US3212039A - Variable voltage transformer - Google Patents

Description

Oct. 12, 1965 w, KOBER 3,212,039

VARIABLE VOLTAGE TRANSFORMER Filed June 8, 1961 2 Sheets-Sheet 1 INVENTOR.

BY William Kobar,

ATTORNEYS Oct. 12, 1965 w. KOBER 3,212,039

VARIABLE VOLTAGE TRANSFORMER Filed June 8. 1961 2 Sheets-Sheet 2 F194. FJ'Q5. FiQd INVENTOR. WJJZJam ffober,

ATTORNEYS. v

United States Patent Office 3,212,039 Patented Oct. 12, 1965 3,212,039 VARIABLE VOLTAGE TRANSFORMER William Kober, Fairport, N.Y., assignor, by mesne assignments, to The Garrett Corporation, Los Angeles, Calif., a corporation of California Filed June 8, 1961, Ser. No. 115,669 15 Claims. (Cl. 33677) This invention relates generally to the electrical control art, and more particularly to a new and useful variable voltage transformer.

Pending application Serial No. 695,394, filed November 8, 1957 in the name of Norbert N. Bojarski, and now abandoned in favor of continuation application Serial No. 179,881 filed February 8, 1962, now Patent No. 3,154,766, issued Oct. 27, 1964, discloses a multipurpose transformer intended to produce an output voltage which can be varied smoothly and continuously in infinitesimal increments, and which does not require brushes or other current carrying moving parts. Such a transformer has a magnetic armature section movable relative to a primary and two secondary legs to divert primary flux from one secondary leg to the other. This varies the secondary or output voltage which is intended to be determined by the relative area of working contact between the movable armature and the respective secondary legs.

However, such a transformer construction poses certain problems which it is the primary object of this in- .vention to solve. These problems arise from the fact that the division of primary flux between the secondary legs is determined not only by the relative area of Working contact between the armature and the secondary end faces, but also by the saturation level of the magnetic material. The flux is not constant, but varies approximately sinusoidally, whereby only at peak levels does the flux limitation by saturation act in a compelling manner. At instantaneous flux levels below the maximum, such as one-half the maximum, a restricted area of contact between the armature and an end face could pass twice the amount of flux needed. As the instantaneous flux level rises, restriction by positioning of the armature becomes determining, but is positively so only at peak flux when the iron is saturated. Therefore, at instantaneous flux levels below peak, the division of primary flux is not necessarily determined by the relative areas of working contact between the armature and the secondary legs.

This non-linear action produces two undesirable characteristics. .First, the output wave form is very distorted. Second, the voltage regulation or ability to maintain a substantially constant output voltage over a range of electrical loading, is poor. This is because at lower instantaneous flux levels there is a permeable path comprising the armature and both secondary legs, with the secondary coils in additive, series connection. This path has considerable inductance impedance, which varies with the instantaneous value of the flux, being high at low flux values and relatively loW at peak flux values.

Thus, while such a transformer construction has very important advantages, it is characterized by a poor output wave form and poor output regulation.

The primary object of my invention is to provide a variable voltage transformer construction which has no moving, current carrying contacts or the like, and which has good output Wave form and good output regulation.

Another object of my invention is to provide the foregoing in an extremely simple, highly effective, durable and dependable construction which is little more expensive than simple, fixed transformers of like capacity.

In one aspect thereof, a variable voltage transformer constructed in accordance with my invention is characterized by the provision of a transformer core having a primary leg and two secondary legs, a primary winding on the primary leg and a secondary winding on at least one of the secondary legs, and an armature having one magnetic portion arranged for working contact with the primary leg and one of the secondary legs, thereby to complete one magnetic circuit therethrough, and another magnetic portion arranged for working contact with the primary leg and the other secondary leg, thereby to complete another magnetic circuit therethrough, with one of the armature and core being movable relative to the other to vary the relative area of working contact between the magnetic armature portions and the primary leg and thereby vary the division of primary flux between the secondary legs.

In another aspect thereof, a variablevoltage transformer constructed in accordance with my invention is characterized by the provision, in a transformer construction of the type described in the immediately preceding paragraph, of means automatically operable in response to variations .in flux density across the primary leg to maintain substantially constant flux density thereacross adjacent the armature, whereby division of primary flux is determined by the relative area of working contact of the primary leg with the magnetic armature portions at all instantaneous flux levels.

