Welding power supply transformer

Information

  • Patent Grant
  • 6611189
  • Patent Number
    6,611,189
  • Date Filed
    Tuesday, May 22, 2001
    23 years ago
  • Date Issued
    Tuesday, August 26, 2003
    20 years ago
Abstract
A welding-type power supply transformer including a bobbin, a first coil and a second coil is disclosed. The first coil is wound around the bobbin. The second coil is magnetically coupled to the first coil.
Description




FIELD OF THE INVENTION




The present invention relates generally to electrical transformers. More specifically, it relates to high voltage, high current electrical transformers for use in welding power supplies, plasma cutters and induction heaters.




BACKGROUND OF THE INVENTION




High frequency transformers operating at high voltages and high currents are commonly used in welding power supplies. The output stage of a welding power supply, for example, may include an electrical transformer to transform the high bus voltage of the welding power supply into a high current welding output. Transformer primary coil voltages on the order of 465 volts at 20 to 100 Khz and secondary coil currents on the order of 400 amps are typical. Welding power supply transformer coils (e.g., primary and secondary coils) are made from large diameter wires (3-14 gauge wire is typical) in order to handle the temperatures generated by these large voltages and currents.




Most of these transformers include a central bobbin having a coil winding window disposed about a central opening in the bobbin. The central opening is provided to receive one or more laminated or ferrite magnetic cores. Standard off-the-shelf magnetic cores are available in a wide variety of sizes and shapes, many of which have square or rectangular cross-sections. The coil windings typically also have rectangular or square cross sections wound close to the magnetic cores. This is because it is generally desirable to keep the coil windings close to the magnetic core to maximize the magnetic coupling between the magnetic core and the coil windings.




Having coil windings with rectangular or square cross sections can be problematic in welding applications however. This is because the large diameter wires used in welding power supply transformers have a tendency to deform or bulge at locations where the winding direction changes quickly (e.g., at the corners when wound around a bobbin having a square or rectangular cross section). This is especially true for Litz wire, a stranded woven type of wire used extensively in high frequency (e.g., 20 Khz to 100 khz) welding power supply transformers. The outer insulation that is placed over these large wires can also bulge and deform.




The width of the overall coil winding in the area of the deformations tends to be wider than the width of the remaining portion of the coil because of the bulging wires. As a result, the coil may not fit within the winding window of the bobbin in those areas. At the very least, extra manufacturing steps, typically manual, must be taken during the coil winding process to properly fit the deformed coil into the winding window in the vicinity of the bulges or deformations. It is desirable, therefore, to have a bobbin winding window cross section that does not have quick changes in winding direction. Preferably, the central opening in the bobbin will still accommodate standard size, readily available, magnetic cores having rectangular or square cross sections.




Another problem with using large diameter wires in welding power supply transformers is that the wire leads to and from these transformers tend to be less flexible than smaller wire leads. Extra space has typically been available inside of the welding power supply chassis around these transformers to allow the high voltage and high current transformer leads to be safely routed and connected to the rest of the welding power supply.




The current trend in designing welding power supplies, plasma cutters and induction heaters, however, is to make these devices smaller. One way to accomplish this is to pack the various power supply components closer together inside of the chassis. As a result, other power supply components are placed closer to the high voltage, high current transformers in these designs. Less room is thus provided to safely rout the leads from the transformer to the rest of the power supply.




It is desirable therefore to have a welding power supply transformer wherein the leads exit the transformer in a known and repeatable manner. Preferably, the transformer structures will have smooth edges and surfaces in the vicinity where the leads exit the transformer to prevent damage to the transformer leads.




Another problem with welding power supply transformers, especially welding power supply transformers operating at high frequencies, is leakage inductance. The presence of high leakage inductance in these transformers can cause several problems. A leaky output transformer can reduce the output power of the welding power supply. The primary and secondary coils in leaky transformers are more susceptible to overheating. Finally, the energy stored in the leakage inductance can be detrimental to transistor switching circuits in the welding power supply. Release of this stored energy can cause ringing, transistor failure and timing issues. Reducing or minimizing the leakage inductance in welding power supply transformers is therefore generally desirable.




Leakage inductance results from primary coil flux that does not link to the secondary coil. The amount of primary coil flux linked to the secondary coil is dependent on the physical orientation and location of the primary and secondary coils with respect to each other. Reducing or minimizing the mean distance between the turns of the primary coil and the turns of the secondary coil will typically reduce or minimize leakage inductance in a transformer. Reducing or minimizing the mean length of the turns in a coil will also typically reduce or minimize leakage inductance.




It is desirable, therefore, to reduce or minimize the mean distance between the turns of the primary coil and the turns of the secondary coil in welding power supply transformers. Preferably, the mean length of the turns in the coils of the transformer will also be reduced or minimized.




SUMMARY OF THE PRESENT INVENTION




According to a first aspect of the invention, a welding-type power supply transformer includes a bobbin having elongated top and bottom surfaces and first and second substantially semi-circular end surfaces connecting the top surface with the bottom surface to form an elongated first coil winding surface having a central axis. A first coil is wound around the first coil winding surface of the bobbin. A second coil is magnetically coupled to the first coil.




In two embodiments, the transformer also includes an insulating shroud disposed between the first coil and the second coil. The insulating shroud includes elongated top and bottom surfaces and first and second substantially semi-circular end surfaces in one of the embodiments. The substantially semi-circular end surfaces connect the top surface with the bottom surface to form a second coil winding surface. The second coil is wound around the second coil winding surface in this embodiment. The second coil includes a plurality of second coil turns in another embodiment. The transformer includes a plurality of locating bosses in this embodiment disposed on the second coil winding surface to maintain each of the plurality of second coil turns in a desired location.




In the other embodiment, the insulating shroud includes a second coil winding surface and first and second insulating shroud sidewalls. The sidewalls are each disposed along opposite sides of the second coil winding surface. The second coil winding surface substantially conforms to the shape of the first coil in this embodiment and the second coil is wound around the second coil winding surface between the first and second insulating shroud sidewalls.




The bobbin includes a central opening disposed inside of the first coil winding surface in another embodiment. A magnetic core is disposed in the central opening. The magnetic core has a rectangular cross-section immediately adjacent one of the first or second substantially semi-circular end surfaces. In yet another embodiment, the second coil includes a plurality of second coil turns. A plurality of locating spacers are disposed to maintain a desired spacing between each of the plurality of second coil turns. The plurality of locating spacers are disposed such that there is at least one locating spacer between each second coil turn in one embodiment and such that there is at least one locating spacer on each side of each second coil turn in an alternative embodiment.




In another embodiment, the bobbin includes first and second bobbin sidewalls. Each sidewall is disposed along opposite sides of the first coil winding surface to form a winding window. The bobbin also includes first and second wire exits adjacent to and in open communication with the winding window. The first coil includes a first lead end exiting the winding window through the first wire exit and a second lead end exiting the winding window through the second wire exit. The first lead end and the second lead end exit the bobbin in a direction that is substantially perpendicular to the central axis in this embodiment.




The second coil is wound concentric to the first coil in one other embodiment. The transformer includes a cover disposed such that the first coil and the second coil are compressed between the first coil winding surface and the cover in this embodiment.




