USRE14473E - fortesctle - Google Patents

Description

C. vLE G. FORTESCUE.

TRANSFORMER.

APPLICATION FILED MAY 4. IQIE- Reissued May 21, 1918. ,47

12 $HEETSSHEET I.

. ES I l IIIII III/II III/L I I I I I I I l I I I I I I! II I ll IIIIYIIIIIIIIIII INVENTOR Charles L9G. Forfescue 7 ATT'ORNEY 0. LE 6. FORTESCUL TRANSFORMER.

APPLICATION FILED IIAY 4. I916.

Reissued May 21, 1918. 14,473.

l2 SHEETS-SHEET 2.

[ha/g4 [e6 frfescue ATITORNEY C. LE 6. FORTESCUE.

TRANSFORMER.

APPLICATION FILED MAY-4.1916.

Reissued May 21, 1918. 14,47 3.

12 SH EETSSHEET 3.

WITNESSES INVENTOR 7 [bar/es ZM/Zrfesme C. LE G. FORTESCUE.

TRANSFORMER.

APPLICATION FILED llAY 4. 19m.

Reissued May 21, 1918. 14,473.

'2 SHEETSSHEET 4.

Fig. 5.

WITNESSES: E g g g g Charles iga l 'gslescus BY ATro'RNEY C. LE G. FORTESCUE.

TRANSFORMER.

APPLICATION FIL'ED MAY 4. l9l6.

Reissued May 21,1918. 14,473.

12 SHEETS-SHEET 5- INVENTOR [bar/es Z96. fZrfescue in. m].

WITNESSES C. LE G. FORTESCUE.

TRANSFORMER.

APPLICATION FILED MAY 4. I916.

Reissued May21, 1918. 14,473.

[2 SHEETSSHEET 6.

Char/ea L26. Frfescue.

; ATTORNEY C. LE G. FORTESCUE.

TRANSFORMER.

APPLICATION FILED MAY 4. l9l6.

Reissued May 21, 1918.

a u c a mm e m a WITNESSES ATTORNEY C. LE 6. FORTESCUE.

TRANSFORMER.

APPLICATION FILED IAY 4. 1916.

Beissued May 21, 1918.

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INKBRNUKBRRKNRSNBGRSUGRRRNNI WITNESSES ATTORNEY 0. LE 6. rormscua.

TRANSFORMER.

APPLICATION '|LED MAY 4.191s.

Reissued May 21, 1918. 14,473-

12 SHEETS-SHEET 9.

WITNESSES: INVENTOR 4 WMZM. MAM

ATTORN'EY C. LE G. FORIESCUE.

TRANSFORMER.

APPLICATION FILED MAY 4.191s.

"Rcissued May 21, 1918. 14,473.

I2 SHEETSSHEET ID- ig. I l.

YI///////////////I////Z//// INVENTOR Charles LeflFarTgscue ATTRNEY C. LE G. FOR'IESCUE.

mmsronman.

. APPLICATION FILED MAY 4.19l5- Reissued May 21, 1918. .14,473

. 7 l2 SHEETS-SHEET ll.

F/glz.

WITNESSES: INVENTOR Q (fi' Char/es LeG. Forfescue.

C. LE G. FORTESCUE.

TRANSFORMER.

APPLICATION FILED MAY 4. 191a.

Reissned Ma '21, 1918. v 14,473.

l2 SHEETSSHEET lZ.

L I l WITNESSES: INVENTOR 1 Q Char/e; LeG 5r escue 60' 7 ATTORNEY UNITED STATES PATENT OFFICE.

m LE G. FOBTE SCUE, OI PITTSBURGH, PENNSYLVANIA, OR TO HOUSE ELECTRIC AND IANUI'ACTUBING COMPANY, A CORPORATION OF PENNSYL- VLNIA.

rmsronm Specification or lcluued Letters Patent. Reisgued May 21, 1918.

Original No. 1,189,468, emu Feb!!! as, 1015, Serial No. 510,:54, filed August, 1900. Application m- To all whom it may concern."

