Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1995-06-22
2002-11-19
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S261100, C310S071000
Reexamination Certificate
active
06483220
ABSTRACT:
TECHNICAL FIELD
This invention relates to a precision-wound rotor for a high speed dynamoelectric machine, and more particularly to a structure and a method for facilitating the manufacture of such a rotor.
BACKGROUND
Many dynamoelectric machines, including certain types of electric motors or generators, utilize a rotating member, which is known as a rotor, having a winding formed from layers of turns of wire wound about a rotor core of magnetic material. Rotors which provide superior performance and compact physical size can be produced by precision-winding the turns of wire about the rotor core.
In such precision-wound rotors, as shown in
FIG. 1
, the turns of wire
1
-
23
are precisely positioned within generally planar, overlapping layers
144
,
146
,
147
of the winding
118
in a side-by-side fashion with each turn in a given layer closely abutting an adjacent turn in that layer. The turns are preferably offset by one-half wire diameter in adjacent layers, so that each turn of wire will rest in a groove
148
formed between adjacent turns of wire in the preceding and any subsequent layers of the winding
118
.
The precision-wound winding is generally contained in a slot
116
or channel of the rotor core
102
. Ideally, as shown in
FIG. 1
, the winding
118
is formed in such a manner that the outer turns of wire
1
,
8
,
16
,
23
in the radially innermost and outermost layers
160
,
162
, and the outer turns in alternating intermediate layers, bear simultaneously against a wall
132
,
134
of the slot
116
and/or one of more adjacent turns of wire in the winding
118
, to form a densely packed structure.
In such a densely packed structure, the space occupied by the turns is minimized and remains highly consistent from one rotor to another, thereby allowing such precision-wound rotors to be physically smaller and more tightly toleranced than non-precision-wound rotors. Precision-wound rotors are also inherently more structurally self-supporting due to the interlocking nature of the turns within the slot
116
, thereby allowing a precision wound rotor to operate safely at high rotational speed without fear of centrifugal forces causing the turns to shift, in contrast to non-precision-wound rotors in which shifting of the turns is known to occur.
Where cooling fluid is pumped through the winding
118
, precision-winding provides superior heat transfer, thereby allowing wire size and/or coolant flow to safely be reduced without fear of the winding overheating. This improved heat transfer results from the turbulent fluid flow which occurs in the small interstices
156
which are formed between adjacent turns of the precision wound rotor. In non-precision-wound rotors, the interstices are larger, thereby causing laminar instead of turbulent fluid flow, which results in lower heat removal capability and the need for larger wire sizes and/or coolant flow rates in order to maintain acceptable temperatures in the winding. Commonly assigned U.S. Pat. Nos. 4,583,696 and 4,603,274 to Mosher are illustrative of precision-wound rotors as described above.
For precision-wound rotors having an odd number of layers of turns, as illustrated in
FIG. 1
, the tightly wound winding
118
supported by walls
132
,
134
of the slot
116
as described above, may be readily manufactured with minimal difficulty due to the fact that the first and last layers
160
,
162
can be configured to extend entirely across the width W
2
of the slot
116
in the core
102
. However, as illustrated in
FIGS. 2 and 3
where the winding
118
includes an even number of layers having each turn nested in a groove
148
formed by turns in an adjacent layer as described above, either the innermost layer
160
or the outermost layer
162
of the turns will not extend entirely across the width W
2
of the slot
116
, and will thus not be fully supported by the slot walls
132
,
134
.
Stated another way, for the desired nesting of turns to occur in adjacent layers of turns, the turns in one layer of each pair of adjacent layers of the winding
118
must be offset by one-half wire diameter from the turns in the other layer of the pair of layers. For a slot
116
having parallel walls
132
,
134
, this means that if one member of the pair of layers has n turns of wire, the adjacent member of the pair of layers must have either n+1 or n−1 turns. Therefore, if the slot
116
has a width W
2
equal to (n+1)×(the wire diameter D), either the innermost
160
or outermost
162
layer of the winding
118
will have only n turns, and thus will not extend entirely across the slot
116
, or be supported by the walls
132
,
134
.
If the outermost layer
162
has only n turns, additional structure or winding retaining means may be required to preclude shifting of the turns as the result of centrifugal forces acting on the turns incident with rotation of the rotor. It would appear to be preferable, therefore, to have the innermost layer contain only n turns, as depicted in
FIG. 3
, since an overlying layer of n+1 turns, which extends entirely across the slot
116
will trap the innermost layer against the bottom surface
130
of the slot, thereby precluding movement. However, with the innermost layer
160
having only n turns, and not extending entirely across the slot width, some means of fixturing the innermost layer during fabrication of the winding must be provided to ensure that the subsequent layers having n+1 turns will fit properly within the slot width and simultaneously nest within the grooves between adjacent turns in the innermost layer of turns. Such fixturing increases the difficulty and cost of manufacturing the precision-wound rotor. The inconvenience and cost of providing such fixturing becomes even more acute with respect to repair or re-manufacturing of a damaged rotor in need of having the winding
118
replaced. Repair or re-manufacturing operations are often preferably carried out at repair centers or depots remote from the facility in which the rotor was originally manufactured. If special fixturing is required for precision winding, duplicate sets of such fixturing will need to be maintained at every remote repair or re-manufacturing facility. In many instances, the cost of maintaining and utilizing such duplicate fixturing at the remote sites will be so prohibitively high that damaged rotors will have to be shipped back to the initial manufacturing facility for repair, or worse yet, simply discarded and replaced with a new rotor, thus greatly increasing the cost of ownership of the dynamoelectric machine.
Accordingly, it is an object of my invention to provide a precision-wound rotor having an even number of layers of turns which is self-fixturing, and may thus be more readily manufactured at low cost without specialized fixturing or tooling. It is also an object of my invention to provide such a rotor in a form which may be readily repaired by re-winding the rotor at a remote repair facility or depot, without the use of specialized fixturing.
SUMMARY
My invention accomplishes these objects in a precision-wound rotor through inclusion of a self-fixturing wire-guiding feature, such as a shoulder or a chamfer, in the corners of slots in the rotor core which contain the precision-wound winding.
Specifically, the precision-wound rotor of my invention includes a magnetic core having a slot therein for receipt of a winding having a first layer of n turns of wire and a second layer of n+1 turns of wire. The slot includes a generally planar bottom surface thereof, and sidewalls intersecting with the bottom surface to form corners of the slot. The sidewalls are disposed equidistant from a slot centerline bisecting and extending perpendicularly outward from the bottom surface of the slot. A self-fixturing wire-guiding feature is provided for centering a first and a second layer of the winding about the slot centerline within the slot in such a manner that when the first layer is formed by winding the turns of the first layer in a side-by-side fashion across the bottom surface
Hamilton Sundstrand Corporation
Hamilton Sundstrand Corporation
Nguyen Tran
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