Concentric EMI Choke Layout for High-DC Inverter Filtering
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Solution Overview
Problem
Conventional EMI filters and chokes require significant space and are not suitable for high direct currents, limiting their applicability and efficiency in inverters.
Innovation Solution
A compact EMI filter design featuring a choke with a magnetic inner core and outer core, where conductors pass through only once between the cores, forming a gap that allows for both common and differential mode interference filtering without windings, utilizing a dielectric gap and materials with high magnetic permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional EMI filters use multiple magnetic cores arranged in E-shape, C-shape, U-shape, or I-shape, then the filtering performance is improved, but the space requirement increases significantly
Solution Approach 1:
The patent combines the inner core and outer core into a single integrated choke structure where the inner core is positioned within the outer core, eliminating the need for separate E-shaped, C-shaped, or U-shaped magnetic cores. This merging of core structures significantly reduces the overall volume while maintaining the dual-mode filtering capability through the concentric arrangement of cores and conductors
Solution Approach 2:
The patent implements a nested configuration where the inner core is placed inside the outer core, and conductors are arranged between them. This nesting of magnetic cores and conductors in concentric layers achieves compact space utilization while preserving the electromagnetic filtering functions for both common mode and differential mode interferences
2Reliability
If conventional chokes use multiple magnetic cores inside one another, then the filtering capability is enhanced, but the device cannot be used for high direct currents
Solution Approach 1:
The patent applies local quality by creating gaps between the inner core and outer core, and between the conductors, which prevents magnetic saturation in high direct current conditions. This localized gap structure allows the choke to handle high DC currents while maintaining filtering capability, as the gaps provide magnetic flux pathways that accommodate DC bias without saturation
Solution Approach 2:
The patent incorporates gaps between magnetic cores and conductors as a preliminary design feature to prevent magnetic saturation before high direct currents are applied. This pre-established gap structure ensures the choke can immediately handle high DC currents without requiring additional design modifications, enabling versatility across different current conditions
3Reliability
If conventional EMI filters use windings around magnetic cores, then the inductance is increased, but the device complexity and space requirement increase
Solution Approach 1:
The patent extracts the winding operation entirely from the design by using straight conductors positioned between the inner and outer cores. The required inductance is achieved through the magnetic circuit formed by the concentric cores and the conductor arrangement, eliminating the need for complex winding processes and reducing both device complexity and space requirements
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 design achieves efficient filtering of electromagnetic interferences in both common and differential modes while being space-saving and adaptable to high direct currents, with improved electromagnetic properties and simplified assembly.
Implementation Method 1
The magnetic flux in the common mode is thereby directed around the choke according to the right-hand rule with respect to the current direction of common-mode current in the conductors
Implementation Method 2
A gap is thus in each case formed between the inner ring, the outer ring, and the respective conductors, which are adjacent in the circumferential direction
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to an EMI filter (1) comprising a choke (2). The choke (2) has a magnetic inner core (9), a magnetic outer core (10), and at least one conductor pair (11) comprising two electrically conductive conductors (12a, 12b). In the choke (2), the inner core (9), the outer core (10), and the respective conductors (12a, 12b) extend along a longitudinal central axis (LA). The inner core (9) is arranged in the outer core (10), and the respective conductors (12a, 12b) are arranged between the inner core (9) and the outer core (10). The respective conductors (12a, 12b) are arranged spaced apart from one another in a circumferential direction, and the inner core (9) and the outer core (10) are arranged spaced apart from one another in the radial direction. A gap (14) is thus in each case formed between the inner ring (9), the outer ring (10), and the respective conductors (12a, 12b), which are adjacent in the circumferential direction. The invention also relates to an inverter comprising the EMI filter (1) according to the invention.