US2942217A

US2942217A - Electrical coil

Info

Publication number: US2942217A
Application number: US681405A
Authority: US
Inventors: James G Ford
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1957-08-30
Filing date: 1957-08-30
Publication date: 1960-06-21
Anticipated expiration: 1977-06-21

Description

June 21,1960 J. G. FORD ELECTRICAL COIL Filed Aug. so, 1957 |5 Linters on Conductors Limers on Insulating Spacer I NVENTOR James G. Ford.

' ATTORNEY ELECTRICAL con.

James G. Ford, Sharon, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 30, 1957, Ser. No. 681,405

Claims. (Cl. 336-205) The invention relates generally to electrical coils and more particularly to transformer coils.

This application is a continuation-in-part of application Serial Number 424,105, now abandoned, James G. Ford, entitled Layer Insulation for Distribution Trans formers, filed April 19, 1954, and assigned to the assignee of the present application.

In the art a number of methods have been adopted for holding or anchoring the turns of an electrical coil to .resist movement when subjected to the flow of current and electromagnetic forces tending to move them out of position. A commonly practiced method is to cement the turns of the coil to the layer insulation by the use of resinous adhesives. This method has not been entirely satisfactory since by filling the coil with such resinous materials it is rendered impervious ot the penetration of .oil which is essential to the building up of high impulse strength in transformers.

An object of the invention is to provide an electrical coil, the turns of which are so anchored as to offer high resistance to displacement when subjected to high electromagnetic stresses.

Another object of the present invention is to provide for preventing lateral movement of the turns of an electrical coil by providing ridges on the layer insulation which serve as obstructions to prevent lateral movement of the turns of the coil. m

It is also an object of the invention to prevent movement of the turns of a coil by providing means which anchor the turns of the coil to the layer insulation but which does not present 'an' impervious mass which prohibits the penetration of oil into the coil.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises an article of manufacture possessing the features, properties and the relation of elements which will be exemplified in the arpanying drawing, in which:

Figure 1 is a view in side elevation of a transformer with a portion cut away to show a coil embodying the invention as it is mounted and immersed in oil;

Fig. 2. is a view in section of a coil constructed in accordance with the teachings of this invention;

Fig. 3 is a view in side elevation of a portion of a coil with parts cut away to show details of the structure of a coil embodying the features of the invention; and

Fig. 4 is an enlarged view in section of a coil showing generally how it is constructed.

Referring now to Fig. l, a coil shown generally at is disposed in a transformer case 11 and immersed in a dielectric liquid 12. The construction of the coil will be described in detail hereinafter and the function of the dielectric liquid will appear as the description proceeds.

United States Patent 0 2 ,942,217 Patented June 21, 1960 In the structure shown in Fig. 2, a tube or support 13 is provided for the turns of the coil. The tube 13 may be manufactured in accordance with the general practice in the art. For example, a tube of pressboard, the layers of which are bonded together by polyvinyl alcohol, is quite satisfactory. Satisfactory tubes may also be made by scarfing the ends of a sheet of solid pressboard and then joining the scarfed ends by a suitable adhesive such as polyvinyl alcohol, cellulose acetate or a phenolic resin. However, for some types of apparatus the coil may be wound without any supporting tube or form.

The first step in building the coil involves applying to the tube or support 13 a sheet of layer insulation 14. This layer insulation is usually kraft paper treated to give it the desired physical and electrical characteristics based on the design requirements. The methods for applying such layer insulation to a tube or support are well known in the art and need not be detailed in this specification.

The layer insulation may be made in different ways. It has been found satisfactory to make it as a continuous sheet which, after or during the processing, is wound into a roll. When it is to be used, it is cut into individual sheets of the proper size and applied as layer insulation in the making of a coil.

Another method that has proved satisfactory in the practicing of this invention is to apply layers of kraft paper during the coil winding operation. In this method, after a layer of kraft paper has been applied, soft paper or linters, which will be described hereinafter, will be superimposed on the layer of kraft paper and bonded thereto. This operation is followed by a layer of turns ofthe conductor.

In order to meet manufacturing requirements the insulating material may be prepared and supplied to shops either in rolls or sheets. A long narrow sheet wound into a roll is convenient for handling.

