US3516040A - Transformer structure - Google Patents

Description

June 2, 1970 J. F. RIPLEY ET AL TRANSFORMER STRUCTURE 2 Sheets-Sheet 2 Filed Aug. 5. 196e /A/ VEA/TORS WALLACE/4. MEA/KE JOHN F R/ LEY fan-v @u .um/ 5y T Hg 5,

United States Patent Oice 3,516,040 Patented June 2, 1970 3,516,040 TRANSFORMER STRUCTURE John F. Ripley, Park Ridge, Ill., and Wallace W. Menke,

Lake Geneva, Wis., assignors to Micron Sealing Corporation, Stone Park, Ill., a corporation of Illinois Filed Aug. S, 1968, Ser. No. 750,150 Int. Cl. H01f 27/04; H02h 7/04 U.S. Cl. 336-96 10 Claims ABSTRACT OF THE DISCLOSURE A compact machine tool transformer having an encapsulated coil with L-shaped terminal lugs embedded in the encapsulant; one leg portion of the terminal lug is secured in the encapsulant while the other leg extends over the encapsulant and is tapped to accommodate terminal screws which also extend into screw-receiving sockets under the tapped portion of the lug. Flanges extend from the encapsulated coil between the lugs to provide corona barriers. A fuse clip carrying adapter is provided with legs to extend into the cavity formed by the flanges of the encapsulated coil. A laminated core extends into the window of the coil.

This invention relates to transformer structures and to their method of fabrication. More particularly, the invention is directed to transformers in which the wound coil is encapsulated and protected against environmental hazards, the terminals of the windings are rmly supported to provide markedly improved physical torque rating, transformer-integrated fuse mounting means protect equipment and the coil windings, and physical barriers ensure enhanced arc track resistance from terminal to terminal and from terminal to core. The barriers also protect against accidental contact with or shorting of the bare terminals. Preferred embodiments of the present invention are directed to machine tool transformers.

Many types of machine tool transformer structures have been proposed and devised for specific applications. These transformers have taken varied physical forms and structural arrangements and many different fabrication techniques have been utilized. Nevertheless, no completely satisfactory transformers have heretofore been produced, each of the previously manufactured electrical components having one or more undesirable or objectionable features deterring their acceptance and use. Some of the prior art transformers have been unduly bulky and cumbersome. In others the terminals have been inadequately supported physically and have been exposed to damage and breakage, and to electrical shorting. Many prior art transformers are readily susceptible to damage from atmospheric and ambient conditions and from environmental hazards. It is, therefore, the aim of the present invention to provide an improved transformer which obviates the shortcomings of the prior art structures and which functions effectively under all conditions experienced in industrial use.

It is a principal object of the invention to provide a compact transformer in which the coil is completely encapsulated and in which the terminals are mechanically supported and rmly secured.

It is a related important object of the invention to provide a transformer structure in which the terminals are protectively recessed to obviate accidental shorting and inadvertent contact, and to improve arc track resistance.

Yet another object of the invention is to provide a transformer in which integrated fuse-holding clips carry fuses serving as protective elements for the coil windings and for energized machines.

Still another object of the invention is to provide a transformer in which the terminals have markedly increased physical torque ratings, to facilitate attachment of terminal-connected leads without damage to terminals and to winding leads.

It is an important feature of the transformer structure of the invention that the terminals are embedded or anchored in and are firmly secured in the molded mass which encases the coil and that the lugs of the terminals overlie the coil itself to minimize overall size of the assembly.

It is a related feature of the invention that the terminal-securing molded casting is formed to include threaded sockets which are adapted frictionally to receive the terminal screws therewithin and to secure the screws against inadvertent loosening due to vibrations or other dislodging forces.

Yet other important features of the invention are fuse clips which are attachable to overlie the transformer structure so as to maintain a minimum mounting area for the transformer.

Another important object of the invention is to provide a fuse-clip carrying adapter which may conveniently and readily be secured to the transformer to provide fuse means for the windings of the transformer, as required.

It is a feature of the invention that the fuse clips are mounted directly on the terminals, effecting cost savings and space conservation, and providing a stable support.

