Yoke clamp component for a transformer core

A yoke clamp bracket for a transformer core. The yoke clamp bracket may comprise a body portion having a plurality of center holes near each end, a plurality of slots for coil barriers, a plurality of slots for wiring, and attachment points for side brackets and vertical supports. The yoke clamp bracket may be mounted to a transformer core by connectors extending through the plurality of center holes. The yoke clamp bracket may be constructed from a lightweight material with low density such that it displaces a larger quantity of tank oil and reduces the weight of a distribution transformer.

BACKGROUND

Distribution transformers are used in AC power systems in order to convert high-voltage electricity carried by power lines to lower-voltage electricity that may be used by consumers. Several varieties of distribution transformer exist: pole-mounted transformers (mounted on a utility pole), ground-level pad-mounted transformers (generally mounted on a surface-level concrete pad), and underground transformers. These transformers may include, among other components, a core clamping structure that keeps the coils of the transformer in place.

These distribution transformers are legally required to meet efficiency standards set forth by the Department of Energy (DOE). Because of these requirements, and because of the demands of a competitive marketplace, it may generally be necessary to maintain stray losses in a given distribution transformer at as low a level as possible. Stray losses in a distribution transformer design can be caused by metallic structural components such as the transformer core clamps (typically made from mild steel), the tie plates, the transformer tank, and other similar metallic structural components.

Some of these components, such as the mild steel core clamps, may also add significant weight to the overall transformer. This may also be undesirable, especially in those cases where the distribution transformer is intended to be mounted on a utility pole; increased transformer weight may mean increased material and installation costs or increased risk of failure. As such, it is competitively very important to reduce both the sources of stray losses in a distribution transformer and the weight of the distribution transformer, so long as each can be done cost-effectively.

SUMMARY

A yoke clamp bracket for a transformer core may be disclosed. A yoke clamp bracket may comprise: a body portion, the body portion including a front and back face, a top and bottom face, and a left side and right side face disposed respectively at left and right ends of the body portion; the body portion further having a plurality of center holes disposed in close proximity to either end of the body portion, the plurality of center holes extending through the body portion in a direction perpendicular to the planes of the front face and the back face; the body portion further having a first coil barrier slot and a second coil barrier slot extending inward from the top face of the body portion, the first coil barrier slot being located at a point approximately equidistant from the second coil barrier slot and the left side face, the second coil barrier slot being located at a point approximately equidistant from the first coil barrier slot and the right side face; the body portion further having a plurality of vertical slots, each of the vertical slots extending inward from the bottom face of the body portion, and a plurality of horizontal slots, each of the horizontal slots extending inward from the front face of the body portion, wherein at least a vertical slot and a horizontal slot are located on each of the left and right sides of the first coil barrier slot and in close proximity to the first coil barrier slot, and wherein at least a vertical slot and a horizontal slot are located on each of the left and right sides of the second coil barrier slot and in close proximity to the second coil barrier slot; wherein the body portion is constructed from a substantially rigid, lightweight, and non-conductive material.

According to another exemplary embodiment, a transformer incorporating a plurality of yoke clamp brackets into its design may be disclosed. The transformer may comprise: a transformer core, the transformer core comprising a lower yoke and an upper yoke, and a plurality of transformer limbs, wherein each of the transformer limbs supports a transformer coil; a plurality of yoke clamps, each of the plurality of yoke clamps comprising a pair of yoke clamp brackets, wherein each of the yoke clamp brackets comprises: a body portion, the body portion including a front and back face, a top and bottom face, and a left side and right side face disposed respectively at left and right ends of the body portion; the body portion further having a plurality of center holes disposed in close proximity to either end of the body portion, the plurality of center holes extending through the body portion in a direction perpendicular to the planes of the front face and the back face; the body portion further having a first coil barrier slot and a second coil barrier slot extending inward from the top face of the body portion, the first coil barrier slot being located at a point approximately equidistant from the second coil barrier slot and the left side face, the second coil barrier slot being located at a point approximately equidistant from the first coil barrier slot and the right side face; the body portion further having a plurality of vertical slots, each of the vertical slots extending inward from the bottom face of the body portion, and a plurality of horizontal slots, each of the horizontal slots extending inward from the front face of the body portion, wherein at least a vertical slot and a horizontal slot are located on each of the left and right sides of the first coil barrier slot and in close proximity to the first coil barrier slot, and wherein at least a vertical slot and a horizontal slot are located on each of the left and right sides of the second coil barrier slot and in close proximity to the second coil barrier slot; wherein the body portion is constructed from a substantially rigid, lightweight, and non-conductive material; wherein a lower yoke clamp in the plurality of yoke clamps is coupled to the lower yoke of the transformer core; and wherein an upper yoke clamp in the plurality of yoke clamps is coupled to the upper yoke of the transformer core.