In preparing the insulating material a sheet of kraft paper has applied thereto a coat of an adhesive, such as shellac, phenol aldehyde type resin, melamine resin, oleo resin, or any other oil insoluble resin known in the art. In applying these resins, the common practice is to first dissolve in a suitable solvent the particular resin or resins to be. utilized. In the case of shellac, alcohol will be employed as the solvent; a phenol aldehyde type resin will be dissolvedin a mixture of alcohol and aromatic hydrocarbon, such as benzene or toluene.

In the preparation of the insulating material after the adhesive, such as a suitable resin dissolved in the solvent, has been applied to the kraft paper, and While still soft or in a sticky state, cotton linters or some other suitable shredded fibrous material is applied and distributed evenly over the adhesive surface. A well known method suitable for this operation is to deliver linters or fibrous materials to the adhesive surface by means of an air stream flowing through a nozzle. It will be readily appreciated that if the adhesive is in a sticky or tacky condition, the fibers will adhere and will be bonded to the paper when the resin dries.

Linters or other fibers applied to the adhesive surface in this manner will be in a random arrangement. Many of the linters or other fibers will be only in part contact with the adhesive and will, thus, stand on end and at different angles to the surface of the paper. When the adhesive has been dried, the product will comprise a sheet of kraft paper with a layer or mat of linters or fibers firmly bonded to it. In working with this material, it has been found that linters or fibers of a length of from of an inch to of an inch, properly bonded to a sheet of kraft paper, is quite satisfactory, and good results have been obtained in building coils withsuch material.

Satisfactory layer insulation, which also is in accordance with the teachings of this invention, may be made by laminating a sheet of kraft paper and a sheet of soft paper such, for example, as the soft paper from which Kleenex is made. Other soft papers, similar to the paper from which the well-known Kleenex is made, may also be used. It will be readilyappreciated that there are a number of such papers.

The manufacture of insulating sheet by the process of laminating a sheet of kraft or similar paper and a sheet of soft paper, such as that from which Kleenex is made, may be practiced in a variety of ways. The kraft papers and the soft paper may both be employed as long continuous sheets, and the product wound onto a roll. Of course, in some instances, it may be desirable to laminate the kraft paper and the soft paper in small pieces, depending on the requirements of the operation in which it is to be employed.

In laminating kraft paper and soft paper, the laminating may be effected when the solution of resin is applied to either sheet, preferably the kraft paper, and the two brought together when the resin is in a tacky or sticky condition. Good success in bonding the kraft paper and the soft paper may also be effectedwhen the resin is in a thermoplastic state after the evaporation of the Solvent.

It is preferable in the laminating process to passthe two sheets after the adhesive has been, applied between pressure rolls. In order to help the laminating procedure, the application of some heat may give good results. It has been foundthat when heat is applied in the laminating procedure, the material produced is less likely to delaminate at the temperatures at which coils are utilized in service.

The preparation of the insulating material in rolls is desirable for plants where automatic machines are employed for cutting it into sheets or pieces of the required size for the manufacture of coils. In this way, the machines can be set to cut a large number of pieces of the desired size for the making of coils of predetermined design.

While the foregoing procedure is preferable in the making of coils in manufacturing plants where automatic machines are utilized, the linters may be'applied in other ways. In applying the linters to the kraft paper in the process of winding the coil, the procedure adopted will be somewhatdiife'rent.

In applying the linters in the making of the coil, an adhesive will be applied to the tube 13. A layer of kraft paper 14 is then applied to the tube 13. -After "the layer of k'raft paper is firmly in position, an adhesive layer, such as described hereinbefore, is applied to the sheet 14 by means of a brush or spray or some other method well known in the art; care being observed to prevent the application of an excessive amount of adhesive. Linters are then applied to the adhesive layer in some well-known manner. The most usual practice is to discharge the linters through a nozzle by the use of compressed air. In the application of the linters, they should be evenly distributed to form a soft mass on the kraft paper.

In some instances, it may be desirable to coat the linters after they have been applied with a light spray of suitable varnish or solution of resin. In this manner, a bonded spongy mat is formed on the kraft paper. The resins in solution described hereinbefore can be employed for this spray to be applied to the linters.

