Patent Grant
7978040
The present invention relates to a winding element for conducting current, which is a component of a coil winding, and to a transformer arrangement that includes a primary winding and a secondary winding.
Although the present invention is described below essentially with reference to resistance welding systems, it is not limited to an application of this type.
In the case of known transformer arrangements, in particular welding transformer arrangements for resistance welding systems that must provide a relatively high power output, there is a need to adequately cool the electrical components of the secondary/output circuit in particular. It is known, for example, to use reshaped copper pipes as the secondary winding, and to conduct a cooling fluid or a cooling medium through the copper pipe during operation in order to adequately cool the winding. In order to improve the weak mechanical strength of this design, the copper pipes are typically welded to carrier components, e.g., the surfaces, in order to connect the winding. However, heat is added to the material in the welding process, which negatively affects the mechanical properties of the material and may also cause areas to oxidize; these areas must then be cleaned, which is a time-consuming process.
Adequate cooling is also required in the region of the output rectifier due to the relatively high power loss at the rectifier diodes. Known solutions, according to which the rectifier diodes are cooled using cooling bodies, have the disadvantage that the heat dissipation and, therefore, the power output of the transformer arrangement is indirectly limited by the relatively small cooling surfaces. As an improvement, it is proposed in DE 103 34 354 A1 to provide a liquid cooler for power semiconductors, in the case of which two mutually electrically insulated contact members—between which the power semiconductor element is situated—include a groove on their inner surfaces which face the semiconductor component; the groove is open toward the power semiconductor element and is used as the cooling duct. In this solution, the power semiconductor is in direct contact with the cooling medium, which may result in corrosion taking place, and which results in the need for additional sealing. In addition, punctiform areas where a great deal more heat forms (“hot spots”) are difficult to cool if they are located outside of the direct contact area between the semiconductor and the cooling medium.
The conventional placement and orientation of the rectifier diode plane in the main direction of flow also make cooling difficult due to the poor access, and they result in a relatively expensive design, since expensive flexible connectors, such as laminated strips, are required.
The object of the present invention, therefore, is to provide a winding element and a transformer arrangement which may be cooled more easily and effectively, and which have a robust and stable yet economical design.
The object is attained by a winding element having the features of claim 1, and by a transformer arrangement having the features of claim 5. Advantageous embodiments are the subject matter of the dependent claims and the description that follows.
The winding element according to the present invention is used to conduct current, e.g., as a component of a coil winding, in particular in a (welding) transformer arrangement. The winding element includes fastening means for fastening the winding element to a carrier component. As the carrier component, a connecting component in particular, e.g., of a rectifier assembly, may be provided inside a transformer arrangement. Using the solution according to the present invention, a secure and robust fastening means is attained that does not have material-altering or material-influencing side effects, and good thermal conductivity may be attained by using an advantageous, solid design of the winding element. Using the fastening means provided, it is possible to fasten the winding element to a carrier component without the addition of heat, as is the case, e.g., in a welding or soldering procedure. In addition, the design does not need to be cooled or cleaned after assembly.
Advantageously, at least one interior cavity for receiving a cooling fluid is provided. The cooling fluid, in particular water, may circulate inside the winding element and thereby easily dissipate the heat that is produced. The coolability is greatly improved as a result, thereby making it possible to attain higher electrical output.
The fastening means are advantageously designed as threaded fastening means, in particular as a threaded hole. As a result, the winding element may be easily connected in a fixed manner to the carrier component; it may also be designed to be removable, e.g., for repair or maintenance, in order to prevent the addition of heat. Due to the threaded connection, it is possible to prevent more complex and, therefore, more expensive manufacturing and assembly methods.
According to a particularly preferred embodiment, the winding element is E-shaped in design and includes a back and three legs. It is understood that a C-shaped design or any other type of design is also possible. In the case of an E-shaped design, the winding element may be designed to be particularly robust, and it may be connected to the carrier component, e.g., to the three legs, in a particularly stable manner. In the case of an E-shaped design, there are two openings between the three legs, which may be filled, e.g., with an iron core. Due to the sizing, the use of an E-shaped design also guarantees that the impedance of the winding element will be low in a medium frequency range which occurs in the case of resistance welding transformers in particular. Due to its solid form, an E-shaped winding element may be easily fastened to the remaining structure, e.g., using screws, thereby simplifying and reducing the costs of assembly as compared to known systems in which assembly is carried out using brazing or welding.
