US2422037A

US2422037A - Electric induction apparatus

Info

Publication number: US2422037A
Application number: US443309A
Authority: US
Inventors: Konstantin K Paluev
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1942-05-16
Filing date: 1942-05-16
Publication date: 1947-06-10
Anticipated expiration: 1964-06-10

Description

2 Sheets-Sheet l W l l l u. I l

K. K. PALUEV ELECTRI C INDUCTION APPARATUS Filed May 16, 1942 @if f June 10, 1947.

Z7 Inventor: Konstantin K. Faluev,

I-lls Attorney June 10, 1947. K, K PALUEV I 2,422,037

ELECTRIC INDUCTVION APPARATUS I Filed May 16, 1942 2 Sheets-Sheet 2 4 y f/ J2 36 5 Inventor: Konstantin K. Palpev,

b9 )f7/Wat JM@ His Attorney.

Patented .Iune 10, 1947 ELECTRIC INDUCTION APPARATUS Konstantin K. Paluev, Pittsfield, Mass., assgnor to General Electric Company, a corporation of New York Application May 16, 1942, Serial No. 443,309

10 Claims. l

My invention relates to electric induction apparatus and to an insulated winding therefor and to a method of applying the insulation.

An object or my invention is to provide an electric apparatus with an improved winding structure so as to provide a relatively high space factor.

Another object of my invention is to provide a winding structure with an improved arrangement for insulating the winding and for facilitating the conduction of heat from the winding.

A further object of my invention is to provide an improved method for applying an insulating covering to a winding.

Further objects and advantages of my invention will become apparent from the following description referring to the accompanying drawing, and the features of novelty which characterize my invention. will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In the drawing Figl l is a side elevation in partial section of a transformer which is provided with an embodiment of my invention; Fig. 2 is a perspective View of a partially wound winding for the transformer illustrated in Fig. 1, illustrating a method of applying my improved insulating construction; Fig. 3 is a sectional side elevation of a portion of one of the windings of the transformer illustrated in Fig. 1 and insulated as shown in Fig. 2; Fig. 4 is a sectional side elevation of a portion of the winding of a transformer showing a modication of my invention; Fig. 5 is a side view, partly broken away, of one of the windings of the transformer illustrated in Fig. 1 and showing my improved method of applying insulation to a winding with irregularities on the surface thereof; Fig. 6 is an enlarged view of a ,portion of the winding illustrated in Fig. 5 showing insulation applied by my improved method; Fig. 7 illustrates one of the dislfcoils of one of the windings of the transformer of Fig. l, illustrating a modied method of insulating the coil; Fig. 8 is a perspective view of a strand of wire insulated for use in the disk coil illustrated in Fig. 7; Fig. 9 is a perspective view of a portion of a strip of insulating tape which is employed to insulate the coil illustrated in Fig. 7, and Fig. 10 is a perspective view of one end of the windings of Fig. 2, illustrating a modified arrangement of insulating the Coils.

In the arrangements illustrated in the drawing, I have shown my invention as applied to an electric induction apparatus such as a transformer, but it will be understood that my invention has 2 application to any other suitable electric apparatus. The illustrated embodiment of my invention includes a winding having a plurality of axially disposed coils, each of the coils having a plurality of concentric turns or strands. Solid insulation is provided on the inside and outside peripheries of the windings having a relatively,T high dielectric strength to fill up any irregularities on the outer surface of the windings and provide a smooth outer insulated winding surface. Such a structure contributes to a relatively high space factor since the dielectric strength of the lsolid insulation around the windings is in the Iarea in which corona is liable to first take place. lIn a so insulated winding a duct is provided through which a fluid may ow to conduct heat therefrom; and when the concentric turns of a Winding are connected in parallel so as to provide strands they will be at substantially the same voltage so that substantially no insulation need be providedfon the surfaces of the duct structure. In this manner a maximum amount of heat may be conducted from the various strands to a cooling fluid in the duct. The axially disposed coils are insulated from each other by an edgewise wound strip of insulating material such as pressboard and the solid insulating material` may be provided on the outer periphery of the winding by placing a wet cellulosic insulating material around the winding, and then allowing the insulating material to dry and shrink around the winding.

