CA1133599A - Transformer with varying voltage outputs - Google Patents

Abstract

Abstract of the Disclosure A device ror transformation of alternating current-voltage which includes a core, a primary winding subassembly and a sec-ondary winding subassembly. One or both of the primary and secondary winding subassemblies consists of at least one pair of equal turn and approximately equal resistance windings wrapped co-directionally around the core, and each having an equal num-ber of tapped sections. A special tandem switch selectively interconnects tapped sections within winding pairs to provide a desired output terminal winding array such that all sections connected through the switch are energized, and are in the cur -rent carrying path at all selected switch positions, with selec-tively seriesed and selectively paralleled portions of the switch-coupled winding pairs being selectively encircuited at each switch position. The functioning primary and secondary windings are asymmetrically disposed in relation to each other at most of the switch positions, and the leakage reactance is unequal through the several paired windings when they are con-nected by said transformer switch to place less than all of the tapped sections of each in parallel.

Description

1:133S99 Background of the Invention 1. Field of the Invention This invention relates generally to alternating-current trans-former devices, and more particularly, but not by way of limitation, to an improved adjustable transformer and switching device for relatively high voltage applications, such as providing varying voltage outputs for energization of oil field equipment and the like.

2. Description of the Prior Art The prior art includes many types of adjustable transformers which include means for adjustment, not only in the secondary but in the primary, or in both widings. The prior art devices have used tapping or switching output structures for selecting the trans-former turns ratio, and therefore, for obtaining a selected voltage transformation, but most of such transformer devices have done so by merely selecting a certain portion of the overall windings in accordance with desired output characteristics. Such devices, in relatively random selection of parts of the overall windings, have failed to optimize minimization and uniformity of core and winding losses in order to effect more efficient use of the volume of winding and core space, a consideration which becomes particularly important in high voltage energization applications as here contemplated re-lative. to the present invention.
In U.S. Patent 3,083,331 to M. A. Spurway, a transformer con-struction is proposed in which a multiple winding primiary (or .~ .

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secondary) is utilized in the transformer with a selective switching arrangement in which the multiple windings thus pro-vided can be seriesed or paralleled in the primary circuit to varyin~ degrees -to provide a selective output. In the Spurway trans~ormer, the multiple windings oE the primary are disposed symmetrically in relation to the secondary, ~nd under all con-ditions of operation ol the transformer, the leakage impedances of corresponding sections of the primary windin~s, as intercon-~ nected by thê switch in respect to each other, are equal. The switching arrangement allows sections of the multiple windings to be selectively interconnected so that progressive variation LS ob~ained ~rom ~ wholly elec~rical series connection of t~e ~in~ings with each other, to wholly elec-trical parallel connec-tion.
While the Spurway series-parallel transformer winding ar-ransement provides good selective control of output voltage over a wide range of voltayes, and reduces core and winding losses, -;
its construction necessarily contemplates the placement of the several windings or sections of the primary around the core of - -the transformer by e~tending these windings or sections in oppo- `;
~,. ...
site directions around the core in order to achieve the desired symmetry in respect to the secondary winding. This is necessary :: .
in order to maintain the leakage impedance through interconnec-ted ~arts of the two primary windings or sections at an equal value. ~`
Sun~ary o~ the Present Invention ~ ;
The present invention contemplates a high voltage, adjust- l; ;
able transformer device wherein the secondary and/or primary -~
winding of the transformer is utilized in the form of pairs of ¦
:
separa-te equal turn windings, each subdivided down into an equal . ~ ~ ;,. ..

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: ' -` -` `~ 1:1335~9 . ~. .
number of tapped sections such that individual sections of each winding pair within the secondary and/or prin~ary is controlled tnrough a multi-position tandem switch of unique construction fo~ intel-connection and interaction to thereby allow a wide variation of the transformation ratio witll minimal ~ariation in winding loss and greater power and capacity within a lesser vol-u~e of physical space, i.e., a smaller mass of core and conduc-tor material The transformer~ as in the case of the Spurway transformer, makes cross connections between corresponding ends of each one of the multiple windings characteristic of either the secondary or primary o~ the transformer, so that the inter-connected windings can be selectively and progressively varied from a wholly electrical series connection with each other to a wholly electrical parallel connection with each other.
The transformer-of the present invention constitutes an im-proved cons-truction in relation to -the Spurway transformer in ;;
that the multiple windings used in either or both the primary ';
and secondary are concurrently and co-directionally wound upon the core of the transrormer and onto a common insulating paper which separates the turns of the winding, as well as the several windings, from each other. Although this construction prevents the transformer of the present invention from characteristically having e~ual leakage reactance across corresponding winding pair j~
sections during all operational modes, as is attributable to the Spurway transformer, the operation of the transformer is not thereby significantly adversely affected. The winding loss and winding tempera-ture rise resulting are only very slightly great- ~ ~ `
er than they would be if the currents flowing through the paral- !: ~:
lel paths constituted by winding sections so connected through t: :
the tandem switch were exactly equal as a result of equal

-3-reactance in the parallel connected sections.
The abilit~ to construct the transformer of the present in-vention by concurrently placin~ the multiple secondary or pri-mary windings thereof on a comn~on insulating paper.sheet with co-directional wrappin~ or winding of the turns about the core, ~ .
allot~s very signi~icant labor savings over a construction of the type advocated by Spurway, and moreover, and importantly, in-creases short-circuit strength of tl~e transformer over that char-~ acteristic of the Spurway device. This results from the winding of the conductors forming the multiple windings of the primary or secondary upon a co~mon insulating material, as opposed to ~ .`
utilizing two separated insulation sheets wound in opposite di-rections at different times as required in the Spurway construc-tion. :~
Broadly described, the transformer of this invention com- `
prises a core, a primary winding wound about the core and a `.
secondary winding wound abou-t the core. Either the primary ~ ;
winding or the secondary winding, or both, are divided into one .;.
or more pairs of subwindings. The subwindings within each pair are characterized in having an equal number of turns, and an `:
approximately equal resistance. The subwindings within each ;;~
subwinding pair are physically separated from each other, and are wound co-direc-tionally abou-t the core upon a c~n~on physi~
cally integrated insulating material which physically intercon- -nects the subwindings within each subwinding pair, and resists their separation from each other under short circuiting forces. :~
The subwindings within each subwinding pair are characterized in having an equal number of tapped sections.
A special tandem switch in-terconnects the subwindinys with-in each pair to each other so that, by the use of.the tandem

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:1133599 switch, the tapped sections within each subwinding in ~he L~air can be selec~ively interconnected to place equi~alent numbers o~ tapped sections in each of the paired subwindings in paral-lel, with the remainder of ~he sections in series, within the circuit which contains the paired subwindings. The special tan-dem switcn thus functions to selectively interconnect tapped sections within subwindings of each pair of subwindings to pro-vide a ~esired output terminal winding array such that all of - the sections within each subwinding pair are energized, and are in the current carrying path at all of the optional switch pGSi-tions. By reason of the co-directional winding of the sub- ~ ~' windings wi-thin each subwinding pair about the core of the ,~
translormer, coupled with the manner in which the special tan-dem switch is used to selectively place certain tapped sections of such subwindings,in parallel with each other, the paralleled sections of the subwindings are, at most of the selected switch positions, asymmetrically disposed in relation to the other winding or windings (primary or secondary) of the transformer ~
employed to induce current flow in t~e subwindings, and the . :
leakage reactance is therefore unequal through the several -' ' paired tapped sections of such subwindings.
In a preferred embodiment of the inven-tion; the leads from '~
the secondary subwinding pairs are extended to a special com- ..
pound tandem switch assembly which comprises a pair of spaced .
tandem rotary switches mounted on a supporting structure in l~''' :~';
staggered or offset relation to each other to facilitate acces-sibility to each of the switches, and the ease with which the leads from the tapped subwindings of the transformer can be connected thereto. Each oE the tandem rotary switches includes a common operator shaf-t and handle which functions to concur~

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, rently advance a pair of wiper elements between selected sub- ~-windin~ lead terminals connected to tapped sections of each of the subwinding pairs. The switch terminals to whlch the respec-tive subwinding leads are connected are spatially orien-ted to minimize overlap and in-terference between incoming leads, and are physically spaced and supported by minimum structure of economical character.
An im~ortant object of the present invention is to provide - a transformer which can be more easily and economically con-structed due to the manner in which the windings of the trans-former are placed about the core, which economical construction is accomplished ~ith minimal increase in windin~ and core power losses, and in windins temperature increase during operation.
An additional object of the invention is to provide a ;;
transformer which i~ of high short-circuit strength.
A further object of the present invention is to provide a transformer having an improved switching structure for selec- ~
~ively con-trollins the input or output voltage at transEormation --ratios over a wide range.
Another objec-t of the invention is to provide a transformer ;~
.... .. ..
ha~ing increased power handlin~ capability relative to its size and weight.
Yet another object of the invention is to provide a trans-former of adjustable transformation ratio, in which transformer the ~lu~ in the core remains substantially constant, i.e., the core loss remains substantially constant.
A further object of the invention is to provide an adjust-able transformer wherein all winding portions are used during all output and/or input tapped positions employed in adjus-ting ~;~

the transformation ratio.
.~:

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`` 1133~9 Yet another object of the invention is to provide an adjustable transformer device capable of providing a wide range of voltage variations at substantially constant voltage-ampere output as compared to previous types of transformer devices, and wherein the winding losses are minimized and are approximately equal for all adjusted voltages.
Another object is to provide an improved compound tandem switch assembly for use in a transformer which has multiple pairs of secondary or primary subwindings.
Thus, a transformer according to the present invention comprises a first electrical winding; two physically spaced inductive subwindings having an equal number of turns therein `;
and each of said subwindings having a plurality of first through n + 1 section outputs connected thereto with each - ;
consecutive pair of section outputs defining first through n winding sections each having a predetermined number of turns within the respective winding section; means for inductively -linking said first winding with said two inductive subwindings;
and switch means having two synchronously operative wiper contacts, each wiper contact being in coaction with a respective plurality of first through n + 1 selectively connectable contacts which are connected to a respective one of said first through n + 1 section outputs for a respective one of said subwindings, said wiper contacts coacting with said selectively connectable contacts for selectively inter-connecting respective ones of said winding sections of each of said subwindings in parallel with each other to provide co-directional current flow therein and for concurrently placing the remaining winding sections, if any, of said subwindings which are not in parallel in electrical series with those winding sections which are in parallel. -Additional objects and advantages of the invention will be evidence from the following detailed description