Advantageously, the winding element is made of a solid, in particular one-pieced, material element. This may be, in particular, a material block or a material sheet. The cavity and/or the cooling lines may be bored or milled in the material element; openings that exist only for reasons of manufacture and that are not needed for the subsequent cooling circuit may be sealed using a suitable sealing material. Copper or aluminium are particularly suited for use as the material, since they have low electrical resistance and high thermal conductivity.
A transformer arrangement according to the present invention, in particular a welding transformer arrangement, includes a primary winding and a secondary winding. The primary winding and/or secondary winding include(s) at least one winding element according to the present invention.
The use of a winding element according to the present invention in a transformer arrangement greatly simplifies assembly, since the presence of fastening means obviates the need for a welding or soldering procedure. In addition, the cooling of a transformer arrangement can be greatly simplified. For the rest, reference is made explicitly to the advantages described in conjunction with the winding element according to the present invention.
According to a preferred embodiment, an output rectifier arrangement is connected downstream of the secondary winding; the secondary winding includes at least one winding element according to the present invention. A transformer arrangement in particular which includes an output rectifier arrangement may be improved as a result.
It is expedient when the at least one winding element is fastened to the output rectifier arrangement using a threaded connection in particular. Additional lines for conducting current may be advantageously eliminated by connecting the winding element and, therefore, the secondary winding to the output rectifier arrangement. A threaded connection makes the attachment particularly stable, and it may be detached. In all, manufacturing and assembly costs may be reduced as a result.
In a particularly preferred embodiment, the output rectifier arrangement includes at least one rectifier assembly in which a disk-shaped rectifier diode is located between two contact plates, it being possible to act on at least one contact plate using a cooling fluid on its side facing away from its rectifier diode. Effective cooling of the rectifier diode may be attained as a result without the rectifier diode being in direct contact with the cooling fluid. The contact plate is cooled by the cooling fluid and helps to protect the rectifier diode from corrosion in particular; it also ensures even cooling of the diode, since a preferred contact plate material such as copper or aluminum has a higher thermal conductivity than does the semiconductor material which is typically silicon. As a result, the “hot spots” described above may be cooled more effectively. The contact plate functions simultaneously as a current conduction contact and a cooling surface. Effective cooling is required in particular for rectifier diodes at which output is typically relatively great, and this is achieved using the embodiment described. Since there is no direct contact between the rectifier diode and the cooling fluid, the sealing may be simplified, since, in particular when a defect occurs, only the diode between the contact plates needs to be replaced, and there is no need to access the sealing material. It is advantageous to conduct the cooling fluid through cooling ducts on the side of the contact plate facing away from the rectifier diode; the surface area between the cooling fluid and the contact plate in the region of the diode should be as large as possible. At the same time, the configuration and placement of the ducts should have minimal influence on the uniformity of the current density through the diode. In addition, in designing the ducts, care should be taken to attain a minimal drop in pressure when the cooling fluid flows through the ducts; this may be attained, e.g., by using the largest possible duct cross section and parallel branches.
It is advantageous when at least one contact plate is pressed against the rectifier diode using a spring force. A specifiable, floating fixation of the diode may therefore be attained, thereby ensuring, in particular, that the clamping forces required by the diode manufacturer for those types of diodes that must be kept as still as possible despite temperature-induced expansions are provided, and thereby ensuring that the pressure on the diode surfaces is as uniform as possible. It is therefore possible to ensure that there is minimal resistance between the diodes and the contact plates, that the current density through the diodes is as uniform as possible, and that the diodes are cooled evenly and across their surface area via the contact plates.
Advantageously, the rectifier assembly includes two connecting elements which include at least one cavity; each of the connecting elements is connected to one of the contact plates, and the at least one cavity is designed to receive a cooling fluid. It is therefore possible to attain an extremely compact and robust design in which only a few stable components are required in order to attain a closed current conduction and cooling functionality. In particular, one of the connecting elements is connectable directly to the secondary winding or a related carrier component, thereby making it possible to avoid the use of further electrical or mechanical components.
According to a further preferred embodiment, at least one cavity of the at least one winding element is connected to at least one cavity of the at least one rectifier assembly. It is therefore possible to form a continuous cooling circuit, which greatly simplifies the conduction of cooling fluid.
