Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-12-18
2002-12-24
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S091000, C310S051000
Reexamination Certificate
active
06498417
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to the power generation industry and, more particularly, to the field of mounting frames supporting stator cores.
BACKGROUND OF THE INVENTION
In the power generation industry, generator stator cores are supported on mounting frames. As is known in the art, generator stator cores generally include keybars positioned along an outer peripheral surface of the generator stator core. During operation of a power generation system, the generator stator core experiences an “oval mode” condition during which the generator stator core cyclicly deforms. The generator stator core temporarily deforms into an oval shape during operation. The deformations take place along both the horizontal and vertical axis. The “oval mode” condition experienced by the generator stator core accounts for some of the tangential and radial forces on a power generation system. Manufacturers of power generation systems are often faced with the problem of designing an efficient stator core frame support that can compensate for the “oval mode” condition experience by the generator stator core during operation. Current frame supports are very large and inefficient.
Power generation systems also experience transient faults during operation. When the power generation system experiences a transient fault, the generator stator core is suddenly displaced or rotated and it is difficult for a frame or frame support to sustain the forces associated with the transient fault. Manufacturers and users of high voltage generator stator cores often have great difficulty providing an efficient support for the generator stator core. In order to provide a frame support that is sufficient enough to sustain the forces associated with transient faults experienced during operation of the generator stator core, the frame support is normally very large and extremely inefficient.
Current power generation systems conventionally provide generator stator cores that have a higher tuned natural frequency. A generator stator core having a higher tuned natural frequency makes the power generation system more expensive and complex. A less stable power generation system requires a large core supporter that is also not cost effective and extremely inefficient.
Some generator stator core support frames incorporate an outer frame surrounding the core that is then attached to a bedplate or lower frame such as seen in U.S. Pat. No. 6,091,177 by Carbonell et al. titled “Spring Mounting For An Electric Generator.” The mounting frame surrounds the core and connects to all of the keybars positioned on the outer peripheral portions of the core. The surrounding frame is then attached to a lower frame using side and lower connecting members. The combination of these connecting members provides a support frame that is inefficient and cumbersome. Furthermore, the combination of the surrounding frame and the support frame provides a support apparatus with an increased load path, i.e., the load from transient faults and vibratory forces must travel an increased distance.
A similar arrangement for such an apparatus can be found in U.S. Pat. No. 4,891,540 by Cooper et al. titled “Generator Core Support System.” This support system connects to the generator stator core around the outer periphery of the generator stator core where the keybars are positioned. Similarly, the support system provides a complex and inefficient connection between the generator stator core and the support frame. This rigid connection does not relieve lateral and tangential forces associated with transient faults. Accordingly, excess force from transient faults can cause damage to the generator stator core and frame if the core is not properly fastened to a frame support that can withstand these forces.
As understood by those skilled in the art, it is common to support a power generator stator core on a support frame that includes a connecting member between the generator stator core and the frame support in the six o'clock or twelve o'clock positions, i.e., a connecting member between the lower outer portion of the generator stator core and the stator core frame support. It is also common to support a power generator stator core on a support frame that includes a connecting member between the generator stator core and the frame support in the twelve o'clock position, i.e., a connecting member between an upper outer portion of the generator stator core and the stator core frame support. These configurations of frame supports provide inefficient connections that do not allow for the elimination of lateral forces associated with transient faults that occur during operation.
Additionally, it is costly and time consuming to provide support systems for power generators due to the cumbersome size and configuration of the current support frames necessary for accommodating transient faults and the oval mode experienced by power generation systems during operation. Some current support systems are so cumbersome that it is not possible to assemble the core and the core support system separate from one another. Presently, the core and the core support system must be constructed simultaneously. The simultaneous construction of the core and the support frame is extremely costly and time consuming.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention advantageously provides a high voltage power generation system including an apparatus for attaching a generator stator core to a frame support and methods of stabilizing a power generation system, reducing vibration and eliminating lateral movement of a generator stator core, low tuning the natural frequency of the generator stator core during operation, and compensating for an “oval mode” condition that occurs during operation of the power generation system that are efficient and cost effective. More particularly, the present invention advantageously utilizes spring supports to allow for a generator stator core to be supported by a generator stator core frame support in a manner that eliminates any rigid connections in the power generation system. The present invention also advantageously provides an apparatus and methods for protecting a power generation system from the forces associated with transient faults. The present invention further advantageously compensates for temporary deformations that result in radial and tangential forces that are encountered when the generator stator core experiences an “oval mode” condition during operation. The present invention still further advantageously compensates for the stresses applied to a power generation system associated with a generator stator core having a high tuned natural frequency by low tuning the natural frequency of the generator stator core.
More particularly, the present invention provides a power generation system that includes a stator core frame support member having a lower inner surface portion and a lower outer surface portion. The lower inner surface portion, for example, can have a substantially semi-annular shape. The lower outer surface portion is positioned to contact a support surface. The system also includes a generator stator core that can likewise have a substantially annular shape. The generator stator core preferably includes a plurality of keybars positioned spaced-apart and extending along the outer peripheral portions. The generator stator core is positioned to overlie the lower inner surface portion of the stator core frame support member and has a lower end portion positioned spaced-apart from and not in contact with bottom portions of the lower inner surface of the stator core frame support member. The upper end portion of the generator stator core is also positioned spaced-apart from and not in contact with the stator core frame support.
The system further includes a core supporter connected to the stator core frame support member. The core supporter is positioned to contact a plurality of keybars that are positioned along outer side peripheries of the generator stator core. The core supporter
Nguyen Tran
Siemens Westinghouse Power Corporation
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