Rotor End Plate Annular Cavity Design
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Solution Overview
Problem
Conventional rotor end plates for electrical machines face challenges in providing optimal radial force reaction, sealing, and balancing while being difficult to manufacture with materials like titanium, leading to stress and weight issues in high-speed applications.
Innovation Solution
A rotor end plate with an annular design featuring a fully annular cavity and surface without anti-rotation projections, balanced by circumferential bores, and made using a lathe process, which includes an annular insulator sheet for electrical isolation and a roll pin for anti-rotation, allowing for thinner and lighter construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional rotor end plates with anti-rotation projections and discrete pockets are used, then anti-rotation capability and sealing are provided, but manufacturing difficulty increases and stress concentration occurs particularly with titanium materials
Solution Approach 1:
The end plate is divided into a hub portion and a blade portion with a fully annular cavity between them, allowing each section to be optimized independently. The hub portion contains fastener bores for attachment, while the blade portion features a smooth annular cavity that eliminates stress concentration points associated with discrete pockets and anti-rotation projections.
Solution Approach 2:
Instead of adding anti-rotation projections and discrete pockets to the end plate surface, the invention inverts the approach by creating a fully annular cavity that provides anti-rotation capability through the cavity geometry itself. The smooth inner surface of the annular cavity engages with the rotor without requiring protruding features, thereby eliminating stress concentration while maintaining functional requirements.
2Strength
If conventional rotor end plates are designed with thick construction for strength, then structural integrity is improved, but weight increases which is problematic in high-speed applications
Solution Approach 1:
The fully annular cavity introduces curvature and streamlined geometry to the end plate structure. The smooth, continuous annular shape distributes stresses more evenly throughout the structure, allowing the end plate to maintain structural integrity with reduced thickness. The curved geometry of the annular cavity avoids stress concentration at sharp corners or protrusions, enabling weight reduction while preserving strength.
Solution Approach 2:
The end plate is specifically designed for use with titanium materials, which provide a high strength-to-weight ratio. The combination of titanium's inherent material properties with the optimized annular geometry allows the end plate to achieve the required structural integrity at reduced weight compared to conventional designs using thicker sections of less optimal materials.
3Productivity
If conventional rotor end plates include anti-rotation features and discrete pockets, then functional requirements are met, but manufacturing complexity and time increase
Solution Approach 1:
The invention merges multiple functions into the fully annular cavity structure. The cavity simultaneously provides anti-rotation capability, sealing surface, and structural support that would otherwise require separate features. The smooth, continuous annular geometry can be manufactured in a single machining operation, eliminating the need for multiple steps to create discrete pockets, anti-rotation projections, and sealing features.
Solution Approach 2:
The fully annular cavity serves multiple functions: it provides anti-rotation engagement with the rotor, creates a sealing surface between the end plate and rotor, and distributes mechanical loads evenly across the blade portion. This multi-functional design eliminates the need for separate dedicated features for each function, simplifying the overall structure and reducing manufacturing complexity.
Data Source
AI summary
An electrical machine includes a rotor including windings circumferentially spaced apart by rotor wedges. The electrical machine includes a rotor end plate mounted to the rotor. The rotor end plate includes an annular end plate body with an interior surface and axially opposed exterior surface. The interior surface includes a cavity for engaging the rotor. The interior surface has a base that is bounded by an inner rim and an outer rim radially opposite the inner rim. The interior surface is free of anti-rotation projections extending axially therefrom. The outer rim is free of anti-rotation features extending radially inward therefrom.