Be it known that I, Cumulus LE G. Fon- TESCUE, a'- subject of the King of Great 'Britain, and a resident of Pittsbur h in the county of Allegheny and State 0 fennsylvania, have invented a new and useful Improvement in Transformers, of which the following is a specification.

My invention relates to electrical apparatus and it has special reference 'to the windings andiasulation of transformers which are adapted for use with very high-voltage circuits.

The general object of m invention is to provide such a winding an such an insulatin structure that the stress exerted by the vo tage of the coils shall be properly dis tributed through the insulation wlth a view to reducing the space occupied by, and the manufacturing cost of, high-voltage transformers and apparatus of this class.

My invention is applicable to all ty es of transformers, but it is particularly adapted for application to transformers of the core t e.

ihe fact that the voltage which a given thickness of insulating material is capable of withstandin is dependent, not only upon the character 0 the insulation, but also upon the form of the conductors or terminals which are separated by the insulation, is well known. For. example, when two needle points are connected to the terminals of a high voltage circuit and are gradually brought nearer together in airor some other insulating medium, it has been observed that the distance between them when an arc is formed is materially greater than.the distanee between spherical terminals of rela-f tively large radlus under similar conditions. This phenomenon is due to the difference in the stress distribution in the insulating medium when the different forms of conducting terminals are used. With certain forms of terminals the stress is very much hi her 'in those portions of the insulatin me ium near one or both of the termina s than in the intermediate portions which are more re-. mote. Consequently, the insulating properties of the nearer portions are first diminished, forming a corona at the terminals,

rem fled my 4, 1818. Serial No. 95,510.

which causes an increased stress on the more remote or intermediate portion of the dielectric and results in a complete break- .down.

It is evident that when two conductors are subjected to a difference of potential, a minimum thickness of dielectric between them is required to resist any given difference of potential when their form is such that the rate of change of potential through the insulation is uniform or when the electrical potential at any point in the insulation is proportional to its distance from the terminals. Theseeonditions exist when the conductors arei'n the form of parallel plates of infinite size, and are approximately when two parallel plates which are large relative to the distance between them, or when concentric hollow cylinders, of large diameters and of great length relative to the difference in their radii, are used. Under the aforesaid condition, which may be designated as the condition of uniform stress in the dielectric,

no corona is produced but breakdown occurs at all parts of the dielectric simultaneously.

When a uniform stress obtains in the dielectric interposed between two charged parallel plates or two charged concentric cylinders, as mentioned above, a. uniform field is established in which the electrical potential at each point in said dielectric is proportional to its distance from the charged members.

' However, it is obviously impossible, in the practical construction of transformers and other electrical-devices, to maintain the most desirable conditions by modifyin the form of the current-conductin parts, but I have introduced means for efi'ecting this result independently of the form of the .coils or other conductors. By introducing a plurality of plates or conducting cylinders between the current-conducting parts, such as the winding of the transformed, and the the proper stress distribution is obtained. 'By making the areas of the conducting plates, which are'close to the high potentiaL nearest low-potential conducting body, such lio- conductor, sufiiciently large, the stress in the layers of the insulation which space them apart a may be materially relieved. Each succeeding conducting plate serves to so redistribute the stress that, by making the areas of the more remote conducting. plates substantially equal to the areas of the which tend to disturb the equality of the distribution which would otherwise be effooted and, consequently, it has been proposed to definitely fixthe potential of intermediate conducting plates by severally connecting them to proper potential points in the transformer winding or some other body which is electrically charged andfor which protection is desired. Some difiiculties are overcome by this means, but electric disturbances are liable to be introduced, by reason of the fact that the conducting plates form a series of condensers, which, under certain conditions, rupture the insulation immediately surrounding the charged conductor.

According to m present invention, I so dispose the coils o the transformer winding and so connect them to the conductors in the insulating medium as to thoroughly and effectively insulate all of the parts, the ar- 5 rangement being such, in some cases, as to produce a substantially uniform distribution of potential within the insulating medium, and in other cases, to produce a distribution similar to that which would exist 0 if the opposing surfaces that are insulated from each other were extended infinitely, or as far as possible. The coils are spaced from the core memberand from the tank or casing in accordance with their differences of potential therefrom, andthe insulation and the conductors therein are so shaped, disposed and connected with reference to the coils that all of said arts 00- operate to rotect each other wit out unduly encum ering the transformer.

