US3676579A

US3676579A - Transformer lead insulator and method of making same

Info

Publication number: US3676579A
Application number: US167939A
Authority: US
Inventors: Thomas J Lanoue; John G De Neef
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1971-08-02
Filing date: 1971-08-02
Publication date: 1972-07-11
Anticipated expiration: 1989-07-11
Also published as: YU197372A; FR2148148A1

Abstract

High voltage lead insulator for shell-form transformers and method of constructing same. Hollow cylindrical members, being constructed of pressboard and having one of their ends flared, are coaxially positioned with respect to each other and are mounted over a circular opening in a U-shaped channel member. Adhesive is disposed between the flared surfaces to reinforce the structure.

Description

United States Patent Lanoue et a1.

[451 July 11,1972

[54] TRANSFORMER LEAD INSULATOR AND METHOD OF MAKING SAME [72] Inventors: Thomas J. Lanoue, Muncie; John G. De

Neel, New Castle, both of Ind.

[73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.

[22] Filed: Aug. 2, 1971 [21] Appl. No.: 167,939

[52] U.S.Cl. ..174/138 R, 156/293, 174/167, 285/189, 285/D1G. 16 [51] Int. Cl ..H0lb 17/58, H0lf15/10, H01f27/32 [58] FieldofSearch ..174/l37 R, 138 R, 138 E, 1526, 174/153 G, 167; 156/293; 285/189, 200, DIG. 16; 336/192 [56] References Cited UNITED STATES PATENTS 2,425,443 8/1947 Soreng ..336/ 192 FOREIGN PATENTS OR APPLICATIONS 611,557 3/1935 Germany ..l74/l67 713,738 1l/l941 Germany ..336/l92 OTHER PUBLICATIONS Laib, PT s Are Getting Smaller, Allis-Chalmers Electrical Review, First Quarter 1952, pages 20- 22.

Primary Examiner-Laramie E. Askin Attorney-A. T. Stratton et al.

57 ABSTRACT High voltage lead insulator for shell-form transformers and method of constructing same. Hollow cylindrical members, being constructed of pressboard and having one of their ends flared, are coaxially positioned with respect to each other and are mounted over a circular opening in a U-shaped channel member. Adhesive is disposed between the flared surfaces to reinforce the structure.

6 Claims, 4 Drawing figures P'AfTENTEDJuL 11 m2, 3. 676-; 579

SHEET 2 OF 2 TRANSFORMER LEAD INSULATOR AND METHOD OF MAKING SAME BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates, in general, to electrical inductive apparatus and, more specifically, to lead insulating structures suitable for bringing out a high voltage lead from a shell-form power transformer winding.

2. Description of the Prior Art High power transformers, particularly of the shell-form type, require extensive insulation structure arrangements to prevent corona discharges within the transformer. The insulation structure which surrounds the high voltage lead of the transformer winding is of particular importance. This structure must not only provide sufficient dielectric strength in the region adjacent to the high voltage lead to prevent corona discharges, but it must also provide some structural support for the high voltage lead, which may be relatively large. In order to keep the lead from bending and coming close to the other parts of the winding structure, an insulated cylindrical tubular member is usually disposed over the high voltage lead and attached or secured to the insulation structure of the winding. Although this type of lead insulator performs satisfactorily, it is not readily available in the United States. Lead insulators may be purchased from foreign manufacturers, but because of complex construction details of the presently available lead insulators, the price for such is excessive.

It therefore is desirable, and it is an object of this invention, to provide a transformer lead insulator which may be easily constructed from inexpensive materials by semi-skilled personnel.

SUMMARY OF THE INVENTION The lead insulator disclosed herein is constructed of pressboard members which are shaped to permit easy assembly and to provide an electrically and mechanically efficient structure. A hollow cylindrical member, which has its lower end flared, is inserted through an opening in a U-shaped channel member. An adhesive is disposed between the contacting surfaces. A second hollow cylindrical member is telescoped over the first cylindrical member until the flared portion of the second cylindrical member contacts the channel member. A suitable adhesive is placed between the flared end and the channel member, and between the two cylindrical members. Additional cylindrical members may be telescoped similarly if additional electrical and/or mechanical strength is desired.