- 7 -- 1~33S9g when read in conjunction with the accompanying drawings which illustrate the invention.
Brief Description of the Drawings Figure 1 is a side elevation view of a transformer constructed in accordance with the present invention and illustrating a portion of the transformer can or housing hroken away to illustrate components positioned inside the housing.
Figure 2 is a schematic illustration of the trans-former outside its housing, and illustrating, with the coreremoved, the manner in which the primary and secondary windings of the transformer are disposed in relation to each `
other.
Figure 3 is a sectional view taken along line 3-3 of Figure 2.
Figure ~ is a sectional view through a portion of the primary winding used in the transformer. ;
Figure 5 is a schematic drawing of an adjusta~le~
tran~formèr ~èvice~-c~nstructed-in-accordance with the present invention.
Figure 6 illustrates multiple views of paired sub- ~
windings interconnected in different switching positions, ;
along with "' - 7a -:~' ;''"-, :~133599 their respective calculated losses for the condition of equal turns per section of each winding. It is here assumed for pur-poses of the calculations that the turns of all are of equal reslstance and that the current divides equally and that the wincding is carrying the same volt-ampere rating at all positions.
Figure 7 is a side elevation view illustrating one type of compound tandem rotary tapping switch employed in the trans-former of the present invention.
_ Figure 8 is a front elevation view of the tapping switch illustrated in Figure 7.
Fïgure 9 is a sectional view taken along line 9-9 of FicJure 7.
Figure 10 is a rear elevation vie~ of the switch illustra-ted in Figures 7-9.
Figure 11 is a side elevation view of a different embodi-ment of a compound rotary tapping switch which can be utilized in the transformer of the present invention.
Figure 12 is a sectional view taken along line 12-12 of -Figure 11. ~ -~
Figure 13 is a rear elevation view of one of the two rotary tandem switches utilized in the compound rotary tapping switch -sho~n in Figure 11. ;
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Figure 14 is a sectional view taken along line 14-14 of Figure 13.
Figure 15 is a sectional view taken along line 15-15 of Figure 13.
Figure 16 is a sectional view taken along line 16-16 of Figure 13.
Figure 17 is a sectional view taken along line 17-17 of Figure 16. ,

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.,', '~;''' ~133599 Detailed Descrip-tion of Preferred Embodiments o:E the Invention Referring initially to Fiyure 1 of the drawin~s, the trans-former o~ the invention as there illustrated includes a gener-ally cylindrical housing 10 in which the trans~ormer core and 5 windin~, desi~nated ~enerally by reference numeral 12, are loca- .
ted. Pairs o~ insulated secondary terminals are provided on the outer side of the housing. In the illustrated and ~escribed em-bodiment of the invention, two pairs Xl, X2, X3 and ~4 of said _ secondary te~minals are provided in correspondence to the t~o ~ :
pairs of secondary subwindings to which reference ~ill be herein-a~ter made ~t the upper side of the transformer, a pair of primary insulated primary terminals Hl and H2 are provided.
The trans~or~er structure located inside the housin~ 10 in-cludes a so~t iron core 18 of low-loss ~rai~ oriented silicon lS steel in a distributed gap construction. The windings o~ the trans~ormer are wrapped about a leg of the core 18 extending centrally there-through, and are enclosed within an insulating paper shell 20. A group 22 of electrically conductive leads ~ :
e~tends from a pair of subwindings constituting one portion of ~;
the secondary of the transfo.rmer, and a second group 24 of elec- ~:
trically conductive leads extend upwardly from a point of con- .~. .
nection to tapped sections within a second pair of subwindings constituting another portion of the secondary of the transformer. ^
The leads 22 and 24 are connected at their upper ends to a pair `
25 of compound rotary tandem switches 26 and 28 which selectively ~
interconnect.various corresponding winding sections within the ~ .
two pairs of subwindings of the secondary to provide ad]ustable transformation of voltage from the primary input to the second-ary output. Appropriate switch structure for connecting input alternating current to the primary winding of the transformer is _9_ :' `~

` ~.133~i99 . .
disposed on the outer side oE -the housing 10 at the opposite side thereof from that shown in Figure 1.
Figures 2-4 of the drawings illus-trate the manner in which the windings of the transformer are oriented and constructed.
The core 18 has been removed from the windings to facilitate description of the winding construction. In ~igure 2, which is a somewhat schematic illustration, the central opening which re-ceives one leg of the core is designated by reference numeral 30 - and is surrounded by a suitable relatively stiff paper insula-10 ting ma~erial 31. A winding mandril is inserted in this opening for purposes of forming the windings therearound.
In laying on the windings of the transformer, there are `
,. . .~
initially concurrently wrapped about the core opening 30, in a plurality of generally concentric wraps, a pair of spaced sec-ondary subwindings which will be hereinafter alluded to as S-A
and S-B, and which are so designated in the drawings. Each of the subwindings S-A and S-s consists of a plurality of super-- , . .
imposed convolutions of a flat, elongated sheet or strip of thin ~ , aluminum metal. Such sheet as used in subwinding S-A is desig- ~-nated by reference numeral 32 in Figure 3. The aluminum sheet .,.. ~ :
32 of the subwinding S-A as schematically illustrated includes - concentric convolutions 32a, 32b, 32c, 32d and 32e. In actual-ity, in the construction of the transformer, a much greater ;~
number of concentric convolutions of the aluminum sheet 32 will be wrapped about the central core space 30 as the transformer is -~constructed.
Interpositioned between adjacent convolutions of the alumi-:.
num sheet 32 are a plurality of sheets 36 of strong paper having ~
electrically insulating properties. Each sheet 36 of the insu- ;"

lating paper will be perceived -to extend completely through the .,:`, ~-'`
- 1 0 - ' ; ` ~ : '`'`''`' ~ "'`' ' :,-~, . , ~` 1133599 axial thickness of the windings of the transformer as measured in a direction parallel to the ~lat faces of the aluminum sheet conductors as they are wound in concentric convolutions. The interposed sheets 36 of insulating paper carry a thermal settin~ ;
adhesive on opposite sides thereof so that a bond is establish`ed between the abutting surface areas of con-tact between the alu-minum sheets in each convolution o~ the subwindings of the secondary and the contiguous sheets of insulating paper. It - should be pointed out that each convolution of the aluminum sheet 32 extending around the central core opening 30 may be thought of as including one or several turns of the subwinding S-A for purposes of the discussion which follows.
In similar manner to the method of placement of the concen-tric coils or turns of the subwindings S-A about the winding mandril, convolutions or turns of the secondary subwinding S-B
are also concentrically wound about the central core opening 30.
The subwinding S-B is also made of an elongated sheet of elec-trically Gonductive aluminum metal, which shee-t is designated by reference numeral 38. The several convolutions of the sheet conductor 38 are designated by reference numerals 38a, 38b, 38c, 38d and 38e. As in the case of the subwinding S-A of the sec-ondary, the several convolutions of the subwinding S-B can be ` ~`
considered as one or more separate turns of this subwinding `
susceptible to tapping in selected increments of the total sub- ~-winding as hereinafter explained.
It will be noted in referring to Figure 3 that the super-imposed convolutions or turns~of the subwindings S-A are axially ~;`
spaced from the superimposed convolutions or turns of the sub-winding S-B.
In the construction of the transformer, the subwindings S-A `

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1~L33S9~
and s-s are wound about -the core opening 30 occupied by a rotat-ing winding mandril during winding of the coiis of the trans-former. r.~indin~ is commenced by initially placing one end of each oE the aluminum conduc-tor strips 32 and 38 opposite each other so that the winding of these conductor strips is commenced concurrently and at the same location in rela-tion to the core opening 30. The winding then proceeds by rotation of the wind-ing mandril with concurrent feeding of the elongated strips of - sheet aluminum to the subwindings being formed. The sheets of aluminum conductor are fed superimposed upon a sheet of paper insulating material 36 so that as each convolution is completed, the underlying pairs of transversely spaced convolutions in the subwindings S-A and S-B are covered by a sheet of insulating paper 36, and are thereby insulated from the nex-t succeeding convolution or turn of the aluminum conductor. This procedure is continued until the two subwindings S-A and S-B are built up with the total number of turns therein which may be desired in the particular transformer under construction. The location of ~ -these two subwindinys of the secondary is that which is shown ln Figure 2 as lying between the dashed line 40 and the central -~
core opening 30.
As the sheet aluminum conductors 32 and 38 are wound about the central core opening 30 to build up the several turns within the subwindings S-A and S-B, the winding is intermittently ar-rested and elec-trical leads are extended from these conductors at certain points spaced along the length thereof. Thus, at the commencement o~ the winding o~ the sheet conductors 32 and 3~
an electrically conduc-tive lead 101 is secured to the flat face oE the convolu-tion or turn 32a of the conductor 32, and is en-cased within a flexible tube of electrically insulating material .

-` 1133599 44. In like fashion, an electrically conductive lead 110 is e~tended in a flexible tubular insulator 48 past the convolu-tion 32a of the conductor 32, and is attached at one end to the convolution 32a of the sheet conductor 38. In similar fashion, a number of additional electrically conductive leads are con- -nected to each of the sheet conductors 32 and 38 at spaced in-tervals therea`long. Corresponding pairs of leads to the two sheet conductors are located at equally spaced in-tervals along _ -.he respective sheet conductors so as to define between spaced leads secured to each of the sheet conductors, equal numbers of turns within corresponding lead spacing intervals.
For purposes of discussion, it will be assumed that nine of such leads are s~aced along the length of each of the sheet con-ductors 32 and 38 so as to terminate at a final lead 109 pro~ec-ting outwardly from the final convolution 32e of sheet conductor 32, and a final lead 118 projecting outwardly from the final con-volution 38e of sheet conductor 38. Interpositioned at spaced intervals along the sheet conductors between the leads 109 and ~;.
118 located at the end of the final and outlying convolutions thereof are the leads 102-10~ attached to the sheet conductor 32, and the leads 111-117, attached to the sheet conductor 38.
This arrangement is schematically illustrated in Figure 5. It will be understood that each of the leads 101-118 is insulated .
by ~ fle~ible sleeve of insulating material of the type typified ~``
by the sleeves 44 and 48. ~;~
After the subwindings S-A and S-B of thè transformer sec- ' ondary have been wound around the central core o~eniny 30, tlle winding of the prîmary P of the transformer is commenced. The primary P is constructed of suitable copper or aluminum wire and ~ `
is wound around the subwindings S-A and S-B of the secondary in . ,,, ~ . ., ; .

