Arcuate Coil Support Members for Vacuum Interrupter Mechanical Integrity
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Solution Overview
Problem
Vacuum interrupters face mechanical integrity challenges due to increased stress forces during high voltage and high current operations, leading to deformation of axial magnetic field coils, which impair their performance and require costly replacements.
Innovation Solution
The electrode assembly incorporates a coil structure with support members and filler material to reinforce the arcuate arms, maintaining a gap between them and the contact plate, enhancing mechanical strength and resistance to tensile and compressive forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the arcuate coil arm length is increased to increase the self-generated axial magnetic field for higher voltage and current rating, then the magnetic field strength is improved, but the mechanical strength of the coil becomes weaker and the long cantilever arm becomes prone to deformation at its connection to the base
Solution Approach 1:
The coil structure is divided into multiple arcuate arms (typically three) spaced around the circumference, each arm being a separate structural element. This segmentation allows the magnetic field generating function to be distributed while reducing the mechanical stress on any single arm compared to a single continuous structure
Solution Approach 2:
The cross-sectional area of the arcuate arms is increased specifically at the connection region to the base, creating a local reinforcement zone. This allows the arm to withstand higher tensile and compressive forces at the critical connection point without requiring a uniform increase in the entire arm's dimensions, thus maintaining mechanical strength while preserving the extended arm length needed for magnetic field generation
2Reliability
If the arm length is extended to generate maximal axial magnetic field, then the interruption capability is improved, but the coil experiences larger tensile and compressive forces during opening and closing operations leading to deformation
Solution Approach 1:
The arcuate arms are designed with non-uniform cross-sections, featuring enlarged cross-sectional areas at the connection regions to the base and contact plate. This local quality enhancement provides targeted reinforcement at the most stressed locations during opening and closing operations, allowing the arms to resist deformation from tensile and compressive forces while maintaining the extended length necessary for generating maximal axial magnetic field
Solution Approach 2:
The coil structure combines copper or copper alloy materials that provide both electrical conductivity for magnetic field generation and enhanced mechanical properties through specific alloy compositions. The material selection optimizes the balance between electrical performance for interruption capability and mechanical strength for structural integrity under stress
3Strength
If the cross-sectional area of the connection is increased to reduce arm length, then the mechanical strength is improved, but the axial magnetic field produced by the coil is reduced
Solution Approach 1:
The arcuate arms feature non-uniform cross-sections with enlarged areas specifically at the connection regions to the base and contact plate, while maintaining smaller cross-sections along the span of the arms. This localized reinforcement provides the necessary mechanical strength at critical stress points without requiring a uniform increase in the entire arm's cross-sectional area, thereby preserving the arm length and current path needed for generating strong axial magnetic field
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 reinforced coil structure increases the useful life of vacuum interrupters by withstanding large stress forces without deformation, improving mechanical integrity and extending the lifespan of the components.
Implementation Method 1
An arc is typically formed between the contact surfaces when the contacts are moved apart to the open circuit position while carrying current. The arc generally is initially in a constricted, columnar form that creates a thermal plasma.
Implementation Method 2
One technique of encouraging formation of a diffuse arc is by imposing an Axial Magnetic Field (AMF) in the region between the contacts. The field can be self-generated by the current in coils located behind each contact.
Data Source
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AI summary
An electrode assembly for a vacuum interrupter includes a contact plate, an electrode coil, an inner support, a lower support, and at least one support member. The electrode coil includes a base for attachment to a terminal post of the vacuum interrupter. The electrode coil also includes at least one arcuate arm between the base and the contact plate extending along a curved path in a plane substantially perpendicular to a direction of travel of the electrode assembly. Each arcuate arm includes an aperture that is positioned to align with a corresponding aperture of an adjacent arcuate arm or the base of the electrode coil. Each support member is partially positioned within aligned apertures to maintain a gap between the arcuate arms and the base. The support members and the lower support may be slotted to decrease the current flowing through the supports.