Low-pass filter with air gap choke for saturation
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Solution Overview
Problem
Current low-pass filters face challenges with magnetic saturation due to differential currents in current-compensated chokes, leading to reduced or lost filter effects, and the use of single chokes increases production costs and size.
Innovation Solution
A low-pass filter design incorporating a current-compensated choke with an air gap in its core, which stores excess magnetic energy instead of causing saturation, combined with a capacitor connected in parallel, allowing for reliable interference suppression without core saturation and enabling the use of a single inductor for multiple lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a current-compensated choke without air gap is used, then the filter size and production cost are reduced, but the core saturates when differential currents are present, causing loss of filter effect
Solution Approach 1:
An air gap is introduced locally into the magnetic core at specific positions where magnetic flux concentrates, creating a region with different magnetic properties. This local modification prevents core saturation at critical points while maintaining the overall compact structure and current-compensated design benefits.
Solution Approach 2:
The magnetic circuit parameters are changed by introducing an air gap, which alters the magnetic permeability and flux distribution in the core. This parameter change allows the core to handle differential currents without saturation, maintaining filter effectiveness while preserving the compact single-inductor design.
2Reliability
If single chokes are used instead of current-compensated chokes, then core saturation is avoided, but production costs and filter size increase due to requiring separate cores for each current line
Solution Approach 1:
Multiple current lines are merged into a single current-compensated choke with a shared magnetic core. The air gap enables this merged structure to handle differential currents that would otherwise require separate chokes, achieving both compactness and reliable filter performance across multiple lines.
Solution Approach 2:
The single magnetic core with air gap serves multiple functions: it provides magnetic coupling for current compensation, handles differential currents without saturation, and supports multiple current lines. This universal design replaces what would otherwise require multiple dedicated cores.
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 filter maintains performance across differential currents, is cost-effective, and compact in size, effectively removing transient and high-frequency noise while avoiding core saturation, with enhanced tolerance to differential currents compared to traditional designs.
Implementation Method 1
the core is configured to have a magnetic circuit, wherein the core has an air gap... excess energy in the form of a magnetic field can be stored in the air gap, which has low magnetic permeability
Implementation Method 2
If a differential current occurs between the coils in a current-compensated choke with an air gap, this does not bring about saturation in the core. The difference in energy is instead stored as a magnetic field in the air gap
Implementation Method 3
Chokes, that is to say coils or inductors, which have a frequency-dependent inductive resistance with which undesired high-frequency components and interference can be filtered out
Implementation Method 4
the capacitor is connected in parallel with the current-compensated choke and is connected to a reference potential
Data Source
AI summary
A low pass filter is disclosed. In an embodiment a low-pass filter includes a current-compensated choke, a reference potential and a capacitor connected in parallel with the current-compensated choke and to the reference potential, wherein a core of the current-compensated choke is configured to have a magnetic circuit, and wherein the core has an air gap.