Rotor Strain Imaging for Non-Disassembly Generator Testing

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Solution Overview

Problem

Large-sized rotating electric machines, such as turbine generators, face significant stress due to centrifugal forces, leading to potential rotor breakdowns, requiring frequent and costly disassembly for testing and maintenance.

Innovation Solution

A method using digital image correlation to generate strain change information from test image data, allowing for efficient non-invasive testing of rotor condition by imaging retention rings and processing with an image processing device to assess strain distribution and detect potential damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If disassembly testing is performed on rotating electric machines, then measurement precision of rotor condition is improved, but loss of time and productivity deteriorate due to frequent disassembly

Engineering Contradiction:

Improverotor condition assessment accuracyVSAvoidtesting time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces mechanical disassembly testing with optical field-based digital image correlation technology. By using imaging devices to capture surface deformation patterns and analyzing strain distributions through digital image correlation algorithms, the system achieves accurate rotor condition assessment without mechanical disassembly, thus eliminating time loss while maintaining measurement precision

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent creates optical copies (images) of the rotor surface and retention rings using imaging devices. These image copies are then processed through digital image correlation to extract strain information, replacing the need for physical disassembly and direct mechanical measurement while preserving measurement accuracy

Inventive Principle:

Principle #26Copying

2Reliability

If disassembly testing is performed on rotating electric machines, then reliability of rotor condition assessment is improved, but device complexity increases due to disassembly procedures

Engineering Contradiction:

Improverotor condition assessment reliabilityVSAvoidtesting procedure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent substitutes complex mechanical disassembly procedures with a simplified optical measurement system. Imaging devices capture surface patterns, and digital image correlation algorithms automatically analyze strain distributions, eliminating the need for manual disassembly while maintaining or improving assessment reliability through objective digital analysis

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The retention rings and rotor surfaces serve as their own measurement indicators. The existing surface patterns and deformation characteristics under operational loads provide self-contained information about rotor condition, eliminating the need for external disassembly procedures and complex testing apparatus

Inventive Principle:

Principle #25Self-service

3Strength

If retention rings are firmly fixed to rotor core by shrink fit, then strength of retention connection is improved, but stress concentration in retention ring worsens

Engineering Contradiction:

Improveretention connection strengthVSAvoidstress concentration in retention ring

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The patent applies local quality by designing specific geometric features (such as chamfers, radii, or stepped structures) at critical locations of the retention ring to distribute stress locally. This allows the retention ring to maintain strong shrink fit connection overall while reducing peak stress concentrations at specific high-stress areas through localized geometric modifications

Inventive Principle:

Principle #3Local quality

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

Enables rapid and efficient testing of rotor condition without disassembly, facilitating timely repair or replacement, thereby extending the lifespan of rotating electric machines.

Implementation Method 1

acquiring test image data by imaging a test target portion which is a part of the rotor by an imaging device

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 2

generating, as strain change information, change in a strain distribution in the test target portion by digital image correlation on the basis of the acquired test image data

Methodology Applied

Scientific EffectDigital image correlation: Image Processing

Data Source

PatentUS11913991B2Rotating electric machine test method, rotating electric machine test device, and rotating electric machine

Publication Date: 2024.02.27 MITSUBISHI GENERATOR CO LTD

AI summary

A rotating electric machine includes a stator and a rotor. An imaging device images a test target portion which is a part of the rotor, to generate image data of the test target portion, and transmits the generated image data to an image processing device. The image processing device generates strain change information representing change in the strain distribution in the test target portion by digital image correlation on the basis of the test image data generated by the imaging device. The state of the rotor is tested using the generated strain change information.