According to a second aspect of the invention, a welding-type power supply transformer includes a bobbin, a first wire exit, a first coil and a second coil. The second coil is magnetically coupled to the first coil. The bobbin has a central axis and a first winding window located about the central axis. The first winding window includes a first coil winding surface and first and second bobbin sidewalls each located on opposite sides of the first coil winding surface. The first wire exit is in open communication with the first winding window. The first coil is wound around the first coil winding surface and includes a first lead end. The first lead end exits the first winding window through the wire exit such that the first lead end exits the bobbin in a direction that is substantially perpendicular to the central axis.




The transformer includes a second wire exit in open communication with the first winding window in another embodiment. The first coil includes a second lead end exiting the first winding window through the second wire exit such that the second lead end exits the bobbin in a direction that is substantially perpendicular to the central axis in this embodiment. Each of the wire exits is disposed adjacent to the first winding window in another embodiment.




In one embodiment, each wire exit includes an outside wall and a rear wall. The rear wall is connected to the bobbin sidewall along a first edge and is connected to the outside wall along a second edge. The first and second edges are radiused on the inside of the wire exits in this embodiment.




In another embodiment, the second coil includes a plurality of second coil turns. A plurality of locating spacers are disposed to maintain a desired spacing between each of the plurality of second coil turns. The plurality of locating spacers are disposed such that there is at least one locating spacer between each second coil turn in one embodiment. The plurality of locating spacers are disposed such that there is at least one locating spacer on each side of each of the plurality of second coil turns in an alternative embodiment.




The second coil is wound concentric to the first coil in one embodiment. The transformer includes a cover disposed such that the first coil and the second coil are compressed between the first coil winding surface and the cover in this embodiment.




According to a third aspect of the invention, a welding-type power supply transformer includes a bobbin, a first coil, a second coil and a cover. The bobbin has a first coil winding surface. The first coil is wound around the first coil winding surface. The second coil is wound concentric to the first coil. The first coil and the second coil are compressed between the first coil winding surface and the cover.




The transformer further includes a plurality of compression bosses in one embodiment. Each of the plurality of compression bosses contacts one of the first or second coils to compress the first coil and the second coil between the first coil winding surface and the cover in this embodiment. At least one of the plurality of compression bosses is located on the cover in one embodiment and at least one of the plurality of compression bosses is located on the first coil winding surface in another embodiment.




The second coil is disposed on the outside of the first coil and an insulating shroud is disposed between the first coil and the second coil in other embodiments. The second coil includes a plurality of second coil turns in one other embodiment. The plurality of locating spacers are disposed to maintain a desired spacing between each of the plurality of second coil turns in this embodiment.




According to a fourth aspect of the invention, a welding-type power supply transformer includes a first coil and a second coil magnetically coupled to the first coil. The second coil includes a plurality of second coil turns. A plurality of locating spacers are disposed to maintain a desired spacing between each of the plurality of second coil turns.




Each of the plurality of locating spacers is disposed such that there is one locating spacer between each second coil turn in one embodiment. The plurality of locating spacers are disposed such that there is one locating spacer on each side of each of the plurality of second coil turns in another embodiment.




According to a fifth aspect of the invention, a method of reducing the leakage inductance in a welding-type power supply transformer includes providing a first coil. A second coil is wound concentric to the first coil. The first coil and the second coil are compressed together to reduce the leakage inductance between the first coil and the second coil to a desired value.




Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

shows a block diagram of a welding power supply according to one embodiment of the present invention;





FIG. 2

shows an exploded view of an electrical transformer according to one embodiment of the present invention;





FIG. 3

shows an isometric view of a bobbin used in the electrical transformer shown in

FIG. 2

;





FIG. 4

shows an isometric view of a first coil wound around the bobbin shown in

FIG. 3

;





FIG. 5

shows an isometric view of an insulating shroud wrapped around the first coil shown in

FIG. 4

;





FIG. 6

shows an isometric view of a third coil wound around the insulating shroud shown in

FIG. 5

;





FIG. 7

shows an isometric view of a second coil wound around the insulating shroud shown in

FIG. 5

;





FIG. 8

shows an isometric view of a cover disposed about the second coil shown in

FIG. 7

;





FIG. 9

shows an isometric length wise cross-sectional view of the electrical transformer shown in

FIG. 2

; and





FIG. 10

shows a width wise cross-sectional view of the electrical transformer shown in FIG.


2


.











Before explaining at least one embodiment of the invention in detail it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. Like reference numerals are used to indicate like components.




DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




While the present invention will be illustrated with reference to a particular electrical transformer configuration having particular features, the present invention is not limited to this configuration or to these features and other configurations and features can be used. Similarly, while the present invention will be illustrated with reference to a welding power supply having a particular configuration and particular features, other welding and non-welding power supplies having other configurations and features can also be used. Finally, the present invention is also not limited to use in power supplies, but rather can be used in other non-power supply applications as well.




Generally, the present invention involves an electrical transformer for use in a welding power supply. Although discussed herein with reference to its use in a welding power supply, the present invention can also be used with other types of power supplies including plasma cutters and induction heaters. The term welding-type power supply as used herein includes plasma cutters and induction heaters as well as welding power supplies.




The electrical transformer includes a bobbin having an elongated coil winding surface disposed about (e.g., symmetrical about) a central axis in one embodiment. The elongated coil winding surface includes a pair of straight, flat (substantially straight and substantially flat in other embodiments) surfaces disposed between a pair of substantially semi-circular end surfaces in this embodiment (the end surfaces are semi-circular in another embodiment). Semi-circular as used herein means half of a circle (e.g., 180 degree arc). A pair of upwardly directed bobbin sidewalls disposed on opposite sides of the coil winding surface define a bobbin winding window.




A primary coil is wound around the coil winding surface of the bobbin inside of the bobbin's winding window. The curved slowly changing substantially semicircular end surfaces prevent bulging in the large diameter individual turns of the primary coil as the turns are wound around the bobbin. The bobbin also includes a central opening for receiving one or more magnetic cores.




The magnetic cores in this embodiment are standard sized, off-the-shelf E shaped ferrite cores. In other embodiments, other core shapes are used including rectangular, square, I-shaped, T-shaped, round, etc. . . . The E-shaped cores used in this embodiment have rectangular or square cross-sectional legs. For example, the middle legs of the magnetic cores disposed in the central opening of the bobbin have a rectangular cross-section in this embodiment. This includes the two cores located immediately adjacent (e.g., closest) to each of the substantially semi-circular end surfaces. Rectangular cross-section as used herein includes square cross-sections and rectangular cross-sections having beveled, rounded or angled corners.




A pair of elongated channel shaped wire exits are provided, one on each side of the winding window of the bobbin. These wire exits are in open communication with the winding window and are used to guide the primary coil leads out of the winding window in a known and repeatable manner. The primary leads are guided out of the bobbin by the wire exits in a direction that is substantially perpendicular to the central axis of the winding window in this embodiment. In other embodiments, coil lead ends are guided out of the bobbin by wire exits in a direction that is perpendicular to the central axis.




It should be understood that he present invention is not limited to elongated channel wire exits and other wire exit configurations can be used. Wire exit as used herein includes any structure that can be used to guide large diameter wire lead ends out of a bobbin but does not include pins used for mounting a transformer to through holes in a circuit board.




An insulating shroud completely surrounds the primary coil in this embodiment. The insulating shroud also has an elongated coil winding surface with substantially semi-circular end surfaces. The shape of the coil winding surface of the insulating shroud conforms to the shape of the primary coil. A pair of upwardly directed insulating shroud sidewalls disposed on opposite sides of the coil winding surface define an insulating shroud winding window.