:1133599 that space lying bet~een the dashed lines 40 and 50 on the Figure 2 schematic illustration of the transformer windings.
It will thus be noted that the primary lies radially outwardly from the secondary subwindings S-A and S-B, and the coils of the primary are further displaced radially ~rom the innermost convolutions or turns 32a and 38a o~ the sheet conductors 32 and 38 than from the outermost coils or turns 32e and 38e of these sheet conduc-tors. It-is important to keep in mind this asymmet-~ rical relationship between these two generalized locations of parts of the subwindings S-A and S-B of the secondary in rela-tion to the primary winding when the operation of the trans-former is subsequently discussed herein.
The detailed construction of a portion of a suitable pri-mary winding is illustrated in Figure 4. A plurality of turns ~
of the copper or alu~inum conductor 52 are wound in superimposed ';;
concentric relation upon each other, and in side-by-side rela-tion about the secondary subwindings. The copper or aluminum conductvr 52 carries an insulating film material which allows the turns to be laid down in contiguous side-by-side relation as the primary is being wound. After one layer across the transverse dimension of the transformer has been laid down, this layer of the contiguous side-by-side turns of the primary is covered with a sheet 54 of paper material. Second sheets 55 ~ ~
of paper insulation material are then extended over suitable ~ `
spacer blocks 57. The spacer blocks 57 are spaced at random ~- -intervals around the underlying primary winding layer, and be-tween it and overlying layers of contiguous turns of the con- ~
ductor 52. The spacer blocks are preferably constructed of a ;-;
high density paper press board and are bonded by a suitable ad- ~' hesive to the paper sheet 56. The spacer blocks function to ~

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-` 1133S9~ .
space random contiguous layers of the primary winding from each other, and thus allow circulation of oil through the primary.
At -the beginning and end of the primary winding, a pair of elec-trical leads 58 and 60 are secured to the conductor (see Figure 5) and are extended upwardly from the body of the windings simi-larly to the manner in which the leads 22 and 24 from the sub-windings S-A and S-B from the secondary are extended upwardly within the housing 10. The lead 58 is surrounded by a tube or ~ sheath of insulating material 62 as illustrated in Figure 4.
On the radially outer side of the primary winding, and on the opposite side thereof from the subwindings S-A and S-B of the secondary, an additional pair of secondary subwindings S-C
and S-D are located. Tllese subwindings S-C and S-D are wound co-directionally around the primary by concurrent winding of a pair of elongated sheets or strips oE aluminum conductors in exactly the same manner in which the subwindings S-A and S-B are wound. The subwindings S-C and S-D, of course, lie to the out-side of the line 50 shown in Figure 2. A plurality of electri-cal leads are attached to the aluminum sheet conductors making up subwindings S-C and S-D, with the method of attachment and the spatial arrangement of these leads being substantially iden- ~
tical to that which has been described as characteristic of the leads 101-118 which are attached to the sheet conductors 32 and ; .~ :
38 oE the subwindings S-A and S-B. As will be better understood from the following discussion and a consideration of Figure 5, the several leads which project upwardly from the subwinding S-C .;
are, in consecutive sequence, from the start to the end of this .
subwinding as spaced therealong, denominated by reference numer~
als 128-136, and the leads attached at spaced intervals to the subwindin~ S-D are denominated by reference numerals 119-127.

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~13359~31 In ~i~ure 5 of -the drawings, the schematic illustration o~
the arran~ement of the primary and secondary windin~s is illus-trated, showing the leads ~rom the several subwindings of the secondary and the manner in which these leads are connected to tandem switches for e~fecting adjustment of the voltage trans-formati~n ratio in a manner hereinaf-ter described. The priMary winding P is, as previously explained, connected at its opposi~e ends to leads 58 and 60 ~7hich termi~ate at appropriate input _ terminals ~1 and H2. These terminals are, as previously s~ated, mounted on an outer side of the transformer housing 10. It should be understood that the primary winding P may be a tapped primary ~ihicn includes an interchangeable series-parallel input scheme, or the primary may be cons-tructed of several subwindings in a manner similar to the construction of the secondary winding network as hereinbefore alluded to, and subsequently discussed in detail.
It should further be understood that where the terms "wire"
an~ "wiring'` are used herein, these terms are used in the broad sense o~ including electrical conductors which can be either round or of other shaped cross-section, and such terms will also `~
be employed -to include the aluminum sheet conductors employed in the secondary subwindings.
The secondary network includes a firs-t pair of subwindings S-A and S-B positioned at a location radially within the primary ;~
winding P of the transformer, and a second pair ot subwindings S-C and S-D positioned at a location which is radially outward of the primary winding. Each oE the subwindings within each of -the two pairs of subwindings is identical in winding composition, i.e., subs-tantially equivalent wire parameters and equal numbers oF turns are characteristic oE each subwinding within a given '"~
-16- ~

" ~.
, ' '~ `' pair. Moreover, in the illustrated embodiment of the invention, all of the wire parameters and numbers of turns in all four of the subwindings are equal to each other, although in other embodiments not illustrated, the number of turns within the subwindings in one pair might d:iffer from the number of turns within the subwindings of another pair.
Each of the subwindings S-A, S-D is divided by tapping into a plurality of equal-turn winding sections 60, 62, 64 and 66, respectively. The leads 101-136 hereinbefore described as being connected to the several secondary subwindings S-A, S-D, thus constitute plural tapping or section leads, and these leaas are illustrated in Figure 5 as terminating at their ends opposite the ends connected to the aluminum sheet conductors used in the secondary subwindings in terinals positioned to be contacted by wiper elements of compound tandem selection switches hereinafter described in detail. It is to be noted that for an n number of winding sections within a subwinding, the number of leads extending from the n sections as section leads or outputs is n + 1. It should be pointed out, for ~
better comprehension of the following discussion, that, though ~ ~ -four subwindings of the secondary have been illustrated, any number of pairs of such subwindings can be utilized so that subwindings up to an even number n can be included in the apparatus. In the illustrated embodiment, each of the sub~
windings includes an equal number of turns, and is therefore of equal rated voltage, but each of the respective ones of the subwindings S-A, S-D need not necessarily be equal to all ;~
others, since it is only required that equality apply to respective ones of first through n winding sections 60-66 as between each inductive winding. This flexibility of construc-tion will be better understood as the invention is further explained subsequently herein.
The first novel compound tandem rotary switch 26 to . .

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~ ~3~S99 which the leads 22 from the subwindings S-A and s-s are connected includes a first switching section 26a. Contacts or terminals at the ends of leads 101-109 coact with a switch wiper contact arm A. A second switching section 26b includes a wiper arm B which contacts terminals at the ends of leads 11~-118. More generally, each switching section includes n ~ 1 selectable contacts or terminals, each of which is connected to a respective one of the n -~ 1 section outputs of the corresponding subwinding; and each wiper contact arm is movable from a first through an n + 1 position relative to the n + 1 selectable contacts. Wiper arms A and B are mechanically interconnected as shown by mechanical linkage 78, and undergo tandem movement so that rotational movement of the ~-wiper arms will always maintain them in the same relative angular orientation. Thus, when wiper arm A is on the terminal -of lead 104, wiper arm B will be on the terminal of lead 115.
From the described arrangement and construction of the compound tandem rotary switch 26 and its interaction with ;
the leads from the secondary subwindings S-A and S-B, it will ;;;
thus be seen that the leads from the several equal turn sec-tions of secondary subwinding S-A are contacted in consecutive sequence, running from the terminals 101 to 109, as the wiper :;:
arm A of switch section 26a is rotated. It will further be , perceived that the terminal of lead 109 is connected via a '~
suitable lead or conductor 80 to the wiper arm B of switch section 26b. The contact or terminal at the end of lead 101 `~
is connected via lead or conductor 82 to the output terminal -Xl hereinbefore described. In like manner, but opposite in orientation, respective successive ones of the leads from subwinding S-B are interconnected to the wiper arm B. Contact or terminal 110 is connected via a lead or conductor 86 to wiper arm A of switch section 26a, and contact 118 is ;
connected by a conductor 88 to the output terminal X2.

- ` 1133599 In similar fashion, the equal turn sections of subwindings S-C and S-D are similarly connected through the leads 24 to a second compound tandem rotary switch 28 which includes tandem functioning wiper arms C and D. Thus, .secondary subwinding S-D

~. ,.
,: , ~, .

:
: :.
:-: ;;~

. ~,, :
:.
~' ',,"~-,~

:

- 18a - ., ,~I'.. i'' ~' 1~335~9 and each of the equal turn sections thereof are connected by the previously described leads 119-127 to contacts or terminals at the ends of -these leads, with the contact at the end of lead 127 being connected by a lead or conductor 94 to wiper arm C, and the contact or terminal at the end of lead 119 being connected by lead or conduc-tor 96 to output terminal X3. Switch section 28b is wired in the same manner as switch section 26b, and the wiper arm C successively contacts the terminals at the ends of - leads 128-136, but in opposite rotational sequence to those con-nected to switch section 28a. The contact at the end of theterminus of lead 128 is connected by lead 97 to wiper arm D, while the final contact at the end ol lead 136 is connected by lead or conductor 98 to output terminal X4. In the compound tandem rotary swi-tch 28, the wiper arms C and D are similarly mechanically interconnected for rotational synchronization by a mechanical linkage 100. ~ ~
In operation, the transfor~er of the invention is particu- : , larly desirable for certain types of high voltage equipment energization, such as that required in downhole operations in ;~ `
oil field wor~. Many times, in the oil industry, there are dif- .~
~: ~
ferent values of operating electrical loads required, and it is desired to have a transformer device, such as that of the pres-ent invention, which can be utilized to provide any of the -~ `
various required voltages, and to enable rapid set-up and oper- ~ -;
ation of equipment. Thus, primary taps need not be used to change secondary voltage, although primary tap variation still remains an option within the contemplation of the present inven-tion to accommodate multiple primary voltages in some instances.
No ma-tter what output voltage is selected through interactive function of the compound tandem switches 26 and 28, the core . ' ' ' ':

~L133S~9 flu~ of the transformer will remain substantially constant.
That is, upon selection of the desired output voltages, which include selected shorting of output terminals Xl-X4 as between series and parallel operations, and attendant selections by 5 means of compound tandem switches 26 and 28, all winding sec- ~`
tions within the several secondary subwindings S-A through S-D
are u~ilized to enable more efficient utilization of subwindin~
space, conservation of core and packing ma~rials, and a de-~ crease in cooling requirements.
It is requisite that when the several output terminals from the secondary are connected in parallel (i.e., Xl-X3 and X2-X4), all oE the rotary wiper arms A,.B, C and D of the switches 26 and 28 must be in the same angular position. When output con-nection of the several terminals Xl-X4 is in series, the rotary tandem switches 26 and 28 may be offset or removed from each other, i.e., the position of wiper arms A and B may differ from the wiper arms C and D in terms of advance to the various se-~uenced terminals at the end ol the respective leads of the re- `"
' spective secondary subwindings.
?
Adhering to these criteria, and assuming ideality in the transformer construction and the premise tha-t the resistance of each turn within each subwinding section is equlvalent to the resistance in every other turn within each subwinding section, -~
,:
`~ the transformer losses will remain very nearly constant through- ~
out the entire top range. The core loss and primary winding ; ~`
loss will remain constant for a selected voltage and kilovolt .
ampere (kVA) rating, and the secondary losses will vary from a minimum at the extreme switch positions to a maximum at the ourth position of the tandem swi-tch wipers, which maximum is only 12.~ percent higher than such minimum. This loss factor is ~ .

