Coaxial Varistor Fuse Element for Arc Suppression
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Solution Overview
Problem
Existing overvoltage protection solutions for electric installations, particularly in photovoltaic systems, face issues with arc formation and explosion risks due to the separation of varistors and thermal switches, requiring additional components and increased space, and existing fuse solutions either require separate casings or fail to effectively manage high currents.
Innovation Solution
A varistor fuse element comprising a cylindrical varistor and fuse, serially connected with a melting member and arc extinguishing material, where the varistor and fuse are coaxially arranged, with the melting member having a weak portion to interrupt the circuit upon overload, and the use of silica for arc extinguishing within the tubular structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal switch is serial connected with the varistor to interrupt the circuit when the varistor overheats, then the circuit can be protected from permanent damage, but an arc may occur in the thermal switch which cannot be managed and may cause explosion
Solution Approach 1:
The patent introduces a fuse as an intermediary component between the thermal switch and the varistor. When the thermal switch opens due to overheating, the fuse provides a controlled path for arc extinction. The fuse body contains arc-quenching material that safely dissipates the arc energy, preventing explosion while maintaining circuit protection functionality.
2Ease of manufacture
If a varistor and thermal switch are separated into different casings, then each component can be optimized independently, but additional components and wirings are required which increase device complexity and space requirements
Solution Approach 1:
The patent combines the varistor and thermal switch into a single integrated casing. The varistor is positioned within the same housing as the thermal switch, with direct electrical connection between them. This merging eliminates the need for additional external wirings and reduces the overall number of separate components, while still allowing each component to maintain its optimized design characteristics.
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
This configuration provides efficient overvoltage protection, prevents arc formation outside the fuse, and ensures reliable interruption of high currents in a compact form, enhancing safety and reducing the risk of explosion in photovoltaic installations.
Implementation Method 1
When exposed to an overvoltage impulse, e.g. due to a lightning strike, the resistance of such varistor is essentially decreasing, and the undesired overvoltage stroke is transmitted to the earth.
Implementation Method 2
As soon as the body is then overheated due to current conducted by the nominal voltage, the solder is molten and the circuit is then interrupted by means of such switch.
Implementation Method 3
The main deficiency of such switch is the arc, which may occur in such switch and cannot be managed by the switch... the use of silica for arc extinguishing within the tubular structure.
Data Source
AI summary
The purpose of the invention is to create such a varistor fuse element, which should within a single housing include both a varistor (1) as well as an electric fuse (2), wherein said varistor part i.e. a varistor (1) is intended to protect each electric installation against overvoltage impulses and consequently against current strokes, while the fuse (2) is capable to transmit the current stroke due to increased voltage and to interrupt each permanently increased electric current, which might occur due to defects on the varistor (1). Moreover, such varistor fuse should not exceed dimensions of already known and widely used protective means, in particular melting fuses. In accordance with the invention, the fuse (2) with its round tubular casing (20) and the varistor, which is also embedded within a round tubular casing (10), are serial interconnected and arranged coaxially within each other.