A boost coil and a secondary coil are wound around the coil winding surface inside of the winding window of the insulating shroud in this embodiment. The boost coil is wound first and uses smaller diameter wire than the secondary coil. The secondary coil is wound over the boost coil. Locating bosses on the surface of the coil winding surface of the insulating shroud are provided to maintain the turns of the boost coil in their desired locations between the turns of the secondary coil and to initially locate the individual turns of the secondary coil in their desired locations across the width of the insulating shroud winding window.




The individual turns of the secondary coil are spaced apart from one another in this embodiment to reduce the leakage inductance of the transformer to a desired value. A two piece cover is positioned over the secondary coil. The cover includes a plurality of locating spacers. In one embodiment, a locating spacer is disposed between each coil turn of the secondary coil to help maintain the desired spacing between the secondary coil turns. A locating spacer is disposed on either side of each turn of the secondary coil to help maintain the desired spacing between the secondary coil turns in another embodiment. The cover also provides insulation between the secondary coil and the magnetic cores.




Desired value of leakage inductance, as used herein, for a particular application utilizing a transformer according to the present invention includes values which allow the transformer to be used for its intended purpose in that particular application. Desired value of leakage inductance may be a range of values and may vary from application to application depending on the specifics of the application. Desired spacing between the individual turns of a coil, as used herein, for a particular application utilizing a transformer according to the present invention includes spacing which allows the transformer to be used for its intended purpose in that particular application. Desired spacing of coil turns may be a range of values and also may vary from application to application depending on the specifics of the application.




A plurality of E-shaped magnetic cores surround the bobbin in this embodiment. The middle leg of each E-core fits snugly into the central opening of the bobbin and the top and bottom legs of each E-core fit snugly over the two piece cover to compress the secondary coil and the primary coil together between the cover and the coil winding surface of the bobbin. Compressing the coils together reduces the mean distance between the turns of the primary coil and the secondary coil reducing or minimizing the leakage inductance of the transformer to a desired value. To further compress the coils together, the inside surface of the two piece cover includes a plurality of compression bosses. One compression boss is disposed on the outside of each secondary coil turn in this embodiment.




Compressing the primary coil and the secondary coil together as used herein means squeezing the primary coil and the secondary coil together but does not require that the primary coil and the secondary coil actually touch each other (e.g, (there may or may not be another structure disposed between the two coils such as an insulating shroud). Similarly, compressing two coils together as used herein does not require a reduction in the size or volume of either coil.





FIG. 1

shows a block diagram of a welding power supply


100


according to one embodiment of the present invention. Power supply


100


includes an input circuit


101


, an output circuit


102


and a transformer


103


. Transformer


103


is connected between an output


104


of input circuit


101


and inputs


105


and


113


of output circuit


102


in this embodiment. The overall operation of power supplies of the type shown in

FIG. 1

are well understood by those of ordinary skill in the art. Two such power supplies include the Alt


304


welding power supply and the Auto Invision 6500 welding power supply, both of which are manufactured by Miller Electric Mfg. Co. of Appleton, Wis.




Generally speaking, input circuit


101


is configured to receive an input signal from an external source of power at its input


106


. Input signal and output signal as used herein include voltage signals, current signals and power signals. Source of power as used herein includes any source of power that can be used by a welding-type power supply to obtain a welding-type output signal suitable for welding, plasma cutting or induction heating and includes utility power sources (such as line voltages), generators, batteries, etc. . . .




The input signal received at input


106


is processed by the various circuitry of input circuit


101


and the processed signal is provided to transformer


103


at output


104


. The output signal from input circuit


101


is received by transformer


103


via its input


107


and transformed to its outputs


108


,


112


. In one embodiment, transformer


103


includes a primary coil


109


connected to the output


104


of input circuit


101


and a center tapped secondary coil


110


connected to the input


105


of output circuit


102


. Secondary coil


110


is disposed inside of transformer


103


to magnetically couple with primary coil


109


.




In addition to secondary coil


110


, this embodiment also includes a boost coil


111


disposed to magnetically couple with primary coil


109


. Boost coils are well known in the art and are typically used to maintain the welding arc during stick welding. The output


112


of boost coil


111


is provided to output circuit


102


at input


113


.




In another embodiment, secondary coil


110


of transformer


103


is not a tapped coil while in other embodiments, secondary coil


103


is tapped at different locations such as quarter tapped or two-thirds tapped. In yet other embodiments, multiple secondary coils are provided such as two, three or four secondary coils, some or all of which may be connected to output circuit


102


. In yet another embodiment, coil


109


is the secondary coil and coil


110


is the primary coil.




The output signal from secondary coil


110


is received by output circuit


102


at input


105


. The input signal is processed by the various circuitry of output circuit


102


and the processed signal is provided at output


114


as a signal suitable for welding. As used herein, the term welding-type output means an output signal that is suitable for welding, plasma cutting or induction heating.




Input circuit as used herein includes any circuit capable of receiving an input signal from a source of power and providing an output signal usable by a transformer. Input circuits can include as part of their circuitry, microprocessors, analog and digital controllers, switches, other transformers, rectifiers, inverters, converters, choppers, comparators, phased controlled devices, buses, pre-regulators, diodes, inductors, capacitors, resistors, etc. . . .




Output circuit as used herein includes any circuit capable of receiving an input signal from a transformer and providing an output signal suitable for a desired purpose, such as welding-type output signal (e.g., suitable for welding, plasma cutting or induction heating). Output circuits can include microprocessors, analog and digital controllers, switches, other transformers, rectifiers, inverters, converters, choppers, comparators, phased controlled devices, buses, pre-regulators, diodes, inductors, capacitors, resistors, etc. . . .




An electrical transformer configuration for transformer


103


according to one embodiment of the present invention is shown in FIG.


2


. Transformer


103


includes a transformer bobbin


201


(also called a coil former), a first coil


202


(see FIG.


4


), a second coil


203


(see FIG.


7


), a third coil


204


(see FIG.


6


), an insulating shroud


205


(see FIG.


5


), a two piece cover


206


, a plurality of laminated magnetic cores


207


and a pair of mounting brackets


208


.




Bobbin


201


is located at the center of transformer


103


. First coil


202


is wound around bobbin


201


and is the primary coil in this embodiment. Insulating shroud


205


is located over primary coil


202


. Second and third coils


203


,


204


are wound around insulating shroud


205


with second coil


203


wound over the top of third coil


204


in this embodiment. Second coil


203


is the secondary coil in this embodiment while third coil


204


is the boost coil. In other embodiments, first coil


202


is the secondary coil and second coil


203


is the primary coil. Two piece cover


206


is then positioned over second coil


203


.




Magnetic E-cores


207


are installed into and around coils


202


,


203


and


204


such that there are five cores on each side of bobbin


201


. The legs from the cores on one side of bobbin


201


abut up against the legs of the cores on the other side of bobbin


201


to form two core winding windows for coils


202


,


203


, and


204


. A plurality of paper insulating strips


211


are placed between the ends of each abutting E-shaped core leg to adjust the overall magnetization of the transformer core.




Mounting brackets


208


are mounted on either side of bobbin


201


and are secured in place using bolts


209


and nuts


210


. A rubber gasket


212


is placed between each bracket


208


and cores


207


to prevent damage to cores


207


during final assembly. When completely assembled, all of the creepage distances between the various coils in transformer


103


and between the magnetic cores of transformer


103


and the various coils of transformer


103


in this embodiment conform to the creepage distance standards set forth in IEC 60974-1 for welding-type power supplies.




