US3091744A - Transformer with magnetic leakage shield - Google Patents

Description

y 8, 1963 F. c. OWEN 3,091,744

TRANSFORMER WITH MAGNETIC LEAKAGE SHIELD Filed March 16, 1962 3 Sheets-Sheet 1 a1 2135 H615. 20 3o INVENTOR. 5 Freaen'ck C. Owe 7 q, l 2 ATTOR/VZ May 28, 1963 F. c. OWEN 3,091,744

TRANSFORMER WITH MAGNETIC LEAKAGE SHIELD Filed March 16, 1962 5 Sheets-Sheet 2 1 FIG. 6

L f 47 2 25 44 31 33 .nnnnnn 7 L- /30 A? I l7 INVENTOR.

Frederick C. Owen BY @7 v @mu? ATTORNEY y 8, 1963 F. c. OWEN 3,091,744

TRANSFORMER WITH MAGNETIC LEAKAGE SHIELD Filed March 16, 1962 3 Sheets-Sheet 3 1:33 INVENTOR. Freder/ck C. Owe/7 3,091,744 TRANSFGRMER WITH h iAGNETHC LEAKAGE SHIELD Frederick C. Owen, 206 Fenton Place, Charlotte, N11. Filed Mar. 16, 1962, Ser. No. 180,257 12 Claims. (Cl. 336--87) My invention relates broadly to transformers and more particularly to high magnetic leakage-type transformers having magnetic leakage shields.

One of the objects of the invention is to provide shielding means for high magnetic leakage-type transformers to enable the same to be encased within a metal container.

Another object of the invention is to provide a construction of high magnetic leakage-type transformer in which the magnetic leakage is diminished and confined, thus enabling such transformers to be used in the vicinity of other electrical equipment without adversely affecting the same, a feat heretofore unattainable.

Another object of the invention is to provide a construction of high magnetic leakage-type transformer in which the magnetic leakage flux is conserved and utilized for varying the transformer output current.

Still another object of the invention is to provide a construction of transformer with a magnetic leakage shield, in which the shield is provided with a transformer output current control system.

A further object of the invention is to provide a construction of transformer with a magnetic leakage shield having flux diverting means for varying the transformer output current from maximum to minimum and minimum to maximum with very little effort.

Still a further object of the invention is to provide a construction of welding transformer having a magnetic leakage shield with means for varying the welding transformer output current to affect the welding arc voltage but which will not affect the open circuit voltage.

Other and further objects of the invention reside in the construction of and manner of manipulating the hunt device extending intermediate the magnetic leakage shield and core in both the preferred and modified forms of the invention as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

FIG. 1 is a front elevational view of the transformer and magnetic leakage shield of the invention;

FIG. 2 is a side elevation view of the magnetic leakage shield and particularly showing the rack gear shunt adjustment mechanism;

FIG. 3 is a top plan view of the structure of FIGS. 1 and 2;

FIG. 4 is an enlarged sectional view taken substantially along line 4-4. of FIG. 1, with parts broken away to show the manner in which the magnetic shield is secured together;

FIG. 4A is an enlarged cross sectional view taken substantially along line 4A-4A of FIG. 1 and particularly showing the construction of the optional second shunt;

FIG. 5 is an enlarged fragmentary cross sectional view taken substantially along line 5-5 of FIG. 3, and particularly showing the adjustable shunt mechanism;

FIG. 6 is an enlarged fragmentary top plan view similar to FIG. 3 but showing a modified construction of shunt adjustment mechanism;

FIG.'7 is a fragmentary cross sectional view taken substantially along line 77' ofFIG. 6;

FIG. 8' is a diagrammatic view of a, transformer and shieldembodying the features of the invention and showing one arrangement of transformer. windings applicable to. the invention;

FIG. 9 is a front elevational' view of a modified form 3,91,?44 Patented May 28, 1963 of the invention, particularly showing a modified arrangement of adjustable shunt;

FIG. 10 is a fragmentary front elevational view similar to FIG. 9, showing a modified construction of the adjustable shunt of FIG. 9; and

FIG. 11 is a diagrammatic view of the modified structure of the invention as shown in FIGS. 9 and 10 and showing in electrical schematic one arrangement of transformer windings; applicable to the teachings of the invention.

