Coiled Fuse Element Structure for Faster Arc Quenching

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Solution Overview

Problem

Existing fuses face challenges in quickly extinguishing arcs formed during overcurrent conditions and require cost-effective manufacturing with reduced components and steps, especially as they shrink in size to accommodate smaller electrical circuits.

Innovation Solution

A fuse design featuring a coiled fusible element with diagonal central wire, which enhances thermal cycling reliability, mechanical bonding, and arc confinement through magnetic fields, allowing for higher surge current handling and faster arc quenching using arc quenching materials like silicone.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional straight fusible elements are used, then manufacturing is simpler, but arc extinguishing capability is insufficient

Engineering Contradiction:
Improvearc extinguishing capabilityVSAvoidfusible element structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The fusible element is formed into a coiled configuration instead of a straight wire, creating curvature that increases the path length and improves arc extinguishing capability through extended arc path and better arc quenching material interaction

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Adaptability or versatility

If fuse size is reduced to accommodate smaller circuits, then adaptability improves, but manufacturing cost reduction becomes more difficult

Engineering Contradiction:
Improvesize adaptabilityVSAvoidmanufacturing cost
Core Design Contradiction:
Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The coiled fusible element is nested within the fuse body, allowing the fuse to maintain functional performance in a compact size. The coil structure fits efficiently within the available space, enabling smaller overall fuse dimensions while preserving arc extinguishing capabilities

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The fusible element is integrated directly into the fuse body without requiring separate arc quenching chambers or additional components. The coil structure itself serves both as the current-carrying element and as a means to generate magnetic fields for arc control, reducing total component count

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If coiled fusible element is used, then arc extinguishing capability improves, but manufacturing complexity increases

Engineering Contradiction:
Improvearc extinguishing capabilityVSAvoidfusible element structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The coiled fusible element generates its own magnetic field during operation, which automatically confines and controls the arc without requiring external magnetic shielding or additional arc control components. The structure serves its own arc containment needs through electromagnetic induction

Inventive Principle:
Principle #25Self-service

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 coiled fusible element design improves arc extinguishing capabilities, increases surge current handling capacity, and reduces manufacturing complexity while ensuring faster and safer operation in high surge applications.

Implementation Method 1

the coiled fusible element promotes robust element-termination bonding/connection beneficial for thermal cycling reliability

Methodology Applied
Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

When an overcurrent condition occurs, an arc may be formed between the melted portions of the fusible element

Methodology Applied
Scientific EffectArc: Electric Arc

Implementation Method 3

the fusible element melts or otherwise opens to interrupt the circuit path

Methodology Applied
Scientific EffectMelting: Melting

Data Source

PatentEP3640966B1Coiled fusible element for high reliability fuse
Publication Date: 2025.01.08 LITTELFUSE INC
  • EP3640966B1 patent drawingFigure 1
  • EP3640966B1 patent drawingFigure 2
  • EP3640966B1 patent drawingFigure 3~4

AI summary

A fuse 100 includes a body 102 including a center portion 132 extending between a first end 106 and a second end 110, and a first endcap 104 surrounding the first end and a second endcap 108 surrounding the second end. A fusible element 120 is disposed within a central cavity of the body 102, wherein the fusible element includes a first coil 122 disposed within the first endcap 104 and a second coil 124 disposed within the second endcap 108. The fusible element further includes a central wire 128 extending diagonally between the first and second coils. Solder 130 may be disposed between the first end and the first endcap, and between the second end and the second endcap. In case of a solderless design, the coiled free ends of the fusible element provide a good mechanical bond with mechanical structures of the endcaps such as tubes (234, 236).