The present application is directed to distribution transformers and, more particularly, to supports for cores of distribution transformers.
A frame for a core of a distribution transformer provides mechanical stability to the transformer by compressing the yokes of the core and holding the overall assembly together. The construction of a conventional transformer core frame typically involves welding to connect component members of the core frame. The production and assembly of such core frames is time-consuming. Additionally, welded core frame members tend to corrode and become unstable over time.
An object of the present invention is to provide a transformer core frame having interlocking members. The core frame encloses a ferromagnetic core having at least one core limb extending between upper and lower yokes. The core frame is formed of first and second core clamps and leg plates. The first and second core clamps compress the upper and lower yokes, respectively and the leg plates are placed on opposing sides of the at least one limb. The first and second core clamps have cut-out portions formed therein to receive tabs of opposing ends of the leg plates to form an interlock between the first and second core clamps and leg plates.
Another object of the present invention is to provide method for forming a distribution transformer. The method includes:
In the accompanying drawings, structural embodiments are illustrated that, together with the detailed description provided below, describe exemplary embodiments of a transformer having an interlocking core frame. One of ordinary skill in the art will appreciate that a component may be designed as multiple components or that multiple components may be designed as a single component.
Further, in the accompanying drawings and description that follow, like parts are indicated throughout the drawings and written description with the same reference numerals, respectively. The figures may not be drawn to scale and the proportions of certain parts may have been exaggerated for convenience of illustration.
A dry-type distribution transformer 50 having an interlocking core frame 16 embodied in accordance with the present invention is shown in
Referring now to
The at least one limb 62, 64 is comprised of an inner limb 64 and two outer limbs 62 in a three-phase distribution transformer 50. Further, the core limbs 62, 64 and yokes 61, 65 typically connect to form a pair of core windows 67. A coil assembly 34 is disposed around the at least one limb 62, 64 and comprises high-voltage and low-voltage coil windings. The high-voltage and low-voltage coil windings are often arranged concentrically along the length of the at least one limb 62, 64. In one embodiment, the high-voltage winding is arranged around and encompasses the low-voltage winding. The coil assemblies 34 may be encased in a polymeric material or an epoxy material to form an outer surface from which high-voltage bushings 52 and tap projections 36 containing at least one tap extend.
The transformer core 30 is enclosed within the core frame 16. The core frame 16 retains the coil assemblies 34 in about an equally spaced-apart manner on the core 30. The coil assemblies 34 fill the core window 67 as completely as possible without allowing the contact of adjacent coil assemblies 34.
The core frame 16 is formed from a pair of first core clamps 10, a pair of second core clamps 20 and leg plates 40. The first core clamps 10 are placed on opposing sides of the upper yoke 61. The second core clamps 20 are placed on opposing sides of the lower yoke 65. The first and second core clamps 10, 20 compress the upper and lower yokes 61, 65, respectively.
The leg plates 40 are placed on both sides of the at least one core limb 62, 64. In a three-phase distribution transformer 50 core frame 16, the at least one core limb 62, 64 is comprised of outer and inner core limbs 62, 64 and six leg plates 40 are utilized. In that same embodiment three cut-outs portions 60 are formed in each of the first core clamps 10 and each of the second core clamps 20, respectively. Further, each of three leg plates 40 are in contact with the front side of the corresponding at least one core limb 62, 64 and each of three leg plates 40 are in contact with the rear side or opposing side of the corresponding at least one core limb 62, 64.
In a single-phase embodiment, the core 30 has two core limbs 62 and four leg plates 40. In that same embodiment, each of the first and second core clamps 10, 20 have two cut-out portions 60 formed therein.
The first and second core clamps 10, 20 and the leg plates 40 may be constructed from a different material than the core 30. For example, the first and second clamps 10, 20 and the leg plates 40 may be comprised of regular, non-electrical grade carbon steel, which has different magnetic properties than grain-oriented silicon steel or amorphous metal.
