US1777256A - Transformer - Google Patents

Description

Sept. 30, 1930.

J. c. DALEY Fr A1. `1,777,256

TRANSFORMER v med July 1e. 192s -s sheets-sheet 2 JoJe/U J 50X Sept. 30, 1930. J C. DALEY ET AL` 1,777,256

TRANSFORMER I' Filed July 16. 1928 3 Sheets-'Sheet 5 l. /Z "y i ,f3 A? '5/ .ff

,5 James C. Daley Patented Sept. 30, 1939 UNITED STATES PATENT I ori-lcs JAMES C. DALEY, O' RIVER FOREST, AND EDWIN G. GODDABD AND JOSEPH J'. SOLA, Ol' CHICAGOLILLINOIS, ASSIGNORS T JEFFERSON `EIIZECJIIR'IG COMPANY, 0F CHICAGO,

ILLINOIS, A CORPORATION OF ILLINOIS v 'ranusroam l Application lled July 16,

upon the transformer illustrated and described in the co-pending application of and Edwin G. Goddard filed November 11, 1927, Serial N o. 232,523.

The present invention has particular utility in connection with gaseous tubes and the like which require relatively high initial or breakw down voltages and a lower subsequent or normal operating voltage, but it is to be understood that the invention is not limited to a particular use or purpose, but may be employed for ignition purposes or wherever ,5 suitable or desired, as for example, Wherever 20 invention in common with the invention of a relativelyhigh initial voltage is desired, followed by a reduced or relatively low voltage fora decrease in load.

Although not limited thereto, the present the co-pending application above referred to, relates particularly to a shell or confined type transformer in which there is practically no effect from adjacent magnetic materials 2;. in which great compactness is permitted, par- :lo vides for. obtaining maximum brilliancy uniform operation. lYhere thin sheet steel' U the magnetic flux density,

ticularly so far as the location or disposition of magnetic materials is concerned.` Also in common with the copending application above referred to, the present lnvention proand casings are employed, the device. is substanltlally freed of changes thereby and any ob-` jectionable vibration and noises are practi- 1' cally eliminated. The rating and operation yof the device is not affected by its disposition with respect to its steel-housing or casing. The present invention further provides a better distribution and aj better balancing of particularly in the secondary, and a better uniformity inthe i. secondary output and', also, a generally improved and simplified construction that may be produced and assembled economically and expeditiously.

Theinvention is illustrated in the accom- .panying drawings, in Which- Fig. 1 is a top plan view of a transformer 3o embodying the present invention;

and

192B. Serial No. 2Q3,28B.

Fig.' 2 is a side elevational view of the transformer shown in Fig. 1;

Fig. 3 is an end view;

Fig. 4 's a sectional view taken on the line 4 4 of Fig. 2;

Fig. 5 is a transverse section taken on the line 5 5 of- Fig. 1;

Fig. 6 is a wiring diagram of the transformer illustrated in Figs. 1 to 5; L

Fig. 7 .is a more or less diagrammatic section'similar to Fig. 4 of another. embodiment of the invention;

u F1g.,8 is a sectional view of another emboiment, taken onthe line 8-8 of Fig. 9; an

E ig. -9 is a section taken on the line 9---9` of.

1 8. Jeferring tothedrawings, each form of transformer 'shown is of the shell or conlined ty having a magnetic envelope which preferagley completely surrounds and encloses the coi-ls" and which also preferably encloses the shunt path or paths of the transformer as well.

In Figs. 1 to 5, the core 5 comprises two stacks 6 and 7 of iron or other suitable core laminations. `The laminations 6 and 7 are for facility and convenience of similar configuration l`suitably shaped to form central legs or extensions around which the primary coil 8 and secondary coils 9, 9 are wound and outer legs which form a laminated iron ring or envelope surrounding or enclosing the coils 8 and 9.