Bobbin


201


, insulating shroud


205


and cover


206


are molded pieces in this embodiment made from a glass filled polyester such as Rynite® FR-530 manufactured by DuPont Corporation. The present invention is not limited to this material however and in other embodiments other materials are used. Likewise, in other embodiments, one or more of the above mentioned parts are not molded parts.




Bobbin


201


as shown in

FIG. 3

includes top and bottom coil supporting surfaces


215


,


216


(coil supporting surface


216


is on underside of bobbin


201


), first and second semi-circular end coil supporting surfaces


217


,


218


, first and second sidewalls


219


,


220


, first and second elongated channel wire exits


221


,


222


and a central opening


223


in this embodiment. Top and bottom coil supporting surfaces


215


,


216


are connected at their ends to curved coil supporting surfaces


217


,


218


to form a continues coil winding surface


224


. Coil winding surface


224


is symmetrically disposed about a central axis


225


.




Coil supporting surfaces


215


,


216


are elongated and disposed parallel to each other with curved end coil supporting surfaces


217


,


218


being semi-circular in this embodiment. In alternative embodiments, coil supporting surfaces


215


,


216


are disposed substantially parallel to each other. Likewise, in alternative embodiments, curved end coil supporting surfaces


217


,


218


are substantially semi-circular.




Although coil supporting surfaces


215


,


216


are referred to as top and bottom surfaces herein, the terms top and bottom are used to refer to the drawings only and the actual orientation of these surfaces can vary when transformer


103


is installed. For example, top and bottom coil surfaces can be oriented vertically, horizontally or at any angle in various embodiments of the present invention.




Upwardly directed bobbin side walls


219


,


220


are located on opposite sides of continuous coil winding surface


224


. Sidewalls


219


,


220


combined with coil winding surface


224


define a coil winding window


226


around bobbin


201


. Coil winding window


226


is also symmetrically disposed about central axis


225


in this embodiment.




Each sidewall


219


,


220


is integrally connected to winding surface


224


and intersects coil winding surface


224


along an inside edge


227


and an outside edge


228


. In this embodiment, both inside edges


227


and outside edges


228


are radiused to provide a smooth transition between each sidewall


219


,


220


and coil winding surface


224


. In other embodiments, one or both of bobbin sidewalls


219


,


220


are not integral with coil winding surface


224


, but rather are separate pieces that slide over coil winding surface


224


from each side.




Molded into each sidewall


215


,


216


at one end of bobbin


201


are wire exits


221


,


222


. In this embodiment, wire exits


221


,


222


are essentially three sided elongated channels open on the fourth side to winding window


226


(e.g., in open communication with winding window


226


). Each wire exit is disposed about a wire exit axis


245


. Each of the wire exit axes


245


are perpendicular to central axis


225


in this embodiment. In other embodiments, one or more of the wire exit axes are substantially perpendicular to central axis


225


.




Wire exits


221


,


222


are also disposed adjacent to winding window


226


in this embodiment. The phrase adjacent to the winding window as used herein means that the entire winding window in the vicinity of the wire exit is available for use by other coils. In an alternative embodiment, one or more of wire exits


221


,


222


are not adjacent to winding window


226


, but rather are disposed fully or partially inside of winding window


226


.




Wire exits


221


,


222


are similar in construction and only wire exit


221


will be described in detail herein. The discussion of wire exit


221


is equally applicable to wire exit


222


in this embodiment. Wire exit


221


includes an outside wall


229


, a top wall


230


, a bottom wall


231


and a rear wall


232


. The intersection of rear wall


232


with bobbin sidewall


215


defines a first inside edge


233


while the intersection of rear wall


232


with outside wall


229


defines a second inside edge


234


. Similarly, outside wall


229


intersects top and bottom walls


230


,


231


at inside edges


235


,


236


respectively and top and bottom walls


230


,


231


intersect bobbin sidewall


215


at inside edges


240


,


241


respectively Each of the inside edges


233


,


234


,


235


,


236


,


240


,


241


are radiused and smooth in this embodiment.




In addition to the radiused edges between the various walls of wire exit


221


, the open ends of each wall are also beveled and smooth. For example, the open end


237


of outside wall


229


includes a bevel at its end. Similarly, the open ends


238


,


239


of top and bottom walls


230


,


231


are similarly beveled.




Although radiused edges and ends are desirable to help prevent damage to the coil windings, they are not required. In other embodiments, for example, some or none of the inside edges and open ends of wire exits


221


,


222


are radiused and smooth. Likewise, although elongated wire exits


221


,


222


have a generally square cross-section in this embodiment, the present invention is not limited to wire exits having square cross-sections. In other embodiments of the present invention, other cross sections are used including rectangular, curved and semi-circular.




The present invention is also not limited to two wire exits. In an alternative embodiment, for example, a single wire exit is provided. In other embodiments, more than two wire exits are provided including three, four, five and six wire exits (e.g., two for the primary coil wire lead ends, two for the secondary wire lead ends and two for the boost coil lead ends).




The location of wire exits can also vary depending on the particular application for which the transformer is to be used. Generally speaking, one or more wire exits can be located at any point around the perimeter of bobbin


201


. For example, in other embodiments, one or more wire exits are located on one end of bobbin


201


while one or more wire exits are also located on the other end of bobbin


201


. For instance, the primary coil wire lead ends exit bobbin


201


from opposite ends in one embodiment. In other embodiments, one or more wire exits are located on the top and bottom of bobbin


201


.




Bobbin


201


also includes several reinforcement ribs


242


and


243


. These are added to strengthen bobbin


201


and to add rigidity. With respect to ribs


243


, these ribs are also used as locating ribs (or flanges or spacers) to locate magnetic cores


207


(see

FIG. 2

) inside of central opening


223


when transformer


103


is completely assembled.





FIG. 4

shows first coil


202


wound around coil winding surface


224


inside of winding window


226


. Primary coil


202


includes a single layer of thirteen (13) individual turns that completely fill the width of winding window


226


in this embodiment. Primary coil


202


is made from 10½ gauge stranded and woven Litz wire and has a diameter of 4.14 mm (0.163 inches). In other embodiments, primary coil


202


is made from wire of a different gauge in the range of 6 to 14 gauge wire including 8, 10, 12 and 14 gauge wire. The overall width of primary coil


202


in this embodiment is 53.82 mm (2.119 inches).




Primary coil


202


includes a first lead end


250


and a second lead end


251


. Each lead end is terminated with a conventional lug fastener


252


,


253


. An insulating Teflon® sleeve


254


,


255


is also slid over each lead end


250


,


251


in this embodiment to provide added protection to the lead ends against cutting or abrasion. Wire lead ends


250


,


251


exit bobbin


201


via wire exits


221


,


222


in a direction that is perpendicular to central axis


225


.




Insulating shroud


205


as shown in

FIG. 5

in detail includes top and bottom elongated coil supporting surfaces


260


,


261


, first and second semi-circular end coil supporting surfaces


262


,


263


, first and second insulating shroud sidewalls


264


,


265


and a plurality of locating bosses


266


. Top and bottom coil supporting surfaces


260


,


261


are disposed parallel to each other and are connected at their ends to semi-circular end coil supporting surfaces


262


,


263


to form a second continuos coil winding surface


267


symmetrically disposed about central axis


225


of bobbin


201


. In an alternative embodiment, coil supporting surfaces


260


,


261


are disposed substantially parallel to each other and curved end coil supporting surfaces


262


,


263


are substantially semi-circular.




