Fuse With Internal Switching Element And Constricted Fusible Conductor
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Solution Overview
Problem
Existing fuses are not reliable in switching off due to moderate currents, leading to oversized designs that fail to detect continuous slight overloads, and are ineffective in networks with limited short-circuit currents, such as PV systems, where normal fuses do not trip during low short-circuit events.
Innovation Solution
A load current-carrying fuse with an internal switching element, featuring a fusible conductor with a constriction containing a melting agent of lower softening point and a voltage-sensitive element, allowing for targeted switching off even with moderate currents, and an internal switching element that monitors and responds to overcurrents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If normal fuses are used in networks with limited short-circuit currents, then the fuse structure remains simple, but the fuse does not trip during low short-circuit events
Solution Approach 1:
The fuse element is segmented into a fusible conductor and a non-fusible conductor, each with different functions. The fusible conductor melts under overcurrent conditions to open the circuit, while the non-fusible conductor provides a parallel path that limits the arc duration and intensity, preventing false tripping during normal switching operations.
Solution Approach 2:
The invention applies local quality by creating a constriction in the fusible conductor at a specific location. This constriction creates a controlled weak point with lower softening point material that melts at lower currents, enabling the fuse to trip during low short-circuit events while maintaining overall structural simplicity.
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 disconnection during both high and low overcurrent conditions, reducing the need for oversized fuses and improving protection levels without compromising system availability, by using a fusible conductor with a melting agent and a voltage-sensitive element to trigger the fuse effectively.
Implementation Method 1
the fusible conductor has an electrically conductive flux in the area of the constriction, the flux having a lower softening point than the fusible conductor itself
Implementation Method 2
an internal switching element that monitors the protective element internally and can bring about a targeted switch-off, the internal switching element being a voltage-sensitive element
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The invention relates to a load current-carrying fuse comprising an internal switching element having a protective element (F), wherein the protective element (F) has a first connection (FA1) for connection to a first potential (L) of a supply system and has a second connection (FA2) which can be connected to a second potential (N) of the supply system by means of a device (Z) to be protected, wherein the protective element (F) has a fusible conductor (D) which connects the first connection (FA1) and the second connection (FA2) of the protective element (F), wherein the protective element (F) further has a third connection (FA3) which can be connected to the second potential (N) of the supply system and which is arranged adjacent to, but electrically insulated from, the fusible conductor (D), wherein the fusible conductor (D) has a constriction (E) in the region of the adjacent connection (FA3), wherein the constriction is designed such that the fusible conductor (D) has an electrically conductive fusible means (SM) in the region of the constriction (E), wherein the fusible means (SM) has a lower fusion point than the fusible conductor (D) itself, wherein the load current-carrying fuse further has an internal switching element which internally monitors the protective element (F) and can implement targeted disconnection, wherein the internal switching element has a voltage-sensitive element (TVS) which is connected to the first connection (FA1) by way of a connection, and which is arranged adjacent to a further connection of the overvoltage-sensitive element (TVS) but electrically insulated from the fusible conductor (D) and adjacent to, but electrically insulated from, the third connection (FA3).