Heat-Resistant Varistor Disconnect Structure for Arc Breaking
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Solution Overview
Problem
Existing thermally protected varistors fail to effectively break arcs caused by lightning currents above 50 A, leading to material melting and potential fire, endangering equipment and personnel safety.
Innovation Solution
A thermally protected varistor design featuring a slider between the electrode and varistor, made of a heat-resistant material with a melting point above 350°C, and a heat-resistant wrapper, along with remote signaling electrodes for automatic disconnection and alarm, ensuring reliable arc breaking and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a varistor is used for surge protection, then electrical surges are clamped, but the varistor degrades and becomes thermally unstable over time
Solution Approach 1:
A thermally conductive member is introduced as an intermediary between the varistor and the printed circuit board. This mediator component has a thermal conductivity greater than 1 W/m·K and forms a thermal pathway that conducts heat away from the varistor, preventing thermal accumulation and instability while maintaining the varistor's surge protection function.
Solution Approach 2:
The thermal conductivity parameter of the mounting structure is enhanced by using a thermally conductive member with thermal conductivity greater than 1 W/m·K. This parameter change transforms the thermal management capability of the system, enabling effective heat dissipation from the varistor to prevent thermal runaway.
2Ease of manufacture
If the varistor is mounted directly on the printed circuit board, then assembly is simple, but thermal management is insufficient leading to thermal runaway
Solution Approach 1:
A thermally conductive member serves as a mediator between the varistor and the printed circuit board. This intermediary component maintains the electrical isolation and mechanical support functions while adding critical thermal management capability, conducting heat away from the varistor without complicating the assembly process.
Solution Approach 2:
The mounting structure uses a composite approach combining the printed circuit board with a separate thermally conductive member having thermal conductivity greater than 1 W/m·K. This composite structure provides both mechanical support and enhanced thermal management, preventing thermal runaway while maintaining ease of assembly.
3Power
If high energy surges are absorbed by the varistor, then protection is effective, but the varistor undergoes thermal runaway and fails
Solution Approach 1:
The thermally conductive member provides beforehand cushioning by establishing a pre-configured thermal pathway that actively manages heat during surge events. This preventive thermal management cushions the varistor against thermal runaway, allowing it to absorb high energy surges reliably without failing.
Solution Approach 2:
The heat that would normally cause thermal runaway and failure is converted into a beneficial outcome through the thermally conductive member. By conducting heat away from the varistor, the harmful thermal energy is transformed into effective heat dissipation, enabling the varistor to reliably absorb high energy surges repeatedly.
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
Effectively breaks arcs and prevents melting or fire, ensuring equipment safety and providing reliable remote signaling for maintenance, enhancing protection and reliability.
Implementation Method 1
a thermally conductive member having a thermal conductivity greater than 1 W/m-K and forming a thermal pathway with the varistor and the heat sink
Implementation Method 2
varistors are commonly used to protect electronic circuits from the harmful effects of in-rush current and electrical surges
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The present disclosure relates to a thermally protected varistor, including 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 technical solution of the present disclosure, 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, thereby effectively protecting the safety of equipment and personnel.