It is an important feature of the transformer of the invention that they operate at significantly lower temperatures through improved conduction and through effectively increased radiation area.

A further object of the invention is to provide a transformer of exceptional reliability and improved overall appearance.

Other and further objects, advantages, and features of the invention will become aparent from a reading of the following specification taken in conjunction with the drawings in which:

FIG. 1 is a perspective view, with. parts cut away, of a transformer constructed in accordance with the invention;

FIG. 2 is a perspective view of a prior art transformer, in which the terminals extend, unsupported, outwardly from the transformer body;

FIG. 3 is an end elevational view of a transformed constructed in accordance with the invention, and including fuse holding clips connected to each of the windings of the encapsulated coil;

FIG. 4 is an end elevational view of a transformer similar to that shown in FIG. 1 but provided with a centered through or recess serving as a central wiring channel;

FIG. 5 is a perspective view of the transformer of FIG. 1 and showing a fuseholding adapter mounted thereon;

FIG. 6 is a cross sectional view taken on the line 6 6 of FIG. 8 and showing the manner of securement of the terminal-holding screws in the cast, coil-encapsulating ring;

FIG. 7 is a perspective view of a transformer coil, with terminal lugs temporarily held in place prior to encapsulation of the coil;

FIG. 7A is a schematic diagram of the winding connections of a machine tool transformer fabricated according to the invention and providing a v. secondary output with either a 230 v. or 460 v. input to the primary windings;

FIG. 8 is a perspective view of the casting produced in encapsulating the coil of FIG. 7, and showing the lugplate-isolating webs and flanges;

FIG. 9 is a perspective View of the fuse-holding adapter of the invention;

FIG. is a cross-sectional view taken on the line 10- 10 of FIG. 1, and showing the cast coil-encapsulating ring embraced in the laminated core; and

FIG. 1l is an exploded fragmentary view indicating the structural arrangement of the laminated core of one embodiment of the invention.

The transformers of preferred embodiments of the present incention are machine tool type transformers specially designed with low impedance so as to operate safely devices which demand high inrush current. In a typical structure the primary windings accommodate 230 and 460 volts and the output of the secondary winding is 115 volts. The specific parameters of the transformers themselves do not constitute elements of the invention, and the inventive concepts disclosed and described are applicable equally to all transformers of the general type described.

The aims and objects of the invention are accomplished by providing in a transformer a hermetically sealed, encapsulated coil in combination with an embracing laminated core, the coil terminals being embedded and sup ported physically in the coil encapsulating medium with terminal plates overlying the coil itself. The terminal plates are recessed and protected, and in preferred examples of the invention one or more fuse clips are mounted on the terminals for overload protection of the coil windings and equipment connected thereto. A compact, high strength, transformer of increased load capacity and of improved safety features is achieved.

Referring now to the drawings, and particularly to FIGS. l, 7 and 8, for purposes of disclosure, the transformer of the invention is shown embodied in a machine tool transformer 20 including a molded ring 24 encasing a coil 30, a metal core or laminate 40 encircling and clampingly embracing the molded ring 24, and terminals or lug assemblies 50 connected electrically to ends of the coil windings and firmly secured in the composition of the molded ring 24.

The internal structure of the coil itself is not critical, playing no significant role in the subject invention. The manner in which the windings are connected is of interest, however. The coil of an exemplary transformer 20 includes three windings (FIG. 7A) consisting of a first primary windings 554 connected at its ends to terminals A and B of the transformer, -a second primary winding 58 connected at its ends to terminals C and D, and a secondary -winding 62 connected at its ends to terminals X1 and 52. In the example illustrated in FIG. 7A, the series connection of the primary windings is for a 460 volt input, and the parallel connection of the primary windings is for a 230 volt input. In each case, the secondary coil provides a 115 volt supply.

In the specific illustrative form of the invention shown the molded ring 24 (FIG. 8) which encases the coil 30 is generally rectangular in peripheral contour and includes a pair of front and rear walls 80 and 82 and a pair of opposed side walls 86 and 88 integrally molded with the front and rear walls to provide a unitary integral assembly consisting of a block with a through opening 92 which extends through the center of the encapsulated coil itself.