`:
. ! ;

~133599 based on a constant kVA output and eight equal winding section increments or switch steps, and assumes equal current division through parallel paths, as typified by the schema-tic illustra-tion in Figures 5 and 6.
The manner in which the loss factor varies is illustrated in Figure 6 of the drawin~s, which shows different switchable ;;
connections of secondary windings S-A and S-s by the respective tandem switch 26 associated therewith, and its wiper arms A and - s. The calculated loss is illustrated for each case.
Before discussing Figure 6, it should be pointed out that the purpose of illustrating -the variation in the loss factor as illustrated in Figure 6, and assuming ideality in the sense Gf equivalent resistance and equivalent leakage reactance in each parallel turn of each subwinding, is to show the manner in which transformers constructed in accordance with this invention, and including a plurality of selectively series-parallel intercon-nected subwinding sections, attains advantage with respect to conven-tional transformers in which the selective interconnection of sectors of paired subwindings partially in parallel and par~
tially in series is not employed. It will be understood from the subsequent discussion herein that neither leakage reactance nor resistance is precisely equivalent in the case of each of the turns within each subwinding of the secondary of the trans-former of this invention, and that therefore such ideal trans-former analysis is not strictly applicable to the -transformer of this invention. Nevertheless, the foregoing and immediately following discussion dealing witll Figure 6 illustrate the ad-vantages which characterize transformers of both the type herein presented and under discussion, and that type which is typified ;~
by the disclosure of Spurway U. S. Patent 3,083,331. The com- ;
'.' . .

-1133~99 parative merits oE the transformer of this invention vis-a-vis a transformer of the Spurway type are dealt with hereinafter.
Referring to Figure 6, the diagram 140 illustrates the complete parallel switching connection as is shown in Figure 5, i.e,, wiper arm A of switch 26 is on the terminal or contact at the end of lead 101, and wiper arm B is connected to the contact or terminal at the end of lead 118. Thus, assuming the lead -resistance negligible, each winding section within each sub-winding S-A and S-s has a rated voltage E and a resistance such that a rated current I can be equated in -terms of power rating or volt-ampere rating (VA).
~hat is, for the situation of an assumed eight equal wind- ~
ing sections, ~ ' I VA (1) Since parallel resis,tance will be equal to 82R , then ` ,' Loss L = 4R(VA)2 = R ~V~)2 (2) Loss L = .0625R(E-The diagram 142 illus-trates a situation wherein the wiper '~
arms A and B are moved in a clockwise direction by one position to the contacts at the ends of leads 102 and 117 from the sub~
windings S-A and S-B, respectively. In this status, the rated voltage would be equal to 9E, with resistance equal to 72R ~ 2R or llR , which in terms of loss equates L llR (VA) = 0679(VA) or about 1.0864L (3) Similarly, for the midpoint switch position as shown in ~ , diagram 14~, i,e., wiper arm A on the contact at the end of lead ' 105 and wiper arm B on the contact at the end of lead 114, the rated voltage will be 12E with a resistance of 2R + 8R, or ''`' ' ''', '' . .

' `.' :.:
' `

335~9 sum of 10~, and the loss equates as L4 = 1R(1-2-E) = 0694(E-) or l~ L (4) The loss value may be similarly equated for each of the remaining diagrams 146 and 148 which illustrate rotation through the cycle o~ wiper arms A and B until the diagram 148 configura-tion wherein the subwindings S-A and S-B are completely in ser-ies. It can be noted that in the series configuration, the loss factor L is once again at its unity or lowest value. At no time .;, during the s~itch rotation or successive series-paralleling ar-rangement will the loss have more than a 12.4 percent increase over the unity value L. Tt can be shown that for any -tap ar-rangement, this number never increases above 12.5 percent. This ' is indeed a minimal factor, especially when considering that the loss in the secondary winding is generally less than 40 percent -~
of the total loss of the transformer.
., ~. ,.
! It will be apparent in referring to Figure 6 that the current induced in the subwindings S-A and S-B of the secondary must, of course, flo~ in the same direction through the inter-connected paralleled sections of the respective subwinding as the tandem switch 26 is switched to various positions to place equivalent sections of the subwinding of varying numbers of turns in parallel with each other. It is also true that current i flowing in the secondary windings of the transformer must flow in contiguous windings in the same direction around the core, rather than in opposite directions, in order that the magnetic `~ :
`~ flux around each adjacent winding not be cancellative with re- -spect to the ma~netic Elux in the other adjacent winding.

In any transformer in which the leakage impedance of the ;~ paired paralleled sections of switch interconnected subwindings ;~ 30 is to be equal for all conditions of operation of the trans-` ,!
~ -23-' ' ,, ~33S99 former, tne paralleled subwinding sections must be symmetrically located in relation to the other winding of the trans~ormer which functions to magnetically induce current flow in such paralleled subwindings. Stated dif~erently, in a transformer, 5 ~or exam~le, in which sect}~ns within sub~7indin~s of a secondary are selectively placed in parallel, as in the present invention, if the deside~atum of equal leakage impedance to current flow through these parallel sections is to be met for all conditions _ of operation'of the transformer, the paralleled sections of the subwindings must be equidistant and spatially symmetric in their ~-location and position with respect to the primary of the trans-Former. Othe~.~ise, a dif~erent leakage reactance component impedance will necessarily characterize the two subwindings.
~hen the described necessary attributes of current flow through the subwindings of the transformer are considered, it will be seen that the symmetry condition for equal leakage im-pedance ~annot be met in a transrormer construction in which the subwindings are wound side-by-side and co-directionally about a central core space. For example, when Figure 6 is considered, .. . :: .
it will be noted that in the switch position illustrated by dia-gram 1~2, the turns of the aluminum sheet conductor 32 which are between leads 102 and 109 are in parallel with the turns which are between leads 110 and 117 extending from the aluminum sheet conductor 38 forming the second subwinding S-B. It will further be noted that the first group of paralleled turns of the alumi-num sheet conductor 32 of subwinding S-A arè displaced to the -right with respect to the location of the turns in that portion of the subwin~ing S-B which are connected in parallel therewith.
This schematically illustrates that spatial displacement which ~ ~`

... .
actually e~ists wi-thin -the transformer, as cons-tructed, as a -24- ;

;~ .
'~

~L33599 result of ~he -turns of subwinding S-A which lie between leads 102 and 109 being located radially closer to the primary winding than are the turns of the subwinding S-B which are positioned between leads 110 and 117. When diagram 144 of Figure 6 is con-sidered, it Will be perceived that the displacemen~ of theparalleled sections of the two subwindings S-A and S-B becomes even more pronounced. This is to say that it is necessary to proceed further along the alun~inum sheet conductor 32 which makes - up subwinding S-A toward the end thereof, and through a greater number of wraps around the central core opening, before the lead 105 is reached and the paralleled section is placed in the cir-cuit, -than is true of the portiQn of the subwinding s-s which is then in parallel as a result of the position of the switch at ~ this time. The latter section lies relatively further in a 15 radial direction fro~ the encircling primary than does the sec-tion of the subwinding S-A which is paralleled, and which is between tne leads 105 and 109. Symmetry thus cannot exist in this status of the transformer -- that is, when the switching position is such that sections are paralleled in the manner shown in 144 of Figure 6, and thus equal leakage impedance : :, across the paralleled sections does not exist at this time. The ;~ ~
sa~e asymmetry and lack of equality of leakage impedance is -true : ~:
of all the switch positions attainable except that shown in dla-grams 140 and 148 of Figure 6 in which subwindings S-A and S-B ;~
are fully paralleled or fully seriesed.
! In one type of transformer construction, a desideratum has been to provide equal leakage impedance across paralleled sec-tions of subwindings in order to reduce the winding loss and winding -temperature characteristics of the transformer. To at- .

tain such equal lea]cage impedance, it is necessary that sub-:' -25- .. `

- ~L1335~9 windings employed be disposed symmetrically in relation to that inding of the transformer utilized to induce current flow in such subwindings, whether it be the primary or the secondary.
~Ihere the primary is the winding ~hich is subdivided into a pair o~ subwindings, as ty~i~ied by the transformer described in Spurway U. S. Patent 3,083,331, this means that the two sub-windin~s of the primary, as thus provided, must be disposed in a symmetric relationship to the secondary winding, and it fur-- ther requires that the paralleled sections of the primary sub-windings through which divided current flows during operation of the transformer must also at all times be symmetrically disposed in relation to the secondary.
This condition necessarily requires that the convolutions or wraps of the two subwindings of the primary must be turned in opposite directions about the central core opening of the trans-former. Winding the convolutions o~ the conductors in the two sub~7indings in opposite directions requires either very compli-cated and expensive machinery and equipment for concurrently passing the conductors in opposite directions around the core, ~O or winding of the two subwinding conductors at different times during the manufacture o~ the transformer. In either case, the ;~
cos~ and expense of manufac-turing the transformer is relatively high.
~loreover, in a transEormer construction which seeks pre- ;
cisely equal leakage impedance through the paralleled sections of subwindings, as in the Spurway construction, the requiremen-t to extend the several convolutions of the subwindings in oppo- ~ ;
site directions about the core makes it essential that insula-ting materials positioned between contiguous overlying convolu-tions be separat~:Ly placed for each of the two differen-t .;~
subwindin-~s. In the -transformer construction of -this invention, as has previously been e~plained, the sheet of insulaking paper employed can be placed beneath the axially spaced aluminum shee-t conductors used in each of the two subwindings concurrently during the winding of the subwindings as a result of their co-directional winding. This greatly improves the short-circuit strenqth of the transformer since, in the event of short-circuitiny of the transformer, the significant forces which are ~ developed and tend to separate the subwindings from each other, thus damaging or destroying the transformer, are strongly op- ~-posed by the bonding strength afforded by the single or unitary sheets of paper extended between the spaced subwindings and bonded to each convolution of the two subwindings.
The advantages described with respect to the construction of the transformer of the present invention in terms of reduced ~ `
cost or e~pense of construction and higher short-circuit streng-th in the finished transformer more than offset the slight-ly greater reduction in power loss which can be realized where the subwindings of the transformer are oppositely wound and placed in symmetrical relationship to the current-inducing wind-ing. Thus, for e~ample, comparative calculations for power loss ~
resulting in the secondary subwindings of the transformer of the ;
present invention, as compared to a similar transformer construc-ted in accordance with the Spurway patent, were developed. The calculations were developed Eor a status in which two subwindings of the secondary in each type of transformer were interconnected : ,.. .
so that the number of parallel sections in the S-A subwinding and the S-B sub~inding of the present transformer were compared to an equivalent number of paralleled sections in a Spurway-type ~;~
(counterwound) transformer.

