Rotor Finger Repair Using Stress-Reducing Plugs
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Solution Overview
Problem
Rotors of rotating electric machines face material damage due to cyclic loading and fatigue, leading to potential cracks, even in non-cracked fingers, which can result in premature failure after maintenance if not adequately addressed.
Innovation Solution
A method involving the removal of damaged but non-cracked material, where screws and support blocks are removed, holes are drilled and reamed to accommodate stress-reducing plugs, and these plugs are inserted using non-destructive testing to ensure crack detection, followed by gluing or brazing for secure connection, thereby reducing stress and extending rotor lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional welding repair is performed on cracked rotor fingers, then the structural integrity is restored, but the risk of fatigue damage and new crack formation increases
Solution Approach 1:
The invention extracts the damaged material from the rotor finger by drilling holes to remove cracked or fatigue-damaged zones. This eliminates the source of potential crack propagation while maintaining the structural integrity of the remaining healthy material.
Solution Approach 2:
The invention changes the physical state and distribution of stress in the rotor finger by introducing holes at strategically located positions. This modifies the stress field parameters, redirecting stress away from critical fatigue zones and reducing the likelihood of new crack formation.
2Loss of time
If no action is taken on non-cracked rotor fingers during maintenance, then maintenance time and cost are reduced, but the risk of future crack formation due to fatigue damage increases
Solution Approach 1:
The invention performs preliminary action by drilling holes in non-cracked rotor fingers during maintenance to prevent future crack formation. This proactive measure addresses fatigue damage before it manifests as visible cracks, extending the rotor's service life without requiring extensive downtime.
3Reliability
If material is removed from rotor fingers to eliminate damaged zones, then the cause of fatigue damage is removed, but the structural strength and load-bearing capacity are reduced
Solution Approach 1:
The invention applies local quality by selectively removing material only from specific zones where fatigue damage or cracks are present, while preserving the intact material in other areas. This localized approach eliminates the cause of fatigue damage while maintaining the overall load-bearing capacity of the rotor finger.
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 method effectively extends the rotor's lifetime by addressing the root cause of damage and ensuring secure, stress-reduced connections, even in non-cracked areas, thereby preventing future cracks and maintaining rotor integrity.
Implementation Method 1
The purpose of the plugs is to reduce the stress around the holes
Implementation Method 2
The plugs 16 are then glued or brazed
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
A rotor has a rotor core (7) with protruding fingers (8) defining slots (9) for conductors (10) and support blocks (12) at the axial ends of the fingers (8) fixed by screws (13). The fingers (8) have holes (14) for housing the screws (13). The method for repairing the rotor (3) includes removing the screws (13) and support blocks (12), drilling the holes (14) to increase the diameter thereof, providing plugs (16) into the holes (14).