Generator Rotor Assembly With CTE Spacers for Stable Diode Preload

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Solution Overview

Problem

Conventional generator rotor assemblies experience significant preload increase at high temperatures, leading to potential deformation and reduced preload at room temperature due to axial growth mismatch between diode holders and rotor housings, causing stress and deformation issues.

Innovation Solution

Incorporating CTE compensation spacers with a third coefficient of thermal expansion, different from the diode holder and rotor housing materials, to mitigate temperature-induced stress by shrinking and adjusting for relative length changes, and using threaded fasteners to secure the diode holder within the rotor housing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If set screws are used to axially preload the diode holder at room temperature, then the diode holder is securely fixed, but significant preload increase occurs at high temperature causing deformation

Engineering Contradiction:

ImprovepreloadVSAvoiddeformation

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The patent applies thermal expansion principles by selecting materials with different coefficients of thermal expansion (CTE) for the diode holder, rotor housing, and CTE compensation spacers. The CTE compensation spacers are specifically chosen to have a CTE that compensates for the differential expansion between the aluminum diode holder and stainless steel rotor housing, thereby maintaining stable preload across temperature variations and preventing deformation

Inventive Principle:

Principle #37Thermal expansion

Solution Approach 2:

The patent changes the physical parameter of thermal expansion coefficient by introducing CTE compensation spacers made of materials with specific CTE properties. This parameter change allows the assembly to compensate for thermal growth differences between dissimilar materials, maintaining optimal preload conditions from -65°C to +200°C without deformation

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If conventional preloading methods are used, then assembly is simple, but temperature-induced stress grows significantly

Engineering Contradiction:

Improveassembly structureVSAvoidtemperature induced stress

Core Design Contradiction:

Device complexityVSStress or pressure

Solution Approach 1:

The CTE compensation spacers act as intermediary elements between the diode holder and rotor housing. These spacers mediate the thermal expansion differences by being trapped within slots in mounting tabs, providing a controlled interface that reduces temperature-induced stress while maintaining the relative positioning and connection between the diode holder and rotor housing

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If dissimilar materials are used for diode holder and rotor housing, then material properties are optimized, but relative length change causes stress

Engineering Contradiction:

Improvematerial selectionVSAvoidrelative length change

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent employs composite material strategy by combining aluminum diode holder, stainless steel rotor housing, and CTE compensation spacers made of materials with intermediate or negative CTE properties. This composite approach allows optimization of individual material properties (electrical conductivity, mechanical strength, thermal stability) while the combination compensates for the relative length changes through differential thermal expansion characteristics

Inventive Principle:

Principle #40Composite materials

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

The solution effectively reduces or eliminates temperature-induced stress and preload variations, preventing deformation and maintaining axial fixation of the diode holder within the rotor housing, thereby enhancing the assembly's stability and reliability.

Implementation Method 1

The one or more CTE compensation spacers can be configured to have a third CTE different than the first CTE and the second CTE to compensate for relative length change between the diode holder and the rotor housing to prevent and/or reduce temperature induced stress growth

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the CTE compensation spacer can include a negative CTE such that the CTE compensation spacer shrinks with increasing temperature

Methodology Applied

Scientific EffectNegative thermal expansion: Negative Thermal Expansion

Data Source

PatentEP4277091A1Generator rotor assemblies

Publication Date: 2023.11.15 HAMILTON SUNDSTRAND CORP

Figure 1~2

AI summary

A generator rotor assembly can include a diode holder (101) configured to hold one or more diodes. The diode holder can be formed of a first material having a first coefficient of thermal expansion (CTE). The assembly can include a rotor housing (103) configured to hold the diode holder within the rotor housing. The rotor housing can be formed of a second material having a second CTE. The second CTE is different than the first CTE. The assembly can include one or more CTE compensation spacers (107) interfacing the diode holder to the rotor housing such that the diode holder and the rotor housing are connected via the one or more CTE compensation spacers. The one or more CTE compensation spacers can be configured to have a third CTE different than the first CTE and the second CTE to compensate for relative length change between the diode holder and the rotor housing to prevent and/or reduce temperature induced stress growth at the interface of the diode holder and the rotor housing.