BRIEF DESCRIPTION OF THE DRAWINGS Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawings, in which:

FIG. 1 is a view of a shell-form transformer showing the placement of the lead insulator constructed according to the teachings of this invention;

FIG. 2 is a view of a lead insulator constructed according to the teachings of this invention;

FIG. 3 is an exploded view of a lead insulator constructed according to the teachings of this invention illustrating the construction techniques; and

FIG. 4 is a partial cross-sectional view of the lead insulator shown in FIG. 2 and taken along the line IV-IV.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description similar reference characters refer to similar members in all Figures of the drawmg.

Referring now to the drawings, and FIG. 1 in particular, there is shown a laminated magnetic core of the shell-form type. The winding structure 12, illustrated partially in phantom, includes a plurality of disk or pancake coils 14 which are 5 jects from the winding structure 12 and may be connected to a high voltage bushing on the transformer casing. The high voltage lead 18 extends through the lead insulator assembly 20 which comprises the lead insulators 22 and 24. The lead insulator 22 is constructed of a tubular member 26 and a channel member 28. The lead insulator 24 is similarly constructed, except that the members which form the lead insulator 24 have dimensions which permit its placement within the outer lead insulator 22. The channel member 28 includes side portions which extend radially inward between the coils and/or insulating spacers. Means, not shown, may be provided for securing the channel member 28 to the winding structure 12.

The lead insulator assembly 20 provides structural support for the high voltage lead as well as electrical insulation therefor. The number of lead insulators which are concentrically disposed depends largely on the size, class, type and voltage rating of the transformer. Only one lead insulator may be sufficient, or more than two lead insulators, as illustrated, may be necessary.

The lead insulator 22 is shown in FIG. 2 illustrating in greater detail the shape of its members. The tubular member 26 is attached to the channel member 28 by the joint 30. The channel member 28 includes the top portion 32 and the

side portions

34 and 36. The tubular member 26 is positioned over a circular opening in the top portion 32 of the channel member 28. The joint 30 is formed by the operations which are performed during the construction of the lead insulator 22.

FIG. 3 is an exploded view of the lead insulator 22 shown in FIG. 2, illustrating the method of construction as taught by this invention. The channel member 28 is constructed of a suitable material, such as pressboard, and contains a circular opening 38, around which the pressboard has been cut and flared. The diameter of the opening 38, before flaring, is slightly less than the outside diameter of the hollow cylindrical member 40. The hollow cylindrical member 40 has its lower end 42 flared as illustrated. The cylindrical member 40 is inserted through the opening 38 from the inside of the channel member 28 and pushed, upwardly as illustrated, until the flared end 42 contacts the'inside of the flared opening flange 52. The cylindrical member 44 also has a flared end 46. The inside diameter of the cylindrical member 44 is slightly larger than the outside diameter of the cylindrical member 40. This permits the cylindrical member 44 to be telescoped over the cylindrical member 40, thus producing a structure laminated tubular member. The cylindrical member 40 is pushed, downwardly as illustrated, until the flared end 46 contacts the flared opening flange 52. If additional structural or dielectric strength is desired, another cylindrical member, such as 48 with the flared end 50, may be telescoped over the cylindrical member 44. It is also within the contemplation of this invention that additional cylindrical members may be so telescoped. An adhesive material is applied between the flared portions of the members, as well as between the surface walls of the cylindrical members to bond the members together. Any suitable adhesive may be used, such as pressboard putty which comprises a mixture of polyvinyl chloride, water and pressboard particles. A mixture of polyvinyl chloride, water and virgin pulp particles may also be used.

Specific construction techniques are helpful in constructing lead insulators according to this invention. For normally sized lead insulators, the circular opening 38 in the channel member 28 may be cut with a diameter which is three-eighths inch less than the outside diameter of the cylindrical member 40. The pressboard adjacent to the opening 38 is moistened prior to being flared in order that the pressboard may be bent without cracking. The flared end portions of the cylindrical members are also moistened before being flared. The adhesive material is disposed on the outside of the flared end 42 and the inside of the flared opening flange 52. The cylindrical member 40 is inserted into the opening until the flared end and the flange contact each other and may be held firmly in this position until the adhesive has cured. A suitable die or fixture may be inserted into the cylindrical member 40 to help maintain its shape while drying.