As indicated in FIG. 7, the terminals or lug assemblies 50 are generally L-shaped in veritical section and include downwardly extending legs 100 and horizontally disposed plates 106, the legs 100 being embedded within and firmly secured in the molded ring 24 (FIG. 8) and the plates being turned inwardly of the assembly to overlie opposed front and rear walls 80 and 82 of the ring and the coil 30 embedded therein. This novel and highly useful arrangement ensures maximum physical stability for the lugs and effects important space savings. The plates 106 are formed with tapped screwreceiving openings 110, the screws 116 themselves extending through the plates and into in-line threaded sockets 120 (FIG. 6) formed in the molded ring 24. The sockets 120 are partially restricted, radially, and constitute receptacles adapted to receive the terminal screws 116 in firmly gripping engagement whereby the screws are frictionally held against inadvertent loosening due to vibrations and other dislodging forces. This unique structural arrangement obviates the need for lock washers or other securement means. In a preferred fabricating technique of the invention, the threaded sockets are formed by casting the molded ring with the terminal screws in place.

'Ihe terminal-carrying front and rear walls 80 and 82 of the molded ring 24 are formed with 'integral parapetlike webs or flanges extending upwardly between the lug assemblies or terminals 50 and with upstanding back plates to establish three-walled, forwardly (and rearwardly) opening receptacles at each lug assembly. The webs 130 and the back plates 140 serve as corona barriers and ensure that there is the requisite flash distance (e.g., one-half inch) from terminal-to-terminal and from terminal-to-core in the final assembly. Recessing of the lug assemblies or terminals 50 also provides important protection to preclude contact with objects accidentally drop ped onto the transformer, and prevents shorting.

The elements of the lamination or core 40 of the transformer may take any preferred physical form, but in the specific embodiment of the invention illustrated (FIG. ll) the core consists of a sandwich array of reversely arranged interleaved and intermeshing generally E-shaped plates with arms 160, 162 and 164 vertically disposed.

The center arms 162 pass through the opening 92 of the molded ring 24 and the cross plates 166 abut the upper and lower bounding faces of the ring with arms and 164 embracing opposed side walls 86 and 88, so that the core encircles the body and fills the central opening of the encapsulated coil 30. Upon assembly, the entire laminate structure is secured with rivets 168 or in any other conventional manner and a protective coating of resin or varnish applied.

Important features of the invention are the fuse clips 184 which are secured to the lug assemblies or terminals 50 and overlie the coil 30. This structural arrangement facilitates the use of space which would otherwise be Wasted and makes possible elimination of remote, panelmounted fuses in favor of more convenient transformercarried fuses 190. A transformer with a fuse clip connected to the secondary winding is shown in FIG. 1, and transformers in which both primary windings and the secondary winding are fused are shown in FIGS. 3 and 5.

In a somewhat modified form of the present invention, fusing of the transformer primary windings is achieved through the use of a novel adapter 200, such an adapter being illustrated in FIG. 9 and shown, connected to a transformer, in FIG. 5. The adapter includes a base or oor plate 206 to which are secured a pair of two-piece fuse clips 210, 210a and 214, 214a, each adapted to hold a fuse 1'90. Integrally formed with and extending downwardly from floor plate 206 are a pair of legs or wedges 220 and 222 laterally spaced in correspondence with the spacing of recesses or receptacles housing terminals (A and D) of the assembly, and the screws 230 and 232 which secure the clip elements 210 and 214 to the adapter 200 are threadedly received in the sockets 120 and fasten the adapter 200 of the molded ring 24. The same screws 230 and 232 establish electrical contact between the fuseclip elements 210 and 214 and the lug plates 106 (A) and 106 (D) therebelow.