It is particularly preferred when the main direction of flow from the secondary winding to the rectifier assembly is essentially perpendicular to the main extension plane of the disk-shaped rectifier diode. In this case, the rectifier diode or the rectifier assembly may be connected directly to the secondary winding, thereby making it possible to avoid the use of expensive current connections such as a laminated strip. In addition, this design reduces the amount of installation space required. The transformer arrangement may be made smaller in size and manufactured more economically.
Advantageously, the primary winding includes at least one self-supporting coil element in which a strip-type line is guided in two connected, adjacently situated, oppositely wound windings. Due to the self-supporting design, it is possible to eliminate a bobbin or winding assembly. As such, it is possible to attain a higher space factor and a larger line cross section. In addition, it is easier to cool the coil element, since it is more adaptable to the existing structure. Finally, the manufacturing costs are lowered.
It is advantageous to design the cross section of the strip-type line in such a manner that the self-supporting coil element has a low impedance at medium frequencies. The coil element may therefore be advantageously used for resistance welding transformers. For example, a cross section of approximately 1 mm×8 mm may be used with approximately 9 to 10 turns per oppositely wound winding.
In a particularly preferred embodiment, the secondary winding includes four winding elements, and/or the output rectifier arrangement includes two rectifier assemblies, and/or the primary winding includes six self-supporting coil elements. It is therefore possible to create a medium-frequency welding transformer arrangement that is particularly robust in design, easy to assemble, and has good coolability.
It is particularly preferable for the secondary winding to hold—via the winding elements—an iron core which is enclosed by the primary winding, and to be screwed onto the output rectifier arrangement. In this manner, the entire transformer arrangement may be assembled using only a few screws, and without using a welding or soldering procedure. The output rectifier arrangement supports the secondary winding which, in turn, holds the iron core on which the primary winding is installed. The entire structure of the transformer may be installed using threaded connections, thereby eliminating the need to add heat and preventing a change, in particular a deterioration, of the mechanical material properties. The entire arrangement has good thermal contact within a narrow space, which improves the coolability significantly. The contact and connecting surfaces of the structure may be prepared and/or treated as needed before they are screwed together, in order to prevent oxidation of the contact surfaces which would change the electrical properties of the structure.
It is understood that the features mentioned above and which are described below may be used not only in the combination described, but also in other combinations or alone, without leaving the scope of the present invention.
The present invention is depicted schematically in the drawing with reference to an embodiment, and it is described in detail, below, with reference to the drawing.
An electrical wiring diagram of a welding transformer arrangement is shown schematically in
Secondary circuit 120 is designed as a rectifier arrangement, and it supplies transformer output voltage U2. For this purpose, secondary winding 133 includes a mid-tap A which is connected to the negative output terminal (−) of arrangement 100. Starting at mid-tap A, secondary winding 133 is divided into two partial windings which have N2 and N3 turns and are connected to winding taps B and C, respectively. Two rectifier diodes 134 are connected downstream of winding taps B and C, the outputs of which are connected to the positive output terminal (+) of arrangement 100.
Secondary winding 133 includes, as a component, at least one preferred winding element as described in greater detail with reference to
A preferred embodiment of a winding element is shown in a flat sectional view in
Winding element 200 includes fastening means which are designed as threaded holes 205. Using preferred threaded holes 205, it is possible to fasten winding element 200 in a robust and reliable manner to a carrier component, in particular to a component of an output rectifier arrangement. Furthermore, winding element 200 includes cavities which are designed as cylindrical holes or cooling ducts 206, and which are used to receive cooling fluid. Cylindrical holes 206 are situated in the interior of winding element 200 in such a manner that they form one continuous cooling fluid line or a cooling circuit. An opening 207 in cylindrical hole 206 that extends longitudinally inside back 202 of the winding element, and which is used to connect the cooling ducts or cylindrical holes that extend in legs 203, is sealed off toward the outside using a closing element. Further openings 208 in cooling ducts 206 are provided with circumferential recesses for receiving sealing elements, and they are used as supply and discharge lines for the cooling fluid.