Coil winding surface


267


in this embodiment substantially conforms to the shape of primary coil


202


. In other words, the shape of coil winding surface


267


is substantially the same as the shape of primary coil


202


when primary coil


202


is wound on coil winding surface


224


. Making the shape of coil winding surface


267


substantially conform to the shape of primary coil


202


reduces or minimizes the mean distance between the individual turns of secondary coil


203


(which is wound around coil winding surface


267


) and the individual turns of primary coil


202


.




Upwardly directed insulating shroud sidewalls


264


,


265


are located on opposite sides of continuous coil winding surface


267


. Insulating shroud sidewalls


264


,


265


combined with coil winding surface


267


define a second coil winding window


268


around insulating shroud


205


. Each insulating shroud sidewall


264


,


265


is integral with coil winding surface


267


and intersects coil winding surface


267


along an inside edge


269


and an outside edge (not shown). In this embodiment, both inside edges


269


and the outside edges are radiused to provide a smooth transition between each insulating shroud sidewall


264


,


265


and coil winding surface


267


. In other embodiments, one or both of insulating shroud sidewalls


264


,


265


are not integral with coil winding surface


267


, but rather are separate pieces that slide over coil winding surface


267


on either side.




Insulating shroud


205


in this embodiment is comprised of two separate segments


271


,


272


that mate together at an overlapping joint


273


. Two separate pieces are used to allow insulating shroud


205


to be easily installed over primary coil


202


after primary coil


202


has been wound around coil winding surface


224


. In other embodiments, insulating shroud


205


is a one piece shroud or is comprised of more than two separate pieces or segments.




Segments


271


,


272


of insulating shroud


205


are identical in this embodiment. Segment


272


is merely reversed to allow it to interengage with segment


271


. The two segments are brought together over first winding


202


by simply sliding each segment in from the opposite ends of bobbin


201


until segment


271


overlaps with segment


272


in the middle of winding window


226


at joint


273


. To facilitate overlapping of the two segments, one end of each segment


271


,


272


includes a slightly raised coil supporting surface portion


274


and a pair of insulating shroud sidewall portions


275


that jog slightly inward. The raised coil supporting surface of one segment then slides on top of flat coil supporting surface of the other segment at overlap joint


273


. Likewise, the inwardly jogged sidewall portions on one segment simply slide inside of the insulating shroud sidewalls on the other segment at joint


273


. A similar overlapping joint is created on the bottom side of bobbin


201


when the two segments are brought together.





FIG. 6

shows third coil


204


wound around coil winding surface


267


inside of winding window


268


of insulating shroud


205


. Third coil


204


in this embodiment is a boost coil. Boost coil


204


includes a single layer of five (5) turns equally spaced across winding window


268


of insulating shroud


205


. Locating bosses


266


on coil winding surface


267


are provided to maintain the desired equal spacing between each individual turn of boost coil


204


. Boost coil


204


is made from 15 gauge stranded and woven Litz wire and has an outside diameter of 2.69 mm (0.106 inches) in this embodiment. In other embodiments, boost coil


204


is made from wire of a different gauge including 12 gauge wire.




The lead ends


280


,


281


of boost coil


204


in this embodiment exit bobbin


201


on the opposite end from where lead ends


250


,


251


of primary coil


202


exit bobbin


201


. In an alternative embodiment, one or more of the boost coil lead ends exit bobbin


201


on the same end as lead ends


250


,


251


. In other embodiments, one or more of the boost coil lead ends exit bobbin


201


through wire exits that guide the boost coil lead ends out of bobbin


201


in a direction perpendicular or substantially perpendicular to central axis


225


.




Second coil


203


is shown in

FIG. 7

wound around coil winding surface


267


inside of winding window


268


of insulating shroud


205


. This coil is the secondary coil in this embodiment and is wound over the top of boost coil


204


. Secondary coil


203


is a single layer coil comprised of a total of four (4) individual turns each of which is located between locating bosses


266


(see FIG.


10


). The coil includes a first lead end


292


and a second lead end


291


each of which is terminated with a conventional lug fastener.




Secondary coil


203


also includes a center tap in this embodiment which divides the coil into two segments. Secondary coil


203


is center tapped by connecting secondary wire lead ends


290


,


293


together on the outside of transformer


103


. Each segment of secondary coil


203


includes two of the four turns (e.g., two turns are located on each side of the center tap). Electric current flows through only one segment of secondary coil


203


at a time when transformer


103


is used in power supply


100


. In other embodiments, however, current is flowing in both segments at the same time.




The individual turns of center tapped secondary coil


203


in this embodiment are wound in a bifilar manner (e.g., interleaved with each other). For example, turn


294


and turn


296


(the first and third turns) comprise the two turns in one segment of secondary coil


203


(e.g., on one side of the center tap) while turns


295


and


297


(the second and fourth turns) comprise the two turns of the other segment of secondary coil


203


(on the other side of the center tap). To illustrate this another way, starting with wire first lead end


292


, secondary coil


203


is wound around bobbin


201


once (turn


294


), twice (turn


296


) and then exits bobbin


201


at end


290


. End


290


is connected to end


293


to form the center tap. Coil


203


then continues from end


293


around bobbin


201


once (turn


295


) and twice (turn


297


) and finally exits bobbin


201


at lead end


291


.




In an alternative embodiment, secondary coil


203


is not wound in a bifilar manner in which case turns


294


and


295


are on one side of the center tap and turns


296


and


297


are on the other side of the center tap.




Winding secondary coil


203


in a bifilar manner reduces or minimizes the leakage inductance between primary coil


202


and each of the segments of secondary coil


203


to a desired value. This is because the mean distance between each turn of primary coil


202


and each turn of each segment of secondary coil


203


is reduced or minimized as compared to the case where center tapped secondary coil


203


is not wound in a bifilar manner. In other embodiments of the present invention, secondary coil


203


is not tapped or is tapped at other locations such as quarter tapped or two-thirds tapped.




Secondary coil


203


is made from 4 gauge stranded and woven Litz wire (1625 strands of 36 gauge wire) and has an outside diameter of 8.28 mm (0.326 inches). In other embodiments, secondary coil


203


is made from wire of a different gauge in the range of 3 to 10 gauge wire including 6, 8 and 10 gauge wire. The overall width of secondary coil


203


in this embodiment is approximately 44.1 mm (1.736 inches). Secondary coil


203


in this embodiment does not completely fill winding window


268


. Rather, secondary coil


203


is centered width wise inside of winding window


268


(and also width wise inside of winding window


226


of bobbin


201


) and each of the individual turns of secondary coil


203


are spaced apart from each other equally (see FIG.


10


). In other words, the pitch between coil turns of secondary coil


203


is greater than the diameter of the wire used for secondary coil


203


. In this embodiment, the spacing between individual turns is approximately 0.144 inches from the outside surface of each turn (0.470 inches center to center).




Equally spacing the individual turns of secondary coil


203


apart from one another reduces the mean distance between the individual turns of primary coil


202


and secondary coil


203


in this embodiment. By reducing or minimizing the mean distance between turns, the leakage inductance of transformer


103


is reduced or minimized to a desired value.




