Toroidal Inductor Network Filter for 3-Phase Converter
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Solution Overview
Problem
Existing network filters for converters connected to 3-phase supply networks are inadequate in suppressing electrical disturbances and improving electromagnetic compatibility, particularly due to limitations in asymmetric inductance and frequency range coverage.
Innovation Solution
A network filter design incorporating a toroidal inductor in series with a commutation inductor and a Y-capacitor circuit, featuring ferrite-cored toroidal inductors and iron-cored commutation inductors, effectively addresses the suppression of common-mode disturbances and radio-frequency interference by providing asymmetric inductance and frequency-specific damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional iron-cored commutation inductors are used in network filters, then the structure is simple and cost-effective, but the asymmetric inductance is reduced and suppression characteristics in the radio-frequency range are insufficient
Solution Approach 1:
The patent combines a toroidal inductor with ferrite core and iron-cored commutation inductor in series within each phase branch, merging two different inductor types to achieve both asymmetric inductance for low-frequency suppression and high-frequency damping capabilities, thereby resolving the contradiction between suppression characteristics and structural simplicity
Solution Approach 2:
The patent employs composite material structures by using both ferrite core (for high-frequency losses) and iron core (for asymmetric inductance) in the filter circuit, leveraging the complementary properties of different magnetic materials to achieve broad-spectrum suppression while maintaining reasonable structural complexity
2Adaptability or versatility
If a Y-capacitor circuit is added to damp radio-frequency range, then frequency range coverage is improved, but the device complexity increases
Solution Approach 1:
The Y-capacitor circuit is designed to serve multiple functions: damping radio-frequency disturbances, working in conjunction with the toroidal inductor for high-frequency suppression, and complementing the commutation inductor's low-frequency filtering, thereby achieving broad frequency coverage while minimizing additional complexity through multi-functional integration
3Reliability
If connecting lines for Y-capacitor circuit are arranged on short paths, then parasitic inductances are reduced, but the installation complexity increases
Solution Approach 1:
The patent applies local quality optimization by specifically minimizing the path length of connecting lines for the Y-capacitor circuit to reduce parasitic inductances at critical locations, while accepting increased installation complexity only where necessary to achieve the performance improvement
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 proposed network filter design significantly enhances suppression characteristics, achieving better performance than prior art by effectively managing parasitic inductances and capacitances, resulting in improved electromagnetic compatibility and compliance with radio interference standards in a compact, cost-effective form.
Implementation Method 1
one toroidal inductor per phase, connected in series with a commutation inductor of the converter
Implementation Method 2
a toroidal inductor, preferably a ferrite-cored inductor, is therefore additionally connected in series in each phase of the supply network
Implementation Method 3
a Y-capacitor circuit comprising at least four capacitances, wherein a first, a second and a third of the four capacitances are connected to a respective one of the phases of the 3-phase supply network, and a fourth of the capacitances is connected to ground
Implementation Method 4
a toroidal inductor, preferably a ferrite-cored inductor
Implementation Method 5
These toroidal inductors are preferably designed for a frequency range between 5 and 15 MHz, in conjunction with the Y-capacitor circuit
Data Source
AI summary
A network filter for connecting a converter to a 3-phase supply network includes in each phase a toroidal inductor which is connected in series with a commutation inductor at a respective first connection point, and a capacitor circuit having at least four capacitances, wherein first terminals of a first, a second and a third capacitance is connected in one-to-one correspondence to a respective one of the first connection points. Second terminals of the first, second and third capacitance are connected at a common second connection point, with a fourth capacitance being connected between ground and the common second connection point. The windings of the toroidal inductors can be formed of the connecting lines which connect the corresponding first terminals to the three phases of the supply network.