Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-07-29
2001-02-27
Nguyen, Ngoc-Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S065000
Reexamination Certificate
active
06194807
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to generator rotors and, more specifically, to the blocking of end arc portions of the field windings of generator rotors.
Generator fields with C-coil windings in tapered rotor slots have special blocking requirements in the end arc region of the windings. The space between end arcs in adjacent coils is larger for turns located closer to the axis of rotation of the rotor than it is for turns located closer to the peripheral surface of the rotor. Normal assembly procedure calls for location of spacer blocks between coils after the coils have been wound into the field. For windings located in parallel sided rotor slots, such blocks have parallel faces. This allows the blocks to be assembled after all of the coils have been wound. However, for designs with turns located in tapered slots, the blocks need to be wider at the radially inboard end than at the radially outboard opening where they are inserted. These tapered blocks must be assembled against each coil stack as the field is wound. This arrangement, however, does not allow for any adjustment after winding, and does not allow the blocks to be removed without first disassembling entire coils from the rotor.
BRIEF SUMMARY OF THE INVENTION
The invention consists of two primary elements. One involves a change in the construction and arrangement of the coils. The other involves a change in the construction of the blocking components (or, simply, the “blocking”) between the end arc portions of the coils.
In accordance with an exemplary embodiment of this invention, individual turns in the end arc portion of a field winding in tapered slot designs are secured against axial movement by adjusting the location of edgewise bends so as to align the edges of the turns in a given coil stack along a common edge, and then inserting appropriately tapered two piece blocking between adjacent coils.
More specifically, and with respect to the coil construction, copper bars are normally arranged in a tapered coil slot with each bar arranged symmetrically with respect to the coil slot centerline. The same is true, of course, for copper bars seated in slots having parallel sides. Normally, in both cases, the symmetry is preserved as the bars progress around the pole face to form the end turns. To facilitate accessibility for a practical blocking strategy in a tapered slot design, however, the coil construction in accordance with this invention is altered to permit the edgewise turns to be aligned along a common edge, i.e., they do not maintain symmetry with the slot centerline. In addition, all of the copper bars are formed to have a common straight length and a common radius of curvature for each of the edgewise bends. Thus, whether the bar has a wide width or a narrow width, the axial separation between inside edges for any given coil remains the same.
The resultant spacing between coils now makes possible the introduction of a two piece blocking that can be assembled into position from above the winding, even though the opening is narrower at the top than at the bottom.
The two mating parts that make up the proposed blocking include a slide and an anchor which share a common inclined but flat mating surface. The slide has two protruding pins which are arranged to line up and fit inside a groove formed into the anchor piece. The groove allows the slide to be assembled radially downward into the block, yet provide restraint against peripheral misalignment. The same effect can be obtained by replacing the two pins with a rectangular protrusion, thus providing a tongue and groove arrangement.
The exposed surface of the slide follows the contour of the coil stack while the exposed surface of the anchor lies against the aligned edge of the next coil stack. Insertion of the slide along side the anchor thus fills the space between coils and provides support for all of the turns in the coil stack. Though the blocks are now wedged tightly in position, there remains the possibility that with thermal cycling, the block assembly could loosen sufficiently that the anchor block shift radially inward. To prevent this occurrence, a plate can be secured across the top of the block, such that it spans the anchor, the slide and the top turn of the adjacent coil.
Thus, in the broader aspects, the invention relates to an end turn arrangement for windings in a rotor where individual turns are stacked in tapered radial slots in the rotor, with successive turns having a smaller width in a radial inward direction, the end turns of the individual turns of each stack being aligned along a common edge.
In another aspect, the invention relates to a blocking separator for use between end turns of windings in a rotor, the blocking separator comprising a first anchor component having a first planar exterior surface and a second planar interior engagement surface; and a second slide component having a first non-planar exterior surface and a second planar interior engagement surface; the anchor and slide components having mating guide elements permitting the anchor and slide components to move relative to each other along a straight assembly path.
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Kaminski Christopher Anthony
Lloyd Robert Francis
Walko Steven Charles
General Electric Co.
Nguyen Ngoc-Tran
Nixon & Vanderhye
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