Filtering Choke Arrangement for Power Electronics Harmonic Attenuation
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Solution Overview
Problem
Existing filtering choke arrangements for power electronics appliances with active network bridges are inefficient in attenuating both difference-mode and common-mode harmonics, leading to high space and cost requirements, and poor attenuation of common-mode currents, which cause significant high-frequency interference.
Innovation Solution
A filtering choke arrangement with two separate three-phase windings connected in series, where phase-specific capacitors can be connected between the windings, and the magnetic cores and connecting pieces are designed to provide independent impedance control for difference-mode and common-mode currents, allowing for effective attenuation of both types of harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate three-phase chokes are used in the filtering unit, then the filtering capability is provided, but the space requirements and cost increase significantly
Solution Approach 1:
The patent combines two separate three-phase chokes (L1 and L2) into a single integrated choke with two separate three-phase windings connected in series. This merging reduces the space requirements and component count while maintaining the filtering capability for both difference-mode and common-mode currents.
Solution Approach 2:
The integrated choke serves multiple functions simultaneously: it filters difference-mode harmonics, attenuates common-mode currents, and provides impedance for both types of currents. This multi-functionality eliminates the need for separate chokes and reduces overall system complexity.
2Reliability
If traditional choke arrangements are used, then difference-mode harmonic filtering is achieved, but common-mode current attenuation is insufficient
Solution Approach 1:
The patent applies different magnetic path designs to different parts of the choke structure. The first and second magnetic cores provide different local magnetic paths for difference-mode and common-mode currents, enabling independent optimization of filtering characteristics for each current type without compromising the other.
Solution Approach 2:
The choke uses composite magnetic structures with multiple magnetic cores and connecting pieces made of magnetic material. This composite magnetic path design enables the choke to provide substantial impedance for both difference-mode and common-mode currents simultaneously, achieving superior attenuation of both types of currents.
3Object-generated harmful factors
If additional filtering chokes are added to attenuate common-mode currents, then high-frequency interference is reduced, but the device complexity and space requirements increase
Solution Approach 1:
The patent merges the common-mode filtering function into the existing filtering choke structure by adding a second three-phase winding connected in series with the first winding. This integration eliminates the need for separate common-mode chokes and reduces overall device complexity.
Solution Approach 2:
The integrated choke with two series-connected windings simultaneously provides difference-mode harmonic filtering and common-mode current attenuation. This multi-functionality reduces the total number of filtering components needed while achieving comprehensive interference suppression.
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 effectively reduces harmonics and common-mode currents, minimizing space and cost requirements while improving interference attenuation, making it suitable for use in PWM frequency converters and motor circuits.
Implementation Method 1
two separate three-phase windings connected in series, to the connection point between which it is possible to connect phase-specific capacitors. The choke has at the same time, apart from an impedance that attenuates the difference-mode harmonics of the network current, also a substantial impedance that attenuates the common-mode currents.
Implementation Method 2
The directions of the windings are such that the fluxes produced in the magnetic cores of each phase current are of opposing directions, in which case the flux produced by the difference-mode current circulates via the connecting pieces from one magnetic core to another.
Implementation Method 3
With the selections of the magnetic materials of the cores and of the connecting pieces (which can be different), with the number of turns of the windings and with possible air gaps e.g. around the connecting pieces, it is possible to set the inductance that limits the harmonics of the difference-mode current.
Implementation Method 4
with possible air gaps e.g. around the connecting pieces, it is possible to set the inductance that limits the harmonics of the difference-mode current. The fluxes produced by the common-mode current instead circulate purely in the magnetic core without passing via the connecting pieces from one core to another.
Data Source
AI summary
A polyphase filtering choke arrangement of a power electronics appliance, more particularly of a frequency converter. which arrangement comprises two separate magnetic cores, around both of which a polyphase winding is arranged, particularly for filtering the harmonics of a network current and the common-mode noise currents, wherein both the magnetic cores (1, 2, 101a-101c, 102a-102c, 130a-130d, 140a-140d) are shaped to form a closed magnetic circuit, the magnetic cores (1 and 2, 101a-101c and 102a-102c, 130a-130d and 140a-140d) are arranged one on top of the other, the magnetic cores are connected to each other with connecting pieces (11-13, 11a-13b, 111-113, 121-124), and the winding directions of the windings of the magnetic cores are opposing with respect to each other, in which case the fluxes produced in the magnetic cores of each current are of opposing directions, in which case the flux produced by the difference-mode current circulates via the connecting pieces from one magnetic core to another.