Double-fed Asynchronous Machine Rotor Bracing
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Solution Overview
Problem
Double-fed asynchronous machines in the 20 MVA to 500 MVA power range face challenges in effectively securing the rotor winding against centrifugal forces while maintaining optimal magnetic flux path and avoiding damage to insulating layers, as existing bracing methods do not adequately differentiate between mechanical and electrical areas.
Innovation Solution
A radially separated pressure plate system is introduced, comprising a detachable inner and outer pressure plate, where the inner plate applies higher axial pressure in mechanical areas and lower pressure in electrical areas, with shear and tension bolts used to manage forces, and the outer plate can be tilted relative to the inner plate for enhanced absorption of centrifugal forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single pressure plate is used to brace the laminated rotor body, then the structure is simple, but the different requirements for bracing in mechanical and electrical areas cannot be met
Solution Approach 1:
The pressure plate is divided into two separate pressure plates: an inner pressure plate for the mechanical area and an outer pressure plate for the electrical area. This segmentation allows each pressure plate to be independently designed and optimized for its specific functional requirements, enabling different bracing characteristics in different regions of the rotor body.
Solution Approach 2:
Each pressure plate is designed with locally optimized properties: the inner pressure plate has higher axial pressure capability for the mechanical area where greater bracing is needed, while the outer pressure plate has lower axial pressure for the electrical area. This local quality differentiation allows each region to receive precisely the pressure it requires without compromising the other area.
2Strength
If high axial pressure is applied to the mechanical area, then centrifugal forces are absorbed effectively, but insulating layers in the electrical area may be damaged
Solution Approach 1:
The pressure plate is segmented into inner and outer portions that independently apply pressure to the mechanical and electrical areas respectively. This allows the inner pressure plate to exert high axial pressure on the mechanical area for effective centrifugal force absorption, while the outer pressure plate simultaneously applies lower pressure to the electrical area, preventing insulation layer damage.
Solution Approach 2:
The bracing pressure is made locally adaptive: the inner pressure plate provides high pressure in the mechanical area where strength is critical, while the outer pressure plate provides lower pressure in the electrical area where insulation protection is critical. This local quality differentiation resolves the contradiction between needing high pressure for strength and low pressure for insulation protection.
3Stability of the object's composition
If the pressure plate is rigidly fixed, then structural stability is maintained, but centrifugal forces cannot be effectively absorbed
Solution Approach 1:
The outer pressure plate is designed to be tiltable relative to the inner pressure plate, introducing dynamic capability to the otherwise rigid structure. This allows the outer pressure plate to tilt in response to centrifugal forces during rotation, enabling effective force absorption while the inner pressure plate maintains structural stability through rigid connection to the rotor shaft.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution optimizes force distribution across the rotor core, preventing vibrations and insulation damage while maintaining sufficient frictional force, thereby enhancing the operational efficiency and reliability of the machine by allowing tailored pressure application to different areas.
Implementation Method 1
Since the rotors of double-fed asynchronous machines carry a rotor winding, this must be secured against the centrifugal forces that occur.
Implementation Method 2
maintaining sufficient frictional force
Implementation Method 3
As a result, the centrifugal forces acting on the outer press plate can be effectively absorbed.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a rotating electric machine, particularly a double-fed asynchronous machine in the performance range between 20 and 500 MVA, comprising a rotor which rotates about an axis and is concentrically surrounded by a stator. According to the invention, said rotor comprises a rotor sheet metal body (14) which is composed of metal sheets which are layered and pressed together in the axial direction using a pressing plate (19) to form a composite, said rotor sheet metal body being divided in the radial direction into an inner mechanical region (14b) and an outer electric region (14a). A rotor winding (18) is accommodated in the electric region (14a). Said electric machine is characterized in that the axial tensioning of the rotor sheet metal body is optimized in that the pressing plate (19) is radially divided into a separate inner pressing plate and a separate outer pressing plate, corresponding to the radial division of the rotor sheet metal body (14).