer 10 can be temporarily reduced by mounting the current transformer secondary winding assembly in the non-operating position.

In many instances on high voltage transformers the electrical bushings are mounted in a tilted position. In such situations, a current transformer utilizing the bushing as its primary winding must also be mounted in a tilted position. FIGS. 6-12 illustrate an embodiment of our invention in which the current transformer is mounted in a tilted position. Since a bushing can be attached to the tilted current transformer in the same manner as in the embodiment of FIGS. l-S, it has been omitted from the drawing for the purposes of clarity. In FIG. 6, the current transformer is shown in its operating position above the upper surface of the enclosure 13. The secondary windings 21 may be clamped between, respectively, a supporting plate 37 at one end, and a supporting plate 31' at the other end in the same manner as the embodiment of FIGS. l-S. However, the plates 37 and 31 are not identical in shape in this embodiment. To tilt the windings 21 at the proper angle, a plurality of mounting brackets are welded or otherwise secured in notches 41 at the corners of the bottom supporting plate 31', as shown in FIG. 7. In FIG. 8 an end bracket 42 for the upwardly tilted end of the current transformer is shown extending in one direction beyond the plate 31 and resting on a lug 32. In FIG. 9 another end bracket 43 for the downwardly tilted end of the current transformer is shown extending in the opposite direction beyond the plate 31 and resting on another lug 32. Mounting brackets 44 may be secured to the intermediate corners of the plate 31' at the proper height in relation to the end brackets 42 and 43, and it will be apparent to those skilled in the art that the relative tilt of the bushing and current transformer can be varied by altering the distances at which the mounting brackets 42-44 extend either above or below the plate 31. A housing 35 may be secured to the ring 33' around the current transformer in the same manner as in the embodiment of FIGS. `1-5.

FIGS. 10 and l1 illustrate the tilted current transformer embodiment when it is in the non-operating position. To mount the current transformer secondary in the non-operating position, a pair of extension plates 45 are removably attached to the top plate 37', with corners of the plates 45 extending beyond the periphery of the plate 37. These corners rest on the lugs 32 as shown in FIG. l0. Once the plates 45 have been secured to the mounting plate 37', the current transformer can be lowered to the non-operating position merely by rotating it so that the mounting brackets 42-44 clear the lugs 32. As shown in FIG. 10, the corners of the plate 31 are approximately 45 out of line with the corners of the plates 45. Consequently, the current transformer need not be rotated back to the original angular position. Then a cover plate 40 can be applied to the top of the transformer in the same manner as in the embodiment of FIGS. 1-5. The current transformer can be returned to the operating position by repeating the above steps in reverse sequence. In other respects the embodiment of FIGS. 6-12 is the same as that of FIGS. 1-5 and possesses the advantages of the latter modification that once the current transformer is installed and its secondary leads connected, it need not be disconnected from the transformer 10 in order to reduce the height of the apparatus to an acceptable dimension.

Thus, by providing the secondary winding of a current transformer Z with mounting means at both ends thereof, the height of apparatus associated with the current transformer can be reduced to obtain road clearance by lowering the current transformer secondary to a nonoperating position below the upper surface of the apparatus 10. Also, once the current transformer leads 23 have been connected to the appropriate terminals on the apparatus 10, the leads need not be disconnected for shipment. This results in a reduction in the cost of the apparatus because the current transformer need not be packed and shipped separately. Also, by mounting the current transformer on the interior of the enclosure 13 it is protected from damage and not subject to contamination by moisture or dirt.

It will be understood, of course, that while the form of the invention herein shown and described constitutes the preferred embodiment thereof, it is not intended herein to illustrate all of the equivalent forms or ramiiications thereof. For example, current transformers in accordance with our invention can be associated with velectrical devices other than transformers. It will also be understood that the words employed are words of description rather than of limitation, and that various changes may be made without departing from the spirit or scope of the invention herein disclosed. It is intended in the appended claims to cover all such changes as fall within the true spirit and scope of the invention.