A schematic diagram of the coil connections and windings of the transformer is shown in FIG. 7A, with terminals A and C shorted (for example, with a conductive band), and with terminals b and D shorted, the primary windings 54 and 58 are connected in parallel and a circuit for a 230 v. input is established, the input to be connected to fuse terminals 210a and 214a. If a 460 v. input is to be used, terminals B and C are shorted to connect primary windings 54 and 58 in series. In either case postulated, the output of the secondary of the transformer is 115 volts. From the foregoing description it will be appreciated that the adapter 200 constitutes a simple and effective medium for fusing both sides of the primary winding of the transformer. No modification of the transformer itself is necessary and no additional space is required.

Many of the procedural steps and techniques utilized in fabricating the transformer of the invention are well known in the prior art. There are, however, several important and novel features of the overall process which contribute significantly to the success and effectiveness of the final assembly. Accordingly, the general procedure, according to the invention, is described briey below.

In order to eliminate moisture and occluded gases the transformer coil is subjected to a degassing baking step at a temperature considerably higher than the anticipated "temperature reached during operation of the transformer. The coil is then impregnated with a relatively fluid composition such as an epoxy preparation to protectand to secure the windings in place. The impregnated coil is inserted into a mold cavity, the transformer terminals 50 being supported in place (FIG. 7) within the cavity at opposed sides of the assembly to overlie the coil 30, and the mold cavity, containing the coil, is filled with a hardening resin composition to encase and to seal the coil hermetically to provide a molded ring (FIG. 8) with the terminals mechanically secured to and supported on the ring over the coil. As indicated in FIG. 8, the final ring defines a core-receiving channel extending downwardly through the ring and through the coil encased therewithin. v

In preferred encapsulating formulations used in the practice of the present invention additives are incorporated, including fire retardants to impart quenching or self-extinguishing properties. Other additives ensure high dielectric strength. In addition, fluidizing agents reduce viscosities and promote void-free castings. The final assembly has improved dielectric strength and enhanced insulation values.

Still other additives finding utility in the practice of the invention are plasticizers or flexilizers incorporated to improve the physical properties of the casting and to prevent objectionable brittleness so that the final casting is less vulnerable tomechanical shock.

The carefully prepared and compounded encapsulating composition is subjected to vacuum to remove entrapped air and other gases and moisture and then poured over the coil in the mold, as previously described. The final resin passes flame test Method 111, MIL Standard 202-C, and also meets the self extinguishing standards of the Underwriters Laboratories, Inc.

It has been found that in the final assembly of the invention the heat transfer characteristics permit the unit to operate 30 F. cooler than conventional, prior art unmolded units of generally the same size and capacity. This improved thermo conductivity allows a higher VA rating for a given coil. For example, a 75 VA coil will do the work of a 100 VA coil and still operate within the NEMA temperature standards. It will also be appreciated that the completely impregnated, molded, and hermetically sealed coil obviates the vexing problem of oxygen and ozone deterioration of the insulating materials at elevated temperatures. If desired, any selected dyes may be added to the resin formulation to give a preferred color.

The adapter 200 illustrated in FIGS. and 9 accommodates two fuses. It will, however, be readily evident to those skilled in the art that an adapter for holding only a single fuse may be used. For example, an adapter consisting essentially of one half of the adapter shown in the drawing would find utility where it is desired to fuse one side only of the input circuit.

Epoxy resins are preferred formulation for encapsulation in accordance with the practice of the invention. Other suitable encapsulating media include polyesters, silicone rubber systems, urethane, phenolformaldehyde systems, and plastisols.

While disclosures of preferred embodiments of the invention and preferred methods of fabricating the structural components of the invention have been provided, it will be apparent to those skilled in the art that numerous modifications, changes and variations can be made without departing from the essential spirit and the underlying principles of the invention. It is, therefore, desired by the following claims to include within the scope of the invention all such variations and modifications by which substantially the results of this invention may be obtained through the use of substantially the same or equivalent means.