It will, of course, be understood that, wherever conducting cylinders or are herein referred to as surrounding the" core legs of a transformer, interrupted c linders p or interrupted rings are meant; ot erwise,

the I" alternating flux in the core would obviously set up a short-circuited current in these parts.

My invention is illustrated in the accompanying drawings, in which Figures 1 and 2 are, respectively, a sectional plan view and a side elevation of a transformer constructed in accordance therewith; Fig. 3 is a partially sectional at ic\\' of the transformer core and windings shown in Fig. 2; Fig. 4 is a view corresponding to Fig. 3 in which insulating and conducting cylinders are disposed on all of thetransfornier core legs; Fig. 5 is a. View of a three-phase transformer core and wind- 10 ings corresponding to Fig. 3, and Fig. 6

is a view, corresponding to Fig. 3, of a transfornn-r having a divided secondary winding, one section being adjacent to the transformer core and the other section being outside the primary winding; Fig. 7 shows a modified System of comiections for the high-potential coils of a transformer which is adapted for testing pur oses when it is desired to ground one end 0 the winding and may also be used for groups of transformers which are star-connected, with their neutral point grounded on a threephase circuit; Fig. 8 is a view of a transformer in which the winding is divided. into four groups and is distributed on the four legs of a substantially square or rectangular core instead of on two legs, as is more usual; Fig. 9 illustrates an arrangement of transformer windings which is similar to Fig. 3 except that the insulating barriers between the two groups of high-potential windings are omitted; Fig. 10 is a view of a winding corresponding to Fig. 3, in which rings of conducting material are either embedded in the insulation or are located between insulating cylinders and are connected to intermediate points in the transformer windin in place of the complete conducting. c inders of Fig. 3; Fig. 11 is a view 0 a transformer having insulation composed of a series of alternate layers of insulating and conducting materials, intermediate points in the transformer winding being connected to the conducting layers through external resistances; Fig. 12 is a perspective view of an insulating sleeve having conducting cylinders which are connected to intermediate points in the winding, as in Fig. 13, but are specially constructed to introduce resistance into the condenser or capacity circuit without the use of external resistances; Fig. 13 is a front elevation of a shell type transformer embodying m invention, certain of the parts being bro an away to disclose the coils; Fig. 14 is a plan view of the core and windings shown in Fig. 13, and Fig. 15 is a diagrammaticview showin the circuit connections for the winding of igs. 13 and 14. t

Referring to Figs. 1, 2 and 3 of the drawings, the structure here illustrated comprises a substantially rectangular core 1, a lowpotential winding 2 that is divided into two groups of coils which surroundtwo opposite legs 3 and 4 of the core 1 and are separated therefrom by. insulating sleeves 5, a high-potential winding composed of two groups 6 and 7 of relatively fiat coils, in-

saluting sleeves 8 and 9 located on the revgreferably cruciform in cross-section in orer to economize space and to reduce the mean length of turn in the winding. The insulatin sleeves 8 and 9 are similar to each 7 other an each preferabl comprises a plu- I the shorter ones adjacent to the high-potential winding). By this means, the surface distances etween the conducting cylinders are made adequate to correspond to or to exceed the potential which the insulating cylinders are-capable of withstandmg.