A preferred embodiment of a self-supporting coil element 300 is depicted schematically in a side view and in a sectional view A-A in
An exploded view of a preferred winding arrangement of a transformer is shown schematically in
To assemble winding arrangement 400, an iron core 401 is guided through openings 204 of winding elements 200 and through openings 304 of coil elements 300; coil elements 300 and winding elements 200 are situated next to one another in alternation. Winding elements 200 are fastened to carrier components which are designed as connecting pieces 402, 403, 404. In the preferred embodiment shown, winding elements 200 are screwed onto connecting pieces 402 through 404 using screws 405, not all of which are labelled with reference numerals, to ensure clarity. For this purpose, connecting pieces 402 through 404 include openings through which screws 405 are guided and screwed into threaded holes 205 in winding elements 200. Connecting pieces 402 through 404 also include openings 407 which are connected via ducts to openings 208 of winding elements 200 in order to create a cooling circuit for the cooling fluid.
Connecting pieces 402 through 404 correspond to taps A, B, C shown in
A preferred embodiment of a rectifier assembly is shown in various views in
Connecting element 504b includes a bored inlet/outlet 507 for the cooling fluid which may reach a cavity designed as a cooling line or cooling duct 506 and circulate there. Cooling duct 506 is manufactured such that the surface between the cooling fluid and contact plate 502 is as large as possible in the region of the mounting surface of the diode, and, simultaneously, such that the distribution of the ducts has minimal influence on the uniformity of the current density through the diode. When the cooling fluid flows through the connecting element, the pressure drop is minimal, since the duct cross section is designed to be as large as possible and parallel branches are provided. The cooling fluid exits connecting element 504b through an opening 510 that has been bored and is closed on the underside of connecting element 504b. From opening 510, the cooling fluid flows via a connecting element 509 into connecting element 504a which is designed similar to connecting element 504b and also includes cooling ducts for receiving and conducting the cooling fluid. The cooling fluid flows through connecting element 504a and reaches connected winding elements 200 via further cavities and ducts provided for this purpose.
Rectifier assembly 500 also includes a fastening and spring element 505 which is used to secure assembly 500 and act on the components using a specifiable amount of spring force. It is therefore ensured that a specifiable, floating fixation exists, using which a clamping force specified by the diode manufacturer for rectifier diode 501 may be provided; it is therefore also provided that the pressure on diode 501 is as uniform as possible, and therefore, that the current density through the diode is as uniform as possible.
A preferred embodiment of a welding transformer arrangement is shown in a dissected view in
Transformer housing 601 is realized as a column-shaped hollow body, as described in greater detail, e.g., in EP 1 584 404 A1. The electrical connections for the primary voltage are shown on the top outer side of transformer housing 601 in
Connecting piece 402 is mid-tap A of the secondary winding, and it is connected to a connection plate 602 which is the negative output terminal of transformer 600. Connecting pieces 404 (visible) and 403 (not visible) are each connected to a rectifier assembly 500, as explained in greater detail, above, with reference to
Entire transformer assembly 600 including output rectifier assembly 604 is advantageously assembled using threaded connections, which results in considerable advantages in terms of manufacture, in particular in terms of the time involved, as compared with conventional welded structures. In the case of welded structures, once the welding procedure is completed, the welded structure must be cooled, oxidized layers must be removed, and the surface must be post-treated. In addition, heating the structures to high temperatures changes the mechanical properties of the copper alloy of which the structure is preferably composed. The contact and connecting surfaces of the structure are prepared and/or treated as needed before they are screwed together, in order to prevent oxidation of the contact surfaces which would change the electrical properties of the structure.
It is understood that only particularly preferred embodiments of the present invention are depicted in the figures shown. Other embodiments are also feasible within the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 001 233 | Jan 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/011416 | 12/22/2007 | WO | 00 | 2/24/2010 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2008/083839 | 7/17/2008 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4571669 | Tsujii et al. | Feb 1986 | A |
| 5056214 | Holt | Oct 1991 | A |
| 5331536 | Lane | Jul 1994 | A |
| Number | Date | Country |
|---|---|---|
| 2 285 025 | Oct 1998 | CA |
| 103 34 354 | Jul 2004 | DE |
| 1 584 404 | Oct 2005 | EP |
| 2 551 912 | Mar 1985 | FR |
| 03-283508 | Dec 1991 | JP |
| 03-283511 | Dec 1991 | JP |
| 06-151211 | May 1994 | JP |
| 9844519 | Oct 1998 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20100156583 A1 | Jun 2010 | US |
