Generator Endwinding Blocking Cap for Durable Non-Metallic Retention
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Solution Overview
Problem
Existing retention mechanisms for blocking endwinding coils in generator rotors are expensive, complex, and prone to damage and durability issues due to assembly and operational loads, with metallic components risking electrical shorting.
Innovation Solution
A semi-flexible, durable sheet of material, such as a polymer sheet, is affixed within a slot in the blocking, extending over the top surface and secured with pins, providing vertical and horizontal engagement to enhance tear strength and durability, and can be made entirely non-metallic to prevent electrical shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rivets are used to affix the blocking, then the blocking can be retained in place, but the rivets shear part of the blocking, cannot withstand load, and become easily damaged during installation
Solution Approach 1:
A cap made of flexible, durable non-metallic material is introduced as an intermediary between the blocking and the retaining ring. The cap receives the retaining ring and distributes the retention forces across a larger area of the blocking, preventing the concentrated loads that cause rivet failure and blocking damage.
Solution Approach 2:
The retention mechanism transitions from rigid metallic rivets to a flexible non-metallic cap. This parameter change in material properties allows the cap to deform and accommodate loading variations while maintaining retention, preventing the shearing and damage associated with rigid rivets.
2Reliability
If complex retention mechanisms are used to handle loading, then the blocking can be retained securely, but the manufacturing and installation cost increases significantly
Solution Approach 1:
The complex metallic retention mechanisms (rivets, tie rods, felt) are extracted and replaced with a simple cap and retaining ring assembly. This extraction of complexity reduces manufacturing and installation costs while maintaining retention security through the flexible cap's ability to distribute loads.
Solution Approach 2:
The cap is made of flexible, durable non-metallic material that can deform to accommodate loading variations. This flexibility allows a simple cap structure to provide secure retention without requiring complex rigid mechanisms, thereby reducing manufacturing and installation costs.
3Reliability
If metallic retention mechanisms are used, then the blocking can be retained, but loose metallic components can cause electrical shorting in the generator field winding
Solution Approach 1:
The retention mechanism is replaced with non-metallic materials that, while potentially less durable in some aspects, eliminate the harmful effect of electrical shorting. The cap and retaining ring assembly provides sufficient retention security without the electrical conductivity issues of metallic components.
Solution Approach 2:
The retention system uses composite non-metallic materials for the cap that combine flexibility, durability, and electrical insulation properties. This composite material approach provides both retention security and protection against electrical shorting, eliminating the need for metallic components.
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
Generator field endwinding blocking is described. The endwinding blocking has a spacer block for radial placement between rotor endwindings. The spacer block has a spacer body with a radially inboard end, a radially outboard end, a slot extending from the outboard end towards the inboard end, and at least one transverse hole formed on an outer surface of the spacer body, extending in a perpendicular direction towards the slot. A cap covers at least a portion of the outboard end. The cap has a radially inward portion received in the slot with at least one hole aligned with the at least one traverse hole, and at least one end extending beyond a periphery of the outboard end towards an adjacent endwinding. A fastener placed in the holes of the spacer block and the radially inward portion of the cap, secures the cap with the spacer block.