Generator Rotor Diode Holder Assembly for Thermal Preload Control
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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 connecting the diode holder and rotor housing through these spacers, which can be made of materials like ALLVAR, and using threaded fasteners to maintain axial fixation and control preload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diode holder and rotor housing are rigidly connected without CTE compensation, then the structure is simple and easy to manufacture, but temperature-induced stress increases significantly at high temperatures due to CTE mismatch between aluminum diode holder and stainless steel rotor housing
Solution Approach 1:
A CTE compensation spacer made of Invar alloy is introduced as an intermediary component between the aluminum diode holder and stainless steel rotor housing. This spacer has a CTE of approximately 1.2×10^-6/°F, which is lower than both aluminum and stainless steel, allowing it to compensate for the CTE mismatch and reduce thermal stress in the connection structure.
Solution Approach 2:
The CTE compensation spacer changes its dimensional parameters (length, width, thickness) in response to temperature variations. By selecting Invar alloy with specific CTE properties, the spacer's dimensional changes counteract the relative expansion/contraction between the diode holder and rotor housing, maintaining stable connection under thermal cycling conditions.
2Strength
If set screws are used to preload the diode holder at room temperature, then the assembly is simple to manufacture, but the preload increases excessively at high temperatures causing denting of the aluminum diode holder
Solution Approach 1:
The CTE compensation spacer acts as a mediator that absorbs and compensates for differential thermal expansion between the aluminum diode holder and stainless steel rotor housing. This prevents excessive preload forces from developing in the set screws during temperature cycling, thereby protecting the aluminum diode holder from denting while maintaining proper mechanical connection.
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 ensuring consistent axial fixation of the diode holder within the rotor housing, thereby enhancing the reliability and durability of the generator rotor assembly.
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 at the interface of the diode holder and the rotor housing
Implementation Method 2
the CTE compensation spacer can include a negative CTE such that the CTE compensation spacer shrinks with increasing temperature
Data Source
AI summary
A generator rotor assembly can include a diode holder 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 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 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.