Referring to the form of invention shown in FIGS. 1-8, and particularly to FIG. 8, wherein one arrangement of transformer winding applicable to the teachings of the invention has been shown in electrical schematic, the laminated core of the transformer is generally designated by the reference numeral 1. The laminated core structure of conventional construction and consisting of a plurality of stacked laminae of magnetic material, secured together with insulated bolts 17 or the like, is generally rectangular in shape having end portions 2 and 3, and a central portion 4 disposed intermediate the end portions 2 and 3 and spanning the side portions 5 and 6 which respectively connect corresponding ends of the end portions.

The illustrated arrangement of transformer windings on the various portions of the transformer core is basically that shown and described in Patent 2,365,722, issued to me on December 26, 1944, for Tarnsformer, although FIG. 8 illustrates the transformer in a more simplified form. The transformer shown is an electric welding transformer; however it is to be understood that the teachings of the invention are applicable to a variety of different transformers of the high magnetic leakage type, having a variety of winding arrangements, and the arrangement shown in FIG. 8 is only for purposes of illustrating one such form of high magnetic leakage type transformer to which the teachings of the invention are applicable.

Primary transformer winding 7 having its input leads connected to a conventional alternating current power source, as indicated, of approximately volts or other desired rating, is wound on core end portion 3 while the main secondary windings 8 and 9 are respectively wound on end portions 3 and 2. An auxiliary secondary Winding indicated at in is wound on central portion 4 of the core and is provided with a plurality of taps lit which are adapted for selective electrical connection with the movable tap or plug 12 connected to one end of main secondary winding a, while the other end of winding 9 is connected to the WOIiC 13 in accordance with the usual practice. The secondary transformer circuit is compelted by connection of the other end of auxiliary secondary winding it with one end of main secondary winding S, with the opposite end of winding 3 connected to the welding electrode holder 14. The adjustable tap arrangement of the auxiliary secondary winding provides convenience in selection of the open circuit voltage, the amperage output of the transformer and the welding arc voltage.

A condenser winding 15 having its extremities connected across a bank of capacitors id is wound on core end portion 2 either under or over main secondary winding 9. In like manner main secondary winding 8 is wound either over or under primary winding 7 but for purposes of illustration the secondary windings 8 and have been shown wound over primary winding 7 and condenser winding 15, respectively. The capacitors 116 function to increase the power factor of the input current and act to increase or decrease the frequency of the secondary or welding current, depending upon the size and number of capacitors employed since they are partof an independent oscillating circuit consisting of the capacitance and its exciting winding, and enable the operator to maintain the welding current are as constant as possible as set forth in greater detail in the beforementioned Patent 2,365,722. Thus this transformer arrangement produces an ideal are for vertical, overhead and flat horizontal welding of all types of metals.

The magnetic leakage shield, indicated generally at 18, and comprised of a plurality of stacked laminae of magnetic material, such as iron, and having substantially the same number of laminae as the transformer core 1, is supported in spaced relation about the perimeter of the laminated transformer core by means of insulating blocks 19. The magnetic leakage shield is thus generally rectangular in shape having the core of a high magnetic leakage flux transformer supported interiorly thereof. Angle iron frames 29 and 21 are disposed about the perimeter of the magnetic leakage shield in cooperating relation as shown particularly in FIGS. 2, 3 and 4 and are connected together by means of insulated bolts 22, or the like, to securely clamp together the plurality of laminae comprising the magnetic leakage shield. As shown, the arms of angle iron frames 20 and '21 engage the face and edge portions of the magnetic shield laminae and are insulated therefrom by means of insulation members 23 and 24 which extend around the entire perimeter of the magnetic shield intermediate the laminae and the angle iron frames. Thus the insulation members 23 and 2e and insulation bolts 22 prevent any short circuit of the magnetic flux paths within the magnetic leakage flux shield structure.