Referring more particularly to Fig. l of the drawing, I have illustrated a transformer including a core 26 having winding legs 2| and .22. Around each of the winding legs is provided an insulating winding structure including a winding 23 having a portion 24 wound on a suitable insulating cylinder 25 which surrounds the winding leg 2l. The winding 2s is provided with a second winding portion 2E and suitable spacers 2l lare provided between the portions so as to provide a duct through which a cooling fluid may circulate. A particular winding structure of the portions 24 and 2E will be described below in relation to the description of Figs. 2 and 3. Assuming the winding 23 to be a low voltage winding, a high voltage winding surrounds it including

portions

28 and 29. Suitable insulation may be provided between the high and low voltage windings including an insulating cylinder1 Sil and a second cylinder 3l upon which the winding section 28 is wound. The winding section 29 may be wound on a suitable insulating cylinder S2 which is spaced from the winding section 28 in any suitable manner such as by Spacers 33 so as to provide a duct through which a cooling iiuid may circulate. The high voltage winding structure including the

sections

28 and 29 may take any suitable construction such as that described in my copending application S. N. 441,782, led May 5, 1942, and assigned to the same assignee as this present invention. Around the high voltage winding may be placed another insulating cylinder 34 and a suitable electrostatic shielding arrangement 35.

The

sections

24 and 26 of the winding 23, which may be either the primary or secondary winding of any suitable electric apparatus such as atransformer, include a plurality of coils 36 which are disposed in any suitable relationship such as axially with respect to each other. Th'e coils 35 may have any suitable number of turns such as eight, as is illustrated in Fig. 3. In order to conduct heat from the winding a plurality of spacers 2l are provided for spacing adjacent corresponding turns of each of ythe coils so as to provide an axially disposed duct. The coils 3S may be formed in any suitable manner such as by winding four conductors indicated by the numeral 33, one superimposed upon the other in the method as sh'own in Fig. 2, so as to provide continuous disk coils helically wound around the cylinder 25. The spacers '21 may then be placed over the outer of the strands 38 and a duplicate coil including four more conductors 39 helically wound around the spacers 21 also by the method illustrated in Fig. 2. When the coils 36 of the

sections

24 and 26 are a low voltage winding, the

concentric turns

38 and 39 of the axially disposed coils 3S may be connected in parallel so th'at the low voltage winding includes a plurality of axially disposed coils having concentric strands connected in parallel. This connection may be made at the top by a conductor 40, and at the bottom by a similar conductor. When such a construction obtains, the spacers 21 may be provided between the outer strand 38 and the inner strand 39 with a minimum of insulation on the surface of the strands adjacent the duct, since all the strands in each coil will be at substantially the same potential. In this manner a minimum of insulation is provided in th'e path through which heat is conducted from the various strands to the iiuid which passes through the duct formed by the spacers 21.

In order to suitably insulate each of the axially disposed coils 36, strips of suitable flexible insulating material, such as a cellulosic material as pressboard, may be wound with the plurality of

strands

38 and 39 so as to form radially disposed insulating barriers 4| and 42. In providing insulation between axially disposed coils it has been customary to cut collars from sh'eets of pressboard and then stack the collars between each of the adjacent coils. It will be seen, however, that a Very great saving in material will result if strips of insulating material such as 4| and 42 may be edgewise wound with the conductors which form the coils. I have found that it is possible to edgewise wind insulating material such as pressboard when th'e strip has a suitable width in comparison with the radius of the circle or cylinder upon which the edgewise wound strip is formed and the expansion characteristic of the material. Thus, given a predetermined expansion characteristic P as a fraction of its expansion per unit of length, and if Re is the distance from the center of th'e Wound coil to the outside of the edgewise wound strip, and if Ri is the distance from the center of the coil to the inside edge of the edgewise wound strip; the insulating strip may be so wound without splitting when is equal to or less than l-l-P.

Referring again to Fig. 3 suitable insulation such as that indicated by the numeral 43 may then be placed around the outside surface of the coil 36 and spacers 44 placed around th'e insulation 43 so as to provide another duct when the cylinder 3l is placed around such a construction.

In the design of electric apparatus it is desirable to have as high a space factor as possible, or in other words to have a. maximum amount of conductor which makes up the winding for a given amount of space. In this manner a, maximum amount of kva capacity may be obtained for a given size of the electric apparatus. The amount of conductor which' may be placed in a given space in an electric apparatus is usually limited by the rate at which heat due to the losses may be conducted therefrom so as to maintain the temperature rise of the conductor within a safe maximum value, and the required amount of insulation necessary so as to suitably insulate the windings from ground and from windings which are at diierential potential so as to prevent iiashover. Furthermore, when a potential is impressed across a conductor and anoth'er object of lower potential such as ground, corona will usually develop in the space relatively close to the conductor. Therefore, anything which will contribute to raising the dielectric strength of the space in the vicinity of the conductor will minimize the amount of total insulation required to insulate that conductor from an object of a diiierent potential or ground. Such desirable results are accomplished with the structure illustrated in Fig. 3 since solid insulation h'aving a relatively high dielectric strength in the form of a cylinder 25 and suitable insulation 43 are placed contiguous with the inside and outside peripheries or surfaces of the windings. Furthermore, by providing a, duct inside the coils a relatively high heat transfer characteristic will obtain since only a minimum amount of insulation need be provided between the adjacent concentric turns or strands of each coil in view of the very small potential difference between the various turns. In the structure of Fig. 3 additional insulation in the form of the spacers 44 and a suitable insulating iiuid is provided around the insulation 43. Furthermore, when the turns 38 and-39 are connected in parallel so as to form strands of a coil conductor they will be at substantially the same potential so that a maximum amount of heat may be transferred from the strands toward the center duct so that a relatively large amount of heat may be conducted away from the strands to the fluid passing through the duct formed by the spacers 2l'. In this manner a relatively large amount of conductor may be placed in a relatively small space and the maximum temperature rise maintained at a safe value. Any suitable amount of insulation in the form of the cylinder 25 and the insulation 43 may, therefore, be provided adjacent the surfaces of the coils so as to suitably insulate the coils from either ground or another coil of different potential.

