CuNi Fuse-Link Structure for Medium-Voltage DC Overcurrent Protection
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Solution Overview
Problem
Existing medium voltage fuse-links struggle to provide effective overcurrent protection, especially in medium voltage direct current applications where nominal currents are relatively small compared to breaking currents, and the breaking current range is wide.
Innovation Solution
A medium voltage fuse-link design featuring a precise resistive fuse element made of a copper-nickel alloy (CuNi44) with a specific resistivity and wound around a star-shaped core, enclosed within a fuse tube with an arc quenching medium like silica sand, and electrically coupled with external caps for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fuse element material is used, then the fuse-link can handle high breaking currents, but it cannot provide effective protection at low nominal currents
Solution Approach 1:
The patent changes the material parameters of the fuse element by using a copper-nickel alloy with specific resistivity (r=0,00000049 Ω x m +/-10%) and composition (40%-50% nickel, preferably 44%). This parameter optimization enables the fuse element to operate effectively across a wide current range from low nominal currents (0.1A) to high breaking currents (30kA), resolving the contradiction between reliability at low currents and adaptability across current ranges.
2Temperature
If the fuse element is exposed to external environment, then heat dissipation is improved, but arc quenching becomes difficult
Solution Approach 1:
The patent introduces silica sand as an intermediary arc quenching medium that surrounds the fuse element. This mediator serves dual functions: it provides effective arc quenching by extinguishing the electric arc during fault conditions, while simultaneously allowing heat dissipation from the fuse element. The silica sand acts as the intermediate substance that resolves the contradiction between heat dissipation requirements and arc quenching effectiveness.
Solution Approach 2:
The fuse element is nested within the silica sand filling, which is itself contained within the fuse tube. This nested structure allows the fuse element to be surrounded by the arc quenching medium for effective arc extinction, while the fuse tube provides additional protection and heat dissipation pathways, creating a hierarchical protection system.
3Device complexity
If the fuse element is directly connected to external caps, then electrical coupling is simplified, but heat generated during high current flow compromises safety
Solution Approach 1:
The patent introduces connectors as intermediary components between the fuse element and external caps. These connectors serve as thermal barriers that electrically couple the fuse element to the external caps while providing thermal isolation to prevent heat transfer to the external components during high current flow, thus resolving the contradiction between simplified electrical coupling and heat management.
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 design effectively provides overcurrent protection in medium voltage applications by ensuring reliable arc quenching and heat separation, even at low nominal currents and high breaking currents, thereby ensuring safety and reliability.
Implementation Method 1
an arc quenching medium surrounding the fuse element
Implementation Method 2
The fuse element is made of a precise resistive wire made of an metal alloy based on copper and nickel... resistivity of the metal alloy is r=0,00000049 Ω x m +/-10%
Data Source
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AI summary
The present invention relates to a field of electrical fuses, especially fuse-links, used to provide an overcurrent protect to electric circuits. The present invention relates more particularly to the electrical fuses used in medium voltage applications. A goal of the invention is to provide an overcurrent protection in a medium voltage application, especially in a medium voltage direct current application, where a nominal current is relatively small compared to a breaking current. According to the invention a medium voltage fuse-link comprising a first cap, a second cap, a core with a first end and a second end, wherein on the first end is the first cap, and on the second end there is the second cap, and a fuse element connected to the first cap and the second cap, a first external cap, a second external cap, a fuse tube with a first end and a second end, wherein on the first end is the external first cap, and on the second end there is the external second cap, an arc quenching medium surrounding the fuse element. The first cap is electrically coupled with the first external cap by means of a first connector, and the second cap is electrically coupled with the second external cap by means of a second connector. The first cap, the second cap, the core, the first connector, the second connector, and the fuse element are placed inside the fuse tube. The fuse element is made of a precise resistive wire made of an metal alloy based on copper and nickel.