In the preferred form of the invention the top portion of the magnetic shield is spaced a greater distance from the top portion of the transformer core than the other portions of the magnetic shield from the corresponding portions 2, 3 and 6 of the transformer core.

A magnetic shunt or flux diverter, indicated generally at 25, and consisting of a plurality of laminae 26 of magnetic material of substantially the same number as provided in the magnetic shield structure and transformer structure, securely clamped between guide blocks 27 of insulation material by means of insulated bolts 28 or the like, is positioned intermediate the magnetic shield 18 and transformer core portion 5, as shown more particularly in FIGS. 1 and 5. The laminae 21) of the flux diverter 25 are disposed in alignment with the laminae of the magnetic shield and transformer core with each laminae having substantially the same Width as central portion 4 of the transformer core. The top portion of magnetic shunt 25 is disposed in sliding engagement with the adjacent bottom portion of the magnetic shield 18 and a sheet of insulation material 29 secured to the bottom of the magnetic shunt is disposed in sliding engagement with the top surface of side portion 5 of the transformer core. Provision for the insulation sheet 29 intermediate the magnetic shunt and the transformer core is necessary in order to prevent short circuit of the magnetic flux paths between the shield and the core.

The magnetic shunt or fiux diverter 25 is disposed to be selectively positioned in a plane normal to the plane of the laminae of the various members such that the laminae 26 of the magnetic shunt may be disposed in alignment with all of the corresponding laminae of the shield and transformer core, or may be selectively positioned to be disposed in alignment with only a selected number of the laminae of the shield and transformer core, as shown more particularly in FIG. 5, thus reducing the area of the magnetic shunt flux path interconnecting the shield and core. The angle iron frames 20 and 21 are appropriately notched to allow free movement of the magnetic shunt toward and away from the shield and core. A pair of guide plates 30 and 31, having rectangular apertures therethrough, indicated generally at 32, of a size somewhat larger than the cross sectional area of the magnetic shunt, are clamped together outwardly of angle iron frame members 20 and 21, respectively, by means of insulation bolts 33, such that their corresponding apertures are disposed in registration to form a guide for the magnetic shunt, and are disposed in guiding engagement with magnetic shunt insulation sheet 29 as the shunt is moved in the apertures relative to the guide plates. Support members 34 secured to guide plate 30 by welding, or other suitable means, extend outwardly therefrom and provide guide member 35 on their outward extremity for slidably engaging rack gear 36 securely connected to guide block 27 at one end of the magnetic shunt assembly. Gearing, indicated at 37, journaled for rotation on support mem bers 34 and selectively controlled by hand knob 38, or other suitable means, is disposed in meshing engagement with rack gear 36 such that the shunt 25 is moved inwardly or outwardly with relation to the guide plates 3% and 31 upon turning of hand knob 38.

It is to be understood that the magnetic shunt could just as easily be positioned at the bottom of the transformer intermediate core side portion 6 and the magnetic shield. At the bottom of the transformer a secondary or auxiliary shunt is provided as indicated at 39, comprising a plurality of laminae of magnetic material securely clamped between end members 40 of insulation material, thus being of substantially the same construction as the previously described adjustable magnetic shunt 25. The auxiliary magnetic shunt 39 is clamped in place beneath central portion 4 of the transformer core intermediate side portion 6 and the magnetic shield 18 by means of shunt support plate members 41 clamped in frictional engagement with angle iron frames 20 and 21 by means of insulation bolts 42 passing through said support plates, shunt end members 40 and the auxiliary shunt laminae, as particularly shown in FIGS. 1 and 4A with the top portion of the auxiliary magnetic shunt disposed in abutting engagement with the bottom surface of core side portion 6 and an air gap between the magnetic shield and the bottom surface of the auxiliary shunt. If tolerances are very close it may be necessary to insert a sheet of insulation material between the auxiliary shunt and the magnetic shield.

