Inductor devices – With core clamps – wedges or fasteners
Reexamination Certificate
1998-12-22
2001-04-17
Mai, Anh (Department: 2832)
Inductor devices
With core clamps, wedges or fasteners
C336S196000, C336S234000
Reexamination Certificate
active
06218926
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to reactor and transformer cores and specifically to assembly of the laminated core.
BACKGROUND OF THE INVENTION
The construction of large reactor and transformer cores has been a time and labor intensive task due to the clamp fixturing, lamination alignment, temporary assembly, clamp welding and final assembly which has been required in the assembly process when assembling larger transformers in the 100 KVA to 5,000 KVA power range. The weight of the cores of these transformers ranges from 1000 pounds to more than 15,000 pounds and therefore requires an extremely strong clamp. The core laminations are supported and held in position by clamps, one on each side of the core. It has been the practice to make the clamp from sections of structural steel channel or a combination of structural steel channels and structural steel angles. Structural channels and angles are commercially available in standard sizes. The sizes of structural channels and angles selected for making the clamps are generally those with dimensions closest to the width of the core laminations. Therefore, the clamps provide little if any protection to the edges of the core laminations. The core assembly process starts by fixturing each channel section of the first clamp in proper position with respect to the other channel or angle sections of the clamp. The fixturing must be strong enough to maintain the respective positions of each channel or angle section of the clamp during the laying up of the core laminations. The flanges of channel sections are placed down in the fixture such that the core laminations can be laid on the flat surface of the clamp. Angle sections can be positioned such that flanges are either up or down. When channel and angles are used together, tie straps, which provide a means for alignment and attachment, are welded to each end of the channels. This is done as a subassembly process before core assembly is started. Alignment pins are placed in holes provided in the channels or angles for threaded fasteners used during final assembly of the core. The alignment pins are smooth and slightly smaller in diameter than the threaded fasteners used for final assembly. Each of the many lamination layers of the core consist of thin (5-15 mills thick) segments of magnetizable metal, each individually slidably placed on the alignment pins. Each lamination segment has mitered ends which must be positioned with respect to the adjacent mitered end of the other lamination segments of that layer and with respect to the position of the mitered ends of the previously laid lamination layer segments. After the final core laminations are placed on the stack, the channel and angle sections making up the second clamp are positioned on top of the core stack. A final alignment of the core laminations and clamps is completed and the core assembly is temporarily secured by strapping or banding placed around each leg of the core. Lifting eyes are attached to the clamps and the core assembly is lifted to the upright position. The alignment pins are removed and threaded fasteners installed and tightened. The core assembly is then moved to a welding station where the channel and/or angle sections forming each of the first and second clamps are welded together. After welding, the core assembly is moved to a final assembly area where the coil and various electrical connectors and brackets are installed. Assembling a reactor or transformer core by this method is extremely time consuming and labor intensive. Therefore, it would be desirable to eliminate many of these steps to reduce time and labor cost.
SUMMARY OF THE INVENTION
The present invention provides a solution to the extensive clamp fixturing, lamination alignment, temporary assembly, clamp welding and final assembly steps that have been required in assembling large reactor and transformer cores. The present invention provides a single piece flanged clamp for each side of the laminated core. The flanged clamps are made from sheet or plate steel and can be easily manufactured by conventional sheet metal tooling methods or by computer numeric controlled (CNC) machines and industrial robots. The manufacturing process includes the steps of punching the coil window, the hardware assembly holes, lifting holes, coil bracket mounting holes and flange notches, forming the flanges and welding the corners of adjacent flanges. Manufacturing the flanged clamp from one piece of sheet or plate steel permits the width of the side legs, top leg, bottom leg and the depth of the flanges to be selectively controlled. This permits the side, top and bottom legs to extend out past the edges of the core laminations for better protection. Extending the flanges of the bottom legs provides a more stable platform for the core assembly and can include holes for permanent mounting of the core assembly. Since each flanged clamp is of one piece construction, no assembly fixturing is required. Using a one piece flanged clamp on each side of the core assembly improves the alignment of core laminations, which in turn results in better performance and reduced noise. Core construction is accomplished by placing the first flanged clamp on a generally flat surface such that the edges of the outwardly facing flanges are in contact with the generally flat surface. In this position, the generally flat surface of the flanged clamp forms a horizontal plane on which the core laminations are stacked. Alignment pins are then placed in the holes provided for final assembly fasteners, thus allowing the flanged clamp to serve as a fixture for laying up the core laminations. Each segment of the core lamination is slidably positioned on the alignment pins. After the desired number of laminations have been stacked on the first flanged clamp, the second flanged clamp is positioned on top of the core and the alignment pins are removed. Final assembly fasteners are then placed in the holes previously occupied by the alignment pins and tightened such that the two flanged clamps and the intermediate core laminations are tightly secured together. The core is then completely assembled and can be moved to the upright position for inserting the coil and making final wiring connections. The one piece flanged clamp and construction method of the present invention, as described above, can also be used in the construction of large liquid filled, wound core transformers.
REFERENCES:
patent: 366347 (1887-07-01), Sehmid
patent: 366375 (1887-07-01), Byllesby
patent: 454090 (1891-06-01), Thomson
patent: 916792 (1909-03-01), Selinger
patent: 2731607 (1956-01-01), Gould et al.
patent: 3138774 (1964-06-01), Derbyshire et al.
Golden Larry I.
Mai Anh
Shrout Larry T.
Square D Company
Stacey David R.
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