The lead ends


292


,


291


of secondary coil


203


exit bobbin


201


on the opposite end from where lead ends


250


,


251


of primary coil


202


exit bobbin


201


. In an alternative embodiment, one or more of the secondary coil lead ends exit bobbin


201


on the same end as lead ends


250


,


251


. In other embodiments, one or more of the secondary coil lead ends exit bobbin


201


through wire exits that guide the secondary coil lead ends out of bobbin


201


in a direction perpendicular to or substantially perpendicular to central axis


225


.




Two piece cover


206


as shown in

FIG. 8

is designed to fit over the top of secondary coil


203


. Cover


206


is a two piece cover (the other half of two piece cover


206


is on the bottom side of bobbin


201


and can't be seen in

FIG. 8

) in this embodiment but is comprised of a single piece in other embodiments and is more than two pieces in yet other embodiments. Each half of two piece cover


206


rests inside of bobbin sidewalls


219


,


220


in this embodiment and includes a plurality locating spacers


303


(see FIG.


10


).




Locating spacers


303


are disposed on the underside of cover


206


and project between the individual turns of secondary coil


203


. In addition to the locating spacers that are located between each turn of secondary coil


203


, one locating spacer is also disposed on the outside of each of the outside turns (e.g., turns


294


and


297


) of secondary coil


203


in this embodiment.




Locating spacers


303


are provided for three reasons in this embodiment. First, to help maintain the desired spacing (e.g., equal spacing in this embodiment) between the individual coil turns of secondary coil


203


. Maintaining the desired spacing between secondary coil turns helps to insure that the leakage inductance of the transformer is reduced or minimized to a desired value. Second, locating spacers


303


help insure part-to-part consistency during manufacturing. Locating spacers can be especially useful in this regard when the individual turns of a coil do not completely fill the winding window, such as in the case of secondary coil


203


. Third, locating spacers


303


are disposed directly above the individual turns of boost coil


204


in this embodiment and help maintain those turns in their desired locations between locating bosses


266


.




The term locating spacer or locating boss, as used herein, means any structure that is provided to maintain a desired spacing between two individual turns of a coil. Spacers or insulating layers placed between the various layers of a coil (e.g., layers contain multiple coil turns) are not locating spacers as that term is used herein. It should also be understood that the term locating spacer or boss as used herein includes both structures that are integral with the cover, the winding surface or some other part of the bobbin as well as structures that are separate pieces. Locating spacers can include such structures as fasteners, screws, bolts, washers, nuts, etc. . . .




Although the present invention is shown with locating spacers projecting inward from cover


206


between the turns of secondary coil


203


, the present invention is not limited to this configuration and other configurations can be used as well. For example, a plurality of locating spacers project outward from coil winding surface


267


between the individual turns of secondary coil


203


in an alternative embodiment. In another embodiment, some of the plurality of locating spacers project inward from cover


206


and some of the plurality of locating spacers project outward from coil winding surface


267


. In yet another embodiment, the locating spacers are free floating and are merely inserted between each of the turns of secondary coil


203


.




The use of locating spacers is also not limited to use with secondary coils and in other embodiments locating spacers are used with primary and boost coils as well to maintain a desired spacing between coil turns. In fact, locating bosses


266


are one example of the use of locating spacers to maintain the spacing of the individual turns of a boost coil. In other embodiments, locating spacers project inward from the underside of insulating shroud


205


, project outward from the coil winding surface


224


of bobbin


201


, or project both from the underside of insulating shroud


205


and outward from coil winding surface


224


, to maintain a desired spacing between each of the turns of the coil wound around coil winding surface


224


(e.g., primary coil


202


in this embodiment).




Each cover piece


206


also includes a flat elongated core supporting surface


300


, a pair of core alignment bosses


301


disposed on opposite ends of core supporting surface


300


to define a core window


305


, a plurality of bracket alignment bosses


302


, a plurality of compression bosses


304


(also shown in

FIG. 10

) and a curved cover end portion


306


. Core window


305


is provided to accommodate the top and bottom legs of magnetic E-cores


207


. These legs fit snugly inside of core window


305


between core alignment bosses


301


. Bracket alignment bosses


302


are provided to support and align bolts


209


which are used to secure brackets


208


on either side of transformer


103


. The curved end portion


306


on each cover piece is desirable to help prevent secondary coil


203


from being pushed out the end of bobbin


201


.




The dimensions of transformer


103


in this embodiment are such that the plurality of magnetic E-cores


207


fit snugly into central opening


223


and snugly over two piece cover


206


. This snug fit compresses cover


206


(including curved sections


306


) and bobbin


201


together which in turn compresses secondary coil


203


and primary coil


202


together. This compression further reduces or minimizes the mean distance between the individual turns of secondary coil


203


and the individual turns of primary coil


202


to a desired value thus reducing or minimizing the leakage inductance of transformer


103


to a desired value.




Compression bosses


304


are disposed on the underside of cover


206


(including on the underside of curved sections


306


) and project inward to contact the individual turns of secondary coil


203


to further compress secondary coil


203


into primary coil


202


. In an alternative embodiment, compression bosses are provided on coil winding surface


224


of bobbin


201


and contact each turn of primary coil


202


instead. In another alternative embodiment, compression bosses are provided on both the underside of cover


206


and on winding surface


224


of bobbin


201


to contact some or all of the turns of secondary coil


203


and primary coil


202


. In one other embodiment, no compression bosses are provided.




It should be understood that compression boss as used herein includes both structures that are integral with the cover, the winding surface or some other part of the bobbin as well as structures that are separate pieces. Compression bosses can include such structures as spacers, screws, bolts, washers, springs, etc. . . .




It should also be understood that the present invention does not require that the magnetic cores fit snugly over cover


206


to provide the compression force. In other embodiments, other structures provide the compression force. For example, in one embodiment, the cover is compressed into secondary coil


203


using fasteners such as bolts or screws. In another embodiment, bolts


209


contacting bracket alignment bosses


302


compress cover


206


into secondary coil


203


. In yet another embodiment, springs are used to compress cover


206


into secondary coil


203


.




Assembly of transformer


103


will now be briefly described. Primary coil


202


is first wound around coil winding surface


224


inside of the winding window


226


of bobbin


201


. The turns of primary coil


202


completely fill the width of winding window


226


in this embodiment. Semi-circular end coil supporting surfaces


217


,


218


help prevent bulging in primary coil


202


as it is wound around coil winding surface


224


. As a result, primary coil


202


fits snugly inside of winding window


226


along the entire path of winding window


226


. This is because there are no abrupt changes in coil winding surface


224


as primary coil


202


is wound around bobbin


201


.




Each lead end in this embodiment exits bobbin


201


via one of the wire exits


221


,


222


. For example, as shown in

FIG. 4

, lead end


250


, when exiting winding window


226


, includes a first ninety (90) degree bend


256


into channel wire exit


221


and then a second ninety (90) degree bend


257


to exit channel wire exit


221


. In other embodiments, bends


256


and


257


are substantially 90 degree bends or are something less than 90 degrees such as approximately 60 degrees, 45 degrees, 30 degrees, etc. . . .