After the linters have been impregnated with a suit- :able resinous material, a conductor 16 is wound on the mat carried by the kraft paper. The turns of the conductor 16 are applied under some tension, so as to form a layer of turns completely across the insulating material 14. The winding conductor, under a certain tension, forms grooves 17 in the mat of the linters, and ridges 18 appear between the turns of the layer.

The linters applied in this procedure of winding a coil will preferably be of the same length as linters employed in the embodiment of the invention described for use in a plant having automatic machines. Of course, when the linters are applied in this manner, they will be in a random arrangement as hereinbefore de scribed.

It has been found that the linters or fibers which more or less stand on end arrange themselves to extend between the turns of the coil. When such a mat of linters or fibers has been impregnated with the resins in solution, the linters or fibers bond themselves to the turns 16 of the layer of turns. Therefore, when the resinous material from which the mat of linters 15 is impregnated hardens, the turns 16 of the coil will be anchored to the layer of kraft paper or layer of insulation 14. Further, the hard ridges 18 formed between the turns of the layer of turns will resist lateral movement of the turns.

The composite insulation of kraft paper, either with attached linters or laminated with soft paper, can be used either with or without resin impregnation. In either case, grooves are formed in the soft paper, as shown at 17, with resulting ridges 18 between the turns of the conductor 16. Where the soft paper is previously impregnated with a suitable resin, greater strength and greater resistance to lateral movement of the conductors is obtained.

The foregoing describes methods of "forming a matted insulation in which the conductor 16 can be readily {embedded. The mat of linters or fibers is supported by 'a layer of kraft paper of a suitable dielectric strength. In Winding the coil, successive layers of the conductor 16 and the layer material 14 are built up to give the-required number of complete turns for a coil designed to meet predetermined requirements.

It has been found for some purposes when it is desired to rigidly anchor the turns of the coil that it is desirable to apply a mat of linters or soft fibrous mater'ialto both sides of the sheet of layer insulation. When a mat of linters or the equivalent in other fibrous materialsl' has been applied to the side of the sheet 14 to be applied to the layer of turns of the conductor 16, and the next layer of turns are applied, it will press the mat of softfibers or the equivalent into position between the turns of the conductor 16. As pointed out above, the mat of linters can be impregnated with resin if desired. In the ca'se o'f a mat of linters applied to the inner face of the sheet 14 of layer insulation, the standing linters referred to hereinbefore will project between the turns of the conductor 16. If a resinous material is employed for impregnating the mat when it has hardened, ridges 18' will be formed between the turns of the conductor 16. In this matter the "turns of the first layer of the coil -10will be-firmly anchored in their respective positions and will resist movement even when subjected to strong electromagnetic forces.

The ends of the sheets 14 of the layer insulation will be folded into a V-shape as shown at 19. These V-sha'ped members will be bonded with the lin'te'rs or equivalent fibrous material employed for making the mats and together with the ridges formed on the mats will give a very rigid mounting of the end turns of the coil. Additional strength can be obtained at the coil edges by applying a coating of varnish to the crimped sections 19.

When the required number of layers of turns have been applied, a sheet of layer insulation 14' having a mat 'on only one side will be superimposed on the 'coil with the mat facing inwardly. Of course, it is to be understood that this last sheet of layer insulation couldbe applied without any mat since the next layer below will have a mat which functions to, anchor the turns of the conductor 1o. After an adequate number of layers of turns have been built up, a tube or other protective means 20 may be applied.

Nothing has been said about the size of the conductor 16 employed but it will be readily understood that the size of conductor will depend on the specification cf the coil and the duties which it has to perform.

The materials and turns of the conductor 16 have been so selected .and arranged that the dielectric 12 may readily penetrate the coil. Therefore in the case of transformers and other similar apparatus high impulse strength will be displayed when put in test or use.

Although the soft mat of material or linters have been referred to hereinbefore as being pervious to oil, it is within the scope of this invention to use material for the soft mat or use linters which are not pervious to oil. One such type of material is known in the art as glass fibers. It is also contemplated that coils of the type described herein could be used in dry type apparatus, such as air cooled or dry transformers, wherein the soft mat of material or limiters would not be exposed to oil.