, While the particular shape or conliguration of the laminations 6 and 7 may be varied.4 these laminations are preferably, and

\ are shown as, of .E-shaped form, each having a central or intermediate leg 10 and outer legs 12 extending from a connecting base 13 with coil 'or winding receiving` spaces 14 formed between tbe central and outer legs of each-stack of laminations, these spaces 14 opening from one end of each core stack andembodiment of Figs. 1 to ary winding comprises 14 opendin opposition to the corresponding end of the other core stack 7 and preferably with the central and outer legs and 12 in register and l particularly in Fig. 4. A. closed magnetic ring or envelope 'divided longitudinally by the central legs 10 is thus formed with butt joints between the ends of the two laminated core stacks 6 and 7. Where we usethe expression butt joint or gap between the stacks 6 and 7 ofcore laminations in this specification, or in the appended claims, either term is used in a broad sense land we intend that they be interchangeable. InI the 5, the central and outer legs 10 and l2 are of equal length, and the butt joints between the central and outer legs of the corestacks lie in a common transverse plane substantially centrally between the opposite ends of the transformer, although, of course, this may be varied.

The arrangement of the primary and sccondary windings 8 and 9 is an important aspect of the Apresent invention. The secondone wound about and encircling the bases of the central legs 10 of one core vstack 6, and the other coil 9 being wound circling the bases of the central legs 10 of the other core stack- 7. The secondary coils 9, 9, the turns of which pass through 'the Spaces 14 and between the central legs 10 and outer legs 12l of the core stacks, are space d apart to receive the shunt means and the primary-coil 8 which is preferably disposed substantially centrally between the secondary coils or coil sections 8 is wound about and encircles the adjacent abutting ends of the central legs 10 of the core stacks 6 and 7 with the turns of the primary winding passing through the spaces 14 and' between the abutting ends of the central legs 10 and the yabutting ends'of the outer conininglegs 12. Y

It will now be apparent 'that each of ,thel

core stacks 6 and 7 has an outer secondary core part and that these stacks have meeting primary core parts which cooperate to form the primary core portion of the transformer. The disposition of the two secondary coils about the two sides of the primary coil 8 results in a vbalanced secondary winding the current flowing inany one coil of which does not under anv short circuit or operating condition exceed the total current of the coils,

i.' e., the current in the complete secondary winding. The secondary winding cannot under any condition build up more current in one secondary coil than in the complete secondary winding. With'the primary coil disposed between the secondary coils, all parts lof the secondaries are more uniformlydisposed with respect to the primary. Y

We reserve, ofcourse, the right to correct or supplement the theory of action and ad'- in abutting contact; as shown` two sides or 'coils 9. 9'

9, 9. The primary coil ng8is that the primary coil or winding 8 may be provided ,with intermediate leads or taps for connecting di'erent voltages with the primary winding,depending upon the voltage required byV the gaseous connected across the terminals of' thc secondary coils. The particular manner of connecting the source of cui-rent su ply across thc primary winding and the number of leads or connections therefor may, of course, -be va ricd widely within the scope of the present invention.

Each of the secondary coils 9, 9 is provided with a pair of terminal leads 23 and 24. respectively. The leads 23, 23 areconnected across the gaseous tube or other device which is to be supplied ,from the secondary Winding of the transformer. A gaseous tube 25 is shown, more or less diagrammatically in Fig. 6, as connected across the leads'23, 23. The terminal leads 24, 24 are preferably tied or connected together at 26 and the secondary winding is preferably grounded centrally between the coils 9, 9 by grounding the central connection 26 at 27. The ground connection 27 maybe through the core or frame' of the transformer, in which case the leads 24 may be tied or connected together and with the core or frame, or this groundconnectiou may be made omitted. as desired.

It is to be understood that the turns of the primary and secondary windings are insulated fiom each other and from the inagnetic core, as desired, and in any suitahe or preferred manner, as Well understood in the art. Each of the secondary coils are shown as enclosed in a generally rectangular open 'ended box-like insulating structure of micaniteg orv other suitable insulating niaterial. These structures, designated at 30, form intervening barriers between the sccondary coils and the outer legs 12 of the core stacks, as well as between the secondary coils and thebases 13 of the core stacks. These insulating structures 30 also form intervening insulating barriers between the secondary coils and the shunt means, to be hereinafter referred to.

shown as pro-' air of terminal leads 20 and tube or other device i The shunt means of the resent device comlegs 12 of the c ore stacks 6 and 7 and the laminations of each shunt stack may be suitably' hound together Vas by means of rivets 36. The shunt parts 32* and 321 are disposed in alignment between the primary coil 8 and one of the secondary coils 9 and in the spaces between the central legs 10 and the outer legs 12 of one core stack, and the other shunt parts 34" and 34h are similarly disposed between the primary coil 8 and the other secondary coil 9 and between the central and outer legs of.

the other core stack.

