Parallel Fuse Overcurrent Protection with Current Redirection
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Solution Overview
Problem
Existing overcurrent protection devices for solar inverters and similar electrical power systems are insufficiently safe as they often fail to interrupt excessive currents quickly enough, leading to overheating and potential destruction of components due to reliance on a single fuse.
Innovation Solution
An overcurrent protection device with multiple parallel current paths and fuses, where a first current control element ensures that the resistance of the second current path is significantly higher in overcurrent situations, allowing for controlled and quick shutdown by directing the entire current through the first fuse, followed by the second fuse, thereby preventing component damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single fuse is used to protect the solar inverter, then the device complexity is reduced, but the reliability of overcurrent protection is insufficient because one single fuse is not guaranteed to interrupt quickly enough
Solution Approach 1:
The protection device is segmented into multiple parallel current paths (first current path with first fuse, second current path with second fuse) instead of using a single fuse. This segmentation allows the system to handle overcurrent situations more reliably by providing multiple independent protection mechanisms, resolving the contradiction between improved reliability and increased complexity.
Solution Approach 2:
The system dynamically redirects current flow during overcurrent events through the first current control element. In normal operation, both paths are active; in overcurrent situations, the first current control element opens to redirect essentially the entire overcurrent through the first fuse, creating a dynamic response that improves protection reliability.
2Reliability
If multiple parallel current paths with fuses are used, then the overcurrent interruption reliability is improved, but the device complexity increases
Solution Approach 1:
The protection device uses self-service principles where the first current control element automatically responds to overcurrent conditions by opening to redirect current flow. This automatic response mechanism reduces the need for complex external control systems, thereby improving reliability while limiting the increase in overall device complexity.
3Speed
If the first current control element is configured to be opened in an overcurrent situation, then the overcurrent interruption speed is improved, but the resulting resistance of the second current path becomes substantially higher
Solution Approach 1:
The first current control element is pre-configured and positioned in the second current path to enable rapid response to overcurrent conditions. By having this control element ready in place with the appropriate configuration (to open and redirect current), the system achieves fast overcurrent interruption while managing the resistance effect through proper design of the current paths and control element 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
The solution provides a simple, robust, and cost-effective means to safely interrupt overcurrents, ensuring that fuses blow in a controlled and reliable manner, reducing the risk of component damage and improving system reliability.
Implementation Method 1
the first current control element is configured to be opened - or non-conductive, or OFF - in an overcurrent situation, such that the resulting resistance of the second current path is substantially - at least 10 times, preferably at least 30 times, more preferably at least 50 times, most preferably at least 65 times - higher than the resulting resistance of the first current path
Data Source
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AI summary
In an overcurrent protection device (D) for protection of an electric power system, in particular an inverter, against overcurrents, wherein the overcurrent protection device (D) comprises a first current path comprising a first fuse (2.1), a second current path comprising a second fuse (2.2), wherein the first current path and the second current path are connected in parallel between an input (1) and an output (12) of the overcurrent protection device (D), a first current control element (4.1) is arranged in the second current path, wherein the first current control element (4.1) is configured to be closed in a normal operation mode and the first current control element (4.1) is configured to be opened in an overcurrent situation.