DETAILED DESCRIPTION

According to an exemplary embodiment, and referring to the Figures generally, a yoke clamp bracket100for a transformer core may be provided. Such a yoke clamp bracket100may have a variety of uses inside the core of a transformer and in particular a distribution transformer. For example, according to one exemplary embodiment, the yoke clamp bracket100may be used in order to hold the core-yoke laminations together. According to another exemplary embodiment, the yoke clamp bracket100may be used in order to hold the core against the short circuit forces that may be found within the core of the distribution transformer or other transformer.

According to an exemplary embodiment, the body102of the yoke clamp bracket100may be constructed out of a material that is sufficiently strong to hold up to the forces inside the transformer. For a yoke clamp bracket100that is intended be employed in a distribution transformer, it may not be necessary to construct the body102out of a strong structural material, such as steel; instead, other materials, like other metals, plastics, and organic or inorganic composites may be used instead. Body102material may also be lightweight; according to some exemplary embodiments, the distribution transformer containing the yoke clamp bracket100may be suspended from a utility pole, and it may be desirable to reduce the weight of this distribution transformer as much as possible in order to make it easier to mount and simplify maintenance. According to some exemplary embodiments, body102material may also be inexpensive, or may be easy to work; this may ensure that the yoke clamp bracket100can be created inexpensively, increasing its attractiveness as a design.

For example, according to one exemplary embodiment, the body102of the yoke clamp bracket100may be constructed out of wood. Different types of wood may be used for the body102; for example, a hardwood, such as oak or maple, may be used. Different preparations of wood may also be used; for example, the wood may be plywood, or may be another composite wood or engineered wood. Materials other than wood may also be used; for example, the body102may be constructed from a wood-like material such as engineered bamboo, or from an inorganic composite material, or from any other acceptable material, as desired.

According to an exemplary embodiment, constructing the yoke clamp bracket100from a non-conducting material, such as wood, may reduce or eliminate the electrical clearances that may be required within a distribution transformer. For example, no electrical clearances may be required to be maintained from the current carrying lead, or other leads, to the wooden yoke clamp bracket100. According to an exemplary embodiment, wooden yoke clamp bracket100may be used as a support for the current-carrying leads, or may be used as a routing base for the leads, as desired.

Similarly, a yoke clamp bracket100being constructed from wood or a wooden composite, or another non-conductive and/or non-magnetically-permeable material, may reduce stray losses within the distribution transformer as compared to the use of a steel yoke clamp, as no eddy currents may be induced in the yoke clamp bracket100.

The use of a wooden or otherwise non-conductive yoke clamp bracket100may also allow for higher current densities to be used in the electrical design, which may have numerous advantages. In particular, a higher current density may allow for the sizes of the transformer cores and coils to be reduced, which may in turn allow for reductions in the size of the tank necessary to accommodate the transformer cores and coils, and the amount of oil that is required to fill the smaller tank. It may also allow for reductions in the coil and core weight, which may in turn place less stress on the transformer mounting bracket and on the pole. This may result in general cost reductions for the transformer.