` '' ~'; "

,~ ,', ~33599 Equal output terminal current conditions in the two -trans-formers were assumed, and the necessary condition that current flow divide equally between the paralleled sec-tions of the sec-ondary subwinding in the Spurway-type transformer was used in the calculations. It can be demonstrated that counterwinding equivalent conductors of each subwinding not only will result in equal leakage reactance of parallel sections, but will also re-sult in equal resistance of parallel sections. This fact was ~ used in the c-alculations. It can further be shown that the im-j 10 pedance characteristics of a section of a subwinding is inde- -~
pendent of its direction of rotation about the core. Thus, sec-tions of subwindings which occupy corresponding radial locations will have identical impedance values, regardless of whether the coil is co-directionally wound about the core, as in the present invention, or is counterwound about the core in a transformer of the sort disclosed in the Spurway patent. `
For the purpose of calculating the relative power loss in a pair of secondary subwindings, a 50 kVA transformer of the -present invention was tested to determine the impedance charac-teristics (both resistance and leakage reactance) of each indi- ` ~`~
vidual section of each subwinding, using standard testing metllods employed in the art. ;
.
In the test unit of the present invention, the impedance characteristics of parallel sections varied from the conditon of equal resistance and equal leakage reactance when the sub- ;
windings were fully parallel (that is, all of the sections in `~ one subwinding were in parallel with all of the sections in tlle second subwinding~ to the condition of approximately 10% differ- ~`
ence in resistance and 46~ difference in leakage reactance when ~ `-only one sec-tion of each subwinding was placed in parallel with ' ~:
-2~- ~
"' `- 1133599 a single section of the other subwinding.
Usin~ the measurements obtained by the standard testing technique being used, the secondary win~ing ~ow~r loss was -then calculated for several different series-parallel-series connec-tion arrays of both the co-directionally wound (present inven-tion) secondary pair, and of the counterwound secondary pair. A
-list of power loss calculations based on the impedance measure-ments obtained is set forth in the following Table.

- Illustration Connection of Sections in FIG.6 Calculated Power Loss, Watts u Counter~-oulld Series Parallel Series Present InventiGn Tr~lsfol~er 1 7 1 142 160.1 157.9 2 6 2 not shown 164.9 162.0 3 5 3 not shown 165.6 162.5 4 4 4 144 163.7 160.9 6 2 6 not shown 156.3 154.8 7 1 7 146 151.9 151.1 From the tabulated power loss values, it will be seen that a maximum of only 3.1 watts higher power loss results in the paired secondary subwindings of the transformer of the presen-t invention -than is the case in ~imilarly interconnec-ted series and parallel sections of the subwindings in a counterwound transformer. This maxi~uln power loss occurs when five of the sections in each sub-winding are placed in parallel with each other, leaving three sections of each subwinding connected in series with the paral-leled sections. This slightly greater secondary winding power loss is negligible compared to total power losses inherent in `
transformer operation which, in transformers of the general type uncler discussion, will total around 800 watts. Moreover, tlle slightly higher power loss which is characterïstic of the trans-former of tlle present invention as compared to a paired counter-wound subwinding t:ransformer is more than offset by the greater ;~ `
economy of construction, and the greater short-circuit strengtil ~

:~, -29- ~

~L~33599 wllich characterizes the transEorrner of this invention.
Figures 7-10 illustrate one embodiment of the dual tandem rotary switches 26 and 28 used in the transformer of the inven-tion. The switches 26 and 28 are mounted upon an F-shaped supporting frame 154 which includes a web portion 156 having a top leg 158 projecting normal to one end thereof, and a rela-tively shorter intermediate leg 160 projecting normal to the central portion thereof.
- The switch 26 includes a terminal plate 162 secured to the outer end of the top leg 158 by means of an angle bracket 164.
T~e terminal plate 162 is made of a suitable material of elec-trically insulating properties. A plurality of lead contacts or terminals are secured at spaced circumferential intervals in cir-cular array around the terminal plate 162. Ea~h of the termi-nals, in the illustrated embodiment, is in the form of a threaded bolt extended throu~h the contact plate 162, and having a nut threaded upon the shank of the bolt on the opposite side of the terminal plate Erom the head ofthebolt. It will be noted that terminals 101-109 which project through the upper half of the ;
plate in a semicircular array project through the terminal plate `~
with the shanks outwardly and facing away from the web portion ;~ ~
156 oî the frame 156, whereas the terminals 110-118 positioned ;; ~`
in the bottom portion of the terminal plate 162 are positioned ~-with the threaded shank portions thereof faciny toward the web ~;
portion 156 of the frame 154. -~
A switch shaft 170 of electrically non-conductive material `
is extended throuyh suitable journals or bearings in both the web portion 156 of the frame 154 and the center of the terminal plate 162. The outer end of the shaft 170 is retained in i-ts posi-tion extended through the terminal plate by means of a ~, ~ ' ''; ~
' ~

~3359~ . `

cotter key 172 e~tended through the shaft and bearing against a washer 174 as shown in Figure 10. The washer 174 in turn bears flatly a~ainst the rotary wiper arm plate B. The rotary wip~.r arm plate B is constructed of copper or other suitable electricall~ conductive material, and is keyed to the shaf-t 170 for rotation with the shaft. It will be noted that the outer end of the wiper arm pla~e B is provided with an aperture 175 and is positioned to selectively contact the rounded head of one of the ~.
bolts which form the terminals 110-117 circumferentially spaced in semicircular array around the terminal plate 162 as herein-before describe~. The rotary wiper plate B flatly bears against a fixed common terminal plate 176 which does not rotate with the .
sha~t 170, and extends outwardly and is secured by means of the nut 178 to the threaded shank of a bolt constituting terminal 109 in the upper sem~circular arra~-. This bolt thus concurrent-ly functions as both a common terminal, and as a tap point for contact by the rotary wiper arm plate A as hereinafter described. ~ :.
At the opposite side of the terminal plate 162, a cotter key 180 is e~tended through the shaft, and a helical compression F
spring 182 is positioned between the cotter key and a ~asher 184 ~;
which bears against the rotary wiper arm plate A. The rotary wiper plate A is keyed to the shaft 170 for rotation therewith, but is axially movable on the shaft so that it is continuously X;.-.:
biased axially along the shaft by the resilient urging of the ~ `~
compression spring 182. The rotary wiper plate A is configured at its apertured outer end so that it can make selective contact with the rounded heads of the terminal bolts 101-109 arrayed in ~ :
a semicircle, and positioned on that side of the terminal plate --162 which faces toward the web por-tion 156 of the fraMe 154.
The rotary wiper arm plate A bears against, and is in contact -31- .
,. .~' :

:` ~133599 with, an electrically conductive common terminal plate 188 which is secured a-t its ou-ter end to, and is in electrical con-tact withr one of the bolts constituting ter~inal 110.
The end portion of the shaft 170 which pro~ects on the oppo-site side of the web plate 156 from the termiinal plate 162 is .
journalled -through a hub 190 which is connected to the web por-tion 156 of the mounting plate 154, and supports an apertured position indicator plate 192. It will be noted in referrin~ to ~ Figure 8 that the apertured position indicator plate 192 carries a plurality of semicircularly arrayed position apertures, and I .
that a plurality of numerical indicia are placed adjacent these apertures so that they are numbered from "1" to "9". ~ ~-At its outer end, the shaft 170 carries a handle assembly 194 which includes an elongated handle 196 keyed to the shaft 170 so that rotation of the handle will cause rotation of the shaft 170. The handle 196 carries a threaded locking bolt 198 which is threaded through the handle adjacent an end thereof i~
3~ .,.,. .:
which is opposite the indicator plate 192 so that the locking bolt, during rotation of the handle 196, is consecutively . -aligned with one of the position apertures 1-9 ln the indicator !~ ~.
plate 192. On the opposite side of the point at which the ,~
handle 196 is connected to the shaft 170 from the end of the handle which carries the locking bolt 198, the handle carries a .
~,,j: ~ :.. ;
stop pin 200. The stop pin 200 is positioned to contact one of the lower edges of the indicator plate 192 when the handle 196 ~." .
is rotated on the shaft 170 to such position for contact. This limitation on the extent of rotation which the handle 196 can ~ . .;
undergo assures that the rotary wiper arm plate A will not be ~ ~;
permitted to rotate,- as the handle is turned, to a point where it passes the extreme terminals 101 and 109 in the semicircular ~, :
-32- i `

5~

~13~S9~
array of terminals at the upper side of the terminal plate 162.
The limiting action of the stop pin 200 also similarly limits the rotary wiper arm plate s to movement across the bolt heads ~'~
constituting parts of the terminals 110-118 disposed in semi-circ`ular array around the bottom portion oftheterminal plate 162.
The tandem rotary switch 28 is constructed similarly to the switch 26. Thus, the switch includes a terminal plate 202 se-~ cured by an ahgle bracket 204 to the intermediate leg 160 o~ the F-shaped supporting frame 154. The terminal plate 202 is made of a suitable electrically non-conductive material. A series of bolts having threaded shanks are ~Ised as contacts or terminals, and a semicircular array of spaced bolts project through the ~
upper portion of the terminal plate 202, and constitute terminals k 119-127 as hereinbefore described. Oppositely projecting bolts are extended through the lower portion of the terminal plate in semicircular array and constitute terminals 128-137 as herein-before described. L
A switch shaft 206 of electrically non-conducting material is extendecl through suitable journals or bearings in botn the web portion 156 of the frame 154 and the center of the terminal - ~ plate 202. The outer end of the shaft 206 is retained in posi-tion through the terminal plate by means of a cotter key 208 . ~ .
extended through the shaft 206 and bearing against a washer 210 as shown in Figure 10. The washer 210 in turn bears flatly against the rotary wiper arm plate C which is constructed of k copper or other suitable electrically conductive material, and is keyed to the shaft 206 for rotation therewith. It will be noted that the apertured outer end of the wiper arm plate C is configured and positioned to selectively contact the rounded ; ~ .
--33-- f ,': ;

.
head of one of the bolts which formthe terminals 128-136 spaced in semicircular array around the lower portion of the terminal plate 202 The rotary wiper ann plate C bears flatly against a fi~ed common terminal plate 212 which does not rotate ~ith the shaft 206 and e~tends outwardly and is secured at its outer end by means of nut 214 to the threaded shank of a bolt constituting te~minal 127 in the upper semicircul.ar array of terminals. The s co~mon terminal plate 212 is, of course, of an electrically COII-~ duc~ive material.
At the opposite end of the ter~inal plate 202, a cotter key 216 is extended through the shaft 206, and a helical compression spring 218 is positioned between the cotter key and a washer 220 ~$
w'nich bears a~ainst the rotary wiper arm plate D. The rotary wiper arm plate D is keyed to the shaft 206 for rotation there~
15 wi~n, but is axiallymovable on the shaft so that it is continu-ously resiliently biased a~ially along the sha:Et toward the ter~
minal plate 202 by the resilient urging of the compression spring 218. The rotary wiper arm plate D is configured at its outer end so tha-t it can make selective individual contact with the rounded heads of the terminal bolts 119-127 arrayed in a semi- ~
circle and positioned on that side of the terminal pl~-te 202 which faces toward the web portion 156 of the frame 154. The rotary ~.~iper arm plate D bears against, and is in contact with, ~ ~ -an electrically conductive common terminal plate 222 which is secured at its ou-ter end to, and is in electrical contact with, one of the bolts constituting terminal 128.
The end portion of the shaft 206 which projects on the ~ ~
opposite side of the web plate 156 from the terminal plate 202 ~ ;
is journalled -throu~h a hub 224 which is connec-ted -to the web portion 156 of -the mounting plate 154, and supports an apertured . '~ , ~;' '.

