US2655636A

US2655636A - Variable ratio transformer

Info

Publication number: US2655636A
Application number: US188784A
Authority: US
Inventors: Berthold H Pliske
Original assignee: Ohio Crankshaft Co
Current assignee: Ohio Crankshaft Co
Priority date: 1950-10-06
Filing date: 1950-10-06
Publication date: 1953-10-13
Anticipated expiration: 1970-10-13

Description

Oct. 13, 1953 B H PUSKE 2,655,636

- VARIABLE RATIO TRANSFORMER Filed Oct. 6, 1950 2 Sheets-Sheet l INVENTbR. 55977904 0 fl P1 ASK/6 ArrveA Oct. 13, 1953 s. H. PLISKE 2,655,636

VARIABLE RATIO TRANSFORMER Filed Oct. 6, 1950 2 Sheets-Sheet 2 INVENTOR. 55271404 0 6. Pas K6 Arroe/vsy Patented Oct. 13, 1953 UNITED sTATEs PATENT OFFICE VARIABLE RATIO TRANSFORMER Berthold H. Pliske, Cleveland, Ohio, assignor to. The Ohio Crankshaft Company, Cleveland, Qhiaa o rqrat q of 01.110

Application October 6, 1950, Serial No. 188,784

2 Claims. 1

This invention pertains to the art of stationary electrical transformers and, more particularly to a variable ratio transformer.

The invention is particularly applicable to high-power transformers of the type normally employed in the art of high-frequency induction heating. In such transformers, all parts must be water cooled to remove the heat generated in the transformer by the flow of currents in the transformer or by eddy currents induced throughout the transformer. The inventionwillbe described with reference to such a transformer although, of course, it is not limited to such applications.

Variable ratio transformers, are well known in the transformer art. Normally, the primary or secondary of the transformer, or both, are provided with a pluralit oftaps and flexible leads are provided which may be connected toany one of the taps to give the desired ratio of power transformation. In the art to which this invention applies, theuse. offlexible leads toconnect to the desired tap of; the transformer has been found to be completely impracticable because of the necessity-forwa-ter cooling the'leads. The water cooling of flexible leads is a rather diflicult problem. Furthermore, because. of the high currents which must be. handled, the leads would have to be of a rather large-gage copper and would be extremely stiffand difficult to bandle. For this reason and prior-to the. present invention, it has been conventional to construct fixed ratio transformers to the desired ratio; and, if the ratio of electrical transformation had to be changed, a newtransformer with a different turns ratio was substituted.

In accordance. with the present invention, a transformer is comprised of a multi-turn Watercooled coil having short rigid taps on selected turns. a water-cooled collector bus or buses in close-spaced relationship to the taps and means for selectively connecting the bus or buses to one of the coil taps, these means being relatively short and rigid and cooled by heat conduction to the' Another object of the invention is the provision of a new and improved variable ratio transformer including coils having a plurality of short, rigid taps therealong and a collector bus in spaced proximity to said taps adapted to be selectively connected one at a time to said taps, the coil and collector rings being water cooled and the spacing between the collector and taps being sufiiciently small that a connector placed between the ring and the taps will be cooled by the con duction of heat to both the taps and the collector rings.

The invention is comprised in certain parts and combination of parts, a preferred embodiment of which will be described in this application and illustrated in the accompanying drawings which are a part hereof, and wherein;

Figure 1 is a side elevatienal view of; a variable ratio transformerembodying the. present inven ticn,

Figure 2 is a sectional view of Figure 1 taken approximately on the line 2 2 thereof, and,

Figure 3 is a fragmentary-sectional.view of. Figure 1- taken approximately on theline33ither,eof to show in large detail one of thetaps on the coils and the; collector bus therefor.

Referring-now to the drawingswhereina preferred embodiment of the invention isshownfor the purposes of illustration only, and notfor the purposes oflimitation, the figures show a variable ratio transformer comprised of a core A, a tapped coil B and a pair of collector busesc adapted to be connected selectively to the, coil taps. The busesare, in turn, adapted tobe connected to bus bars or other power leads (not shown) connecting, in turn, to other electrical apparatus.

The core A is relatively conventional in construction and includesthree legs [0, H, l2 extending in spaced parallel relationship from an integral base i 3. A keeper bar l4 extends across the three free ends of the legs to complete the magnetic circuit. The core is made up of a stack of a plurality of relatively flat and thin laminations formed from a magnetically-permeable material. Theselaminations-are interleaved by a plurality of identically-shapedcooling laminationslfi formed of copper or other highheatconducting material, which have tubes ll brazed or soldered along edges thereof through which a cooling medium may be circulated. The stack of laminations is sandwiched betweenwoodstrips 20. Steelframe members l8, ofwhichthere are four, overlay. the wood strips 20; alongthe length of the outer legs and both-sides thereof. The entire stack of laminations, woodenstripslll and frame members I 8 are held in tight assembled relationship by a plurality of transverse bolts I9. The dimensions of the three legs are such that the center leg it has twice the cross-sectional area of any one side leg or, in other words, the sum of the cross-sectional area of the two side legs ill, I2 is equal to that of the center leg 6 l. The invention is, of course, equally applicable to any other type of core, including an air core.

The coils B in the embodiment shown comprise primary and secondary windings 2|, 22 positioned about the center leg I I of the core A. The primary winding is comprised of a single layer of a plurality of spaced continuous turns formed of an edgewise-bent, flat, rectangular tube of copper or the like. These turns are spaced and the secondary turns are disposed in the space between the primary turns. Each secondary turn is comprised of a single turn. The ends of the secondary turns extend radially outwardly for a short distance and are brazed or otherwise suitably jointed to the

respective terminal blocks

24 or 25. The secondary turns are also formed from edgewise-bent, flat, rectangular tubing.