According to an exemplary embodiment, yoke clamp bracket100may be retrofittable. Yoke clamp bracket100may be sized and shaped such that, when an existing transformer is undergoing inspection or refurbishment, yoke clamp bracket100may be installed in the existing design of transformer, if desired. According to another exemplary embodiment, yoke clamp bracket100may be applied to new transformers. According to an exemplary embodiment, yoke clamp bracket100may also be easy to remove and replace, if desired.

According to an exemplary embodiment, yoke clamp bracket100may be easy to modify. Another advantage of using a softer and less expensive material, like wood, to construct the yoke clamp bracket100may be that the material may be easily modified and cut to shape, if necessary and if desired. According to an exemplary embodiment, a yoke clamp bracket100that is easier to modify may likewise be more worker-friendly.

Yoke clamp bracket100may have a plurality of center holes104or mounting holes on or near either end of the yoke clamp bracket100. Center holes104may be used in order to secure the yoke clamp bracket100on a transformer core. For example, according to one exemplary embodiment, a yoke clamp bracket100may be placed on either side of the lower (or upper) portion of a transformer core, and a plurality of small rods, bolts, or other connectors may be passed through the center holes104in order to secure one of the yoke clamp brackets100to the other and secure the transformer core in place. According to an exemplary embodiment, small rods or other connectors may be nonconductive, and may be, for example, constructed from nylon, or another material, as desired. According to an exemplary embodiment, small rods or other connectors may be passed through the center holes104and into the transformer core. According to an alternative exemplary embodiment, small rods may be passed through the center holes104and around the transformer core into another pair of center holes104of a yoke clamp bracket100mounted on the opposite side of the transformer core.

Yoke clamp bracket100may also have a plurality of slots, including vertical slots106and horizontal slots108. According to an exemplary embodiment, vertical slots106and horizontal slots108may be used as guides for a strap or other connector that may be used to attach the yoke clamp bracket100to the transformer core. According to another exemplary embodiment, vertical slots106and horizontal slots108may be used as guides for transformer coil wire.

According to an exemplary embodiment wherein the yoke clamp bracket100is intended to be attached to a transformer core having at least three limbs, vertical slots106and horizontal slots108may be located at points at or near ⅓ of the span of the yoke clamp bracket100and ⅔ of the span of the yoke clamp bracket100. Such a configuration may split the yoke clamp bracket100into three sections of approximately equal length. According to an exemplary embodiment, when the yoke clamp bracket100is installed on a transformer core, the vertical slots106and horizontal slots108may be located at points at or near the spaces between transformer core limbs and/or transformer coils. Other placements of vertical slots106and/or horizontal slots108may also be envisioned, as desired.

Yoke clamp bracket100may also have a plurality of coil barrier slots110. Coil barrier slots110may be used to support a barrier placed between transformer coils, such as an insulating or dielectric barrier, or other barrier, as desired. An edge of the coil barrier may fit in the coil barrier slots110, substantially fixing the coil barrier in place in a position that separates adjacent transformer coils. According to an exemplary embodiment, coil barrier110may be formed from a solid insulating material, such as pressboard, densified or “transformer” wood, another type of wood such as maple or beech wood, or another material such as layer insulation, as desired.

Yoke clamp bracket100may also have a side bracket support112, which may be used to support a side bracket. According to an exemplary embodiment, side bracket may fit onto or otherwise attach to the yoke clamp bracket100at the side bracket support, and may extend to another yoke clamp bracket100that may be placed on the other side of a transformer core. This may be used, for example, to secure the yoke clamp bracket100in place around the transformer core.

According to an exemplary embodiment, yoke clamp bracket100may have a vertical through hole, called a drawdown channel114, disposed near each end of the yoke clamp bracket100. According to an exemplary embodiment, drawdown channel114may extend through the yoke clamp bracket100. Drawdown channel114may be used to, for example, support a tie plate; according to such an exemplary embodiment, tie plate may extend from one yoke clamp bracket on one side of the core, across the top or bottom of the core and to a yoke clamp bracket100on the other side of the hole. According to such an exemplary embodiment, drawdown channel114may accommodate a connector, such as a bolt, which may be passed through the tie plate and the drawdown channel114and used to hold both in place relative to each other. According to an exemplary embodiment, the tie plate may be welded to the core; according to such an embodiment, the drawdown channel114may also serve to connect the yoke clamp bracket114to the core.