It has beenm aim to so arrange and connect the coils o the high-potential winding as to obtain a maximum separation between the hi h-potential' coils and the core, the coils o lower-potential being disposed at shorter distances from the core member in order to utilize the space within the core member to a maximum degree. If the lowest-voltage coils of the highotential wind-- ing are grounded, they may located very close to the core structure, as shown in Fig. 2, but, if the potential difl'erence between these coilsand the core is liable to be great, they should be considerably removed from the core member. The circuit connections for the rimary windings are clearly set forth in Figs. 2 and 3, to which special refence may now be had. As here shown, a connection may be com leted from a high-p tential external circuit through a conducting lead 15, which extends through a terminal bushing to a high-potential coil 17 of the winding. From this coil, a circuit is continued throu h the conducting cylinder 13 of largest iameter of the sleeve 8 to the inner turn of a coil 18. From the outer turn of this coil, a circuit is continued through the conducting cylinder of smallest diameter of the barrier 10 to the outer end of coil 19. Circuit is similarly continued through coils 20, 21, 22, 23, 24, 25, 26, 27 and 28, the free terminal of coil 28 bein grounded or connected to the outer turn 0% a coil 29 of the group 7. The circuit is completed 'through the coils of this roup in the same wa as it was completed through the coils 0 group 6, but in the reverse order, the lead 30 being finally brought out through a terminal bushing 31. By interconnecting the coils through the conducting cylinders, which are a part of 16 and is connected at its inner end the insulating sleeves, the strains imposedupon the insulation are distributed with substantial uniformity,

ective of the areas of the conducting cy inders or the 1 thickness of the insulating cylinders which separate them. In consequence thereof, a uniform electrostatic field is produced which is mapped out by equi-potential contour lines which constitute the exposed ed of the conducting cylinders of the insu ating structure, the potentials of the cylinders being1 fixed at suitable values b ing t em to proper points on the istributed potential winding of the transformer, as indicated. This arrangement approximates the theoreticall correct structure which would obtain i the whole surface of the dielectric or insulating structure were mapped out in equi-- otential contour lines infinitely close toget er, the contour lines being conductors which are charged to the proper values by being connected toa source of potential, in this instance, the distributed potential winding of the transformer. The space occupied by the transformer may be materially reduced for a predetermined voltage, since each insulating cylinder may be called upon to resist a maximum potential connectwithout any tendency for adjacent insulatings isfree from high harmonics. In any event, the disturbances may be obviously avoided-by utilizing certain modified constructions which are hereinafter described. It is my intention to include the use of insulation of the so-called condenser type within the sco of my invention without limiting mysel in this regard.

When a transformer is designed for ve high voltage service, it may be found a vantageous to provide insulating sleeves 32 and 33 on the transformer legs 34 and 35 as shown in Fig. 4 in order to increase the area of the conducting cylinders which are located adjacent to the core member, without enlarging the dimensions of the core member itself. The advantage secured in this manner depends upon the principle which renders condensers of equal capacity desirable for insulation of thistype, the increased areas of the small conducting cylindrical members making possible a reduction in length for a given diameter. These Stl'llltlZlIPO on the sleeves are compowd of conductin cylinders 32" and 33 which are electrlca ly con.-

nected by conductors 32" and 33 to the corher and nearest to them are interconnected, the next larger cylinders are similarly intel-connected but independently of the others,

etc., as clearly shown in Fig. a

The transformer illustrated in F1 5 comprises t core 36 having three paralle legs 37, 38 and 39, and low and'high-potentlal windings disposed on each leg to constltute a three-phase transformer, each ph ase correspondingto one half of the w ndln shown in Fig. This arrangementis wel adapted for three 4 phase star connected transfOl'll'lGl'S having their neutral points grounded. The same arrangement of coils may be adapted for star-connected transformers, 1n

which the neutral point is not grounded, by

providing suflicient insulation between the high-potential coils and the core to withstand the voltage between one of the highpotential line conductors and the neutral point. D

The structure shown in Fig. 4 may, of course, be adapted for use with high-potential polyphase transformers, and thelow-.

potential windings shown in Fig. 3 may be divided into four groups, as shown in Fig. 6, instead of into two groups, a portion of the low-potential winding being disposed outside of the groups of high-potential windings, as well as inside of saidgroups. The advantages obtained from this arrangement are well known. When both endsof each of the transformer winding groups 6 and 7 are maintained at a relatively high-potential above the round, the terminals 6" and 7 which are interconnected are carried away from the core member through bushings 6' and 7" as shown in Fig. 6, in order to avoid grounding.