'lhe shunts 32 and 34 provide shunt paths between the outer legs 12 of the core stacks 1, and the central leg 19 and these shunt paths 32 and 34 each preferably has an open circuit reluctance greater than the reluctance of the core proper and are adapted for shunting the primary flux through the primary part of the core when the reluctance of the secondary core of secondary core parts is increased by the encrgization of the secondary windings. Each of- thc shunt arts 32, 32", 34 and 34 is preferably gappe at its opposite ends from the central and outer legs 10 and 12 as by suitable insulating barriers 38. These vinsulating barriers which may be of red ber or other suitable insulating material provide gaps or insulating barriers in each of the.

shunt stacks, it being understood that, although the particular arrangement shown and described in detail provides two gaps in each shunt stack or part, one gap, or any desired number of gaps, may be provided -in each shunt stackfas suitable orNv preferred. .The shunt stacks are insulated from the secondary coils 9 by the adjacent walls of the box-like insulating structures 30 and the primary coil 8 is also preferably enclosed in a suitable insulating structure 40. The particular insulating structure 40 shown comprises a pair of open ended generally arched or channel-shaped barrier separated by the central legs 10 with one substantially completely embracing each side of the primary coil and extending from the central leg on one side around the coil to the central leg on the other side.

These insulating barriers 40 may also be of red liber or other suitable insulating material and they insulate the primary coil from the shunt parts, as well as from the outer legs 12 of the core` stacks. Internally, the primary and secondary coils may be suitably ifnsulatedl at 45 and 46, respectively, from the central legs 10 of the core.

'f' In operation, the alternating or other suitable exciting current or current supply is applied across the terminals 2O and 21, forexample, o the rimary coil 8. Upon initial energization ofthe primary winding 8 substantially the entire magnetic flux threads through the primary and secondary core parts, as indicated diagrammatically by the dot and dash lines 50 in Fig. 4. In that the central legslO form a common central flux path for both of the outer sides of the core, .these central legs 10 are preferably of greater section than the outer legs 12. This greater section in the central legs may be obtained by making these legs wider and preferably substantially twice as wide as the outer legs 12 as shown, although this maybe varied as desi'red. The relatively great initial intensity thereby produced in the secondary fields provides a high induced initial voltage in the secondary coils 9. This relatively high initial voltage in the secondary windings 9 is particularly desirable in the initial operation or breaking down of, or ionization of, the gases in a Neon or other gaseous tube.

As already pointed out, the shunt paths 32 and 34 each preferably hasareluctance higher than the reluctance of the secondary core portions so that upon initial energization of the primary winding, substantially the entire magnetic tlux threads throu h the core proper to provide the high initia voltage in the secondary windings 9 as referred to, and then upon energization of the secondary coils or windings 9, the opposition set up increases the reluctance of the secondary core proper and thereafter the amount of flux required to saturate the secondary cores. Upon energization of the secondary windings 9 the increase in reluctance of the secondary core portions with the decrease in the amount of flux required to saturate the .Same causes the ma-gnetlc flux threading through the primary core portions to break down or overcome the reluctance of the shunt paths 32 and 34 and at least a part of the primary flux leaks through the shunt paths 32 and 34 and threads back through the primary core portion as indicated by the dot and' dash lines 53, 53 in Fig. 4. As already pointed out, the flux threadin throu h and intensity of the secondary hgeld is t ereby reduced with an accompanylng reduction in the voltage in the secondary windings 9 below the relatively high initial voltage. This is particularly desirable in connection with gaseous tubes and the like where a relatively high initial voltage is required and where thereafter the voltage required to operate or maintain the tube lighted is less.-

The device may. be designed to proportion, as desired', the leakage back through the shunt paths with respect to the linx which threads through the secondary core portions, by means of which the voltage which follows the relatively hi h initial voltage may be reduced as desire and effectively controlled. To this end the shunt stacks 32, 32", 34a and 34b may be adjustably mounted between the legs 10 and 12 of the core, preferably as shown, by means of a pressed fit between said legs 10 and 12, although, of course, the particular vmounting and the particular manner of securing adj ust-ability in these shunt paths may be varied. The pressed fit of the shunt stacks between thecore legs and 12 enables conveniently adjusting the position of the stacks between these legs of the core, and this provides a convenient adjustment for adusting and rating the device.

