Mains Filter Adaptation for Leakage Current Management
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Solution Overview
Problem
Existing mains filters are inefficient in reducing high-frequency leakage currents, leading to increased costs and space requirements due to the need for high-inductance chokes, and can overload during faults, disrupting power supply.
Innovation Solution
A filter system that adapts by detecting fault currents and adjusting its cut-off frequency to reduce ground leakage currents, using low-inductance chokes and adjustable capacitance to manage interference transients, allowing the filter to operate effectively across a broader frequency range without interrupting power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If suppression capacitors are used to short-circuit ground leakage currents, then ground loop extension is prevented, but the filtering effectiveness is limited and requires additional chokes
Solution Approach 1:
The patent makes the suppression capacitor multi-functional by enabling it to handle both ground leakage currents during normal operation and fault currents during abnormal conditions. The capacitor is designed with increased capacitance value and is้ ๅ with a disconnect switch that isolates it only when fault currents are detected, allowing it to serve dual purposes and eliminate the need for separate filtering components.
2Reliability
If chokes with high inductance values are used to attenuate ground leakage currents, then filtering effectiveness is improved, but device cost and space requirements increase
Solution Approach 1:
The patent extracts the inductance function from the system by removing the choke component entirely. Instead of using a choke to provide inductance for filtering, the invention relies solely on the suppression capacitor with optimized capacitance value and switching control to achieve both filtering and fault current management, thereby eliminating the space and cost associated with high-inductance chokes.
3Reliability
If suppression capacitors are designed to cover the frequency range of power currents, then filtering is improved, but fault currents can divert through the filter and overload it
Solution Approach 1:
The patent makes the capacitor circuit dynamic by introducing a disconnect switch that can isolate the suppression capacitor when fault currents are detected. The system transitions from a static capacitor configuration to a dynamic one where the capacitor is connected during normal operation for effective filtering and disconnected during fault conditions to prevent overload, thus adapting to different operational states.
Solution Approach 2:
The patent implements a feedback mechanism where a detection device continuously monitors for fault currents and signals the disconnect switch to isolate the suppression capacitor when fault conditions are detected. This feedback loop ensures that the capacitor is protected from overload while maintaining effective filtering during normal operation, resolving the contradiction between filtering performance and fault current protection.
4Object-affected harmful factors
If the filter is designed to return interference transients from ground to input, then electromagnetic compatibility is improved, but the filter becomes vulnerable to overload during faults
Solution Approach 1:
The patent makes the filter circuit dynamic by introducing a disconnect switch that can isolate the suppression capacitor when fault currents are detected. The system transitions from a static capacitor configuration to a dynamic one where the capacitor is connected during normal operation for effective filtering and disconnected during fault conditions to prevent overload, thus adapting to different operational states.
Solution Approach 2:
The patent prepares for potential fault conditions in advance by designing the capacitor with higher capacitance value than traditionally used and by incorporating a disconnect switch as a protective measure. This prior cushioning ensures that the capacitor can handle increased current demands during faults without overload, while the disconnect switch provides a pre-planned protection mechanism that activates only when necessary.
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 reduces the need for expensive high-inductance chokes, saves space, and ensures continuous power supply by effectively managing ground leakage currents during faults, enhancing the filter's durability and safety.
Implementation Method 1
a filter designed to return interference transients from ground to an input of a source generating the interference transients
Implementation Method 2
a measuring device for detecting a fault current flowing through the filter
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The application discloses a device for improving the filtering effect of a filter (36, 44, 72) connected between an electrical power source (6, 54, 80) and an interference source (14), which is configured to return interference transients (18) from the ground (20) to the input of the interference source (14) generating the interference transients (18). The disclosed device comprises a measuring device (34, 58, 74) for detecting a fault current (28) flowing through the filter (36, 44, 72) and an actuating device (40, 59, 77) configured to change a cutoff frequency of the filter (36, 44, 72) such that the fault current (28) through the filter (36, 44, 72) is attenuated below a predetermined level when the measuring device (34, 58, 74) detects the fault current (28).