Active Filter Device for Electromagnetic Noise Cancellation
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Solution Overview
Problem
Conventional passive filters for mitigating electromagnetic noise on power lines are large and expensive, especially at low frequencies, and often fail to effectively address issues like earth leakage current, spurious tripping of residual current devices, and disturbance to power line communications in the 1kHz to 150kHz range.
Innovation Solution
An active filter device with a unity gain amplifier and high-pass filter, coupled with a bootstrap connection, is used to generate a correction signal that compensates noise signals, allowing for a compact and cost-effective solution by using active components and a power supply to achieve efficient noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive filters are used to mitigate electromagnetic noise on power lines, then filtering capability is achieved, but the filter size and cost increase significantly, especially at low frequencies
Solution Approach 1:
The patent replaces the traditional passive mechanical filter structure (inductors and capacitors) with an active electronic system consisting of sensors, signal processors, and correction signal generators. This substitution enables effective noise filtering without requiring large physical components, particularly at low frequencies where passive filters would be excessively large.
Solution Approach 2:
The invention changes the operating parameters by using active components that can dynamically adjust their characteristics. The system processes sensor signals through high-pass filters and generates correction signals with specific frequency characteristics to counteract electromagnetic noise, achieving filtering without the size constraints of passive components.
2Object-affected harmful factors
If passive filters are used to mitigate electromagnetic noise on power lines, then filtering capability is achieved, but the filter cost increases significantly, especially at low frequencies
Solution Approach 1:
The patent replaces expensive passive filter components (large inductors and capacitors) with more cost-effective active electronic components. The active filter device uses sensors, signal processing circuits, and correction signal generators that can be manufactured at lower cost while providing equivalent or superior filtering performance.
Solution Approach 2:
The invention changes the cost structure by using active components with favorable cost characteristics. The system achieves filtering through electronic signal processing rather than large passive components, significantly reducing material and manufacturing costs.
3Object-affected harmful factors
If passive filters are used, then filtering is provided, but they fail to effectively address earth leakage current and spurious tripping in the 1kHz to 150kHz range
Solution Approach 1:
The patent employs a feedback mechanism where sensors continuously monitor the power line for electromagnetic noise and earth leakage current. The sensor signals are processed through high-pass filters to identify problematic frequencies in the 1kHz to 150kHz range, and correction signals are generated and applied to counteract these disturbances, providing reliable protection against earth leakage current and spurious tripping.
Solution Approach 2:
The invention changes the filtering approach by using active components that can dynamically respond to different frequency ranges. The high-pass filter and correction signal generator are specifically configured to address the 1kHz to 150kHz range where earth leakage current and spurious tripping occur, providing targeted and effective mitigation.
4Volume of stationary object
If active components are used to create compact filters, then filter size is reduced, but a power supply is required for the active components
Solution Approach 1:
The patent integrates multiple functions into the active filter device. The same active components that provide filtering also handle signal sensing, processing, and correction signal generation. The power supply is efficiently utilized to drive these multiple functions within a compact form factor, making the added complexity worthwhile for the significant size reduction.
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 active filter device provides effective noise cancellation with a flat stop band and rapid transition to the pass band, reducing undesirable ringing and achieving significant attenuation of electromagnetic noise, thus addressing the limitations of passive filters.
Implementation Method 1
a high-pass filter being coupled between the sensor terminals and the signal source, wherein the correction signal is generated with dependence on the high-pass filtered sensor signal
Implementation Method 2
a signal source being adapted for generating the correction signal and comprising an unity gain amplifier means
Implementation Method 3
the bootstrap connection comprises a dc blocking capacitor being coupled in series with a resistor and a capacitor that are coupled in parallel
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An active filter device (4) comprising: - sensor terminals (CTN, CTP) for applying a sensor signal depending on a sensed noise signal (Is, Vs), -an output terminal (OUT) for providing a correction signal (Io, Vo) that is suitable for reducing the noise signal (Is, Vs), - a signal source (1, 2, 12) being adapted for generating the correction signal (Io, Vo), -a high-pass filter (HPF) being coupled between the sensor terminals (CTN, CTP) and the signal source, wherein the correction signal (Io, Vo) is generated with dependence on the high-pass filtered sensor signal.