Active EMC Filter with Low Earth Leakage Current
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Solution Overview
Problem
Existing electromagnetic compatibility (EMC) filters face challenges in achieving high attenuation while minimizing earth leakage current (ELC) and maintaining a compact size, with conventional passive filters requiring large components and active filters being less reliable and prone to instability.
Innovation Solution
An active EMC filter design incorporating a transconductance amplifier, high-pass filter, and insulation displacement connector (IDC) for galvanic connection, which isolates the capacitor star point from earth during faults and reduces ELC by using a solid-state relay and auxiliary power supply to manage voltage and current effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-value capacitors and inductances are used to attain required attenuation level, then attenuation performance is improved, but filter size and cost increase
Solution Approach 1:
The patent changes the fundamental operating principle from passive to active filtering. Active elements (operational amplifiers, transistors) are used to create filtering action through electronic circuits rather than relying on the physical size and value of passive L and C components. This allows achieving the same attenuation performance with much smaller component values and overall filter size.
Solution Approach 2:
The patent replaces the mechanical/passive filtering mechanism (large inductors and capacitors) with an active electronic system. The filtering function is achieved through active electronic circuits including operational amplifiers and transistors that actively manipulate the signal, substituting the passive mechanical approach with an active electronic approach.
2Reliability
If high-value capacitors are used to achieve high attenuation, then attenuation performance is improved, but earth leakage current increases
Solution Approach 1:
The patent replaces passive filtering components that generate leakage current with active electronic filtering circuits. The active elements process the signal electronically without requiring large capacitive coupling to earth, thereby eliminating the source of earth leakage current while maintaining attenuation performance.
Solution Approach 2:
The patent extracts or removes the Y-capacitor component that is traditionally connected between the neutral point and earth in passive filters. By eliminating this capacitor, the source of earth leakage current is removed, while the attenuation function is maintained through active electronic filtering mechanisms.
3Reliability
If passive elements are used in EMC filters, then reliability is improved, but filter size and cost increase due to large components
Solution Approach 1:
The patent substitutes passive mechanical filtering elements (large inductors and capacitors) with active electronic components (operational amplifiers, transistors, resistors). This active electronic approach achieves the same filtering reliability with dramatically reduced component sizes and overall filter volume.
Solution Approach 2:
The patent fundamentally changes the filtering mechanism from passive to active, using electronic amplification and signal processing to achieve filtering. This parameter change allows the filter to be much more compact while maintaining or improving reliability through the inherent stability and precision of active electronic circuits.
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 achieves high-frequency attenuation with low ELC, compact size, and fault tolerance, ensuring safety and reliability in both normal and faulty conditions, and is compatible with RCD devices.
Implementation Method 1
incorporating a transconductance amplifier
Implementation Method 2
high-pass filter
Implementation Method 3
insulation displacement connector (IDC) for galvanic connection
Implementation Method 4
isolates the capacitor star point from earth during faults and reduces ELC by using a solid-state relay
Data Source
AI summary
An EMC active filter capable to maintain a low earth leakage current at all times, thus being compatible with RCD devices. The filter of the invention has an especially simple inductor's structure, where typically the power conductors pass straight through the filter, without windings, and most of the components can be implemented in a modular shunt circuit. Preferably the filter is realized by connecting the shunt module by an IDC device to the phase conductors, or directly to the line and load terminal, thus avoiding cutting and splicing high-current cables. The particular protection circuit of the filter prevents in-rush current at power on, and limits earth leakage current even in case of a fault in the line.