Referring to Fig. 4 I have illustrated another construction which has a very high space factor and includes the coils 36 Wound around thecyllnder 25. The spacers 21 provide the centrally disposed duct through which a cooling fluid may pass and insulating strips 4| and 42 are provided between the coils 36. Around the outer periphery of the coils 36 I provide a suitable insulation 56 which may be thicker than the covering 43 since no duct and uid insulation is provided between it and the surrounding winding which includes coils 5|. In this construction the winding provided by the coils 36 may be thelow voltage winding and the winding provided by the coils 5| the high voltage winding. Another section of the high voltage winding including coils 52 may be placed around the coils 5| with spacers 53 providing a duct. Insulation 54 is placed closely adjacent the outside surface of the coils 5| and sufficient insulation in the form of a cylinder 55 may be placed between the coils 5| and 52. However, if the coils 5| and 52 have a sufficiently low potential difference between them, or if they are connected in parallel, the insulation 55 may be omitted. It will be seen that with this construction, solid insuulation having a high dielectric strength is placed around the inside and outside peripheries of the windings, and ducts Will be provided inside the windings so that a minimum amount of insulation will be present to impede the transfer of heat from the copper to the cooling fluid in the ducts.

It will be understood that when coils 36 with their insulating members 42 are wound around an insulating cylinder that a relatively irregular surface will obtain as is illustrated in 5 and in the enlarged view of Fig. 6. Thus, the insulating strips 42 may extend out beyond the coils 35 or not quite to the surface thereof so an irregular surface will result. When a potential of sufficient magnitude is impressedbetween the surface of the coils 36 and another object, corona and breakdown will usually occur adjacent the surface 0f the conductor forming the coils 36, and corona will occur at a lower voltage when the surface has an irregular or sharp edge construction. In order, therefore, to provide an insulating surface which will ll up the irregularities and in turn provide a smooth outer insulated surface, the suitable insulating covering 56 is provided in an improved manner so that it fills up all the irregularities with a relatively high dielectric strength material and thus closely surrounds or is contiguous with the surface of the winding. The covering 50 may be placed around the winding in any suitable manner to accomplish this and I have found that an efficient way of so forming an insulating covering which lls all the crevices and irregularities is to surround the winding with a wet cellulosic material indicated by the numeral 55 in Fig. 5 and tying it in place by tape indicated by the numeral 56. This wet material may be of any suitable material, such as wet pressboard pulp. The so insulated winding is then placed in an oven and suitably heated so as to drive out all the moisture and shrink the insulation so that it fills up all the irregularities and thereby provides an insulated winding with a relatively smooth outer surface having a high dielectric strength. The insulating covering may also be Worked or molded while wet to insure penetration into the irregularities. When a so insulated winding is provided with a fluid duct inside, as is illustrated in Fig, 4, a structure will obtain which has a very high space factor. The covering 54 may be placed in intimate contact with the winding 52 in a similar manner.

In Fig. 7 I have illustrated one of the coils 36 which has suitable turn insulation S0 such as paper which is wound around the conductor which makes up the turns. Thus, the conductor 38, as is illustrated in Figo, may have a thin strip of paper 6| wound around it which will form turn insulation 60. When a plurality of conductors 38 are wound one superimposed on the other as is illustrated in Fig. 2, the outer one will be adjacent the duct formed by the spacers 2l. Since the turn insulation 60 is usually made of a relatively fragile material such as paper the turn insulation on the outer surface adjacent the ducts is liable to deteriorate and be sloughed oli" by the moving insulating fluid. This is particularly true when the cooling iluid is forced through the ducts at a relatively rapid rate. In order to prevent this, the conductor which makes the outer strands adjacent the duct may have a protective coating or covering wound around the paper 60. This protective covering may be of any suitable material, such as including a tape 62 which surrounds the paper 6U. The tape includes a core 63, as is illustrated in Fig. 9, of a suitable porous insulating material such as paper, and a strip of suitable tough material as a cellulose ester such as cellulose acetate 64 having edges 65 bent over the core 63 so as to prevent any tearing at the outer edges of the tape during its application to the conductor. The porous core 63 acts as a wick and absorbs the uid dielectric which displaces the entrapped air. Such a tape, as is illustrated in Fig. 9, may also be applied to the coils 36 by helically winding a tape as is illustrated in Fig. 10 around the outside periphery as is indicated by the numeral 66.

