US2316558A - Transformer - Google Patents

Description

Patented Apr. 13, 1943 UNITED STATES PATENT OFFICE General El New York ectric Company, a corporation of Application July 11, 1940, ,Serial No. 344,937 9 Claims. (Cl. 175-361) My invention relates to transformers and, although not limited thereto, it has particular ap plicatlon to high voltage current transformers.

Heretofore high voltage current transformers have been made with a high voltage winding and terminal leads extending from the windings, the ends of which being provided with connectors so that the high voltage primary winding may be connected in a high 'voltage line whose current is to be measured or controlled. Such a transformer is usually suitably encased and a liquid dielectric placed inside the casing and around the transformer. I'here also has been the practice of providing a plurality of concentric cylinders around a portion of the lead which extends from the high voltage winding, so as to form barriers in the liquid dielectric which surrounds the lead. Such a practice is desirable since it breaks up the body of liquid into a plurality of separate bodies so as to minimize the possibility of arcing through the liquid. When such cylinders are employed, however, the problem presents itself of tightly securing the cylinders so that they will not move during the subsequent drying operation or during transportation to the place of installation. High voltage current transformers, such as the type which has been described above, are also usually provided with a solid insulating material, such as crepe paper, around the high voltage winding and lead and inside the group of concentric cylinders, and, since crepe paper contracts during its heating and drying operation, the cylinders will ordinarily become loosened. Such a result impairs considerably the eiiiciency of the resultant transformer.

It is, therefore, an object of my invention to provide a transformer having a cylinder around its lead with an improved arrangement for securing the cylinder in place so that it will remain in place during the subsequent operations which the transformer receives.

Another object of my invention is to provide an improved insulating arrangement around the projecting edge of a grounded sheath which surrounds the high .voltage Winding of a transformer.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out in the claims annexed to and forming a part of this specication.

In the drawing, Fig. 1 is a side elevation in partial section of a high voltage current transformer which is provided with an embodiment of my inthe extended terminal leads vention; Fig. 2 is a side elevation in partial section oi' a portion of the transformer illustrated in Fig. 1; and Fig. 3 is an end view in partial section ofva portion ofthe current transformer illustrated in Fig. 2.

Referring to the drawing, in Fig. l I have illustrated a high voltage current transformer which includes a primary or high voltage winding Il and a secondary or low voltage winding II which is distributed around a suitable core Ila. Extending from the primary winding and connected thereto I provide suitable lead members I 2 whose ends are connected to the connectors I3. I'he connectors I3 may be in turn connected in the high voltage line Whose current is to be measured or controlled. The high and low voltage lwindings are suitably housed in a casing I4 while I2 are housed in a tubular bushing I5. The winding structure and core may be of any suitable type, such as that disclosed in my copending application, Serial No. 287,032, filed July 28, 1939, which issued as Patent 2,280,625 on April 21, 1942, and which is assigned to the same assignee as this present invention. The winding I0 is therefore surrounded and -spaced from a perforated sheath I 5, which is maintained at substantially the same potential as the winding III. Insulation Il of any suitable type, such as crepe paper, is placed around the sheath I5, and may be applied in any suitable manner, such as by winding in tape form to the desired thickness. This same type of insulation may also be wound around the leads I2. I may also surround the insulation Il with a sheath I8 which may be of any suitable type, such as a metal tape, and it may be kept at ground potential Iby the strap I9 which is connected to the casing I4. 'Ihe casing I4 and bushing I5 are filled with a suitable dielectric fluid, such as oil. to the level 20 and a conservator 2l is provided at the top of the bushing I5 so as to allow for thermal expansion and contraction of the fluid.

When an insulating liquid is placed under a high electrical stress, it is desirable to break up the liquid into a plurality of small bodies so as to minimize the possibility of breakdown, since it is impractical to employ chemically pure iluid in the manufacture of transformers of this type. 'I'hus a small amount of impurities will be contained in the fluid and when the insulating fluid is placed under stress, the impurities will tend to line up, thus lowering its impulse strength and causing failure. Therefore, barriers or insulating cylinders 22, or any suitable number of barriers or insulating cylinders which are coaxial and radially spaced, may be employed around a portion of the leads l2 so that the liquid in, a portion of the bushing may be broken down into any desired number oi small bodies of liquid. Thus, any possibility of creepage or ashover from the ends of the lead adjacent the high voltage terminals I3 to ground will be considerably lessened. Since it is necessary to thoroughly dry the solid insulation I1 before it is impregnated with the fluid dielectric, the problem presents itself of suitably supporting the cylinders so that they will remain in place after the-drying operation or during the subsequent transportation to the point of installation, or during any other operations through which the transformer must pass and which may tend to cause the cylinders to be loosened. I have found that the cylinders 22 may be suitably supported in an eilicient manner by embedding them in insulation. This may be accomplished in any suitable manne such as by providing a. portion 23 of insulating material at the place where it is desired to support the cylinders, placing the cylinder which is to be next to the leads in position as shown in Fig. 2 so that its lower end tightly surrounds this portion 23, and then providing insulation, similar to that used for the portion 23 at 24, or around that portion of the cylinder which surrounds the portion 23 so that insulation is contiguous with the inside and outside periphery of the cylinder.