Reference may now be had to Fig. 7, in which the two groups of high voltage windings are dis osed substantially as they are in Fi 3 o the drawin but are so connecte that one termina is adapted to be maintained at a relatively low potential while theother is adapted for a very high, potential. If a terminal 40 is assumed to connected to a high-potential conductor, thecoil 41 to which it is connected is connected, at its inner end, to a coil 42, the circuit bein continued, through coils 43 and 44,-to coi 45. The opposite end of coil 45 is connected, through one of the conductin cylinders of the insulating sleeve 9, to cm 46 which is connected direct to the coil 47, a circuit being continued in a similar manner from the coil of one group to a second coil of the same inlegs of the core mem-' 'inders of infinite length. In other group, throu h a conducting cylinder, from thence direct y to a coil of the other group,

(:1 rcuit again being continued through a conducting cylinder. The coils are successively connected, in the order of their reference numerals, from 41 to 60, inclusive. This arrangement is specially adapted for use in transformers havingone terminal grounded or in transformers which are star-connected in groups of three, with their neutral point the desired distribution of potential, is such that the total amount of necessary insulating material is reduced to a very small quantity for high voltages, the space usually oceupied by the insulation being occupied by additional transformer coils. A substantially square core member 61, having similar groups of low-potential and high-potential coils disposed on each of the four legs of the core is provided. One terminal of the transformer for the high-potential is connected to a coil 62 which is the eutermost coil of one of the groups, from yvhich coil, a circuit is continue throughcoils 63 as indicated in Fig. 8.

The arrangement of Fig. 9 may be used when-it is desired to omit the barriers between the groups of Fig. 3, the arran ement and connections of the coils being suc as to permit of this modification. From a coil 82, a circuit is established through coils 83 to 109, inclusive, as indicated in Fig. 9. In Fig. 10, the arrangement of" transformer coils is shown which is similar to that of Fig. 3, but instead of the connections between coils being completed through the conducting cylinders which form a part of the insulating structure, a plurality of conducting rings 115, which may be embedded in an insulating bushing 116, are used. The rings. are joined by conduct-in strips 115" which form the circuit connections between coils and, consequently, the otential of each pair of rings is fixed, their ocation relative to the core member being determined by their potential. The rings are so connected to the transformer winding that the potential of each is fixed at a value which corresponds to the potential of the same surface in a field which would exist between the high potential ring and the core member if their parts were concentric conducting cylwords to 81, inclusive,

such a distribution of potential is established extend between the parts to be insulated as over the surfaces of theinsulating body that of the conductors are fixed in the present instance. that the law according to which the potentials of the conductors adjacent to the surfacesof the insulating body are fixed depends upon the shape of the surfaces of the parts to be insulated. For instance, the logarithmic law holds for concentric cylinders and the uniform law for parallel planes. With such an arrangement of parts, no conductor in the insulating structure has a definite capacity to any other conductor, but its capac- 1ty is a function of its own potential and those of the remainin conductors. Therefore, all distortion 0 the normal electric field is avoided and also the energy losses necessarily incidentto such distortion which are manifested in original structures by the necessity of supplying charging currents. In other words, if the capacity of each cylinder is a function of its own potential and the potentials of the remaining cylinders, the necessity of suppl ing charging currents is avoided and the e ectric field is'maintained uniform and undistorted. Consequently, the

potential of each conductor in the insulatingstructure, as determined by its connection to the transformer winding cannot be changed by resonance with the inductance of any portion of the winding of the transformer, be-

cause such a change would at once cause a change in capacity, which would immediately destroy the requisite condition for resonance. By fixing the potential of the conductors or, in this case, the conducting cylinders the electrostatic field thus uniformly established is independent of external influences. The internal electrostatic field is maintained constant and independent of any external influences such as may arise by external electrically charged bodies, because, if external bodies could influence the internal field, the potentials of the conducting cylinders would have to vary, but they having a fixed potential, cannot be influenced and, therefore, the internal field is maintained invariable. The conducting rings may be located between insulatin cylinders instead of being embedded in a hody of insulation, as shown. The rings do'not overlap but their edges preferably come directly opposite each other, in order to obtain the desired stre distribution in the insulation. It is evident that insulatin structures similar tothe bushing 116 may adapted to other winding arran ements and to polyphase transformers an as those illustrated It will, of course, be understood in other figures. It is evident that the conductlng rings described above may be utilized in connection with any well known winding arrangement and that this type of insulation may be combined with other types and structures of insulation within the scope of my invention. For instance, in the transformer shown in Figs. 2 and 3, or n other figures,'the spaced conductors formlng a part of the insulating structure may be connected to such points of the winding as to produce substantially the same field dlstrlbution' (logarithmic) as would exist if the outer cylinders were of infinite length.