~33S99 position indicator plate 226. I-t will be noted in referring to Figure 8 that the apertured position indicator plate 226 carries a plurality of semicircularly arrayed position apertures, and ~ ;
that a plurality of numerical indicia are placed adjacent these ':
apertures so that they are numbered from "1" to "9".
At its outer end, the shaft 206 carries a handle assembly designated generally by reference numeral 228. The handle assem~
bly 223 includes an elongated handle 230 keyed to the shaft 206 so that rotation of the handle will cause rotation of the shaft. ~, The handle 230 carries a threaded locking bolt 232 which is ~ .
threaded through the handle adjacent an end thereof which is ~ -opposite the indicator plate 226. The locking bolt 232, during ~
rotation of the handle 230, is consecutively selectively aligned t~j:
~ith one of the position apertures "1`' to "9" in the indicator plate 226. .......................................................... h The switch assembly made up by the tandem rotary switches 26 and 28 is mounted upon the housing 10 of the transformer so that the switch handles 196 and 230 are accessible on the outer side of the housing as shown in Figure 1. The leads from the ~ -secondar~ subwindings S-A and S-B and constituting leads 101-118 ,~
(included in the generically described group of leads 22) are :
brought up from the coiled subwindings to the location of the bolts constituting the terminals 101-118 on the terminal plate ~ ~`
162. Here the ends of these leads are connected to the terminal ~ ~
bolts by the use of the nuts carried on the thrèaded shanks of r~' '`
these bolts. It will be noted in referring to the manner in which the switch 26 is constructed that the leads 110-118 are brought up and secured at their ends on one side of the terminal ~' , plate 162, while the leads 101-109 are brought upwardly in the ~ p"
housing 10 and secured on the opposite side of this terminal -`" 1133599 plate. Ease of installa-tion and connection of the transformer leads, and ready access to them with clear identiflca-tion, are therefore characteristic of the switch construction and method of its use in the transformer.
In similar fashion, -the leads 128-136 from the subwindinr~ i-S-C are brought up~ardly within the housing lo and the en~s thereo~ secured to the bolt terminals 128-136 secured in semi-circular array around the lower portion of the terminal plate ~ 202. The leads li9-127 are extended upwardly and are secured to the bolt terminals 119-127 at the opposite and upper side of I ~
the terminal plate 202. !` :
t has previously been explained that in the operation or ~ne transformer of this invention, as illustrated by -that em-bodiment of the transformer which includes the two pairs of sec-ondary subwindinc~s S A and S-B, S-C and S-D, the rotary tandem s~itch 26 works by rotating the wiper arms A and B thereof in synchronism, so that corresponding terminals or con-tacts on the ~ ~
several leads are contacted in each rotary position of the ~ ~;
switch. This is accomplished in the switch embodiment illustra- ~ ~
ted in Figures 7-10 by rotating the switch handle 194 to a point i ;
where the locking bolt 198 is positioned opposite one of the apertures "1" - "9" in the indicator plate 192. It will be per-ceived that the nine positions constituted by these nine aper-tures correspond to the nine possible positions of the wiper arms ~ ~`
A and B of switch 26 as shown in Figure 5. Correspondingly, i`
there will be a different selected secondary output voltage de-veloped at the ter~inals Xl and X2 as the handle 194 is rotated ;~
to a selected one of the "1" through "9" positions. The locking bolt 198 can then be threaded farther through the handle and into the selected one of the aligned apertures "1" - "9" in the indi- ~`

~.

':

~i33~9 cator plate 192. 5ui-table informational indicia are provided upon a data plate (not shown) secured to -the outside of the transformer 10 to permit the operator to determine the posi-tion ~.
to which the handle 194 should be moved in order to deliver a certain voltage at the terminals Xl and X2 by selective inter-connec~ion of segments of the subwindings S-A and S-s in the manner hereinbefore described, and as shown in Fi~ure 6.
It will be noted that in the method of connecting the leads -- 101-118 from subwindings S-A and S-B which has been hereinbefore described, the lead 86 between the wiper arm A and the terminal 110 as schematically illustrated in Figure 5 corresponds to the ! ~ -non-moving common terminal plate 188. The stationary common ¦;
terminal plate 176, on the other hand, functions to constantly interconnect the wiper arm plate B with the terminal 109. The shaft 170 to which the movable wiper arm plates A and B are con-nected for concurrent rotation corresponds to the mechanical ç
linkage 78 schematically illustrated in Figure 5 of the drawings.
It is believed that the foregoing description of the manner ~:
in which the tandem rotary switch 26 is operated and is construc-ted will provide sufficient illustration of the manner in which ~ :
the tandem rotary switch 28 is constructed and operates. The ~:
wiper arm plates C and D are concurrently moved to corresponding '~
selected positions of contac-t with selected ones of the termi-nals 119-136, and this switch is also characterized in having ~: .
stationary common terminal plates 222 and 212 which link the " ;
wiper arm plates D and C with the terminals 128 and 127 in cor-respondence to the leads 97 and 9~, respectively, as schemati-cally illus-trated :in Figure 5.
It should further be poin-ted out that the leads 82 and 88 which project from the terminals 101 and 118 to the secondary -37- l` :

i.: ' output terminals ~1 and ~2 are located in the upper portion of ;~
the housing 10 of the transformer, and extend from terminals 101 and 118, as carried on the terminal plate 162, upwardly to a point where they are secured to portions of the terminals Xl and X2 located on the inner side of the housing 10. The same ar- -;
rangement is characteristic of the leads 96 and 98 which project from terminals x3 and X4 mounted on the upper side of the housing 10 of the transformer. It will be perceived that the projection of the secondary outpu-t terminals Xl-X4 on the outer side of the housing 10 of the transformer permits a series or I ~
parallel external interconnection of the paired subwindings S-A, ¦ ;
s-s, and S-C, S-D when it is desired to further vary the output voltage of the transformer, or to selectively interconnect and ¦
employ one or both pairs of the secondary subwindings.
The compound ta~dem rotary switch assembly illustrated in Figures 7-10 of the drawings provides the clear advantage of compact construction in which the terminals connected to the several leads from the secondary subwindings are commonly car- ~ ~
ried on terminal plates and are oriented thereon so that the ~ `
leads can be e~tended to the points of connection to the termi- i nals without interference with each other, and in a way to fa-cilitate rapid and immediate identification. The wiper arms of the two rotary tandem switches are commonly carried on a non-conducting shaft for concurrent, synchronized movement, and the switch assembly is constructed in a way which permits certain common conductor plates to be connected to à bolt type terminal ~ `~
which therefore functions both as an anchor point for the common ~ ;
plate, and as a tap point for the movable wiper arm located on the opposite side of the terminal plate.
A single compressive member or spring is employed on each ~133~;99 of the sha~ts of the two swi-tches to maintain both wipers in a constantly biased s-tatus in which bo-th are in contact with the co~non plates on opposite sid~s of the terminal plate, and are also spring-loaded so as to assure consecutive or sequential contact, during rotation, with each of the rounded bolt heads :constituting the terminals. In this regard, it should be point-ed out that the apertures which are provided in the ends of the .~iper arms A-D provide a sensory indication to -the operator of the switch assem~ly when contact is made between the wiper arm and the terminal as the aperture slips over and mates with the rounded heads of the bolts used as terminals. The two shafts :~
employed on the switches 26 and-28, in extending through a com- :-mon frame, assure that rotation or movement of either terminal plate and associated terminals and wiper arms forming the re-maining portions of the switch as associated with each of the two shafts.
~ different embodiment of the compound tandem rotary switch assembly utilized as a part of the transformer of the invention ~ ~ .
. is illustrated in Figures 11-16. The compound tandem rotary :~;
switch assembly there illustrated is desiynated generally by :reference numeral 240 and is s'nown mounted within a section of the wall of the housing 10 of the transformer. The switch assem~
; bly 2~0 includes a single elongated indicator plàte 242 which .- -replaces the two indicator plates 192 and 226 in the embodiment ., .
of the switch assembly shown in Figures 7-10, and as such in- .
~ cludes the two sets of position apertures "1" - "9" as herein-.~ before described. ~ -~
Projecting through suitable journal hubs 244 and 246 se- -~ ~
cured to the housing 10 are shafts 248 and 250, respectively, : ~`
` 30 which form parts of the respective tandem rotary switches 26 and ~
: - .
~; -39- ~

`` :: '~`

.~ '' -- " 1133599 .
28. The shaft 248 is connected at its end on the outer side of the housing 10 to a handle Z52, and the shaft 250 is similarly connected to a handle 254, also disposed on the outer side of the housing. As previously described in referring to the switch S assembly shown in Figures 7-10, each of the handles 252 and 254 carries a threaded locking bolt 256 which can be extended into registering position apertures in the indicator plate 242 as the handles are rotated to selected switching positions.
- On the opposite side of the wall of the housing 10 ~rom the indicator plate 242, the shaft 250, after projection through the journal hub 246, is keyed to a hub 258. The hub 258 is connec-ted by four radial spokes or web elements 260 to a large annular wiper ring supporting plate 264. The hub 258, spokes 260 and wiper ring supporting plate 264 are constructed of an electri-cally non-conductive material, and are preferably molded inte-grally as a single piece. The wiper ring supporting plate 264 ;~
carries on its side opposite the hub 258, an annular flange 266 which extends normal to the plane of the wiper ring supporting -~
plate. The îlange 266 is provided with a plurali.ty of lugs 268 ~;
which function conjunctively with the flange in retaining a pair of generally semicircular wiper rings 270 and 271 of electrically -conductive material in a peripherally extending position around ~`~
the outer edge of one side of the wiper ring supporting plate ;~ `, 264. One of the ends 270a and 271a of each of the wiper rings 270 and 271 is stopped against a stop flange 272 by turning such end portion of the wiper ring upwardly through a recess in the plate 264 at this location (see Figure 12). ~ ;
An end portiol~ 270b of the wiper ring 270 opposite the end 270a is bent radially inwardly at an angle, passes through an accommodating gap in the annular flange 266, and has a contact ";
i ' -` ' '' ' ~40-~"', ;' end portion 270c which projects radially inwardly to the inner edge of the plate 264 and is there retained between a pair o-f studs 276 formed on the side o~' this plate 264 which is oppo-site the hub 258.
It may be noted at this point in the discussion that the semicircular wiper rings 270 and 271 correspond to the wiper arms C and D of the switch 28 and this correspondence will be better understood upon the subsequent discussion of the compound ~:
- s~itch assembly 240 under discussion. It will also be noted in re~erring to Figure 13 that the respective wiper ring ends 270a ana 271b an~ 270b and 271a are electrically isolated from each other by the stop flanges 272.
The tandem rotary switch 28 further includes an electrical-ly non-conductive synthetic resin terminal ring, designated gen-~rally by reference numeral 280. The terminal ring 280 includes a circular terminal anchoring band 282 which is of circular cross-section and oE a diameter which is slightly greater than ~ ;
the inside diameter of the plate 264 so as to extend under the :~
ends 270c and 271c of the wiper rings 270 and 271. A series of : `
angularly spaced, radial insulating fins 284 project radially outwardly from a shaft-receiving central hub 286 which is rota-tably mounted around the shaft 250 on the opposite side of the ~-.
plate 264 from the hub 258. The terminal ring 280, fins 284 and hub 286 are preferably lntegrally molded, and are resiliently ~ :i biased toward thewiper ring supporting plate 264 by a compres-sion spring 287, which bears against the hub 286, and a retainer `~ i`
~ey 288 e~tended through shaft 250. ;
Near their ~uter ends, each of the radial insulating fins 284 is secured to the terminal anchoring band 282 in the manner best illustrated in Figures 11, 13 and 14. It will be noted in -...
-'Il- ,, ,. ,.,.,.. ;, ;, ,, ~.