The foregoing and other objects, advantages and characterizing features of a variable voltage transformer constructed in accordance with my invention will become clearly apparent from the ensuing detailed description of certain presently contemplated embodiments thereof, considered in conjunction with the accompanying drawings illustrating the same, wherein like reference numerals denote like parts throughout the various views and wherein:

FIG. 1 is a side elevational view of one form of variable voltage transformer of my invention, with the front cover of the enclosing housing removed;

FIG. 2 is a sectional view thereof, taken about on line II-II of FIG. 1; 1

FIG. 3 is a generally diagrammatic side elevational view of the transformer core and armature of F-IG. 1, illustrating the mode of operation thereof;

FIG. 4 is an enlarged, fragmentary, diagrammatic plan view of one form of Working end face of the primary leg thereof;

FIG. 5 is a view corersponcling to that of FIG. 4 but showing a modified primary end face;

FIG. 6 is a view corresponding to those of FIGS. 4 and 5, but showing another primary end face construction; and

FIG. 7 is a view similar to that of FIG. 3 on menlarged scale, showing a modified armature construction, with the primary and secondary windings omitted for ease of illustration.

Referring now in detail to the accompanying drawings, one form of variable voltage transformer constructed in accordance with my invention comprises a corepgenerally designated 1, preferably of a laminated construction known in the art. Core 1 is generally E shaped, having a center primary leg 2, and two outer, secondary legs 3 and 4. The lam-ina-tions comprising core 1' are secured together, as by rivets or the like, and are mounted in a [housing 5 as by means of bolts 6 passing through core 1 and threaded'ly engaging embossme-nts 7 projecting from the rear wall 8 lot the housing. The front of housing 5 normally is closed by a removable cover 9, and ventilating openings 10 are provided through rear wall 8 and cover 9.

I A primary winding -12 is placed on primary leg 2, and

has leads 13, 14 adapted for connection to a source of exciting voltage, not shown. A pair of secondary windings I15, '16 are placed on the two outer secondary legs 3, 4, respectively. Wind- ings 15, 1 6 are oppositely wound and series connected, through a common lead 1'7, to comprise :a differential secondary winding 15, 16 having leads 18 and 19 adapted for connection to the load, also not shown. Openings 1 1, surrounded lay grommets 20 (of insulating material, are provided for passage of primary and secondary leads .13, 14, 18 and 19 out of housing 5.

To vary the net voltage introduced in secondary windings 15, 1 6, means are provided for adjusting the position of an armature 21 relative to the core, and it is a particular rteature of my invention that the division of primary flux determined, not by the relative area of working contact of the armature with the two secondary legs, as in the specific disclosure of the B ojarski application identilied above, but lay the relative area of working contact of magnetically separated armature portions with the primary end face,

To this end, armature '21 is provided with a magnetic section comprising portions '22, 22', of laminated, magnetic material, arranged to complete magnetic circuits between primary leg 2 and secondary legs 3 and 4, respectively, which portions are encircled by a body 37 of electrically conductive material tor a purpose to be described. Armature 21 is confined for reciprocation in the direction of arrows 23, as by guide shoulders 24 depending from opposite sides of the armature and bearing against the primary and secondary legs 3, 4 on opposite sides thereof, thereby confining the armature tor reciprocation in a lengthwise direction in the plane of the core legs. For moving armature 21, I provide a rack 26 projecting from the armature and secured thereto in any desired manner. Rack 26 meshes with a pinion 29 mounted on a shaft 30 journa'lled in a :boss '32 carried on the rear wall 8 of housing 5. Shatt 30 extends through the housing wall tor manipulation by a control knob 33. A boss 35 depends tirom top wall 25 of housing and bears against rack 26 to hold it in meshing engagement'with pinion .29. A spring 36 is carried by top wall 25 and bears against the upper surface of armature 21 to hold the magnetic armature portions 22, 22' in working contact with the end faces of the core legs 2, 3 and 4.

Referring now to'rthe schematic diagram of FIG. 3, the neutral position of armature 21 is shown in lull lines. It will be noted that when armature 21 is in its neutral position, the laminated, magnetic portion 22 thereof is in working contact with the entire end face area of secondary leg 3, and with one-half of the end lace area of primary leg 2, while magnetic portion 22' is in working contact with the entire end face area of secondary leg 4 and with one-half the end face area of primary leg *2. Therefore, all other raotors being equal, the reluctance of each magnetic circuit is the same, the p nrnary flux is equally divided between secondary legs 3 and 4, and because the secondary windings v15, 16 are opposed to each other the voltages induced therein cancel out, producing a zero output voltage. a

When armature 21 is moved to w e extreme left hand position illustrated in phantom in FIG. 3, its magnetic portion 22' is in working contact with the entire end face of primary leg 2 as well as of secondary leg 4, and the magnetic section '22 is out of working contact with the end taco of primary leg 2. Accordingly, the entire primary flux is diverted from secondary leg 3 to secondary leg 4, whereby there is produced a net maximum voltage of one polarity.