It is immaterial, so far as the attainment of this result is concerned, whether the'conductors embodied in the insulation are cylinders extending throughout the length of the structure or rings at its ends only, so longas the said conductors determine the potentials upon the surfaces or boundaries of the insulatmg region in accordance with the logarithmic law. Since the potentials upon the surface of the insulating reg1on are main tained constant, the eflect of external bodies within the region inclosed by the surface is zero or negligible. The spaced conductors forming a partof the insulatin structure, by being connected to such-points of the winding as to roduce substantially the same field distribution as would exist if the outer cylinders were of infinite'length, render the charging currents negligible or substantiall zero since the field is uniformly distribute Referring to Fig. 11, the structure here shown comprises a plurality of insulating sleeves or bushings which are similar to those of Fi 9 except that additional barriers 117 an 118 are introduced between the two groups of transformer coils and between the groups in the tank. These barriers permit of a more compact arrangement. Theconducting cylinders, of which the insulating sleeves are composed, are severally connected to intermediate points in the transformer windings through resistance sections 119. The connections between coilsare completed through conducting strips 120, which are either embedded in insulating sleeves 121, as shown, or may be disposed between concentric insulating cylinders. By connecting the intermediate ints in the winding to the conductin cy lnders of 1118 insulating sleeves throug resistances, the thickness of the sleeves may be materially reduced, since an advanta us distribution of potential through the insulation is maintained without danger of injuring the insulation immediately surrounding the coils, voltage disturbances produced in the lates of the condenser being choked out by t e resistances.

In Fig. 12, the conducting cylinders of the insulating sleeves are provided with slots which are cut altemately from opposite no ends in order to form a zigzag ath for the capacity current, thereby intro ucinga resistance which is non+inductive and which tween the convolutions of insulating mate-- rial, during the construction of the device.

between the Referring to Figs. 13, 14 and 15 of'thedrawings, a shell type transformer is here illustrated, comprising a core member 110, low-voltage coils 111 and high-voltage code 112. 1 The hi h-voltage coils are interposed low-voltage coils and are relatively narrow, bein at the same time centrally located, relative to the adjacent walls of the core member, so that all the coils of the transformer have the same len of mean turn and are all concentric, wh1le the high-voltage coils are separated from the core member in all directlons and the low voltage coils are adjacent to thecore memher, the circuit connections which I prefer being shown in Fig. 15.

, The distribution of the static field within the insulating structure is determined, as before explained, in accordance with the potentials of the con uctors that are embodied therein, which otentials are fixed by the connections of the conductors to the coils. The distribution of the static field external to the insulating structure, however, is determined by the voltage and spacin of the coils which are adjacent thereto. 11 other words, the potential of each coil determines the potential of a plane passing through it substantially normal to the core leg that is surrounded by it. Since the connections of the coils to the conductors constituting a part of the insulating structure determine the potentials of the corresponding cylindrical surfaces that surround the core and include the said conductors, and since the said conductors respectively terminate oppo site to the coils to which they are connected, it will be seen that the ends of the insulating structure, 'or the ends of the region bounded by the said conductors, are shaped to substantially conform to the locusof the intersections of the substantially equipotential surfaces adjacent to the endsof the said structure.

Although most of the drawings illustrate windings applied to core type transformers, those skilled in the art will understand that they are equally applicable to shell type transformers and to other high-voltage being superpo structures, and I desire that modifications which do not depart from the spirit of my body, and a relatively high potentlal winding comprising a plurality of coils, of an insulatin structure interposed between said body an said winding and comprising alternate layers of insulating and conducting materials, the la ers of conducting material seed and constitutin parts of the connections between the 001 s of the winding.