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

l. A current transformer comprising a secondary winding, said winding being rotatable and being axially movable from a non-operating position to an operating position, means at one end of said winding for supporting same in the non-operating position, and means at the other' end of said Winding for supporting same in the operating position.

2. -A current transformer comprising an annular secondary winding having an axial bore for receiving a primary winding, said secondary winding being movable from a non-operating position to an operating position, means at one end of said secondary winding for supporting same in the non-operating position, means at the other end of said secondary winding for supporting same in the operating position, and both the supporting means having an opening therein to permit passage of the primary winding through said axial bore.

3. A current transformer comprising a plurality of annular secondary winding coils each having an axial bore, said axial bores being aligned for receiving a primary winding comprising an electrical bushing, said secondary winding being movable from a non-operating position to an operating position, a plate at one end of said secondary winding for supporting same in the nonoperating position, a plate at the other end of said secondary winding for supporting same in the operating position, said plates each having an opening therein to permit passage of said bushing through said axial bores, and said plates being structurally connected to each other for clamping said plurality of coils together.

4. A current transformer as recited in claim 3 in which one of said plates has a plurality of mounting brackets secured thereto, at least one of said brackets `extending beyond said plate in one direction, and at least one other of said brackets extending beyond said plate in the other direction, whereby said secondary winding and said bushing can be supported in a tilted position.

5. In combination, current carrying electrical apparatus, a current transformer having an annular secondary winding and an electrical bushing, said bushing being removably connected to a lead from said electrical apparatus, said bushing passing through said secondary winding, said secondary winding being movable from a non-operating position to an operating position, means at one end of said secondary winding for supporting same on said electrical apparatus in the non-operating position, and means at the other end of said secondary winding for supporting same on said electrical apparatus in the operating position.

6. `In combination, current carrying electrical apparatus, a current transformer having an annular secondary winding, `and an electrical bushing, said electrical apparatus being connected to said bushing by a lead that passes through the secondary winding of said current transformer so that said lead becomes the primary winding of said current transformer, said secondary winding being movable from yan operating position in which it extends above the upper surface of said electrical apparatus to a non-operating position in which it is below said upper surface, a plate at one end of said secondary winding for supporting same in the non-operating position, a plate at the other end of said secondary winding for supporting same in the operating position, and means attached to the upper surface of said apparatus for supporting the plates, and leads from said secondary winding being connected to terminals on said apparatus when said secondary winding is in both said operating and nonoperating positions.

7. The combination recited in claim 6 in which the plate for supporting said secondary winding in the operating position rests directly on said means attached to the upper surface of said apparatus.

8. The combination recited in claim 6 in which said plate for mounting said secondary winding in the operating position has a plurality of mounting brackets secured thereto, at least one of said brackets extending beyond said plate in one direction and at least one of said brackets extending beyond said plate in the other direction, whereby said secondary winding and said bushing can be mounted in a tilted position with respect to said apparatus.

9. Stationary electrical induction apparatus comprising an induction coil, an enclosure around said coil, there being an opening in the upper surface of said enclosure, a lead from said winding passing through said opening, a current transformer having an annular secondary winding for receiving said lead as its primary winding, said secondary winding being movable from a non-operating position below said enclosure upper surface to an operating position above said enclosure upper surface, and support means attached to said enclosure adjacent said opening and supporting said secondary winding in both the non-operating position and the operating position.

l0. An electrical transformer comprising a core and a plurality of windings surrounding said core, an enclosure surrounding said core and windings, a removable electrical bushing at the upper surface of said enclosure, said bushing being connected to said windings by a lead, a current transformer having an annular secondary Winding adjacent the upper surface of said enclosure, said bushing passing through said secondary winding so that a conductor therein becomes the primary winding of said current transformer, and said secondary winding being movable from a non-operating position in which it is supported below the upper surface of said housing to an operating position in which it is supported above the upper surface of said housing.