The end 46 of the cylindrical member 44 is moistened and flared and the cylindrical member 44 is then telescoped over the cylindrical member 40, with an adhesive material disposed between the inside of the flared end 46 and the outside of the flared opening flange 52. As the moistened flanged end 46 dries, the pressboard shrinks, thereby compressing the adhesive material tightly into any irregularities which may exist around the joint. A small amount of adhesive may be applied to the cylindrical member 40 so that the two cylindrical members will be bonded together.

The end 50 of the cylindrical member 48 is moistened and flared. The cylindrical member 48 is then telescoped over the cylindrical member, with an adhesive disposed between the contact areas of the flared ends 46 and 50. An adhesive may also be applied to the outside of the cylindrical member 44 prior to the telescoping operation to bond the two cylinders together. A suitable adhesive may be packed around the outside of the flared end 50 to reinforce the joint between the flared end 50 and the channel member 28.

FIG. 4 is a partial cross-sectional view of the lead insulator shown in FIG. 2 and taken along the line IV-IV, illustrating, in detail, the various layers of pressboard and adhesive. The

cylindrical members

40, 44 and 48 are coaxially disposed, as shown, over the opening in the top portion 28 of the channel member. The flared end 42 is positioned under the flared opening flange 52, with the adhesive 54 disposed therebetween. The flared end 46 is positioned over the opening flange 52 with the adhesive 56 disposed between their adjacent surfaces. The adhesive 58 is similarly disposed between the adjacent surfaces of the flared ends 46 and 50, with the adhesive 60 disposed over the flared end 50 to give the joint additional strength and smoothness.

Since numerous changes may be made in the abovedescribed apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawings, shall be interpreted as illustrative rather than limiting.

We claim as our invention:

1. A transformer lead insulator comprising a U-shaped channel member having two sides and a top portion, a tubular member having first and second ends and a laminated wall, the first end of said tubular member being attached by a suitable means to the top portion of said channel member and positioned over a circular opening therein, said tubular member comprising a plurality of hollow cylindrical members which are coaxially positioned with respect to each other to form the laminated tubular member wall.

2. The transformer lead insulator of claim 1, wherein the channel member and the hollow cylindrical members are constructed of pressboard, with a suitable adhesive disposed between adjacent cylindrical members.

3. The transformer lead insulator of claim 1, wherein the means for attaching the tubular member comprises a joint which is formed by the ends of the hollow cylindrical members and by the flared area of the channel member which is adjacent to the opening therein, one end of a first cylindrical member being flared and positioned adjacent to the inside of the flared channel member opening, one end of a second cylindrical member being flared and positioned adjacent to the outside of the flared channel member opening, with a suitable adhesive disposed between adjacent flare surfaces.

4. The transformer lead insulator of claim 3, wherein the adhesive which is disposed between adjacent flare surfaces comprises a mixture of polyvinyl chloride, water and pressboard particles.

5. The transformer lead insulator of claim 3, wherein the adhesive which is disposed between adjacent flare surfaces comprises a mixture of polyvinyl chloride, water and virgin pulp particles.

6. A method of constructing a transformer lead insulator comprising the steps of:

providing two hollow cylindrical members, a first of said cylindrical members having an inside diameter which is slightly larger than the outside diameter of the second cylindrical member, flaring one end of said hollow cylindrical members, providing a U-shaped channel member having a top portion,

cutting a circular opening in the top portion of said U- shaped channel member, said opening having a diameter which is slightly less than the outside diameter of the second cylindrical member, flaring the area adjacent to the circular opening in the channel member, inserting the second cylindrical member into said opening from the inside of the channel member, telescoping the first cylindrical member over the second cylindrical member until the flare area of the first cylindrical member is adjacent to the outside of the flare area around the opening in the channel member, and applying an adhesive between the flared surfaces.

Claims

6. A method of constructing a transformer lead insulator comprising the steps of: providing two hollow cylindrical members, a first of said cylindrical members having an inside diameter which is slightly larger than the outside diameter of the second cylindrical member, flaring one end of said hollow cylindrical members, providing a U-shaped channel member having a top portion, cutting a circular opening in the top portion of said U-shaped channel member, said opening having a diameter which is slightly less than the outside diameter of the second cylindrical member, flaring the area adjacent to the circular opening in the channel member, inserting the second cylindrical member into said opening from the inside of the channel member, telescoping the first cylindrical member over the second cylindrical member until the flare area of the first cylindrical member is adjacent to the outside of the flare area around the opening in the channel member, and applying an adhesive between the flared surfaces.