. ., . , , , , , . ; : . ~

refèrring to ~i~ure 14 -that eacl~ radial insulating fin 28~ is joined to the terminal anchor ring 282 at a location where the terminal anchor ring is provided with a cam stud 290 having a rounded surface facing the side of the wiper ring plate 264 which carries the semicircular wiper rings 270 and 271.
Two pairs of angularly spaced, con~lon conductor insulating ~anes radiate outwardly from the hub 286, and include vane pair 292 and 294, and vane pair 296 and 298. At their radially outer ~ ends, the co~mon conductor insulating vanes 292 and 294 carry a retaining toe 300 which projects normal to the plane of the wiper ring plate 264 and extends across the outer periphery of this plate as shown in Figures 11 and 16. An identical retain~
ing -_oe 302 is carried at the radially outer ends of insulating vanes 296 and 298. Each of the toes 300 and 302 has a hollow interior in which is located a resilient helical compression spring 304 (see Figure 16). The location of the compression ;~
spring 304 in the respective hollow retaining toes 300 and 302 is immiediately opposite one of the semicircular wiper rings 270 ~ i or 271.
As shown in Figure 17 of the drawinys, each of the hollow toes 300 and 302 is defined by substantially parallel wall por--tions 306 and 308 which carry inwardly projecting ribs 310 and 312, respectively. At one of their sides, the wall portions 306 -`
and 308 are joined to a respective pair of the common conductor insulating vanes 292 and 294 or 296 and 298 (see Figure 17).
This construction permits each of the hollow toe portions to be ~`
integrally formed with the respective common conductor insula-ting vane pair by an injection molding procedure.
A locking boss 320 is molded integrally with a pair of the radial insulating fins 284 of the terminal ring 280 and projects . . " ' ''~

~33599 radially outwardly from the outer ends of the fins 2~4. The locking boss 320 carries a hub 322 at its outer end which in-cludes a bore which extends substantially parallel, in its lon-gitudinal dimension, to the a~es of the shafts 248 and 250 for the purpose of receiving a flange of a spacing and locking structure hereinafter described.
The tandem rotary switch 26, a portion of which has been hereinbefore described, is constructed substantially identically - to the tandem rotary switch 28 insofar as the wiper ring sup-porting plate, semicircular wiper rings and synthetic resin ter-minal ring are concerned. Moreover, the identity ~urther ex- :
tends to the employment of an identical compression spring .
around a shaft 248 and retained in a biasing position by means :
o~ an identical retainer key, also as characteris-tic of the s~itch 26. For the foregoing reasons, identical reference nu-merals have been used on such identical parts as they are ~:~
characteristic of identical structural elements of switches 26 ~: `
and 28. `.
The s~nthetic resin terminal rings 280 of the t~o switches 2G and 28 are prevented from undergoing rotation upon rotation of shafts 248 and 250 by means of a locking and spacing struc-ture designated generally by reference numeral 328. The loc~ing :~
and spacing structure 328 includes an angulated plate 330 which has a bent over, slotted or bifurcated end portion 332. The ~ :
end portion 332 includes parts disposed on opposite sides of a slot, which parts pass around or straddle the shaft 248. The :
plate 330 bears agains-t one side of the hub 244 opposite the housing 10, and a down-turned end portion 334 of the locking and spacing structure 328 bears against the hub 258 of the switch 26. A lock.ing flange 336 is secured to and extends from `::
-43- ~ :
..

~3599 .
the central portion of the plate 330 and functions to interlock the bored hubs 322 of the locking bosses 320 of each of the switches 26 and 28 to each other so that the s~itches are re-tained in their positions in relation to each other, and the synthetic resin terminal rings 280 there~ are thereby inter-loc~ed against ro-tation with eit'ner of -the shafts 248 or 250 of ~;
the switches 26 and 28 when these switclles are operated by ro-tating the handles 252 and 25~, respectively. The lower end of - the plate 330 is also slotted so that it can be slipped over the shaft 250 and abutted against a side of the hub 246.
With the compound tandem rotary switch assembly 240 mounted in the housing 10 of the transformer in the manner illustrated in Flgure 11, theleads from the several tapped points on the two pairs of secondary subwindings can then be extended upwardly and connec-ted to the appropriate points on the switch assembly. The st~tionary synthetic resin terminal rings 280 are employed for this purpose. Since the mode of connection of the leadcs 101- ~ ~
136 to the terminal rings 280 of the two switches 26 and 28 is ~-substantially identical, reference to this mode of connection ; 20 will be made by referring only to the switch 28. ~;
As hereinbefore explained, the switch 28 controls the man- ~;
ner in which the several tapped sections within subwindings S-C
and S-D are interconnected through selectively dimensioned ;~
paralleled sections. The leads from these tapped sections ~i-th-in these subwindings are those denominated by reference numerals 119-136. Several of these leads are illustrated as connected in Figures 12-16 of the drawings. It may first be commented, how- ~ ~`
ever, that in in-terconnecting the leads 101-136 to the terminaI
rings 280 of the switches 26 and 28, a flat copper conducto- is preferably made to constitute each lead extending from the ~
~- :'' ~, ':'''~
.-, ., -, : ,. ..

1:133~99 respecti~Je subwindings S-A through S-C, and this flat co~per conductor is brought up -to the location of the respective termi-nal ring and ben-t around one section of the anchoring band 282 which is located between an adjacent diverginy, angularly spaced pair of the radial insulating fins 284. This arrangement is il-lustrated in Figures 13-15 of the drawings~
After the flat conductor is reverse bent through an angle of 180 or more so as to, in effect, be hooked over the terminal - anchoring band 282, the end portion may be cut away leaviny only the bight or loop which engages and hooks over the anchoring band. A sufficiently large number of the angularly spaced, radial insulating fins 284 is provided to accommodate all of the leads from the respective sections of the subwindings S-C and S-D, and an equivalent number of radial insulating fins is pro- ::~
vided in the terminal ring 280 of the switch 26 for the purpose : `
of receiving and acconunodating the leads 101-118 from the sub- -. ~
windings S-A and S-B. :
Tn Figures 12 and 13 of the drawings which depict oppositely ~acing views of a portion of the switch 28, the leads 134, 135, 12Q and 121 are shown attached to the anchoring band 282 of the terminal ring 280, and such securement of these leads to the ::anchoring band is typical of the manner in which all of the re-mainder of the leads are secured thereto when all leads are con~
nected to the terminal ring. Leads 112 and 113 are shown connec- ``
ted to the anchoring band 282 of the terminal ring 280 of switch 26 in Figure 11.
In the case o:E the leads 127 and 128, the schematic illus-tration in Fiyure 5 of the drawings shows that these leads are connected via their respective tap point terminals through the common leads 94 and 97, respectively, to the wiper arms C and D, -45~

. . .~
~ .. ., . ~ .. . , ,, ' ' ~ . .

~L~33599 respectively. In the Switch co~strUction u~der discussion, a sin~le flat copper conductor element is employed as the only electrical lead e~tending from the tap point on the two sub- :
windings S-D and s-C to which the leads 127 and 128 are connec-ted, ti~rou~h the terminal poin-ts on the switch 2~ as located ~or contact by the movable wiper rinCJs 270 and 271, and on to the point of function as a common lead for constantly interconnect-ing the terminals 127 and 128 to points on the respective wiper - rings. Thus, in referring particularly to Figure 16, it will be .
noted that the lead 127 from subwinding S-C is brought up to the anchoring band 282 of the terminal ring 280, is then reverse bent around this anchoring band, and then is again bent through a relatively large angle in a reverse direction so as to permit :~
the copper conductor to be extended on through the slot 350 pro- :~ :
vided at one side of the toe 3Q2 and between the arms 296 and 298. From this location, the conductor is extended around the - .
toe and bac~ inside the toe to a position in ~hich an end por-tion of the flat copper conductor is biased by the compression spring 304 into sliding contact with the semicircular wiper ring ~-~
271. Thus, as the wiper rin~ 271 is rotated with the wiper rincJ
supporting plate 264, cons-tant contact is maintalned between the wiper ring and the common electrical lead constituted by the ~ ;
flat copper conductor which dually functions as the lead 127.
The same method of connection and characteristics is true of the flat copper conductor which functions as the lead 128, ~:
provides a tap point on the switch 28 for contact with the mov- ;
able semicircular wiper ring 271 and also constitutes the equi~
valent of the common lead 97 which extends to the wiper arm D
in Fi~ure 5.
It will be apparent from the foregoing discussion tha-t in ~, -46- ~
.

the construction o~ the switch under discussion, -the semicircu-lar wiper rin~s 270 and 271 correspond in their operation to the movable wipers or taps D and C o~ switch sections 28a and 28b in the schematic illustra-tion of Fi~ure 5. It will also be apparent ~ that the shaft 250, in causing rotation of the wiper ring sup-; porting plate 264, and with it, the semicircular wiper rings 270 and 271, is tie equivalent of the mechanical linkage 100 shown schematically in Figure 5.
- For the purpose of consecutively contacting the terminals 119-127 and 128-136 located at the ends of the corresponding leads, the contact end 270c of wiper ring 270 and the contact end 271c of the wiper ring 271 are positioned to move into con~
secutive or sequential contact with the turned over end portions of the leads 119-127 and 128-136 constituted by the flat con-` 15 ductors. This relationship is illustrated in Fi~ures 13 and 14 o~ the drawings. In Figure 13, the lead 123 has been removed ~rom the anchoring band 282 in order to show the manner in which the contac-t end 270c of the wiper ring 270 extends inwardly over the anchoring band. In Figure 14, however, the flat copper con-ductor constituting the lead 123 is illustrated in phantom, and it is perceptible from this figure of the drawings that the turned ~` o~rer end portion of this lead, in passing around -the anchoring band 282 between the spaced radial insulating fins 284, is suf-' ficientl~ protuberant to make contact with and bear against the contact end portion 270c of the wiper ring 270.
As -the wiper ring suppor-ting plate 264 undergoes rotation with the shaf-t 250 in the direction of rotation illustrated by the arrow in Figure 14, it will be noted that the wiper ring con--tact end portion 270c is caused to move in consecutive sequence off the respective flat copper conductor lead 123, up over the ;~