Conversely, when armature 21 is moved to its extreme right hand position shown in phantom in FIG. 3, magnetic portion '22 is in working contact with the entire end face area of primary leg 2, and magnetic portion 22 is entirely out of working contact therewith Accordingly, the primary flux is diverted to secondary leg 3 to produce,

4 in the chosen example, an equal maximum net voltage of opposite polarity. Obviously, armature 21 can be moved to any position between the illustrated extremes to produce a net output voltage continuously variable between no voltage and a maximum of either polarity.

Thus, not only can the output voltage :be readily and continuously varied by infinitesimal increments iirom one extreme to the other, but the two extremes can encompass a reversal of polarity. The primary reluctance is not effected by such variations in output. rimary leg 2 preferably has l2]. cross sectional area equal to that of secondary leg 3 and also that of secondary leg 4, all other things being equal, tor maximum utilization of transformer capacity. The primary leg end face is in working contact with one or the other or 'both of the magnetic armature portions 22, 22' at all positions of the armature, whereby there is no variation in the primary reluctance which is independent of armature position.

Thus, it is seen that the instant invention varies the output voltage by varying the relative area of working contact between the primary leg end face and the mag netic armature portions 22 and .22. However, the diversion of primary [flux to the respective secondaries in proportion to such relative area of working contact of the primary end face with the magnetic armature portions normally would be so determined only at moments of peak flux, when the primary iron is saturated and the primary leg has uni-form flux density thereaoross. At moments of less than peak flux, such division by relative area of working contact would not talce place a s desired because the iron is not saturated, permitting a restricted primary end face area to pass more flux than is the case at saturation, and thereby permitting the division of primary flux other than as determined by the relative areas of working contact.

It is a particular feature of my invention that it provides means enforcing substantially equal or uniform density at all points across the end face of primary leg 2, at all instantaneous flux levels, whereby division of primary flux is determined at alltimes by relative areas of working contact and is not dependent upon saturation. To illustrate how this is accomplished in my invention, reference is had to FIG. 4 showing the end face of primary leg 2 divided by a slot 40 into two equal parts 41 and 42. A closed winding 43 of highly electrically conductive material is placed in slot 40 and around the parts 41, 42 in a figure eight pattern with the winding crossing itself in slot 40. This provides a loop 44 around the primary end face portion 41 and a loop 45 around the primary end face portion 42, with current in loop 44 flowing around the associated primary portion 41 in a direction opposite to the flow of current through loop 45 around the primary portion 42. An alternating flux in the primary portion 41 will produce a voltage in loop 44 of winding 43, and this voltage will cause a current flow in win-ding 43 and through loop 45 in a direction to induce, in primary portion 42, a flux equal to that in primary portion 41 and proceeding in the same direction. Looking at this another way, if the flux present in portion 41 differs from the flux present in portion 42, a voltage will be produced in one of the loops 44, 45 causing a current to fiow in the Winding in a direction forcing equalization of the flux in the two primary portions 41, 42. Only when the flux densities in the portions 41, 42 are equal, is there no flux producing current; and if the conductivity of the winding 43 is high enough no substantial difference in flux density can exist between the portions 41, 42.

To demonstrate this, if B and B are the flux in portions 41 and 42, respectively, the voltage V induced in winding 43 is given by the equation d w ds-Bl.)

and the condition enforced by high'conductivity of winding 43 is that V must be substantially zero, whereby B =B at every instant if the fluxes are alternating.

In FIG. 4, although portions 41 and 42 must have equal or substantially equal flux, it will be seen that the flux can be unequally distributed in either portion 41, 42. Accordingly, a finer sub-division of the primary leg usually is required, and this can be accomplished in at least two different ways.