2. The combination with a windin comprising a plurality of coils, of an a jacent 1nsulatin structure comprising alternate layers 0 insulating and conducting materials, thelayers of conducting material being superposedand constitutin arts of the connections between the coils o the winding.

3. The combination with a low potential body, and a relatively high potential winding comprising a plurallty of coils, of an insulating member interposed between said body and said winding, and conductors adjacent to those surfaces of said member that extend between the said body and said winding constituting parts" of the connections between the coils of the winding.

4. The combination with a ma netizable core and a winding comprising a p urality of coils, of an insulating sleeve separating the coils from the core and having a plurality of concentric conducting cylinders embedded in it. said conducting cylinders constituting portions of the electrical connections. between the coils.

5. A transformer comprising a substantially rectan lar core and a plurality of coils dispose end to end, in two groups, on opposite legs of the core, and insulating sleeves disposed between the coils and the core legs on which they are mounted, the coils being connected in a series of which the middle coils of the groups constitute the terminals. 7 i

.6. A transformer comprising a core, a plurality of coils disposed thereon end to end. and an insulating sleeve separating the coils from the core, the connections between coils being completed through conductors embedded in the insulating sleeve.

V 7. A transformer comprising a core, an

insulating sleeve surrounding a portion of the core, a plurality of coils disposed thereon end to end and connected in a series which successively includes the coilsin the order of their separation from the portions of the core not surrounded'by the coils the connections between coils being completed through conductors embedded in the insulating sleeve.

8 A transformer com rising a core, a plurality of winding coils isposed thereon and toend to form a group, and an insulating sleeve separating the coils from the core, said sleeve comprising a series of concentric conducting cylinders graded in length according to their nearness to the core and separated from each other by insulation, and the middle coils of the winding grou being connected through the conducting cy inders of largest diameter to form a series which is continued to the outer coils of the winding. 9. A transformer comprising a substantially rectangular core, two groups of coils disposed on the respective opposite legs of the core, insulating sleeves separating the coil groups from the core legs and insulating sleeves separating the coil groups from each other, each of sa1d sleeves comprising alternate layers of conducting and insulating materials and said coils being interconnected through the agency of the conducting layers.

10. A transformer comprisin a substantially rectangular core, a plura ity of coils disposed --end to endin two groups on the respective opposite legs of-the core, insulating sleeves separating the coil groups from the core legs and insulating sleeves separate ing the coil groups from each other, each of sand sleeves comprising alternate layers of conducting and insulating materials and the said coils bein connected throu h the agency of the con uctin layers to orm a series having its termina s at the innermost coils of the respective groups.

11. A transformer comprising a core having a plurality of substantially parallel legs, low-voltage coils disposed thereon, insulatin sleeves surroundin the low-voltage coils and groups of big -voltage coils surrounding the insulating sleeves, thecoils of each group being arranged end to end and connected in series from the innermost to a the outermost, and the outer coilsofeach group being, connected together.

12. In a transformer, the combination with a magnetizable core and a winding therefor, of insulatin means disposed between said core and said winding, and means constituting a part of the win ng for ren (lei-ing the distribution of stress in the insulation independent of the core member.

13. In electric apparatus, the combination 'with a magnetizable core and a winding therefor and an insulating structure-'jdis groups of coils disposed on the respective structure comprisin concentric cglinders o conducting materia separated y insulation, disposed between the, groups of coils and the core legs, of similar insulating structures disposed on the core legs not occuied by the winding, the conducting cyllnders of all of the insulating structures being interconnected according to their distance from the core.

15. In a transformer, the combination with a'substantially rectangular core, two grou s of coils disposed on one pair of opposite egs, and insulating sleeves or bushings comprising alternating concentric cylinders of insulating and conducting materials separating the coils from the core legs, of insulating sleeves disposed on the remaining pair opposite legs of the core and an insulating of opposite core legs having alternating concentric cylinders of insulating and conducting materials, the conducting cylinders of the sleeves on core legs not occupied by the coils being electrically connected to the conducting cylinders separating the winding from the core legs to increase the effective area of the latter cylinders.