' n the particular device illustrated, the core stacks 6 and 7 are of substantially the same cross section and the core laminations are standardized, that is, the same laminations are employed 'in both stacksiand these laminations may be standardized with the cere laminations of transformers of` other types. It is to be understood that the core laminationsma be of other configurations than shown an( that the laminations of one stack may bc of different conti the laminations of the other stac The cross section of the primary portion of the core may also be greater than t e cross section of the seconda portions of the core for the purpose of xdecreasing the ilux required to saturate the secondary core portions and for obtaining what appears to be the additional advantage of decreasing the amount of flux which is shunted through the shunt paths 32-and34 upon energizatlon of the secondary windings.

This will enable a reduction` in the sections of the shunt paths which reduces the spaces between the primary and secondary windings and increases the space allowed for these wlndings in a device of given size. The size of the windings may thereby be increased in relatlon to the size of the device and the resulting device is exceedin compact and the cost is low. Adjustaility of the shunt stacks also makes the device particularly flexible for different types of devices and enables the use of the same core iron in different types of devices.

In the embodimentillufstrated in Figs. 1 to 5, the laminations of the'core stacks 6 and 7 are clamped together along'eaeh side between a pair of clamp bars or brackets 60.A

These. bars of brackets may be of angle iron formation, as shown, and their opposite ends pro'ect beyond the closed ends of the core stac 6 and 7. These projecting ends of the bars or brackets 60 are provided with registerin apertures through which extend clampin olts 62, each provided with a head engagea le with one bar or bracket 6() and having threaded engagement at its o posite end 'with a suitable nut 63 for drawing the bars 60 to ther and securely clamping the margins o the core stacks 6 and 7 therebetween. The transformer may be arran ed in any suitable casin or housin whic has been omitted for t e sake of c arity and it may be mounted upon metal brackets or adjacent external magnetic materials without being affected thereby and without any undesirable variation in the action or operation of the device.

ration than With the magnetic envelope enclosing both the primal and secondary coils, aswell as the interna shunts 32 and 34, there is prac tically no effect from adjacent magnetic niaterials.

This permits great compactness, so far as the location of ma etic materials is concerned, and it has en found that an ex ceedingl uniform operation is obtained. These a vantages are particularly important in gaseous tube signs where the conflicting requirements of compactness and maximum brllliancy are imposed. The user of a gaseous tube sign desires uniformoperation and if there are great losses in thc steel casing.

or adjacent or abut-ting magnet-.ic nniterial,

this brilliancy will be objcctionalily reduced. With thc present invention the stccl casing produces practically no effect and uniform operation is obtained. In addition, it is unnecessary to make allowance for losses in the casing and other adjacent materials, and objectionable noises are eliminated.

In the embodiment of Fig. 7, the central legs 10 of the core stacks 6 and 7 are shortcned and a stack of generally H-shaped laminations are interposed between these shortened legs 10 with the legs 72 of the core stack 70 formingxthe shunt paths. Gapping barriers 7 3 are preferably inter osed between the shunt legs 72 and the outer egs 12 of the core stacks 7. VThe butt joints 15 between the outer legs 12 are in a common transverse plane, as before, and the central legs 10' have butt engagement at 74 with the core stack 70, these butts 7l being outof the plane of the butt joints 15. The primary coil is indicated at 8 in Fig. 7 and the secondary coils or coil parts are indicated at 9', 9'. The results produced with this form of the invention are substantially similar to those, produced with the form shown iii Figs 1 to In the embodiment of the invention illustrated in Figs. 8 and 9, the core comprises a pair of five legged laminated stacks and 82 assembled with the inner opcn ends of the legs in register and with the central und outer legs inbutt contact and with the bases 83 and outer legs 84 formin envelope enclosing and confining the coils andl shunt paths. The primary coil 85 is shown wound around the central legs 86, but it is to be understood that the primary and secondary coils of this and the preceding embodiments may be reversed or interchanged. as desired, and the shunt legs 87 form the shunt aths. The central legs are preferably o increased section, as shown, because of the threading of the magnetic flux from each side or each end therethrough, and the secondary coil indicated at 90 encircles or surrounds the primary coil 85 and is wound about the shunt le 87 f and through the spaces 92 between said legs 87 and the outer the magnetic lll lll

legs 84. The butt joints between the central and outer legs of one core stack and the central and outer legs of the other core stack are indicated at 93 and the core stacks may stantially the entiremugnctic flux threadsthrough the primary and secondary core portions as indicated bythe dot and dash lines 95 in Fig. 8, and upon the increase in reluctance of the secondary core ortions and the decrease in the amount of ux required to saturate the 'same upon energization of the secondary winding, the Ymagnetic linx threading through the paths indicated diagrammatically at 95 breaks down or overcomes the reluctance of the shunt aths 87 and at least a part of the primarv ux'leaks through these shunt paths and threads back through the primary portion of the core as 25. indicated at 96, 96 in ig. 8. lTo these ends the shunt aths 87, 87 preferably have a dreluctance gher than the reluctance'o'f the secondary core portions.