Although I have illustrated the auxiliary shunt 39 as being fixed in position, this shunt could also be selectively adjustable in a manner similar to the main magnetic shunt or flux diverter 25. It is also to be understood that this shunt could be completely eliminated thus providing the structure with only a single magnetic shunt. The fixed magnetic shunt 39 is utilized for limiting the maximum current output of the secondary Welding transformer circuit and although the auxiliary shunt illustrated has been shown to contain substantially the same number of laminae as the magnetic shield and transformer core, the number of laminae can be reduced to vary the length of the auxiliary shunt to thus vary the maximum transformer current output. The maximum current output is increased as the number of laminae of magnetic material are decreased in the auxiliary shunt assembly. If a sheet of insulation material is inserted between the auxiliary shunt and the magnetic shield the thickness of insulation will also affect the magnetic shunt path and cause an effect on the transformer output current.

Although the theory of operation is not completely known, it has been found that through experimentation with the device of the invention, the welding arc current may be easily varied by the operator from minimum to maximum and from maximum to minimum by adjustment of the main magnetic shunt or flux diverter 25. If an auxiliary shunt 39 is utilized the maximum current is set by this shunt and the welding current can thus be varied from a minimum to this set maximum by the main shunt 25. The highest welding output current in the transformer secondary circuit is experienced when the magnetic shunt 25 is positioned in its maximum outwardly adjusted position, as indicated in phantom in FIG. 2, where it forms no coupling flux path between the magnetic shield and the transformer core. Conversely, the minimum welding current is experienced when the magnetic shunt 25 is positioned at its. other extreme, so that it lies completely between guide plates 30 and 31, as indicated in full lines in FIGS, 2 and 3, to form the maximum flux path intermediate magnetic shield 18 and transformer core 1. As stated, the theory of operation is not completely known but the laminated magnetic shield 18 apparaently functions somewhat like a transformer core, providing a confining flux path for the magnetic leakage flux, and thus conserves the magnetic leakage flux from the high magnetic leakage flux type transformer. The shield thus reduces the flux leakage from the assembly, enabling the transformer and the shield to be placed within a metal case without short circuiting the transformer. By inserting the magnetic shunt between the shield and the transformer core the leakage flux is diverted back to the transformer and provides control for the transformer output current. By selectively Varying the shunt, the transformer input current, output or welding arc current, and the welding arc voltage are varied. However, the manipulation of the shunt has no effect whatsoever on the open circuit voltage of the welding transformer, that is, the voltage across the secondary before the electrode welding arc is struck Thus, by using the teachings of the invention with the transformer shown in FIG. 8, the open circuit voltage can be maintained at a minimum for operator safety, and when the welding arc is struck the arc current can be easily adjusted from maximum to minimum or conversely by means of the adjustable magnetic shunt. Magnetic leakage from transformers of the high magnetic leakage flux type causes heat losses and loss of secondary power, and these losses are diminished by use of the magnetic leakage shield arrangement of the invention.

A modified construction for adjusting the magnetic shunt or flux diverter 25 is shown in FIGS. 6 and 7, where in lieu of a rack and pinion gear arrangement for selec tively adjusting the shunt intermediate the magnetic shield and transformer core, a screw 43 is provided, journaled for rotation within bracket 44 connected to guide block 27 of the magnetic shunt, and disposed in screw threaded engagement with guide member 45 supported at the extremites of the support members 46 which in turn are secured, in the same manner as support members 34 in the main form of the invention, to the guide plate 30. A crank portion 47, or other suitable means such as a handwheel or the like, is connected to the outward end of screw member 43, whereupon rotation of the crank 47 causes the adjustable shunt or magnetic flux diverter 25 to be selectively positioned in the desired manner intermediate the magnetic shield and transformer core in the same manner as explained in connection with the preferred form of the invention.

Another modified form of the invention is shown in FIGS. 9-1l wherein the construction of the magnetic shield 18 clamped within angle iron frame members 20 and '21 is the same as that indicated in the preferred embodiment of the invention with the shield spaced from the perimeter of the transformer core 1' by insulation blocks I9 in the manner previously described. It should be noted that the insulation blocks are disposed to support the weight of the transformer core and other clamping means may be provided for maintaining the core in position Within the magnetic shield. In the preferred form of the invention, as shown in FIG. 1, other clamping means are not necessary as the guide plates 30 and 31 and the shunt support plate members 41 serve as clamping means between the core and the shield to maintain the transformer core within the shield.