Thus the cylinder is embedded in insulation since it is tightly held between the concentric portions 23 and 24. This operation may be continued for as many cylinders as are needed around the leads. The portion 23 may be built up to a thickness slightly larger than the diameter of the cylinder 22 so that it may tightly squeeze around this portion. When the insulation Il is applied by a mapping operation of the paper in tape form, a. suitable way of forming the portion 23 is to wrap a larger amount of tape at that place so as to form this extended portion. The covering at 2d may also be applied by wrapping tape to a desired thickness. The portions 23 and 26 may be applied, however, in any other suitable manner, or if it is desired, any other type of insulation may be applied which has suitable contraction characteristics. In order that the cylinders may form barriers between portions of the liquid, an arrangement must be provided to space the cylinder next to the lead away from the insulation l1, and to space the cylinders from each other, when more than one is employed. In

order to accomplish this, spacers 25 are provided which are placed on the inside periphery ofthe cylinders and which may be held to the cylinders 22 in any suitable manner, such as by tying at the top by a cord 2B. Thus a suitable number of spacers is employed so that they will fit tightly around the insulation i1, the ends thereof abutting against the top of the extension 23. When the last cylinder 22 has been applied, insulation 21 of the same type employed at 23 and 24 may then be applied to the desired thickness. When this operation is finished, the shield I8 may then have a portion 28 applied so that its outwardly extending edge 29 extends up a. suitable distance around the lead I2.

In order to further minimize the possibility of flash-over, I suitably insulate the extending edge 29 of the shield 23 by providing a sheet of crepe paper 3D around the insulation 21 and then providing a few mappings of insulating tape 3l between the sheet l:ill and the edge 29 s o as to tightly hold the paper 3.0 in place. The insulating sheet may then be bent or folded around the edge 29 as illustrated in Fig. 2, the bent-around end being tightly secured in place by wrappings of tape, as indicated by the numeral 32.

In view of the foregoing, it will be seen that I have provided an improved arrangement for tightly securing insulating cylinders which are placed around the high voltage lead of a transformer. Thus, I have found that when the cylinders are embedded in insulating material, that during the subsequent drying operation the contracting of the insulation will not cause the cylinders to loosen but will cause them to be even more tightly secured in place. I have also illustrated an improved arrangement for insulating the outwardly extending edge of the grounded metallic sheath which surrounds the high voltage winding and extends partway along the insulating lead member by folding over a sheet of crepe paper around the edge and tightly securing it thereto.

Although I have shown and described particular embodiments of my invention, I do not desire to be limited to the particular embodimentsdescribed, and I intend in the appended claims to cover all modications which do not depart from the spirit and scope of my invention.

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

1. A transformer including a winding, a terminal lead connected to said winding, insulation around said winding and lead, a cylinder around said lead and tightly surrounding a portion of said insulation, and insulation similar to said lead insulation around said cylinder and concentric with said portion in order to embed and support said cylinder in insulation so that said cylinder will remain in place during the remaining operations which said transformer receives.

2. A transformer including a winding, a terminal lead connected to said winding, a cylinder around said lead, and insulation having substantially similar contraction characteristics con tiguous and tightly disposed with the inside and outside peripheries of one end of said cylinder in order to embed and support said end of said cylinder in insulation so that said cylinder will remain in place during the remaining operations which said transformer receives.

3. A transformer including a winding, a terminal lead connected to said winding, insulation around said winding and lead, a cylinder around said insulated lead, spacers adjacent the insidel periphery of said cylinder, said spacers being tightly held between said cylinder and said insulation, and insulation similar to said lead insulation tightly surrounding a portion of said cylinder so that said cylinder is embedded and supported in said insulation so that said cylinder will remain in place during the remaining operations which said transformer receives.

4. A transformer including a winding, a terminal lead connected to said winding, insulation around said winding and lead, concentric cylinders around said lead, and spacers between adjacent cylinders, said insulation having a portion in which ends of said cylinders are embedded and supported so that said cylinders will remain in place during the remaining operations which said transformer re'ceives, and a liquid dielectric surrounding said lead and between said cylinders.

5. A transformer including a winding, a terminal lead connected to said winding, insulation around said winding and lead, concentric cylinders around said lead, said insulation having an extending portion in which ends of said cylinders are embedded and supported, and spacers between adjacent cylinders and between said insulation and said contiguous cylinder so as to permit effective drying of said insulationa 6. A transformer including a high voltage winding, a terminal lead connected to said winding, insulation around said winding and lead, concentric cylinders around said lead, said insulation having an extending portion in which ends of said cylinders are embedded and supported so that said cylinders will remain in place during the subsequent drying operation of said insulation, a casing for said winding and lead, an insulating iluid within said casing and surrounding said lead, and spacers between said cylinders so that said fluid'may ilow around each cylinder.

7. A transformer includingV a winding, a high voltage terminal lead connected to said winding, insulation around said winding and lead, a grounded sheath surrounding said insulated winding and a portion of said lead and terminating in an edge, and insulation including a sheet oi fibrous material folded around said edge so as to minimize the possibility of ilashover to said edgeB 8., A transformer including a Winding, a high voltage terminal lead connected to said winding, insulation around said winding and lead, concentric cylinders around said lead, said insulation having an extending portion in which ends of said cylinders are embedded, a grounded sheath surei rounding said insulated winding and a portion of said lead and terminating in an edge, and a folded fibrous insulating material' around said edge so as to minimize the possibility of iiashover to said edge.

9. A transformer including a winding, a high voltage terminal lead connected to said winding, insulation around said winding, a conductive sheath around said insulated winding and terminating in an edge, and insulation including a sheet oi fibrous material folded around said edge so as to minimize the possibility of corona at said edge.

GUGLIELMO CAMILLI.

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