Fuse Visual Indication Low Voltage Operation
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Solution Overview
Problem
Conventional low voltage fuses are inadequate for applications where voltage can vary from rated voltage to very low values, as they fail to provide effective current interruption and visual indication, especially when arcing is minimal or absent, leading to delayed fault detection and replacement.
Innovation Solution
A low voltage fuse design featuring a fusible structure with a high melting point element and a low melting point solder joint, surrounded by a granular dielectric filler, which includes a biasing element and an indicator rod to provide visual indication of operation independent of arcing and voltage, ensuring effective current interruption and fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional indication methods using indicator wires or light emitting devices are used, then visual indication of fuse operation is achieved, but sufficient voltage (5-10 volts or more) is required which is not available in low voltage applications
Solution Approach 1:
The patent replaces electrical indication mechanisms (indicator wires requiring voltage to melt, light emitting devices requiring voltage to operate) with a mechanical indication system. A biasing element (spring) mechanically drives an indicator rod to protrude when the fusible element melts, providing visual indication without requiring operational voltage. This substitution resolves the contradiction by eliminating the voltage requirement for indication while maintaining manufacturability.
Solution Approach 2:
The fuse element itself serves dual purposes: it provides current interruption functionality and simultaneously actuates the indication mechanism through its own melting action. When the fusible element melts due to overcurrent, the mechanical release automatically triggers the biasing element to move the indicator rod, providing self-service indication without requiring separate power sources or additional voltage.
2Reliability
If low melting point material is used to initiate arcing at longer melting times, then suitable TCC curves are provided and excessive component temperatures are prevented, but the joint must be surrounded by fluid (air) rather than sand, reducing interrupting capability
Solution Approach 1:
The patent segments the fusible element into distinct functional zones: a low melting point solder joint section for initiating interruption at longer times (providing suitable TCC curves), and a high melting point element section surrounded by sand for high-current interruption capability. This segmentation allows each zone to optimize its function without compromise, resolving the contradiction between TCC characteristics and interrupting capability.
Solution Approach 2:
Different materials and properties are applied to different parts of the fusible element: the solder joint area has low melting point properties for controlled melting at longer times, while the main element section has high melting point properties and is surrounded by sand for superior interrupting capability. This local differentiation resolves the contradiction by allowing each region to have the quality needed for its specific function.
3Reliability
If high melting point materials are used for the fusible element, then favorable ratios of rated continuous current to short time melting current are achieved, but melting occurs only at reduced cross-sectional areas, requiring precise control of melting time versus current characteristic
Solution Approach 1:
The patent changes the material parameter (melting point) along the fusible element by incorporating a low melting point solder joint section. This allows the element to melt at predictable temperatures and times without requiring precise control of melting at reduced cross-sectional areas. The solder joint's melting point and mass are controlled to achieve the desired TCC characteristics, simplifying manufacturing while maintaining reliability.
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 fuse effectively interrupts currents at both high and low thresholds, providing reliable visual and remote indication of operation, even in conditions with minimal arcing, and enhances dielectric withstand and fault finding capabilities.
Implementation Method 1
surrounded by a granular dielectric filler, the purpose of which is to improve the interrupting capability of the fuse, and to provide a better dielectric withstand after current interruption
Implementation Method 2
The melting occurs, in large part, due to I2R heating of the fusible element
Implementation Method 3
the meltable portion melts when subjected to a threshold current flowing therethrough
Implementation Method 4
The biasing element acts on the movable portion of the fusible structure for moving the movable portion upon melting of the meltable portion
Data Source
AI summary
A fuse including a fuse housing having first and second electrical terminals, a movable partition made from an electrically conductive material movably disposed within the fuse housing, a fusible structure connected between the first electrical terminal and the movable partition, a conductor connected between the movable partition and the second electrical terminal, a biasing element acting on the movable partition to maintain the fusible structure in tension and for moving the movable partition upon melting of the fusible structure and an indicator connected between the movable partition and the second electrical terminal. The conductor, the movable partition and the fusible structure define an electrical path between the first and second electrical terminals and the indicator protrudes out of the second electrical terminal of the fuse housing upon melting of the fusible structure for providing visual indication of an interrupted condition of the fuse when subjected to a threshold current flowing therethrough.