Thermally Protected Varistor Structure for High-Current Arc Breaking
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Solution Overview
Problem
Existing thermally protected varistors fail to effectively break arcs when a lightning current of 50 A or above passes through, causing the disconnecting device to melt and potentially catch fire, thereby threatening equipment and personnel safety.
Innovation Solution
A thermally protected varistor design that includes a slider connected to an elastic member between the varistor and reed electrode, with a heat-resistant wrapper to prevent melting and a remote signaling system for alarm functionality, ensuring safe disconnection and arc breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-melting-point alloy is used as the disconnecting device material, then the varistor can be disconnected from the reed electrode to protect electrical equipment under normal overvoltage conditions, but the material cannot effectively break the arc when a lightning current of 50 A or above passes through, causing the material to melt and potentially catch fire
Solution Approach 1:
The disconnecting device is segmented into two functional parts: the low-melting-point alloy provides the disconnection function under normal overvoltage conditions, while the heat-resisting material wrapper provides the arc breaking capability under lightning current conditions. This segmentation allows each material to optimize its performance for its specific function without compromise.
Solution Approach 2:
The disconnecting device uses a composite structure combining low-melting-point alloy and heat-resisting material. The low-melting-point alloy (melting point 100-350°C) is used for the disconnection function, while the heat-resisting material (melting point above 350°C, preferably 1000-5000°C) forms a wrapper that contains and breaks arcs during lightning current events. This composite approach resolves the contradiction by assigning different material properties to different functional requirements.
2Ease of operation
If the disconnecting device material has a low melting point (100-350° C.) to enable easy disconnection, then the varistor can be effectively disconnected under overvoltage conditions, but the material will melt and catch fire when exposed to high current (50 A or above) lightning strikes
Solution Approach 1:
The heat-resisting material wrapper acts as an intermediary that protects the low-melting-point alloy disconnecting device during lightning current events. The wrapper absorbs and contains the arc energy, preventing direct exposure of the low-melting-point alloy to extreme temperatures, thus maintaining fire safety while preserving the ease of disconnection function.
Solution Approach 2:
The composite structure combines materials with different melting points: the low-melting-point alloy (100-350°C) enables easy disconnection under normal overvoltage, while the heat-resisting material wrapper (melting point above 350°C, preferably 1000-5000°C) provides fire safety during lightning strikes. The wrapper encapsulates the alloy, allowing both properties to coexist without conflict.
3Device complexity
If no heat-resisting wrapper is provided on the slider, then the structure remains simple, but the slider will melt and catch fire when a high current passes through during lightning events
Solution Approach 1:
A heat-resisting material wrapper is provided on the slider, forming a protective shell that encloses the slider. This wrapper has a melting point of 350°C or higher (preferably 1000-5000°C), providing thermal protection during lightning current events. The wrapper acts as a thermal barrier, preventing the slider from melting or catching fire while maintaining relatively simple structural form.
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 solution effectively prevents the slider from melting and ensures reliable arc breaking, providing enhanced safety for electrical equipment and personnel by using a heat-resistant material and a remote signaling system for alarm functionality.
Implementation Method 1
When the varistor encounters overvoltage, the low-melting-point alloy between the electrode of the varistor and the reed electrode melts due to being heated
Implementation Method 2
the low-melting-point alloy between the electrode of the varistor and the reed electrode melts due to being heated
Implementation Method 3
a wrapper made of a heat-resisting material is provided outside the slider
Implementation Method 4
the wrapper made of the heat-resisting material is provided on the slider, so as to prevent the slider from melting and catching fire due to a high current passing through
Data Source
AI summary
A thermally protected varistor includes a frame, a varistor, a slider, an elastic member, and a reed electrode. The slider is provided between the reed electrode and the varistor. The reed electrode is welded to an electrode of the varistor through a low-melting-point alloy. The elastic member is connected to the slider to drive the slider to abut against a connection position between the reed electrode and the varistor. A wrapper made of a heat-resisting material is provided outside the slider. In the thermally protected varistor, the slider connected to the elastic member is provided between the varistor and the reed electrode to achieve automatic disconnection in case of overvoltage, thereby effectively protecting electrical equipment. The wrapper made of the heat-resisting material is provided on the slider, so as to prevent the slider from melting and catching fire due to a high current passing through.