16. In a transformer, the combination with a substantially rectangular core and a plurality of coils disposed end to end on one pair of opposite core legs in two similar groups of insulating sleeves comprising a plurality of alternating cylinders of insulating and conducting materials surroundin the groups and separati them from eacfi other, and sleeves or bus ings comprising concentric cylinders of insulatingbgnd conducting materials, said coil groups ing electrically connected by a conductor threaded through the insulating bushings or sleeves.

17. The combination with two conducting members, of an interposed insulatin structure, and means for establishing a dIStllblltion of potential adjacent to the surfaces of the insulating structure that extend between said members to produce a distribution of the static field in the insulating structure that substantially corresponds to the dis- 1 tribution that would exist'if the opposing surfaces of the conducting members were extended as far as possible or infinitely.

- 18- The combination with two conducting members,- of an interposed insulating structure, conductors terminating adjacent to the ortions of the surface thereof that extend etween said members, and means for fixing ;the potentials of said conductors to roduce I vexist1 for establishing a distribution of potential adjacent to the surfaces of the insulating structure that extend between said members to' reduce a distribution of the static field in 510 insulating structure that substantiall nds to the distribution that woul the opposing surfaces of the conductg members were extended as far as possible or t 20. The combination with two substantially cy1indric 1c0nduct ng members, of an interposed insulating structure, conductors terminating ad'acent to the ortions of the surface thereo that exten between said members, and means for fixing the potentials of said conductors to produce'a distribution of the static field in the insulating structure that substantially corresponds to the distribution that would exist if the conducting members were of infinite length. 21. The combination with two conductin members, of interposed insulating materia and conductors interspersed with the insulating material the potentials of which" are severally fixed at substantially the same values as would exist at the same points if the opposing surfaces of said conducting members were extended in similar form as sists in fixingthe potentials adjacent to the surface of an insulating structure that is interposed between the members at substantially the same values as would exist at the same points if the opposing surfaces of the conducting members were extended in similar form as far as possible or infinitely.

24. The method of insulating two conducting members from each other which consists in fixing the potentials of conductors adjacent to the surface of an insulating structure that is interposed between said members at substantially the same values as would exist at the same points if the opposing surfacesof the conducting members were extended in similar form as far as possible or infinitely.

25. An electrical device comprising a. winding, an adjacent insulating structure that is tapered in opposite directions from an intermediate 'point, and conductors that terminate adjacent .to the tapered faces of intermediate I ting structure that is tapered in opposite directions from an intermediate point,

and conductors that terminate adjacent to the tapered faces of the structure and c0nstitute parts of the connections between the coils.

27. An electrical device comprising a plurality of side-by-side series-connected coils, the coils of higher potential being disposed intermediate those of lower potential, an adjacent insulating structure that is tapered in opposite directions from an intermediate point, and conductorsthat terminate adjacent to the tapered faces of the insulating structure and are connected to the coils.

28. An electrical device comprising an insulatmg structure that is tapered from an rality of side- -side series connected coils, the coils of big er potential being disposed adjacent'to the intermediate portion of the insulating structure and also intermediate the coils of lower'potential, and conductors that terminate adjacent to the tapered faces of, the insulating structure and are connected to the coils.

29. A transformer comprising a plurality of side-by-side coils that are connected in a series beginning with intermediately located coils an ending with outer coils, an adjacent insulating structure that is tapered from an intermediate point towardits ends, and conductors that terminate adjacent to the tapered faces of the insulating structure and are connected to the coils.

30. An electrical device comprising a winding, an adjacent insulatin structure having its ends similarly stepp and ,conductors that terminate adjacent to the steps structure and are respecin the insulatin tively connected to intermediate points in the winding. I

31. The combination with a conductin body having a certain electrical potentia of a conducting electrostatic field flow-line intercepter mounted adjacent thereto, and means for so the potential distribution on'the surface of said interce ter that the electrostatic field between said od said intercepter and in the vicinity of said body is maintained invariable and independ ent of influences arising from charged bodies beyond said intercepter.

82. In an electrical device the combination with a plurality of side-by-side coilsections, of insulating structures respectively within and without the coil-sections each comprising spaced conductors, and connections between the coil-sections including the said conductors.

and

85 ointtoward its ends, a plu-

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