In the modified form of the invention shown in FIGS. 9-l1, I have shown the adaptation of the modified construction to the same transformer winding arrangement as shown in the preferred form of the invention with like reference numerals indicating corresponding components. However, the construction of the transformer core 1 and adjustable magnetic shunt or flux diverter 25 is substantially different. The laminated transformer core 1, of generally rectangular shape, is comprised of end portions 48 and 49, bottom portion 50 connecting corresponding ends of said end portions, and top portions 51 and 52 respectively connected to the opposite ends of end portions 48 and 49, and being separated by an air gap indicated generally at 53 through which passes the adjustable magnetic shunt 25.

The adjustable magnetic shunt or flux diverter comprises a plurality of elongated rectangular shaped laminae 54 of magnetic material of substantially the same number and arranged in the same plane as the laminae of the magnetic shield and transformer core, secured together at their uppermost ends by means of a properly insulated clamping member and insulated bolt assembly, indicated generally at 55, with the lower ends of the laminae 54 terminating in the sheet of insulation material 56 secured thereto by means of adhesive or other suitable means. The transformer auxiliary secondary winding 10 is disposed in fixed position relative to the transformer and the magnetic shunt 25 is disposed through an opening; 57 provided in the top surface of the magnetic shield 18 as shown in FIG. 11, through the air gap 53 of transformer core 1 such that it is in sliding engagement with the terminating ends of the core top portions 51 and 52 and extends downwardly through the fixed auxiliary secondary transformer winding 10 with the insulation sheet 56 contacting bottom portion 50 when the magnetic shunt is in its lowermost position as indicated in full lines in FIGS. 9-11. The opening 57 in the magnetic shield 18 is of sufiiciently larger size than the cross sectional area of the magnetic shunt so that no contact whatever is made between the magnetic shunt 25' and magnetic flux leakage shield 18, to thus eliminate the possibility of short circuiting of the magnetic flux paths between the shield and core. Depending upon manufacturing tolerances it may be necessary to provide an insulation gasket around the edges of opening 57 A supporting tower arrangement, comprised of angle members 58 connected to the top surface of angle iron frames 20 and 21, by welding or other suitable means, extends upwardly from the top surfaces thereof terminating in a guide member 59 of electrical insulation material. The supporting tower arrangement supports the adjusting mechanism for the magnetic shunt to enable it to be selectively raised and lowered, with the lowermost position of the shunt being shown in full lines in the various views and the partly raised position of the shunt being shown in phantom in FIG. 10. It is to be understood that in the uppermost position the end of the shunt 25 is positioned flush with the bottom edge of magnetic shield 18 so there, is an air gap between the bottom of the shunt and the transformer core. In this fully raised position, the secondary output current or welding arc is at its maximum with the minimum welding current being provided when the shunt is in its lowermost position.

As with the preferred form of the invention, various means can be provided for raising and lowering the magnetic shunt or flux diverter 25', and in FIG. 9 I have shown an arrangement of crank and screw 43, 44' and 47', which operates in the same manner as the crank and screw mechanism of FIGS. 6 and 7, and in FIG. 10 I have shown an arrangement of rack and pinion gearing 36' and 37, which operates in a manner similar to the gearing of FIG. 5, for selectively raising and lowering the adjust-able shunt to obtain the desired secondary output current for the welding process.

It should be understood that an auxiliary shunt 39. as described with the preferred form of the invention, can also be used with this modified structure if it is desired to limit the maximum output current to a certain value. Raising and lowering the shunt 25', of the form of the invention shown in FIGS. 9-11, cause the transformer output current to vary in the same manner as experienced with corresponding adjustments of the shunt 25 in the preferred form of the invention, by diverting the trans former magnetic leakage flux back to the transformer core, thus coupling the flux with the transformer windings, and it therefore appears that the theories of 'operation for both forms are substantially the same.

