Parallel Thermal Disconnectors for DC Surge Protection
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Solution Overview
Problem
Surge protection devices face challenges in effectively disconnecting during thermal runaway and withstanding transient overvoltages, particularly in direct current installations, due to limitations in breaking capacity and arc extinguishing, which can lead to electrical fires or equipment damage.
Innovation Solution
The device incorporates two thermal disconnectors with a thermosensitive element and a movable contact that opens when the protection component exceeds a predetermined temperature, along with arc reduction or suppression members, to enhance breaking capacity and ensure safe disconnection, and is designed for compactness and high voltage compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single thermal disconnector is used, then the device structure is simple, but the breaking capacity is insufficient and arc extinguishing is difficult in direct current installations
Solution Approach 1:
The patent divides the single thermal disconnector into two separate thermal disconnectors, each capable of independently disconnecting the protective component. This segmentation increases the breaking capacity by providing multiple disconnection points, making it easier to extinguish arcs in direct current installations while maintaining reasonable structural complexity.
2Reliability
If the thermal disconnector is designed for high breaking capacity, then arc extinguishing is improved, but the device size increases
Solution Approach 1:
Instead of designing one large thermal disconnector with high breaking capacity, the patent uses two smaller thermal disconnectors working in parallel. Each disconnector handles a portion of the breaking capacity requirement, reducing the volume of individual components while achieving the overall high breaking capacity needed for effective arc extinguishing.
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 provides reliable thermal disconnection and increased breaking capacity, preventing electrical fires and ensuring safe operation under transient overvoltages, while maintaining compactness and compatibility with high voltage systems.
Implementation Method 1
a thermosensitive element and a movable contact capable of moving from a closed position to an open position to disconnect at least one protective component from the electrical installation when the temperature of the protective component increases by a predetermined amount
Implementation Method 2
A thermal disconnector typically consists of a low-temperature solder joint that secures a conductive element forming a movable contact. The melting of the solder joint causes the movable contact to move under the effect of the elastic stress, thus disconnecting the varistor.
Implementation Method 3
an element for reducing or suppressing the electric arc that forms when the moving contact moves towards the open position
Data Source
Figure 1~13B
Figure 4~6
Figure 9~10
AI summary
The device has thermal disconnectors provided with two movable contacts e.g. conductor blade (44) and blade (64). One of the movable contacts moves from a closed position to an open position to disconnect an overvoltage protection component i.e. varistor (30), from an electrical installation. A heat-sensitive element i.e. fusible brazed joint, moves the movable contact from the closed position to the open position when the temperature of the component exceeds a predetermined threshold value. The movable contact is soldered to a pole (34) of the component using the brazed joint. An independent claim is also included for a cartridge comprising a case.