The primary and secondary windings may be insulated from each other by impregnating the coils before assembly or by suitable spacer members positioned between each turn after assembly. Cooling water is circulated through the hollow interior of the primary through hose fittings 26 in a conventional manner.

The primary winding H has means for making electrical connection to selected turns along its length. These means are generally all similar in construction and reference to Figure 3 1 shows a typical construction. Thus, the means shown comprise a short, flat copper lug or plate 30 edge brazed to the outer edge of the conductor of the primary winding H at the point where a tap is desired. An L-shaped bracket 3 I, also of copper, is bolted to the lug 38 by a bolt 32. The bracket includes a vertically extending flange 35 which is provided with a threaded opening 36.

As shown, the taps are spaced axially along the coil and preferably adjacent taps are spaced circumferentially on the coil but always on the same side of the core A. To reduce the axial distance between the threaded openings 35, the bracket 3| associated with the uppermost taps may be so positioned that the flange 35 extends downwardly from the lug 30, while the brackets associated with the lower taps have the flange 35 extending above the respective lug 30.

The invention is equally applicable to multilayered coils or to an autotransformer arrangement of coils. The particular construction of taps shown may be altered. The construction shown is simple, rigid and easily adjusted.

The collector bus C comprises rigid watercooled means for making electrical connection selectively to the primary taps. In the embodiment shown, the collector buses each comprise a relatively-thin wide strip of copper or the like, electrically-conductive material rigidly mounted on the core A and so formed as to be in closespaced insulated relationship to the outer radial surfaces of the flanges 35. The buses all have openings 38 aligned with the openings 36 through which a bolt may be inserted to connect a desired tap to the bus.

The buses may be supported relative to the coil in any desired waybut, in the embodiment shown, the ends of the collector bus are fastened to an insulating dowel 39 which, in turn, is

threadably supported on a threaded extension 37 of some of the core bolts l9.

Each of the collector buses C has a copper tube to brazed to one edge thereof having hose fitings ll at each end to which suitable watercooling connections may be made. Other forms of construction of the collector bus may be employed.

When it is desired to connect the collector bus to one of the taps, a copper washer 43 is positioned in the space between the flange and the collector bus. This washer has a groove formed in one surface to guide the washer over the flange 35. The opposite surface of the washer is curved to match the inner curvature of the collector bus. When the washer is placed into position, a bolt 44 is inserted through the aligned openings 38 in the collector bus and the washer 43 and then threaded into the opening 36 of the flange 35 and tightened down securely. With such construction, there is no danger of the collector bus being in any way deformed so as to electrically engage two taps at one time.

In the transformer shown, it will be seen that all elements thereof are subject to artificial cool ing. For example, the core is cooled by the heat in the magnetic laminations being conducted to the cooling laminations and then to the cooling water in the tube. In a like manner, the primary and secondary coils will be cooled by cooling water circulated through the interior of the tubes. The lugs ill which are brazed to the primary coil are short in length and artificially cooled due to the thermal conductivity which will occur from the lug as to the tube H. The collector buses are cooled by the tubes 4!! brazed to the edges thereof. The washers 43 disposed between the collector bus and the flange 35 may be cooled by the conduction of heat both to the collector bus and through the bracket 3| to the lug 38 and then to the cooling water in the primary winding.

The transformer described has proven extremely efficient and effective in practice. All portions through which electrical currents must flow are artificially cooled. Changes in the ratio of the transformer may be readily made without the necessity of moving stiff, flexible leads from tap to tap simply by positioning a washer between the desired tap and the collector bus and screwing a bolt through the openings up tight.

The transformer above described illustrates only one embodiment which the present invention may take. Obviously, many other constructions and arrangements will occur to others upon a reading and understanding of this specification and it is my intention to include all such modifications and alterations insofar as they come within the scope of the appended claims.

Having thus described my invention, I claim:

1. A variable ratio transformer comprising a core, including a center leg and a pair of side legs in spaced parallel relationship to and one on,

side of said center leg; a helical coil formed members extending toward and having surfaces uniformly close spaced from the surface of said bus member facing said coil, said bus member having a plurality of openings, one for each lug member aligned with an opening in the respective lug member; and a conductor member having a thickness generally corresponding to the spacing between the lug and bus members adapted o be selectively positioned between one of said ug members and said bus members, said con- "iuctor member having an opening adapted to be aligned with said lug and bus member openings and means extending through said openings for holding the surfaces of said bus and conductor member and said conductor and lug member in electrically-conducting engagement.

2. A variable ratio transformer comprising a multiturn helical coil formed of a heavy hollow conductor; means for circulating a cooling medium through the center of said conductor; a bus of a heavy, rigid, conductive material mounted in fixed, spaced, relatively-close relationship to a side of said coil; means for artificially cooling said bus; a plurality of conductor lugs fixed to the edges of said coil at predetermined points spaced axially along said coil and on the side thereof adjacent said bus, all of said lugs extending toward said bus and having surfaces uniformly close spaced from the surface of said bus facing said coil; said bus having a plurality of openings; one for each lug, aligned with an opening in the respective lug; and a conductor member having a thickness generally corresponding to the spacing between the lug and the bus adapt ed to be selectively positioned between one of said lugs and said bus, said member having an opening adapted to be aligned with said lug and bus opening and means extending through said openings for holding the surfaces of said bus and member and said member and lug in firm counter-conducting engagement.

BERTHOLD H. PLISKE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,325,810 Strickland, Jr. Aug. 3, 1943 2,459,971 Stanton Jan. 25, 1949 2,474,395 Early et al June 28, 1949