One way of dividing the primary leg is illustrated in FIG. 5, which shows the end face of primary leg 2 divided into five equal parts 46, 47, 48, 49 and 50 by four slots 40. A figure eight winding 51, similar to winding 43, is placed around parts 46 and 47, another figure eight winding 52 is placed around parts 47 and 48, a similar winding 53 is placed around parts 48 and 49, and a like winding 54 is placed around parts 49 and 50. The windings cross upon themselves in slots 40, as before.

From the foregoing analysis it is seen that equality in flux density is enforced as between parts 46 and 47 by winding 51. The same is true as between parts 47 and 48, 48 and 49, and 49 and 50. Accordingly, the flux density must be the same in all parts. Obviously, the primary end face can be divided into a greater or lesser number of blocks or parts.

Another method of accomplishing the desire-d result is by successive subdivision, as illustrated in FIG. 6. Here, it is seen that the portions 41 and 42 of FIG. 4 are each centrally divided, by slots 55, into parts 56, 57, 58 and 59. A figure eight winding 60 is placed around the parts 56 and 57, crossing itself in the slot 55 therebetween, and another figure eight winding 61 is placed around the parts 58 and 59, crossing itself in like manner. The winding 43 remains in place around the major division, as described with reference to FIG. 4.

From this, it is seen that winding 43 forces the total flux in parts 56 and 57 to be the same as in parts 58 and 59, with the winding 60 forcing the flux to be the same in parts 56 and 57, and winding 61 forcing the flux to be the same in parts 58 and 59. As a result, the flux density is the same in parts 56, 57, 58 and 59.

Either system of division and placement of windings can be used, depending upon the specific problem involved, and they may be used simutaneously or in an overlapping manner.

Referring again to FIG. 3, it will be seen that the primary end face is broken up into six equal parts, by five slots with each pair of adjacent parts being linked by a figure eight winding as described with reference to FIG. 5 As a result, each tooth or part has substantially the same flux density as each of the other parts, at any instant, whereby the primary flux is uniformly distributed across the end face of primary leg 2 at all times. The division or diversion of primary flux is determined by the relative areas of working contact between the magnetic armature portions 22, 22', and the end face of primary leg 2, at all times. This avoids the output wave distortion which otherwise would result because uniform distribution of flux is not enforced by saturation of the primary iron other than at peak flux levels.

The problems of secondary reactance and poor regulation are eliminated in the following manner. Normally, at lower instantaneous flux levels an aiding series circuit comprising armature 21, secondary legs 3 and 4, and core portion 63 could be traced. However, with the armature construction of'my invention if flux from secondary 3 attempts to cross through armature 21 to secondary 4, it strikes the separation provided by the notch 27 between the magnetic armature portions 22, 22. This would divert such flux into primary leg 2, and if such flux attempted to reenter the armature, through the magnetic portion 22, it would be blocked by the figure eight windings around the primary end face portions. This is perhaps best understood by reference to FIG. 4, showing that if flux passed from armature portion 22 into primary portion 41, and then attempted to enter armature portion 22' through the primary end face portion 42, the passage of such flux through the loop 44 would produce a blocking current in loop 45 preventin the escape of such flux from the primary leg.

The notch 27 in armature 21 has its sides extending at approximately 45 from center, the optimum angle being determined by the ability of the notch formation to channel flux from the primary end face, broken as it is by the slots therein, without reaching saturation in the armature iron. To block flux attempting to cross notch 27 through air from portion 22 to portion 22', notch 27 can be filled with highly electrically conductive material 28, such as copper. Any passage of flux into such material will induce a blocking current, preventing the transmission of flux therethrough.

A small connecting piece of armature iron may be left at the bottom of notch 27, joining the portions 22, 22 to give smoothness to the sliding or working surface of the armature 21. Alternately, the portions 22, 22 may actually be separated by a small gap, With the two portions held together by a frame which can conveniently comprise the part 37. This frame consists of side pieces 38 and end pieces 39, all of electrically conductive material which, like conductive material 28, function to block air leakage of flux in a manner more fully set forth in my pending application Serial No. 112,477, filed May 24, 1961. The notch material 28 and end material 39 can be soldered or otherwise electrically connected to the sides 38, and the electrically conductive frame can be locked to the laminated magnetic portions 22, 22' as by rivets 65. This provides a mechanically unitary structure for the armature, and blocks unwanted air leakage of flux. Also, as pointed out in my pending application, the guides 24 can be extensions of the sides 38 of this blocking frame 37.