.11. An electrical transformer comprising a core, a winding surrounding said core, =a lead extending from said winding, an enclosure surrounding said core and winding, said enclosure having an opening in the upper surface thereof for receiving an electrical bushing adapted to be connected to said lead, support lugs attached to the inside of said enclosure at its upper surface adjacent said opening, an annular current .transformer secondary winding supported by said lugs on the inside of said enclosure,

said secondary winding having an axial bore aligned with said opening for receiving said electrical bushing, a lead from said secondary winding connected to a terminal that extends through said enclosure, and a removable cover plate closing said opening.

12. An electrical transformer comprising a core, a winding surrounding said core, a lead extending from said winding, an enclosure surrounding said core and winding, said enclosure having an opening in the upper surface thereof for receiving an electrical bushing adapted to be connected to said lead, support lugs attached to the inside of said enclosure at its upper surface adjacent said opening, an annular current transformer secondary winding having support means attached to one end thereof, said support means resting on said lugs on the inside of said enclosure in a non-operating position, said secondary winding being movable through said opening to an operating position, another support means attached to the other end of said secondary winding for supporting same in said operating position, said secondary winding having an axial bore aligned with said opening for receiving said electrical bushing in the operating position, a lead from said secondary winding connected to a terminal that extends through said enclosure, and a removable cover plate closing said opening.

13. An electrical transformer comprising a core, a winding surrounding said core, a lead extending from said winding, an enclosure surrounding said core and winding, said enclosure having an opening in the upper surface thereof for receiving an electrical bushing adapted to be connected to said lead, support lugs attached to the inside of said enclosure at its upper surface adjacent said opening, an annular current transformer secondary winding having a support plate attached to one end thereof, corners of said support plate resting on said lugs on the inside of said enclosure in a non-operating position, another support plate attached to the other end of said secondary Winding, the last mentioned support plate having corners adapted to rest on said lugs for supporting the secondary winding in an operating position above said enclosure, said secondary winding being rotatable in said opening to provide clearance for said last mentioned plate corners to move past said lugs, said secondary winding being movable through said opening to said operating position, said secondary Winding having an axial bore aligned with said opening for receiving said electrical bushing in the operation position, said support plates each having an opening therein to permit passage of said bushing through said bore, a lead from said secondary winding connected to a terminal that extends through said enclosure, and a removable cover plate closing said opening.

14. An electrical transformer as recited in claim 13 in which said secondary winding comprises a plurality of winding coils, and said support plates are structurally connected for clamping said coils together.

l5. An electrical transformer as recited in claim 14 in which the corners of said last mentioned plate comprise a plurality of brackets, at least one of said brackets extending beyond said plate in one direction and at least one of said brackets extending beyond said plate in the other direction, whereby said secondary winding and said bushing can be mounted in a tilted operating position with respect to said transformer.

16. The method of reducing the height of electrical apparatus of the type comprising a current producing device housed in an enclosure and a current transformer having secondary winding leads attached to said enclosure, comprising the steps of rotating said current transformer from a first angular position to a second angular position, lowering said current transformer below the upper surface of said enclosure, and supporting said current transformer on said enclosure.

17. The method of temporarily reducing the height of electrical apparatus of the type comprising a current producing device housed in an enclosure and a current transformer having secondary winding leads attached to said enclosure, said secondary winding being initially supported above said enclosure in an operating position, comprising the steps of rotating said current transformer from a first angular position to a second angular position, lowering said current transformer below the upper surface of said enclosure, rotating said current transformer back to the lirst angular position, and supporting said current transformer on said enclosure in a non-operating position, whereby said current transformer can be re turned to the operating position by rotating same to the second angular position, raising same to above said enclosure, rotating same back to said first angular position, and supporting same as initially above said enclosure.

References Cited in the tile of this patent UNITED STATES PATENTS 2,431,189 Moreton et al. Nov. 18, 1947

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