Varistor Thermal Protection with Movable Insulation Block
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Solution Overview
Problem
Existing thermal protection devices for varistors are not fast and reliable in preventing overheating due to persistently high voltages, leading to potential damage or explosion.
Innovation Solution
A thermal protection device with a housing containing a varistor, an insulating inner wall, and a moveable insulation block that covers a window to insulate the varistor in a fault state, combined with a low temperature solder joint and a spring terminal for rapid disconnection, ensuring safe and quick separation from the contact surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal fuse is used to protect the varistor against overheating, then the varistor is protected against damage, but the response time is not fast enough and the reliability is insufficient
Solution Approach 1:
The patent implements preliminary action by pre-positioning a moveable insulation block and spring mechanism in readiness. When overheating occurs, the thermal expansion of the varistor directly triggers the insulation block to move and disconnect the electrical connection, eliminating the need for complex sensing and actuation systems that slow down conventional thermal fuses.
Solution Approach 2:
The patent replaces the conventional thermal fuse mechanism with a direct thermal-mechanical coupling system. The varistor's own thermal expansion serves as the actuating force that moves the insulation block, substituting complex thermal sensing and mechanical actuation systems with a simpler, faster, and more reliable direct thermal-mechanical response mechanism.
2Ease of operation
If the contact surface of the varistor is left open for connection, then electrical connection is established, but the risk of electric arcs increases and control becomes difficult
Solution Approach 1:
The patent segments the contact surface area through the use of an insulation block that can selectively cover portions of the contact surface. This segmentation allows the system to maintain electrical connection when needed while providing controlled isolation capability to prevent electric arcs, thereby resolving the contradiction between connection ease and arc risk reduction.
Solution Approach 2:
The moveable insulation block serves as an intermediary element between the contact surface and the external environment. It mediates between the need for electrical connection and the need to prevent electric arcs by providing controlled coverage of the contact surface, allowing the system to achieve both ease of operation and harm reduction.
3Reliability
If the varistor is fully embedded in the housing, then protection against environmental influences is improved, but access for connection and replacement becomes difficult
Solution Approach 1:
The patent implements a nested structure where the varistor is partially embedded within the housing for environmental protection, while the terminal extends outward for easy access. This nested arrangement allows the system to achieve both protection against environmental influences and ease of repair by nesting the protected component within the housing while maintaining external accessibility through the protruding terminal.
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
Provides fast and reliable protection against overheating by ensuring a quick disconnection of the varistor, reducing the risk of electric arcs and allowing easy replacement and reset, while maintaining structural integrity and safety.
Implementation Method 1
If a voltage applied to the varistor reaches a characteristic value, the varistor changes from an electrically insulating state to an electrically conductive state and allows a flow of a high current
Implementation Method 2
The current can heat up the varistor to a point of explosion or other damage
Implementation Method 3
the window in the inner wall is covered by a moveable insulation block. Thereby, the contact surface of the varistor would be completely electrically insulated by the covered window and the inner wall
Data Source
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AI summary
The invention relates to a thermal protection device (100) comprising a housing (1) defining at least one cavity. In the housing a varistor (2) is partly embedded. The varistor comprises a contact surface (12). Furthermore, the housing comprises an inner wall (16) of insulating material, which is placed adjacent to the varistor and to the contact surface of the varistor. A movable insulation block (43) can be designed to defy breakdown. A separation of the connection to the varistor contact is secured by two mechanisms if the connection gets loose. Further, the thermal protection device comprises a micro-switch (31).