Safety Fuse With Exothermic Short-Circuit Trigger
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Solution Overview
Problem
Conventional safety fuses struggle to provide effective protection in low-voltage applications, particularly for overvoltage protection devices, due to volatile short-circuit conditions and limited design options, leading to delayed switch-off or damage during impedance-prone short-circuits, and require external switches which are costly.
Innovation Solution
A safety fuse design featuring a fusible conductor between contacts with a short-circuit auxiliary contact and an internal isolating distance, utilizing an exothermic reaction to create a short-circuit path, eliminating the need for external switches and allowing for both low-impedance and impedance-prone short-circuit implementations, with optional parallel fuse elements and a triggerable mechanism for controlled disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fuses are used for overvoltage protection devices, then the fuse can provide basic overcurrent protection, but the fuse cannot ensure reliable switch-off under volatile short-circuit conditions due to impedance-prone short-circuits and arc erosion
Solution Approach 1:
The fuse is divided into two independent conductive paths: a main fusible conductor for normal overcurrent protection and a separate short-circuit auxiliary contact with low-impedance connection for forced switch-off. This segmentation allows each path to specialize in its function, with the auxiliary contact providing reliable short-circuit protection without being affected by arc erosion on the main conductor.
Solution Approach 2:
The short-circuit auxiliary contact acts as an intermediary element that creates a low-impedance bypass path during short-circuit conditions. This intermediary path allows high short-circuit currents to flow without causing arc erosion on the main fusible conductor, enabling reliable and rapid switch-off even under volatile network conditions.
2Reliability
If the fuse is designed with high rated current values to allow high currents to pass briefly, then the fuse can withstand impulse currents, but the fuse cannot switch off early under low residual currents such as mains follow current
Solution Approach 1:
The fuse separates the functions of withstanding impulse currents and detecting low residual currents into different components. The main fusible conductor with high rated current handles impulse currents, while the separate short-circuit auxiliary contact with low-impedance connection detects and responds to low residual currents, enabling early switch-off regardless of the main conductor's high current rating.
Solution Approach 2:
Different parts of the fuse have different electrical characteristics optimized for their specific functions. The main fusible conductor has high current-carrying capacity for impulse protection, while the short-circuit auxiliary contact has low impedance and high sensitivity for detecting low residual currents, creating local quality differentiation that solves the contradiction.
3Ease of operation
If external switches are used to control the short-circuit path, then the fuse can achieve controlled disconnection, but the device complexity and cost increase significantly
Solution Approach 1:
The short-circuit auxiliary contact is integrated directly into the fuse housing, merging the short-circuit control function with the fuse itself. This eliminates the need for external switches or separate control devices, reducing device complexity and cost while maintaining the capability for controlled disconnection during short-circuit conditions.
Solution Approach 2:
The fuse becomes self-sufficient by incorporating the short-circuit auxiliary contact internally. The fuse automatically creates the short-circuit path and controls disconnection without requiring external switching devices, making the system simpler and more cost-effective while maintaining controlled disconnection capability.
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
Enables reliable and cost-effective protection by actively controlling the short-circuit path, reducing rated current and achieving faster disconnection without external switches, ensuring protection across varying short-circuit conditions while maintaining dielectric strength and reducing arc erosion risks.
Implementation Method 1
utilizing an exothermic reaction to create a short-circuit path
Implementation Method 2
at least one fusible conductor located between two contacts and arranged in a fuse housing
Implementation Method 3
The arc or arc erosion to the fusible element has an impedance-like effect, which limits the current
Data Source
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AI summary
The invention relates to a safety fuse for low-voltage applications for protecting devices that can be connected to a power supply system, particularly overvoltage arresters, such as spark gaps or varistors, consisting of at least one fuse element located between two contacts and arranged in a protective housing, and a short-circuit auxiliary contact with an inner isolating distance to the fusing conductor. According to the invention, an externally activatable switching device for overriding the isolating distance is embodied inside the protective housing in order to trigger a low-resistance or impedance-laden short circuit, the switching device comprising an insulating element forming the isolating distance, which experiences a change of state by means of an exothermic activator, and the activator is connected to at least one control connection.