The placement of wire exits


221


,


222


adjacent to winding window


226


allows the full width of winding window


226


to be used by second coil


203


in the vicinity of wire exits


221


,


222


without interference from the primary lead ends


250


,


251


as they exit bobbin


201


. Elongated channels


221


,


222


guide primary coil lead ends


250


,


251


out of bobbin


201


in a known and repeatable direction that is perpendicular to central axis


225


in this embodiment. In an alternative embodiment, one or both of wire lead ends


250


,


251


are guided out of bobbin


201


by wire exits


221


,


222


in a direction that is substantially perpendicular to central axis


225


.




Insulating shroud


205


is next placed inside of winding window


226


over the top of primary coil


202


in this embodiment. Insulating shroud winding window


268


is approximately the same size width wise along its entire path, including in the vicinity of wire exits


221


,


222


, as bobbin winding window


226


in this embodiment.




Boost coil


204


is then wound around second coil winding surface


267


. Each of the individual turns of boost coil


204


are interspersed between the individual turns of secondary coil


203


. Locating bosses


266


are provided on the surface of coil winding surface


267


to maintain the individual boost coil turns in their desired location between the individual turns of secondary coil


203


.




Secondary coil


203


is then wound around second coil winding surface


267


over the top of boost coil


204


. The individual turns of secondary coil


203


are equally spaced apart across the width of winding window


268


. Locating bosses


266


are provided to initially locate and maintain the individual turns of secondary coil


203


in their desired positions.




Two piece cover


206


is now placed over second coil


203


from above and from below bobbin


201


(e.g., one piece is disposed opposite top surface


215


and the other is disposed opposite bottom surface


216


). With cover


206


in place, locating spacers


303


on the underside of cover


206


are disposed in between each turn of secondary coil


203


and one locating spacer is disposed on the outside of each outside turn of secondary coil


203


(see FIG.


10


).




Once two piece cover


206


is positioned over second coil


203


inside of winding window


226


, the plurality of E shaped magnetic cores


207


are positioned. Ten individual magnetic cores are used in this embodiment, five located on each side of bobbin


201


. The center leg of each E-core


207


is inserted into central opening


223


of bobbin


201


while the top leg and bottom leg of each E-core


207


reside inside of core window


305


between core alignment bosses


304


. The ends of the legs of the five E-cores on one side of bobbin


201


abut up against the ends of the legs of the five E-cores on the other side of bobbin


201


to complete the magnetic path around the coils. Paper insulating strips


211


are placed between the ends of the core legs to adjust the overall magnetization of the transformer core.




Brackets


208


are placed one on each side of transformer


103


and are used to hold the transformer assembly together. A rubber gasket


212


is placed between each bracket


208


and the cores


207


to prevent damage to the cores during assembly. Four bolts


209


, one on each corner of the transformer assembly, are used to hold brackets


208


in place. Bolts


209


are inserted through holes in brackets


208


. Core alignment bosses


301


provide horizontal alignment of bolts


209


while bracket alignment bosses


302


provide vertical alignment of bolts


209


. Bolts


209


are secured in place using nuts


210


. Transformer


103


is now completely assembled and ready for installation.




Numerous modifications may be made to the present invention which still fall within the intended scope hereof. Thus, it should be apparent that there has been provided in accordance with the present invention an electrical transformer for use in a welding-type power supply that fully satisfies the objectives and advantages set forth above. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.