Instead of the notch 27, the armature portions 22, 22' can be a unitary member, as shown in FIG. 7, magnetically separated by a short circuited winding 67 of highly electrically conductive material received in a slot 66 in the bottom face of the armature. Winding 67 encircles the armature adjacent the juncture between the portions 22, 22', and need not be turns of wire as shown but can be a single piece of copper or other electrically conductive wire or ribbon short circuited to itself. In either event, any flux attempting to pass from one magnetic armature portion to the other will set up a blocking current in the winding 67, preventing such magnetic linking of the armature portions 22, 22'. Blocking frame 37 can be applied to this armature, as well, and sides 38 can comprise part of winding 67.

Accordingly, it is seen that my invention fully accomplishes its intended objects, and provides a variable voltage transformer useful for a wide variety of purposes, and having good wave form and good regulation. Where reversal of polarity is not desired, the transformer can be connected as an autotransformer, using the primary as a base by tapping the primary windings into the secondary windings. Also, other winding arrangements could be used. For example, the secondary windings could be unequal, and additive. Also, an additional secondary winding can be placed on the same leg as the primary winding, and connected in series with the other secondaries.

While I have disclosed and described in detail only certain illustrative embodiments of my invention, it will be appreciated that this has been done by way of illustration only, without thought of limitation. Variations and modifications such as will occur to those skilled in the art, are intended to be included within the scope of the appended claims.

Having fully disclosed and completely described my invention, together with its mode of operation, what I claim as new is:

1. A variable voltage transformer comprising a transformer core having a primary leg and a pair of secondary legs, a primary winding on said primary leg and a secondary winding on at least one of said secondary legs, an armature having one magnetic portion arranged for working contact with an end face of said primary leg and an end face of one of said secondary legs and another magnetic portion arranged for working contact with said end face of said primary leg and an end face of the other of said secondary legs, said armature and said core being movable one relative to the other thereof to vary the relative area of said primary leg end face in working contact with said magnetic armature portions and thereby divert primary flux from one of said secondary legs to the other thereof, said end face of said primary leg being divided into multiple parts, and short-circuited windings of electrically conductive material linking pairs of adjacent parts in the manner of a figure eight whereby one part of each pair thereof is encircled by a current carrying loop in one direction and the other part of each pair thereof is encircled by a current carrying loop in the opposite direction.

2. A variable voltage transformer as set forth in claim 1, wherein said armature is divided into said magnetic portions by means comprising a notch between said portions substantially separating the same.

3. A variable voltage transformer as set forth in claim 2, wherein said notch is substantially filled with electrically conductive material thereby to block the air leakage of flux across said notch.

4. A variable voltage transformer as set forth in claim 3, together with a body of electrically conductive material encircling the opposite sides and ends of said armature thereby to block the air leakage of flux from said magnetic armature portions.

5. A variable voltage transformer as set forth in claim 2, wherein said armature portions are spaced apart.

6. A variable voltage transformer as set forth in claim 2, wherein said magnetic portions are adjacent the armature face arranged for working contact with said primary leg.

7. A variable voltage transformer comprising a transformer core having a primary leg and a pair of secondary legs, a primary winding on said primary leg and a secondary winding on at least one of said secondary legs, an armature, and means dividing said armature into one magnetic portion arranged for working contact with said primary leg and one of said secondary legs and another magnetic portion substantially magnetically separated from said one portion and arranged for working contact with said primary leg and the other of said secondary legs, said armature being movable to vary the relative area of working contact between said primary leg and said magnetic portions and thereby divert primary flux from said one secondary leg to said other secondary leg, wherein said armature portions are mechanically joined and wherein said means dividing said armature into said magnetic portions comprise a short circuited loop of electrically conductive material encircling said armature between said portions.

8. A variable voltage transformer comprising a transformer core having a primary leg and a pair of secondary legs, a primary winding on said primary leg and a secondary winding on at least one of said secondary legs, an armature, and means dividing said armature into one magnetic portion arranged for working contact with said primary leg and one of said secondary legs and another magnetic portion substantially magnetically separated from said one portion and arranged for working contact with said primary leg and the other of said secondary legs, said armature being movable to vary the relative area of working contact between said primary leg and said magnetic portions and thereby divert primary flux from said one secondary leg to said other secondary leg, wherein said armature portions are mechanically joined and wherein said means dividing said armature into said magnetic portions comprise a short circuited loop of electrically conductive material encircling said armature between said portions and wherein the face of said arma- 8 ture arranged for working contact with said primary leg is slotted to receive said loop.