The first and second core clamps 10, 20, leg plates 40, cut-out portions 60, first slots 38, and other openings 24, 25, 74, 76 are laser-cut to produce precision parts. Each of the first core clamps 10 is bent to produce a U-shape when the first core clamps 10 are connected together as shown in
The first and second core clamps 10, 20 each have first sections 12, 14 that extend outwardly from a second section 18 of the first and second core clamps 10, 20. The first and second core clamps 10, 20 have cut-out portions 60 formed therein for receiving tabs 42 formed in first and second ends of leg plates 40. The precision cut of the tabs 42 and cut-out portions 60 along with the first section 14 holds the leg plates 40 and first and second clamps 10, 20 securely in the interlocking position depicted in
Each leg plate 40 has a tab 42 and a notch 41 formed in opposing ends as depicted in
The leg plates 40 bear the load of the assembled transformer 50 and core frame 16 when in an interlocking position with the cut-out portions 60 of the first and second core clamps 10, 20, respectively. The support edges 17 formed by the bending of the first and second core clamps 10, 20 along broken lines 80, 82, 84 further reinforce and retain the tabs 42 of the leg plates 40 in place in the cut-out portions 60 of the first and second clamps 10, 20.
Referring now to
With reference now to
The front-facing first core clamp 10 of
Referring now to
The eyebolts 22 extend upward through the first slots 38 when the front- and rear-facing first clamps 10 are connected together. The front- and rear-facing first clamps 10 are held together by bolts in openings 24, 25, 74. The bolts in openings 24, 25 hold the front- and rear-facing first clamps 10 together in a position parallel to one another.
The bolts in openings 74 connect the sections 19, 21 together and further connect sections 19, 21 to a roof plate 56. The roof plate 56 is formed of sheet metal that is bent to form a flat center portion having two edge portions that extend obliquely from the flat center portion. The roof plate 56 has second slots 78 similar to first slots 38 to receive the eyebolts 22 of the first core clamps 10. The roof plate 56 in conjunction with first clamps 10 and eyebolts 22 stabilize the core frame 16 when the core frame 16 is lifted, transported and mounted.
The pair of second core clamps 20 each have a C-shape. The second core clamps 20 are connected together using bolts placed through openings 24, 25 and secured by nuts. The second core clamps 20 further connect to a foot 70 as depicted in
The second core clamps 20 each have cut-out portions 60 formed therein. In the three-phase transformer 50 embodiment, each of the second core clamps 20 has three cut-out portions 60 formed therein, each of the three cut-out portions 60 for receiving a corresponding one of the leg plate tabs 42. The second core clamps 20 each have first sections 14 for retaining the leg plates 40 in an interlocking position with the cut-out portions 60.
Referring now to
Referring now to
A method for forming a distribution transformer 50 with an interlocking core frame 16 includes the steps of providing a ferromagnetic core comprising at least one limb 62, 64 extending between the upper and lower yokes 61, 65. First and second core clamps 10, 20 and leg plates 40 are provided for forming a core frame 16 for holding the core 30. The core frame 16 is formed by placing leg plates 40 on each side of the at least one core limb 62, 64 and second core clamps 20 on each side of the lower yoke 65. Then, the tabs 42 of the leg plates 40 are placed into receiving cut-out portions 60 of the second core clamps 10, 20, respectively so that the second core clamps 20 and leg plates 40 are in an interlocking position.
Coil assemblies 34 are mounted to or placed over the leg plates 40 and core limbs 62, 64 so that the leg plates 40 and core limbs 62, 64 extend through the coil assemblies. The upper yoke 61 is secured to the core limbs 62, 64. The first core clamps are placed on each side of the upper yoke 61. Tabs 42 of the leg plates 60 are then placed into the first clamp 10 cut-out portions 60, respectively, so that the first core clamps 10 and leg plates 40 are in an interlocking position.
While the present application illustrates various embodiments of a transformer 50 having an interlocking core frame 16, and while these embodiments have been described in some detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative embodiments, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept.
Filing Document | Filing Date | Country | Kind |
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PCT/US13/64749 | 10/13/2013 | WO | 00 |
Number | Date | Country | |
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61716977 | Oct 2012 | US |