Since certain changes in carrying out the above process, and certain modifications in the article which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In an electrical coil for electrical apparatus in combination, a support, a layer of insulating material carried by the support, a layer of linters applied to the layer of insulating material to form a mat, the ends of the linters extending upwardly, a resinous material applied to the linters and layer of insulating material, the resinous material being capable of bonding the linters to one another and to the layer of insulating material and of hardening, a plurality of turns of a conductor applied to the mat of linters partially embedding themselves in the mat, and ridges formed by the bonding material and the linters between the conductors, the upwardly extending ends of the linters being also bonded to the turns of the conductor, the ridges and the ends of the linters cooperating to oppose lateral movement of the turns of the conductor under stress.

2. In an electrical coil for electrical apparatus in combination, a cylindrical support, a layer of insulating material wound on the cylindrical support, a soft fibrous shredded material capable of distortion applied to the layer of insulating material forming a mat, a resinous material capable of hardening and bonding applied to the mat and layer of insulating material, a plurality of turns of a conductor so wound on the mat that the turns partially embed themselves therein, the ends of the shredded material extending upwardly between the turns of the conductor and ridges formed from the mat and bonding material which extends upwardly between the turns of the conductor, the bonding material bonding the upwardly extending ends of the shredded material to the turns of the conductor, the ridges and bonded ends of the upwardly extending shredded material cooperating to oppose lateral movement of the turns of the conductor when subjected to stresses by the flow of electrical current.

3. In an electrical coil for electrical apparatus in combination, a cylindrical support, a layer of insulating material carried by the support, a layer of linters applied to the layer of insulating material forming a soft mat, a resinous material capable of hardening and of bonding applied to the mat of linters and the layer of insulating material, the ends of the linters projecting upwardly between the turns of the conductor, the bonding material bonding the ends of the linters to the turns of the conducting material, and ridges formed from the bonding material when hardened and the linters coated with the bonding material, the ridges and the ends of the linters bonded to the turns of the conductor cooperating to hold the turns of the conductor against lateral movement, the edges of the layer of insulating material being folded at the ends of the coil to cooperate in retaining the turns of the coil in position.

4. In an electrical coil for electrical apparatus in combination, a cylindrical support, a layer of insulating material applied to the cylindrical support, a mass of linters applied to the layer of insulating material to form a soft material, a resinous material bonding the linters to one another and to the layer of insulating material, a plurality of turns of the conductor wound on the mass of linters, the conductors partially embedding themselves in the mat, the ends of the linters extending upwardly between the conductors, ridges formed between the conductors by the resinous material and linters, the resinous material serving to bond the ends of the linters extending upwardly between the turns of the conductor to the turns, the ridges and ends of the linters when the resinous material has hardened cooperating to oppose lateral movement of the turns of the conductor, a second layer of insulating material having linters bonded thereto to form a mat applied over the plurality of turns of the conductor, the second layer of insulating material carrying the mat of linters being applied with sufficient pressure to form, from the mat of linters and resinous material ridges between the plurality of turns of the conductor, the ridges formed on the opposed layers of insulating material and the ends of the linters bonded to the turns of the conductor cooperating to oppose lateral movement of the turns of the conductor when subjected to stresses caused by the flow of electrical current.

5. In an electrical coil for electrical apparatus in combination, a support, a plurality of layers of insulating material having a mass of linters applied thereto to form relatively soft mats and a plurality of layers of turns of a conductor applied alternately with the layers of insulation, a resinous material capable of bonding and hardening, the resinous material bonding mats of linters to the layers of insulation and to the layers of turns of the conductor, the ends of the linters extending between the turns of the conductor, the layers of the turns of the conductor and the layers of insulating material being so superimposed on one another that the turns of the conductor are embedded in the applied mats of linters, ridges formed in the mats carried by the layers of insulation, the ridges and the ends of the linters projecting between the turns of the conductors cooperating when the resinous material has hardened to resist the lateral movement of the turns of the conductor when subjected to stress by electrical current flowing therethrough.

References Cited in the file of this patent UNITED STATES PATENTS 673,521 Heany May 7, 1901 1,840,139 Turner Jan. 5, 1932 1,975,620 Saul Oct. 2, 1934 1,998,827 Worrell et al Apr. 23, 1935 2,172,445 Lutz Sept. 12, 1939 2,246,159 Work et a1. June 17, 1941