Although I have shown and described particular embodiments of my invention, I do not desire to be limited to the particular embodiments described, and I intend in the appended claims to cover all inodiiications which come within 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 winding including a plurality of axially disposed disk coils7 and insulating means including a strip of insulating material edgewise wound between adjacent coils when Ri-l-i-P where Re is the distance from the center of the coils to the outside edge of the edgewise Wound strip, Ri is the distance from the center of the coils to the inside edge of the edgewise wound strip, and P is the expansion characteristic of the strip per unit of length.

2. In an electric induction apparatus, a winding including a plurality of axially disposed disk coils, each of said coils having a plurality of concentric turns, turn insulation around each of sai-d turns, solid insulation adjacent the inside and outside peripheries of said winding, means spacing turns of said winding to provide a duct through which a fluid may pass to conduct heat from said winding, and a protective covering around the turn insulation adjacent said duct so as to prevent deterioration of said turn insulation due to the flow of the fluid.

3. In an electric induction apparatus, a winding including a plurality of axially 'disposed disk coils, each of said coils having a plurality of concentric turns, turn insulation around each of said turns, an edgewise wound strip of flexible eellulosic insulating material between adjacent coils, solid insulation including a layer of shrunk cn solid cellulosic insulating material adjacent the outside periphery of said Winding, means spacing turns of said Winding to provide a duct through which a nuid may pass to conduct heat from said Winding, and a protective covering Wound around the turn insulation adjacent said duct including a cellulose acetate tape having its edges folded around a strip of solid insulating material so as to prevent deterioration of said turn insulation due to the flow of said fluid.

4. A winding for an electric apparatus including a plurality of turns, turn insulation for said turns, means providing a duct in contact with said winding through which a uid may pass `to conduct heat from said Winding, and a protective covering around the turn insulation adjacent said duct so as to prevent deterioration of said turn insulation due to the flow of said uid, said protectve covering including a strip having porous insulating core and tape of a cellulose ester with edges folded around said porous insulating core.

5. A Winding for electric induction apparatus including two substantially concentric helically wound sections, each section comprising tivo interleaved contiguous helices one of which is a conductor and the other of which is a solid insulator, spacers between said sections whereby they are radially separated to form a cooling duct therebetween, a solid insulating cylinder tightly fitting the inner surface of the smaller section, and a solid insulating cylinder tightly tting the outer surface of the larger section.

6. The winding dened in claim in which said sections are connected in parallel.

7. The winding denned in claim 5 in which said conductors consist of flatwise wound radially superposed strands.

8. The Winding dened in claim 5 in which said conductors consist of individually insulated flatwise Wound radially superposed strands, and a protective covering on the strand which is adjacent said duct.

9. The Winding as defined in claim 5 in which said solid insulator is an edgewise Wound strip of dielectric material.

10. The Winding as defined in claim 5 in which solid insulation conforms to the outer cylindrical surface of said Winding.

KONSTANTIN K. PALUEV.

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

UNITED STATES PATENTS Number Name Date 783,546 Rupley Feb. 28, 1905 1,417,651 Woehr May 30, 1922 1,535,094 Bingay Apr, 28, 1925 1,825,570 Allan Sept. 29, 1931 1,874,722 Turner Aug, 30, 1932 2,195,233 Boyer Mar. 26, 1940 2,205,236 Arnold June 18, 1940 2,217,442 Hendericks Oct. 8, 1940 1,465,092 Respess Aug. 14, 1923 2,314,277 Hurd Mar. 16, 1943 914,941 Fortescue Mar, 9, 1909 1,834,114 Wiggins Dec. l, 1931 1,899,720 Putman Feb. 28, 1933 772,288 Neall Oct. 11, 1904 1,641,272 Horelick Sept. 6, 1927 2,350,887 Goff June 6, 1944 1,422,469 Olivier July 11, 1922 2,034,731 Saalbach Mar. 24, 1936 2,222,729 Ver Planck et al. Nov. 26, 1940 2,227,275 Riddle et al Dec. 3l, 1940 2,286,161 Rights et al June 9, 1942 777,148 Schweitzer Dec. 13, 1904 FOREIGN PATENTS Number Country Date 10,800 Great Britain Apr. 27, 1904