Referring now to exemplaryFIG. 1a,FIG. 1ashows a front view of an exemplary embodiment of a yoke clamp bracket100for a transformer core. The face of the yoke clamp bracket100shown inFIG. 1amay be referred to as the “front” face150of the yoke clamp bracket100, with the opposite side being the “back” face.

Referring now to exemplaryFIG. 1b,FIG. 1bshows a top view of an exemplary embodiment of a yoke clamp bracket100for a transformer core. The face of the yoke clamp bracket100shown inFIG. 1bmay be referred to as the “top” face152of the yoke clamp bracket100, with the opposite side being the “bottom” face.

Referring now to exemplaryFIG. 1c,FIG. 1cshows a top view of an exemplary embodiment of a yoke clamp bracket100for a transformer core. The face of the yoke clamp bracket100shown inFIG. 1cmay be referred to as the “side” or “left side” face154of the yoke clamp bracket100, with the opposite side being the “right side” face.

Referring now to exemplaryFIG. 1d,FIG. 1dshows an isometric view of an exemplary embodiment of a yoke clamp bracket100for a transformer core. The isometric view of the yoke clamp bracket100shown inFIG. 1dmay show front150, top152, and side154faces of the yoke clamp bracket100.

Turning now to exemplaryFIG. 2,FIG. 2displays an exemplary embodiment of a transformer core202to which a yoke clamp bracket100may be fitted204. Transformer core202may include a yoke206and a number of limbs208. According to an exemplary embodiment, yoke clamp bracket100may be slightly longer than the yoke206, such that the center holes104extend past the ends of the yoke206on either side. Side bracket may likewise be attached to a side bracket support112extending past the end of the yoke206. According to an exemplary embodiment, bolts or other connectors may extend through the center holes104, through the side bracket, and out the center holes104of a yoke clamp bracket100mounted on the opposite side of the transformer core202. According to an alternative exemplary embodiment, bolts or other connectors may be passed into the transformer core202, as desired.

According to an exemplary embodiment, a “yoke clamp” may include two yoke clamp brackets100, each yoke clamp bracket100being located on one side of a transformer yoke206, and each yoke clamp bracket100being linked to the other yoke clamp bracket100by a pair of side brackets, each of which is attached to one of the side bracket supports112of each yoke clamp bracket100. Yoke clamp brackets100may further be coupled to a transformer yoke206, for example via the mounting holes. According to another exemplary embodiment, a “yoke clamp” may include only a pair of yoke clamp brackets100, each of which is coupled via bolts to the transformer yoke206rather than being coupled to a side bracket.

According to an exemplary embodiment, transformer limbs208may terminate in another yoke206(an “upper yoke”), to which may be attached another pair of yoke clamp brackets100. Upper yoke may be similar or identical in size and shape to the lower yoke206. Yoke clamp brackets100attaching to the upper yoke of the transformer core202may be substantially identical to yoke clamp brackets100attaching to the lower yoke206of the transformer core202, or may have a different geometry, as desired. Yoke clamp brackets100attaching to either the upper or lower yoke206of the transformer core may have vertical through holes114on either end of the span of the yoke clamp bracket100; vertical through holes may be substantially vertically-facing and may extend through or substantially through the yoke clamp bracket100. Vertical supports may be fitted in the vertical through holes114and may extend upward from the yoke clamp brackets100attaching to the lower yoke206of the transformer core202to the yoke clamp brackets100attaching to the upper yoke of the transformer core. Alternatively, vertical supports may extend to another point, or vertical through holes114may be used to fit another shape or type of support, as desired.

The foregoing description and accompanying figures illustrate the principles, preferred embodiments and modes of operation of the invention. However, the invention should not be construed as being limited to the particular embodiments discussed above. Additional variations of the embodiments discussed above will be appreciated by those skilled in the art (for example, features associated with certain configurations of the invention may instead be associated with any other configurations of the invention, as desired).