Rotor Pole Crossover Joint Stress Distribution

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Solution Overview

Problem

Conventional rotor pole crossovers in large generators face stress and failure due to centrifugal forces and cyclic mechanical and thermal loads, leading to cracking and connection failures between crossovers and coil straps.

Innovation Solution

A rotor pole crossover connection joint using a single piece connector that couples a stack of coil straps to a rotor pole crossover leg, featuring a body member, coil-side and crossover-side connector arms, and radiused shoulders to distribute and reduce stress concentrations, made from high-strength materials like copper alloys to withstand rotational and cyclic forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional rotor pole crossovers are used to connect coil straps, then the generator can operate, but the crossovers experience high stress concentrations leading to cracking and connection failures under centrifugal forces and cyclic thermal-mechanical loads

Engineering Contradiction:

Improveconnection joint reliabilityVSAvoidcrossover connection strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The connector is divided into multiple functional segments: a body member, a coil-side connector arm, and a crossover-side connector arm. This segmentation allows each part to be optimized for its specific function and stress conditions, distributing the mechanical loads more effectively throughout the connection joint.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The connector incorporates radiused shoulders with curved transitions instead of sharp corners. These radiused features distribute stress concentrations more evenly across the connector structure, preventing crack initiation and propagation under cyclic centrifugal and thermal-mechanical loading conditions.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Duration of action of stationary object

If a single piece connector with radiused shoulders is used, then stress concentrations are reduced and joint durability is enhanced, but the manufacturing complexity and material requirements increase

Engineering Contradiction:

Improvejoint service lifeVSAvoidconnector manufacturing ease

Core Design Contradiction:

Duration of action of stationary objectVSEase of manufacture

Solution Approach 1:

The connector integrates multiple functions into a single monolithic component: it provides structural support, electrical connection, and stress distribution all in one piece. This merging eliminates the need for multiple separate parts and assembly steps, actually simplifying manufacturing despite the complex geometry.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The connector uses high-strength copper alloy materials with specific mechanical properties to withstand the demanding operational conditions. The material parameters are selected and optimized to provide the necessary strength, ductility, and electrical conductivity for reliable operation under centrifugal and thermal-mechanical loads.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7966717B2Rotor pole crossover connection

Publication Date: 2011.06.28 SIEMENS ENERGY INC

AI summary

A rotor pole crossover connection joint for use in a rotating electrical machine is disclosed. The connection joint integrally couples a bottom rotor coil strap to a rotor pole crossover connector with a single piece connector that reduces, distributes or otherwise tolerates stress concentrations in the connector. A corresponding method of forming a rotor pole crossover connection and a rotor assembly including a rotor pole crossover connection joint are also disclosed.