While I have described my invention in certain of its preferred embodiments, I realize that modifications may be made, and I desire that it be understood that no limitations upon my invention are intended other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A transformer comprising, a core member, inductively related transformer windings wound on said core member, magnetic leakage flux shield means disposed about the perimeter of said core member in spaced relation, and separate means connected intermediate said core member and said shield means for forming a magnetic flux path between said shield and said core member and setting the transformer output current.

2. A transformer as set forth in claim 1 in which a gap is provided in the magnetic flux path intermediate said separate means and said core member.

3. A transformer as set forth in claim 1 in which a gap is provided in the magnetic flux path intermediate said separate means and said magnetic leakage flux shield means.

4. In combination with a transformer having a primary and secondary, magnetic leakage flux shield means supported in spaced relation about the perimeter of the transformer to confine the magnetic leakage flux field, and flux diverter means connected intermediate the shield means and transformer for selectively setting the trans former output current when the secondary is under load.

5. In combination with a transformer having an inductively related primary and secondary, magnetic leakage flux shield means supported in spaced relation about the perimeter of the transformer forming a confining flux path for the transformer leakage flux, and flux diverter means connected for movement intermediate the transformer and shield means and being selectively positionable between two extreme settings for varying the transformer output current between a selected minimum and maximum when the secondary is under load.

6. The combination as set forth in claim 5 in which said flux diverter means is selectively positionable in a plane normal to the plane of the transformer and shield means.

7. The combination as set forth in claim 5 in which said flux diverter means is selectively positionable in the plane of the transformer and shield means.

8. The combination as set forth in claim 5 in which maximum transformer output current is approached when said flux diverter means is moved from a position intermediate the transformer and shield means.

9. A transformer comprising a core formed with an intermediate leg to divide the core into sections, a primary winding wound on one section of the core, a capacity exciting winding wound on the other section of the core, both of said windings being excluded from said intermediate leg to inductively isolate the two, a secondary winding wound on both sections of the core to inductively couple both of the first said windings when the secondary is under load, magnetic leakage flux shield means supported in spaced relation about the perimeter of said core, and flux diverter means connected for movement above the intermediate leg intermediate said core and said shield means for selectively varying the secondary output current when the secondary is under load.

10. A transformer as set forth in claim 9 and a second flux diverter means beneath the intermediate leg and connected intermediate said core and said shield means.

11. In combination with a transformer having a normally low power factor and including a primary and secondary, a reactance of a character to materially improve the power factor, an energizing winding for the reactance inductively related to the secondary to automatically render the reactance effective only when the secondary is under load, magnetic leakage flux shield means disposed in spaced relation about the perimeter of the transformer, and selectively adjustable means connected intermediate the transformer and said shield means for varying the output current when the secondary is under load.

12. A transformer comprising a core formed with an air gap on one side thereof to divide the core into sections, a primary winding wound on one section of the core, a capacity exciting winding wound on the other section of the core, a secondary winding wound on both sections of the core to inductively couple both of the first mentioned windings when the secondary is under =load, magnetic leakage flux shield means supported in spaced relation about the perimeter of said core and formed with an aperture in registration with the core air gap, and selectively adjustable flux diverter means extending through the aperture of said shield means and the core air gap and being connected for movement relative thereto for selectively varying the secondary output current when the secondary is under load.

References Cited in the file of this patent UNITED STATES PATENTS 2,311,128 Ranney Feb. 16, 1943 2,555,911 Anderson June 5, 1951 2,671,196 Owen Mar. 2, 1954

Claims (1)

1. A TRANSFORMER COMPRISING, A CORE MEMBER, INDUCTIVELY RELATED TRANSFORMER WINDINGS WOUND ON SAID CORE MEMBER, MAGNETIC LEAKAGE FLUX SHIELD MEANS DISPOSED ABOUT THE PERIMETER OF SAID CORE MEMBER IN SPACED RELATION, AND SEPARATE MEANS CONNECTED INTERMEDIATE SAID CORE MEMBER AND SAID SHIELD MEANS FOR FORMING A MAGNETIC FLUX PATH BETWEEN SAID SHIELD AND SAID CORE MEMBER AND SETTING THE TRANSFORMER OUTPUT CURRENT.

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