Double Wound Fusible Element for High Surge Current
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Solution Overview
Problem
Fuses used in circuit protection applications with inductive and capacitive loads face limitations in withstanding high surge currents due to the limited size of wound fuse wires, which restricts their ability to handle excess current and heat transfer, leading to premature melting during overloads.
Innovation Solution
A double wound fusible element configuration, comprising an insulated core with a first wire wound longitudinally and a second wire wound orthogonally about the first wire, increases the mass and heat absorption capacity of the fusible element, allowing it to withstand higher surge currents without melting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single wound fuse wire is used, then the device complexity is low, but the I2t value and heat absorption capacity are limited
Solution Approach 1:
The patent applies nesting by placing one wound wire structure inside another. Specifically, a first wound wire is wound around a core, and then a second wound wire is wound around the first wound wire, creating a nested configuration. This nested structure increases the mass and I2t value of the fusible element without requiring a completely different design approach.
Solution Approach 2:
The patent uses composite materials by combining multiple wire strands (first wound wire and second wound wire) with different orientations and potentially different material compositions. The core may be ceramic or other heat-resistant material, while the wound wires are conductive materials designed for heat absorption and controlled melting characteristics.
2Quantity of substance
If the wound fuse wire size is increased to withstand higher surge current, then the heat absorption capacity increases, but the device dimensions and housing size must also increase
Solution Approach 1:
The patent transitions from a single-dimensional wire to a multi-dimensional structure by winding wire around a core to form a spiral, then winding another layer of wire around that spiral. This adds spatial dimensions to the heat absorption capacity, allowing increased I2t value without proportionally increasing the linear dimensions of the fuse.
Solution Approach 2:
By nesting the second wound wire around the first wound wire, the patent maximizes the use of internal space. This nested configuration allows the fusible element to achieve higher mass and heat absorption capacity within a compact volume, avoiding the need for a larger housing.
3Quantity of substance
If a larger diameter fuse wire is used to withstand higher current, then the current carrying capacity increases, but the heat transfer efficiency between wire and core decreases
Solution Approach 1:
The patent segments the fusible element into multiple components: a core and multiple wound wire layers. This segmentation allows each component to perform its function optimally - the core provides thermal mass and heat dissipation pathways, while the wound wires provide current carrying capacity with maintained surface area for heat transfer.
Solution Approach 2:
The composite structure of core plus wound wires creates a system where heat transfer occurs through multiple interfaces and pathways. The close contact between the wound wires and the core ensures efficient heat transfer, while the total mass of the composite structure provides the necessary heat absorption capacity for high I2t ratings.
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 double wound configuration significantly enhances the I2t value by 250%-300% compared to single wound fuses, enabling the fusible element to handle multiple overcurrent pulses without melting, effectively protecting circuits from high surge currents.
Implementation Method 1
the fusible element comprises an insulated core having a longitudinal axis, a first wire wound about the core along the longitudinal axis of the core, and a second wire wound substantially orthogonally about a longitudinal axis of the first wire such that the fusible element is configured to withstand a plurality of overcurrent pulses without melting
Implementation Method 2
When a circuit overload is encountered, the passage of the excess current through the fuse element causes it to generate heat and thereby elevate the temperature of the fuse wire
Data Source
AI summary
An improved fusible element for use within a circuit protection device is provided which includes a double wound fusible element configured to withstand high surge current associated with inductive and capacitive loads. The fusible element includes an insulated core having a longitudinal axis, a first wire wound about the core along the longitudinal axis of the core, and a second wire wound substantially orthogonally about a longitudinal axis of the first wire such that the fusible element is configured to withstand an over-current surge condition.