,( ' , '' -` 1133599 cam s-tud 2~0, and then back down into contact with the next ad-jacent flat copper conductor constitu-ting the terminal of the ne~t lead in the spaced sequence o~ leads connected to the sub-winding S-D. At the same time that the wiper ring 270 is under- .
~oing this movemen-t to concurrently move the contac-t end 270c `
thereof from lead terminal to lead terminal, the same action is i~parted to the wiper ring 271 also carried on the plate 264.
Thus, the wiper rings are moved in synchronism and function in ~ the manner previously attributed to the wiper arms C and D of t~e switch 28. At all times the common leads constituted by the ~lat copper conductors which also integrally include the leads 127 and 12~ are continuously contacted by the wiper rings as a result oE the arrangement shown in Figure 16 and hereinbefore e~plained.
The same type of cons.truction and mode of operation charac- ~ :
terize the switch 28 constituting the uppermost switch in the compound tandem switch assembly 240 shown in Figure 11.
The compound rotary tandem switch assembly 240 illustrated :. ~
in Figures 11-17 constitutes a preferred embodiment of switch : :
assembly useful in the transformer of the invention. It will be ;~
perceived from the foregoing description of the manner in whi.ch the leads from the secondary subwindings are connected to the :
switch assembly for the purpose of forming self-constituting `~
terminals and tap points thereon, that this switch assembly eli- ~`
minates the need to employ brass bolts and nuts as terminals as is done in the case of the embodiment shown in Figures 7-10.
Electrical contact and interconnection is thus improved vis-a-vis the need to establish contact through brass elements. The cost of manufacturincJ the switch assembly is also thereby sub-stantially reduced. ..

-` ~133599 Further, the method by which -the ends of the flat copper conductors constitu-ting the leads from the secondary subwindings are connected to the terminal anchoring band 282 permits very ra~ld hook-up and positive connection of terminals to the in-ternally mounted switches in the housin~ 10 of the transformer`.
Considerable labor is thus saved by this aspect of the switch construction.
It is also noted that a unique aspect of -the switch assem---- bly constituting the preferred embodiment of the invention is that a single electrically conductive lead functions both as the lead directly out of the subwindings of the transformer to the extreme terminals in the portions of the switch which are asso-ciated with the two movable taps or wiper rings, and that this same electrical conductor then functions as the com~on by ~hich these terminals are interconnected electrically to the two syn-chronously operated wiper rings.
The manner in which the synthetic resin terminal ring 2~0 constituting a major subassembly of the compound rotary tandem switch assembly is constantly biased by a single compression spring acting on a centrally disposed hub of this terminal ring also affords advantage. Thus, the effect of the resilient bias de~-eloped by the spring is to exert a constant force which is . ,:
ultimately brought to bear on the two contact tap points a-t which the contact ends 270c and 271c of the wiper ring are in contact with two of the ter~inals formed by the ends of the -two leads which are interconnected by the tandem switch at any time.
The bias of the spring thus acts at two points around the syn-thetic resin terminal ring 280 which are spaced 180 from each other and, with the hub 286, consti-tute the three spaced points r of forced contact, thus dis-tributing the mechanical forces _ ~ 9 _ `:
.- ' .

, ' , forcing the terminal ring and wiper ring carrying plate ayains-t each other over a large well~distributed area, with yet a mini-mum of frictional drag imposed on the turning wiper ring sup-porting plates.
~lother aspect of the compound switch assembly is that by reason of the use of radial insulating fins 284 having a rela-tively large axial dimension, the tubular insulating sleeves which extend upwardly from the tapped sections of subwindings around the lead conductors can be brought all the way up along the conductors to a location where these sleeves can be term'i-nated between spaced adjacent insulating fins between which the respective sleeved conductor extends. This assures complete and effective insulation of each lead conductor from every other .
lead conductor~ --lS The~ con~mon conductors, at the point where they are turned over the toes 300 and 302 and back into a location ~ontiguous to the wiper rings 270 and 271, are each independently and continu~
ously spring biased into contact with th~ respective wiper rings, thus assuring long and effective service life of the switch as- ~ ~;
sembly without failure of contact between -the wiper rings and ~ -~
the common conductors. The manner in which the cavities or hol-low interiors of the toes 300 and 302 are formed for the accom-modation of the compression springs 304 assures that these ca-vities can be formed by injection molding concurrently with the formation of the rest of the synthetic resin structures consti-tuting the terminal rings 280.
It will also be observed that the provision of the cam . ;
studs 290 between adjacent conductor terminals at the location ,~
where the conductors are bent around the anchoring band 282 assures that there will be sensory indication to an operator of .~
-50- ~-:

il33599 the switch oE the time that the position of the wiper rings is changed to move from one tap point to another. Thus, snap action is imparted to the incremental movement of the several wiper rings as a result of the inclusion of the cam studs 290 in the path of travel of the contact ends of these rings. Moreover, the provision of these cam studs also causes the switch to oper-ate so that contact between the contact end oE the respective wiper ring and the lead terminal is completely broken before the contact end o~ the respective wiper ring is able to touch the conductor at the next tap point.
Finally, an important aspect and advantage of the switch assembly 240 illustrated in Figures 11-17 is that there is no need to provide stop fingers or similar stop elements of the type shown at 200 in Figure 7. This is because even though the handles 252 and 254 of the switches 28 and 26 are rotated past the place where their respective locking bolts 256 are aligned with one of the nine apertures associated -therewith in the indi-cator plate 242, such over-rotation will only carry the comple- ~ -mentary wiper elements 270 and 271 mounted on the wiper ring supporting plate 262 into contact with the next adjacen-t series of contact terminals carried on the anchoring band 282 of the terminal ring 280. In other words, the transformer will remain energized, and an output voltage will be delivered despite such over-rotation, as contrasted with the transformer becoming in-operative or being damaged or broken because of over-rotation, as in the case of the embodiment of the switch assembly illus-trated in Fi~ures 7-10. ~ ;
The transformer of the invention is particularly useful in oil field work and is very adaptable to the exigencies of those situations in areas where secondary voltage requirements may - ~

:~

3~599 .
vary widely. The transformer and control d~vice of Figure 1, for a selected source voltage input, may be utilized, for example, to increment continuously through equal, 60-vol-t steps an output of from 480 volts to 1920 vol-ts. These figures will appl~ for a given input voltage, and it should be understood that the similar range for any selected voltage values is attain-able by variation of the basic device design. Also, it should be understood that for any given voltage requirements, the vol-tage transformation can be reversed, with terminals ~l-X4 re-~, .
ceiving input voltage to provide an output voltage across ter-minals Hl and H2 Although certain preferred embodiments of the transformer ~`
device of ~he invention have been herein described and illus- ~ ~
trated in the accompanying drawings, it will be understood that ~ -various changes and innovations can be made in the illustrated and described structures without departure from the basic prin-ciples ~hich underlie the invention. Changes and innovations of this type are therefore deemed to be circumscribed by the spirit and scope of the invention, except as the same may be necessari-ly limited by the appended claims or reasonable equivalents thereof.

,'

Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A transformer comprising:
a first electrical winding;
two physically spaced inductive subwindings having an equal number of turns therein and each of said subwindings having a plurality of first through n + 1 section outputs connected thereto with each consecutive pair Of section outputs defining first through n winding sections each having a predetermined number of turns within the respective winding section;
means for inductively linking said first winding with said two inductive subwindings; and switch means having two synchronously operative wiper contacts, each wiper contact being in coaction with a respective plurality of first through n + 1 selectively connectable contacts which are connected to a respective one of said first through n + 1 section outputs for a respective one of said subwindings, said wiper contacts coacting with said selectively connectable contacts for selectively interconnecting respective ones of said winding sections of each of said subwindings in parallel with each other to provide co-directional current flow therein and for concurrently placing the remaining winding sections, if any, of said subwindings which are not in parallel in electrical series with those winding sections which are in parallel.

2 A transformer as set forth in claim 1 and further characterized as including output terminals associated with said contacts so that when said wiper contacts are at a synchronized first position relative to said selectively connectable contacts, said two inductive subwindings are in total parallel between said output terminals, and when said wiper contacts are at a synchro-nized n + 1 position relative to said selectively connectable contacts, said two inductive subwindings are to total series between said output terminals, and when said wiper contacts are at intermediate positions relative to said selectively connec-table contacts, said two inductive subwindings are connected between said output terminals in a series-parallel-series con-figuration in which the paralleled sections are asymmetrically positioned positioned in relation to said first electrical winding.

3. A transformer as set forth in claim 1 which includes:
two pairs of said inductive subwindings each inductively linked to said first winding, and each having a plurality of first through n + 1 section outputs; and first and second tandem switches, each functioning in coaction with a respective pair of said inductive subwindings, said first tandem switch wiper contacts connecting through selec-tively connectable contacts connected to section outputs of one of said subwinding pairs with a pair of output terminals and the second tandem switch wiper contacts connecting through selec-tively connectable contacts connected to section outputs of the other subwinding pair with a second pair of output terminals such that said first and second pair of output terminals may be selec-tively connected for series and parallel output.

4 A transformer as set forth in claim 1 that is further characterized in that each selected ones of said first through n winding sections of each inductive subwinding have a substan-tially equal rated voltage.

5. A transformer as set forth in claim 1 further charac-terized in that each selected ones of said first through n winding sections of each inductive subwinding have an equal number of turns.

6. A transformer as set forth in claim 1, wherein:
said means for inductively linking said first winding with said two inductive subwindings includes a central core: and said two subwindings extend co-directionally around said core in a plurality of concentric convolutions lying, in the case of the various convolutions, at varying distances from said first winding.

7. A transformer as set forth in claim 1 and further characterized as including insulator means engaging each of said physically separated subwindings and retaining the two subwindings in their positional relationship to each other during short-circuiting of the transformer.

8 A transformer as set forth in claim 7 wherein said insulator means comprises interconnected continuous convolutions of paper interposed consecutively between successive convolutions of each of said subwindings and adhered to each of said sub-winding convolutions.

9. A transformer as set forth in claim 1, wherein said first winding is spaced radially from said subwindings.

10. A transformer as set forth in claim 1, wherein each of said winding sections is in the path of current flow at all times.

11. A transformer as set forth in claim 1, wherein said selectively connectable contacts are oriented relative to each other to facilitate uncrossed, parallel extension of leads between said selectively connectable contacts and the tap points on said subwindings at which said section outputs are connected.