9. A variable voltage transformer comprising a transformer core having a primary leg and a pair of secondary legs, a primary winding on said primary leg and a secondary winding on at least one of said secondary legs, an armature having one magnetic portion arranged for working contact with said primary leg and one of said secondary legs and another magnetic portion arranged for working contact with said primary leg and the other of said secondary legs, said armature portions being magnetically substantially separated, said armature and said core being movable one relative to the other thereof to vary the relative area of working contact between said primary leg and said magnetic armature portions and thereby divert primary flux from one of said secondary legs to the other thereof, and means automatically operable in response to variations in flux density across said primary leg to maintain substantially equal flux density thereacross adjacent said armature at all instantaneous flux levels, wherein said last-named means comprise means dividing the cross-sectional area of said primary leg adjacent said armature into multiple parts, and flux equalizing windings encircling and thereby linking adjacent ones of said parts.

10. A variable voltage transformer comprising a transformer core having a primary leg and a pair of secondary legs, a primary winding on said primary leg and a secondary winding on at least one of said secondary legs, an armature having one magnetic portion arranged for working contact with said primary leg and one of said secondary legs and another magnetic portion arranged for working contact with said primary leg and the other of said secondary legs, said armature portions being mag netically substantially separated, said armature and said core being movable one relative to the other thereof to vary the relative area of working contact between said primary leg and said magnetic armature portions and thereby divert primary flux from one of said secondary legs to the other thereof, and means automatically operable in response to variations in flux density across said primary leg to maintain substantially equal flux density there across adjacent said armature at all instantaneous flux levels, wherein said last-named means comprise means separating the cross-sectional area of said primary leg adjacent said armature into multiple parts, and shortcircuited windings of electrically conductive material encircling pairs of adjacent parts with each winding providing current conducting loops encircling the associated pair of parts in opposite directions.

lll. A variable voltage transformer comprising a transformer core having a primary leg and two secondary legs, a primary winding on said primary leg and a secondary winding on at least one of said secondary legs, an armature having one magnetic portion arranged for working contact with an end face of said primary leg and an end face of one of said secondary legs, said armature having another magnetic portion arranged for working contact with said end face of said primary leg and an end face of the other of said secondary legs, said armature being movable relative to said core to vary the relative area of said primary leg end face in working contact with said magnetic armature portions and thereby divert primary flux from one of said secondary legs to the other thereof, said primary leg end face being divided into multiple parts of substantially equal cross section, and flux equalizing windings of electrically conductive material encirling said parts in a manner automatically tending to maintain equal fiuX density in all of said parts.

12. A variable voltage transformer as set forth in claim 11, wherein each of said windings is short-circuited and crossed over upon itself to provide a pair of oppositely directed current carrying loops encircling a pair of parts.

13. A variable voltage transformer as set forth in claim 12, wherein said primary leg end face is divided into at least three parts, and said windings encircle each pair of adjacent parts.

14. A variable voltage transformer as set forth in claim 12, wherein said primary leg end face is divided into at least two main parts each further divided into at least two minor parts, said pair of main parts being encircled by one of said windings, and each pair of said minor parts being encircled by another of said windings.

15. In a transformer having a flux producing core section, means automatically operable in response to variations in flux density across said section to maintain substantially equal fillX density thereacross at all instantaneous flux levels, said means comprising, means dividing 10 multiple parts of substantially equal cross-section area, and flux equalizing widings encircling said parts in a manner tending to maintain substantially equal flux densities therein.

References Cited by the Examiner UNITED STATES PATENTS 2,253,705 8/41 Hedding et al 336-134 X 2,430,757 11/47 Conrad et al 177351 2,495,157 1/50 Browne 336-87 2,564,484 8/51 Kuehni 33630 X 2,662,301 12/53 Beach 33-226 2,912,767 11/59 Mittelmann 336135 X the cross sectional area of said flux producing section into 15 JOHN F. BURNS, Primary Examiner.

Claims (1)

15. IN A TRANSFORMER HAVING A FLUX PRODUCING CORE SECTION, MEANS AUTOMATICALLY OPERABLE IN RESPONSE TO VARIATIONS IN FLUX DENSITY ACROSS SAID SECTION TO MAINTAIN SUBSTANTIALLY EQUAL FLUX DENSITY THEREACROSS AT ALL INSTANTANEOUS FLUX LEVELS, SAID MEANS COMPRISING, MEANS DIVIDING THE CROSS SECTIONAL AREA OF SAID FLUX PRODUCING SECTION INTO

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