We do not intend, of course, to be limited 80 to the precise details or arrangements show n or described. A

We claim v 1. In a transformer having magnetic core means, the combination of a secondary comprisi a pair of secondary coils, aprimary coil dlsposed between said secondary coils and inducing a relatively high voltage therein', and shunt means between the primary coil `and the secondary coils for reducing the voltage in the secondary by saturation of the magnetic core. 'V 2. 1n a transformer having -magnetic core means, the combination of a. secondary comprising a pair of seconday'cils, a primary coil disposed between said secondary coils Vand inducing a relatively high voltage therein,- and means'for'reducing the voltage in the secondary by satuation of the magnetic core, said means including a pair of internal shunt paths with one interposed between the primary and each-of said secondary'coils.

3.4 In a transformer havihg magnetlc core means, the combination of'a 4secondarycomprising a pair of secondary'coils, a ,primary coil disposed between said secondary coils and inducing a relatively high voltage therein, and means for reducing the voltage in the secondary by saturation of the magneticcore,

said means lncluding a pair of internal shunt paths with one interposed between the primary and each of said secondary coils, and said, ma etic core means being of the shell type wi a magnetic envelope surrounding and enclosing said coils and said shunt paths. 4. In al transformer having a primary noil `and a pair of secondary coil parts, the combination of a core having a. primary andsec-4 ondary coreportions and a pair ofV shunt paths, one between the primary coil and each of the secondary coil parts, each having a reluctance greater than the reluctance of the secondary core ortons.

5. In a trans ormer havinga primary coil and a pair of secondary coilparts, the combination of a shell t pe magnetic core having primary and secon ary core ortions, and a ma etic envelope complete y surrounding an enclosing said coils, and a pair of shunt path each having a reluctance greater than the r luctance of the secondary core portions,

said shunt paths being disposed between the surrounding or enclosing portions of the core and being also surrounded and enclosed by said surroundin and enclosing core portions.

6. In a trans ormer, the :combination of a pair of laminated core stacks each havinga pair of outer enclosing and central legs in register and in butt contact, primary and secondary coils surrounding the cent-ral legs and enclosed by said outer legs, and a' air of shunt paths between said central and outer legs, one on each of the opposite sides of said buttcontact.

l. In a transformer, the combination of a. pair of 'generally E-shaped core stocks havin primary and secondary' core ortions an central confined and outer encosing legs, a

stacks after initial energization the seconda coils.

8. a transformer, the combination of a pair of generally E-shaped core stacks havin primary and secondary core ortios and central confined and outer enc osing legs, a. pair of secondary coils surrounding the central confined legs and enclosed magnetically by said outer legs, a primary coil disposed between said secondary coils, a pair of-shut paths one between the primary coil and each of said secondary coils and each forming a shunt path for shunting the flux from the secondary portions of said core stacks after initial energizatioi yof the secondary coils, and a grounded connection between said secondary coils.

9. ,In a transformer, the cQmbination y`of a pair of laminated core sta'cks'each having a pair of outer enclosing and central legs in reglster and in butt contact, primary and secondary coils surrounding the central legs and enclosed by said outer legs, a air of shunt paths between said central an outer legs, one on each 0f the opposite sides of d primary coil surrounding the primary coil Aand-said secondary7 vcore 1s saturated the shunts butt contact, said shunt paths comprising laminated stacks having pressed tit between the central and outer legs of said core stacks.-

10. In a transformer, the combination of a pair of laminated core stacks each having outer enclosing and central legs in register and in butt contact, secondary coils surrounding the bases of said central legs and enclosed by said outer legs, and a primary coil interposed between said secondary coils, said primary coil surrounding the adjacent abutting ends of said central legs and also enclosed by said outer legs.