What is claimed is:

1. A transformer comprising:

a coil including a primary winding and a secondary winding,

a resinous molded ring mechanically encasing and hermetically sealing said coil and protecting said coil from physical and chemical environmental hazards,

said ring including front and rear walls and a pair of side walls integrally molded therewith,

said side walls connecting respective opposed ends of said front and rear walls and defining therewith a through opening in said ring,

whereby said ring constitutes a loop substantially rectangular in horizontal cross section, with said opening extending vertically therethrough,

an array of interleaved contiguously disposed metal laminates defining wall means encircling said ring in a vertical plane, said laminates including a pier extending between upper and lower said wall means of said laminates and through substantially to fill said opening in said ring,

terminal means comprising a plurality of generally L shaped metal lugs connected electrically to ends of windings of said coil,

horizontally disposed plates of said lugs overlying said front and rear walls of said ring,

said plates having tapped screw-receiving openings formed therein,

and downwardly extending legs of said lugs constituting anchor elements of said lugs embedded in said molded walls and secured therewithin firmly to support and to secure said plates thereabove.

2. The transformer as set forth in claim 1 wherein said molded front and rear walls have formed to extend downwardly of upper faces thereof and in axial alignment with said tapped openings in said plates of said lugs screwereceiving sockets including thread means formed in bounding surfaces thereof, said sockets constituting partially restricted receptacles adapted to receive in frictionally gripping engagement connection terminal screws extending through said plates of said lugs and into said sockets,

whereby said screws are retained against inadvertent losening due to vibrations and other dislodging forces.

3. The transformer as set forth in claim 1 and further comprising a fuse clip, and fastening means securing said fuse clip to said terminal means to support a clip-gripped fuse on said transformer above a said molded wall of said ring.

4. The transformer as set forth in claim 1 and further comprising corona barrier means integrally molded with said ring and comprising spaced fiange-like parapets constituting extensions of said wall projecting upwardly of said lugs and therebetween, and extending between said lugs and said metal laminates to increase creepage paths and to ensure requisite flash distances from terminal to terminal and from terminal to core,

said extensions defining protected recesses for said terminal means to obviate inadvertent shorting thereof.

5. The structure as set forth in claim 1 wherein said transformer is of a machine tool transformer type.

6. The transformer as set forth in claim 1 and further comprising resin means impregnating said coil to mainmeans connecting said fuse clip to a said metal lugv of said terminal means of said transformer to complete an electrical circuit between said fuse clip and a coil winding of said transformer; y whereby a fuse held by said fuse clip constitutes aprotective element for said coil winding and for an electrically -powered machine tool energized through said transformer. 8. A transformer as set forth in claim 7 wherein said adapter carries a plurality of fuse clips, and electrically conductive means connecting an end of each of said fuse clips to a corresponding end of a coil Winding of said transformer.

9. A transformer as set forth in claim 7 wherein said means connecting said fuse clip to said metal lug of said terminal means also secures said adapter to said molded ring of said transformer. i

10. A transformer as set forth in claim 1 and further comprising a fuse-clip-carrying adapter,-

said adapter comprising an insulative plate overlying said'molded ring and integrally formed with a de pending leg adapted for seating and keying in a recess formed in said molded ring and housing a said terminal means,

` fastener means for securing said adapter to said molded ring, and electrically conductive means connecting a fuse clip of said adapter to said terminal means.

References Cited UNITED STATES PATENTS 1,795,052 3/1931 Sinagusa 336-96 2,464,029 3/ 1949 Ehrman 336-96 2,997,526 8/1961 Kessel et al 336-96 XR 3,346,828 10/ 1967 Buschman 336-205 XR 3,434,087 3/ 1969 Hofmann 336-96 FOREIGN PATENTS 675,894 ll/ 1964 Italy.

THOMAS I. KOZMA, Primary Examiner U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CGRRECTION Patent No 3 ,516 ,O40 June 2 1970 John F. Ripley et al.

It is certified that error appears in the above identified d that Said Letters Patent are hereby corrected as pat ent an shown below:

Column Z, line 29, "transformer" should read transformers line 45, "transformed" should read transformer line 5l,

"incention" d read trough Column 3, line 7,

"through" Shoul Should read invention line 43, "554" should read 54 line 47, "52" Should read X2 line 6l, "Veritical" Should read vertical Column 6, line 56, "losening" should read Signed and sealed this 12th day of January 1971.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

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