Ground Fault Shutoff Circuit That Avoids Core Magnetization
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Solution Overview
Problem
Conventional shutoff devices for photovoltaic systems face reduced detection precision due to magnetic core magnetization by DC currents, which affects the accuracy of current detection.
Innovation Solution
A shutoff device comprising a magnetic core electromagnetically coupled to conductors allowing AC current flow, with a winding, exciter, current detector, DC component detector, contact elements, and a discrimination controller that turns the contact elements on or off based on detected DC component levels, minimizing magnetization and improving detection precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetic core is arranged to be electromagnetically coupled to the direct current paths for ground fault detection, then the ground fault detection function is achieved, but the detection core becomes magnetized by DC current which reduces current detection precision
Solution Approach 1:
The patent introduces an AC current path as an intermediary element that is electromagnetically coupled to the magnetic core. This AC current path serves as a mediator that allows the magnetic core to detect ground faults through AC current while preventing direct DC current magnetization of the core, thus resolving the contradiction between achieving ground fault detection and maintaining current detection precision
Solution Approach 2:
The patent segments the current detection function into two separate paths: an AC current path for electromagnetic coupling with the magnetic core, and a DC current path for ground fault detection. This segmentation allows each path to perform its specific function without interfering with the other, preventing DC magnetization while enabling ground fault detection
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 suppresses the reduction in detection precision by ensuring the magnetic core is hardly magnetized, thereby maintaining accurate current detection and preventing power supply interruptions during ground faults.
Implementation Method 1
a winding 20 wrapped around the magnetic core 10. An exciter 30 is configured to supply the winding 20 with an excitation current that is an alternating current
Implementation Method 2
a magnetic core 10, a winding 20. The magnetic core 10 is electromagnetically coupled to two conductors 90 that allow an AC current to flow through
Data Source
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AI summary
An object of the present invention is to provide a shutoff device capable of suppressing reduction in detection precision of a DC power supply. A magnetic core (10) is electromagnetically coupled to two conductors (90) that allow an AC current to flow through. An exciter (30) is configured to supply a winding (20) with an excitation current that is an alternating current. A current detector (40) is configured to detect a current flowing through the winding (20). A DC component detector (50) is configured to detect a DC component level from the current detected with the current detector (40). Two contact elements (70) are respectively disposed along the two conductors (90). A discrimination controller (60) is configured to: turn the two contact elements (70) on when the DC component level detected with the DC component detector (50) is less than or equal to a threshold; turn the two contact elements (70) off when the DC component level detected with the DC component detector (50) is greater than the threshold; and turn the two contact elements (70) off in de-energized condition.