Claims
  • 1. A welding-type power supply transformer comprising:a bobbin having elongated top and bottom surfaces and first and second substantially semi-circular end surfaces connecting the top surface with the bottom surface to form an elongated first coil winding surface having a central axis; a first coil wound around the first coil winding surface; and a second coil magnetically coupled to the first coil and wound thereto.
  • 2. The electrical transformer of claim 1 wherein the transformer further includes an insulating shroud disposed between the first coil and the second coil, wherein the insulating shroud includes elongated top and bottom surfaces and first and second substantially semi-circular end surfaces connecting the top surface of the insulating shroud with the bottom surface of the insulating shroud to form a second coil winding surface, and further wherein the second coil is wound around the second coil winding surface.
  • 3. The electrical transformer of claim 2 wherein the second coil includes a plurality of second coil turns and further wherein the transformer includes a plurality of locating bosses disposed on the second coil winding surface to maintain each of the plurality of second coil turns in a desired location.
  • 4. The electrical transformer of claim 1 wherein the transformer further includes an insulating shroud disposed between the first coil and the second coil, wherein the insulating shroud includes a second coil winding surface and first and second insulating shroud sidewalls each disposed along opposite sides of the second coil winding surface, wherein the second coil winding surface substantially conforms to the shape of the first coil, and further wherein the second coil is wound around the second coil winding surface between the first and second insulating shroud sidewalls.
  • 5. The electrical transformer of claim 1 wherein the bobbin includes a central opening disposed inside of the first coil winding surface and further wherein the transformer includes a magnetic core disposed in the central opening wherein the magnetic core has a rectangular cross-section immediately adjacent one of the first or second substantially semi-circular end surfaces.
  • 6. The electrical transformer of claim 1 wherein the second coil includes a plurality of second coil turns, and further wherein the transformer includes a plurality of locating spacers disposed to maintain a desired spacing between each of the plurality of second coil turns.
  • 7. The electrical transformer of claim 6 wherein the plurality of locating spacers are disposed such that there is at least one locating spacer between each second coil turn.
  • 8. The electrical transformer of claim 6 wherein the plurality of locating spacers are disposed such that there is at least one locating spacer on each side of each second coil turn.
  • 9. The electrical transformer of claim 1 wherein the bobbin further includes first and second bobbin sidewalls each disposed along opposite sides of the first coil winding surface to form a winding window, and further wherein the bobbin includes first and second wire exits adjacent to and in open communication with the winding window, and further wherein the first coil includes a first lead end exiting the winding window through the first wire exit and a second lead end exiting the winding window through the second wire exit such that the first lead end and the second lead end exit the bobbin in a direction that is substantially perpendicular to the central axis.
  • 10. The electrical transformer of claim 1 wherein the second coil is wound concentric to the first coil, and further wherein the transformer includes a cover disposed such that the first coil and the second coil are compressed between the first coil winding surface and the cover.
  • 11. A welding-type power supply transformer comprising:a bobbin having a central axis and a first winding window located about die central axis, wherein the first winding window includes a first coil winding surface and first and second bobbin sidewalls each located on opposite sides of the first coil winding surface; a first wire exit in open communication with the first winding window; a first coil wound around the first coil winding surface and having a first lead end exiting the first winding window through the wire exit such that the first lead end exits the bobbin in a direction that is substantially perpendicular to the central axis; and a second coil magnetically coupled to the first coil and wound concentric to the first coil about the bobbin.
  • 12. The electrical transformer of claim 11 wherein the transformer further includes a second wire exit in open communication with the first winding window, and further wherein the first coil includes a second lead end exiting the first winding window through the second wire exit such that the second lead end exits the bobbin in a direction that is substantially perpendicular to the central axis.
  • 13. The electrical transformer of claim 12 wherein each wire exit includes an outside wall and a rear wall, wherein the rear wall is connected to the bobbin sidewall along a first edge and wherein the rear wall is connected to the outside wall along a second edge, and further wherein the first and second edges are radiused on the inside of the wire exits.
  • 14. The electrical transformer of claim 12 wherein each of the wire exits is disposed adjacent to the first winding window.
  • 15. The electrical transformer of claim 11 wherein the second coil includes a plurality of second coil turns and further wherein the transformer includes a plurality of locating spacers disposed to maintain a desired spacing between each of the plurality of second coil turns.
  • 16. The electrical transformer of claim 15 wherein the plurality of locating spacers are disposed such that there is at least one locating spacer between each second coil turn.
  • 17. The electrical transformer of claim 15 wherein the plurality of locating spacers are disposed such that there is at least one locating spacer on each side of each of the plurality of second coil turns.
  • 18. The electrical transformer of claim 11 wherein the second coil is wound concentric to the first coil, and further wherein the transformer includes a cover disposed such that the first coil and the second coil are compressed between the first coil winding surface and the cover.
  • 19. A welding-type power supply transformer comprising:a bobbin having a first coil winding surface; a first coil wound around the first coil winding surface; a second coil wound concentric to the first coil; and a cover, wherein the first coil and the second coil are compressed between the first coil winding surface and the cover.
  • 20. The electrical transformer of claim 19 wherein the transformer further includes a plurality of compression bosses wherein each of the plurality of compression bosses contacts one of the first or second coils to compress the first coil and the second coil between the first coil winding surface and the cover.
  • 21. The electrical transformer of claim 20 wherein at least one of the plurality of compression bosses is located on the cover.
  • 22. The electrical transformer of claim 20 wherein at least one of the plurality of compression bosses is located on the first coil winding surface.
  • 23. The electrical transformer of claim 19 wherein the second coil is disposed on the outside of the first coil.
  • 24. The electrical transformer of claim 19 further including an insulating shroud disposed between the first coil and the second coil.
  • 25. The electrical transformer of claim 19 wherein the second coil includes a plurality of second coil turns, and further wherein the transformer includes a plurality of locating spacers disposed to maintain a desired spacing between each of the plurality of second coil turns.
  • 26. A welding-type power supply transformer comprising:a first coil; a second coil magnetically coupled to the first coil, wherein the second coil includes a plurality of second coil turns; and a plurality of locating spacers disposed to maintain a desired spacing between each of the plurality of second coil turns.
  • 27. The electrical transformer of claim 26 wherein each of the plurality of locating spacers is disposed such that there is one locating spacer between each second coil turn.
  • 28. The electrical transformer of claim 26 wherein the plurality of locating spacers are disposed such that there is one locating spacer on each side of each of the plurality of second coil turns.
  • 29. A method of reducing the leakage inductance in a welding-type power supply transformer comprising:providing a first coil; winding a second coil concentric to the first coil; and compressing the first coil and the second coil together to reduce the leakage inductance between the first coil and the second coil to a desired value.
  • 30. A welding-type power supply transformer comprising:a bobbin having a central axis and a first coil winding surface located about the central axis; a first coil wound around the first coil winding surface and having a first lead end; a second coil magnetically coupled to the first coil and wound concentric thereto; and means for guiding the first lead end out of the bobbin and preventing intersection of the second coil wit the first lead end.
  • 31. A welding-type power supply transformer comprising:a bobbin having a first coil winding surface; a first coil wound around the first coil winding surface; a second coil wound concentric to the first coil; and means for compressing the first coil and the second coil together.
  • 32. A welding-type power supply transformer comprising:a first coil; a second coil magnetically coupled to the first coil, wherein the second coil includes a plurality of second coil turns; and means for maintaining a desired spacing between each of the plurality of second coil turns.
  • 33. A bobbin for a transformer assembly comprising:a molded body having a pair of substantially flat coil supporting surfaces and at least two substantially semicircular end coil supporting surfaces, wherein the at least two substantially semicircular end coil supporting surfaces interconnect the pair of substantially flat coil supporting surfaces to form a continuous coil winding surface; and a pair of side walls integrated with the continuous coil winding surface to define a coil winding window.
  • 34. The bobbin of claim 33 having a non-circular central opening between the substantially flat coil supporting surfaces and the at least two substantially semicircular end coil supporting surfaces configured to receive a pole of at least one ferrite core.
  • 35. The bobbin of claim 34 wherein the non-circular central opening elliptical cross-section.
  • 36. The bobbin of claim 33 further comprising an inside edge between the continuous coil winding surface and the pair of side walls, wherein the inside edge has a radius that is configured to match a radius of a first coil winding.
  • 37. The bobbin of claim 33 wherein each of the side walls is located at an end of the continuous coil winding surface.
  • 38. The bobbin of claim 33 wherein the continuous coil winding surface is oval shape.
  • 39. The bobbin of claim 33 further comprising a wire exit passage, wherein the wire exit passage is recessed within one of the side walls and forms a longitudinal tunnel, wherein the longitudinal tunnel is parallel to the pair of substantially flat coil supporting surfaces and located outside of the coil winding window.
US Referenced Citations (37)
Number Name Date Kind
1548388 Shackelton Aug 1925 A
1784833 Hagemann Dec 1930 A
1897604 Clemons Feb 1933 A
2216863 Visman Oct 1940 A
2290680 Franz Jul 1942 A
2865086 Whipple Dec 1958 A
3008108 Baker et al. Nov 1961 A
3068381 Vazquez Dec 1962 A
3648209 Conger Mar 1972 A
3958328 Lee May 1976 A
4157519 Foster Jun 1979 A
4250479 Bausch et al. Feb 1981 A
4363014 Leach et al. Dec 1982 A
4510478 Finkbeiner Apr 1985 A
4546340 Kuchuris Oct 1985 A
4583068 Dickens et al. Apr 1986 A
4763072 Katoh et al. Aug 1988 A
4779068 Sakamoto et al. Oct 1988 A
4808959 Weissman Feb 1989 A
4857877 Dethienne Aug 1989 A
4857878 Eng, Jr. et al. Aug 1989 A
4879536 Taguchi et al. Nov 1989 A
4916424 Kijima Apr 1990 A
4999743 Fontana et al. Mar 1991 A
5220304 Ho Jun 1993 A
5369389 Schrammek et al. Nov 1994 A
5404123 Joseph Apr 1995 A
5440286 Pikul et al. Aug 1995 A
5488344 Bisbee et al. Jan 1996 A
5534839 Mackin et al. Jul 1996 A
5559486 Ikenoue et al. Sep 1996 A
5600294 Buenconsejo et al. Feb 1997 A
5973584 Goseberg Oct 1999 A
5996214 Bell Dec 1999 A
6154113 Murai Nov 2000 A
6191677 Orben et al. Feb 2001 B1
6249204 Larranaga et al. Jun 2001 B1
Foreign Referenced Citations (1)
Number Date Country
5029160 Feb 1993 JP
Non-Patent Literature Citations (4)
Entry
Miller Electric Mfg. Co., Exhibits A, B and I (see attached), Include an assembly drawing, bill of materials, and piece part drawing showing a prior art transformer that was in public use or on sale in the United States more than one year prior to the filing date of the above-referenced application. No date.
Miller Electric Mfg. Co., Exhibits C, D and I (see attached), Include an assembly drawing, bill of materials, and piece part drawing showing a prior art transformer that was in public use or on sale in the United States more than one year prior to the filing date of the above-referenced application. No date.
Miller Electric Mfg. Co., Exhibits E, F, and I (see attached), Include an assembly drawing, bill of materials, and piece part drawing showing a prior art transformer that was in public use or on sale in the United States more than one year prior to the filing date of the above-referenced application. No date.
Miller Electric Mfg. Co., Exhibits G, H and I (see attached), Include an assembly drawing, bill of materials, and piece part drawing showing a prior art transformer that was in public use or on sale in the United States more than one year prior to the filing date of the above-referenced application. No date.