11. In a transformer, the combination of a pair of laminated core stacks'each having outer enclosing and central legs in register and in butt contact, secondary coils, surrounding the bases of said central legs and enclosed by said outer legs, a primary coil interposed between said secondary coils, said adjacentabutting ends of saidv central legs and also enclosed by said outer legs, and a pair of shunt paths between said central and outer legs andl disposed between the opposite sidcso'lssaid 12. A transformerincludinga sed-magnetic core structure,"a primary winding on the core structure, a pairiof. secondary windings on the opposite sides of the rimary winding, magnetic shunts on each si e of the primary winding providing separate shunts for the fluxes linking the respective second ary windings, each of said shunts including v an air ap, whereby when the core is unsaturated t e shunts provide a negligible by-pass `for the flux produced bythe primary winding thereby permitting the induction of a relatively highsecondary voltage, and when the provide an appreciable by-pass for the flux, thereb reducing the voltage induced in the secon ary win'dinv.

3. Transformer means comprising .the combination of magnetic core means, prlmary coil means,.secondary coil means, one of said coil means consisting of a plurality of coil parts, and the other coil means being disposed etween said coil parts and in balanced in-v ductive relation thereto, and shunt means dis posed between the parts of the plural coil part means and the other coil means for reducin the voltage in the secondary coil means by saturation of the magnetic core.

14. Transformer means comprising the combination of magnetic core means; primary coil means, secondary coil means, one of said coil means consisting'of a plurality of coil parts and the other coil means being disposed between said coil parts and in balanced inductive relation thereto, shunt means disposed between the parts of the plural coil art meansand the other coil means for reucing the volta e in the secondary. coil meansby saturation of ther magnetic core,

, means dis f winding ortions,

v thereby,

`combination .of magnetic core means, primary coil means, secondary coil means, one of said coil means consisting of a plurality of coil parts, and the other coil means beingdisposed between said coil parts and in balanced inductive relation thereto, and shunt sed between the arts of the plural 'coi part means and t e other coil means for reducin the voltage in the secondary coil means gysaturation of the magnetic core, said magnetic core,means having a magnetic envelope surrounding and enclosving said coil means.

16. In a transformer, the combinationof u `a pair of laminated core stacks, each having aqpair of outer enclosing and central legs in register, a pair of secondary coil parts surrounding th'e central legs and enclosed by said outer legs, a primary coil disposed between said secondary coil parts and a pair of shunt paths one between the primary coil and each of said secondary coil parts.

I7. In, a stationary transformer, a magnetic core having secondary core portions, a pair of secondary winding portions, a priv mary winding disposed between said secondary winding portions, and stationary magnetic vshunts one between the primary winding and each of said secondary winding portions` the permeability of the secondary core portions being changed by and substantially inversely with changes in load resistance.

18. A stationary transformer having a magnetic core, a pair of secondary winding portions, a primary winding disposed between said secondary winding portions, and stationary magnetic shunts one between the primary winding and each of said secondar winding ortions, said primary and secon ary win ings being completely enclosed magnetically. t l

19. A stationary transformer havinfr a magnetic core, 'a pair of secondary winding portions, a primary winding disposed between said secondary Winding portions, stational-' y magnetic shunts one mary winding and each of between the prisaid secondary and a ground connection between t e secondary winding portions.

20. In a transformer, the combination of a magnetic core having a surrounding magnetic envelope and a magnetic leg enclosed primary coil means surrounding said enclosed leg and enclosed by said magnetic envelope, secondary coil means surrounding saiden closed leg and enclosed by said magnetic envelope, one of said coil means consisting of ya plurality of coil arts and the. other coil means bein 'dis ose between said coil arts and re ative yl stationary shunts enc osed by said magnetic envelope,

one of suifl shunts being disposed between each of the parts of the plural coil part means and the other coil means.

, 2l; 'Transformer means comprising the combination of magnetic core means, primary coil means, secondary coil means, one of said coil'means consisting of a plurality of coil parts, and the other coil means being disposed between said coil parts, and shunt means disposed between the parts of theY plural coil part means and the other coil means for reducing the voltage in one coil means as the core means becomes saturated,

the coil parts of the plural coil part means being connected together uni-directionally.l

In witness whereof, we hereunto subscribe oml names this 11th day of July, 1928.

JAMES C. DALEY Y EDWIN G. GODDARD. JOSEPH J. SOLA.

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