OLTC Housing Fastener Bushing for Dynamic Load Wear Mitigation
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Solution Overview
Problem
On-load tap changers (OLTCs) experience increased wear and failure risk at junctions due to accelerations in moving applications, particularly on floating platforms at sea, necessitating improved robustness.
Innovation Solution
The OLTC incorporates a housing with metal fasteners featuring a bushing and a resilient member, providing a smooth interface and allowing relative movement to mitigate wear, while the bushing extends into a recess for a tight fit and the resilient member absorbs dynamic loading conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fasteners are used to attach metal body to housing body, then the metal body is securely fixed, but wear occurs at the junction between fastener and housing body under acceleration
Solution Approach 1:
A bushing is introduced as an intermediary component between the fastener and the housing body. The bushing is inserted into a hole in the housing body, and the fastener passes through the bushing. This intermediary element absorbs the wear from relative movement under acceleration, protecting both the fastener and housing body from direct wear contact while maintaining secure attachment.
Solution Approach 2:
The bushing changes the interface parameters between the fastener and housing body by providing a smooth bore surface with different friction and wear characteristics. This parameter change reduces the coefficient of friction and wear at the junction, allowing the fastener to maintain secure attachment while resisting wear under acceleration forces.
2Reliability
If tight fit is provided between bushing and metal body, then relative movement is prevented, but assembly precision requirements increase
Solution Approach 1:
A resilient member is introduced as a mediator between the bushing and the metal body. This resilient member fills the gap between the bushing outer surface and the metal body inner surface, providing a tight fit that prevents relative movement. The resilient nature of this intermediary component allows it to compensate for manufacturing tolerances while maintaining positioning stability.
Solution Approach 2:
The resilient member changes the interface parameters by providing elastic deformation capability. This allows the assembly to accommodate manufacturing tolerances through elastic compression, achieving a tight fit and preventing relative movement without requiring extremely precise manufacturing tolerances for the bushing and metal body interfaces.
3Strength
If rigid fastening is used, then structural integrity is maintained, but dynamic loading conditions cause excessive internal stress
Solution Approach 1:
The resilient member changes the mechanical parameters of the fastening system by introducing elasticity. Under dynamic loading conditions, the resilient member deforms elastically, absorbing stress peaks and reducing internal stress in the rigid components. This maintains structural integrity while accommodating dynamic movements without excessive stress concentration.
Solution Approach 2:
The resilient member introduces dynamic compliance to the otherwise rigid fastening system. It allows controlled deformation under dynamic loading, enabling the structure to adapt to changing load conditions at sea. This dynamic behavior reduces stress concentration while maintaining overall structural integrity during acceleration and wave motion.
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 reduces wear on bolts and fasteners, enhances alignment, and absorbs dynamic loads without excessive stress, improving the OLTC's durability and assembly tolerance.
Implementation Method 1
The radially protruding portion of the resilient member will deform elastically upon relative movements between the bushing and the metal member
Implementation Method 2
The bushing provides a smooth interface towards the bolt which mitigates abrasion on the bolt
Data Source
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AI summary
An on-load tap changer (OLTC) (1) comprising a housing, said housing comprising a housing body (2) and a metal body (3) attached to the housing body (2) using a plurality of fasteners (4), each respective one of said fasteners (4) comprising: a bolt (5) configured to extend from an outside of the housing body (2), through a respective hole of the housing body (2), and to engage with a threaded hole of the metal body (3) on an inside of the housing body (2), said fastener (4) further comprising a bushing (6) inserted in the respective hole of the housing body (2), said bushing (6) comprising a central opening through which the bolt (5) extends.