Common Mode Choke Research Articles

Simulation Model of Common-Mode Chokes for High-Power Applications

Linear and nonlinear Cauer-network models for nanocrystalline inductor cores are developed and used for circuit simulations of common-mode chokes for inverter-based drive systems of several hundred kW. Experimental measurements of the chokes' performance in a high-power test bed are compared to the model results. When the model is based on measured characteristics of the material used, the match to measured behavior is good. Damping inherent in the material characteristic is adequate, such that additional damping is not useful. The primary limitation to accurate prediction of loss in practice is the tolerance on specifications of core characteristics, particularly at high frequency where limits are not specified.

Finite-Element Modeling of Saturation Effect Excited by Differential-Mode Current in a Common-Mode Choke

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This letter presents a method for modeling of the differential-mode (DM) current-excited core saturation effect in a common-mode (CM) choke. This is performed by finite-element analysis (FEA) and computation of 3-D magnetic field distribution in the magnetic core of CM choke. The simulation result shows that the DM-current-excited flux is not canceled completely in the core, and some leakage flux remains, which increases the flux density in the core and gives rise to partial saturation of the core. In order to determine the CM inductance of the CM choke when its core is partially saturated by DM current excitation, the letter then presents a method to calculate the dynamic inductance at the operation point of the CM choke with assistance of FEA. Finally, an experiment for CM inductance measurement of a prototype of CM choke under DM dc bias is carried out to validate the method of dynamic inductance calculation. </para>

Scaling Issues for Common-Mode Chokes to Mitigate Ground Currents in Inverter-Based Drive Systems

The additional high-frequency (HF) common-mode (CM) current of inverter-based drive systems can cause parasitic effects such as HF bearing currents. This HF CM current can be significantly reduced by purpose-designed CM chokes that are inserted in the drive at the inverter output. This paper discusses scaling issues related to the design of such CM chokes, of both wound and feed-through toroidal types. The requirements for the design of chokes for these applications can differ from those for CM chokes designed for use in the inverter input, such as those used for the purpose of electromagnetic interference filtering. This difference is notably due to the comparatively large magnitude of the currents involved. The developed correlations allow taking full advantage of the possibilities offered by such chokes to reduce the HF CM current and mitigate the resultant parasitic effects. The discussed relationships are derived analytically, and the results are supported by measurements.

Determination of Dimension-Independent Magnetic and Dielectric Properties for Mn–Zn Ferrite Cores and Its EMI Applications

Simultaneously high permeability and permittivity results in a pronounced dimensional effect in Mn-Zn ferrite cores, which makes the measured complex permeability differ for cores with different dimensions. This paper provides a succinct method to solve an inverse problem of tracing dimension-independent or intrinsic complex permeability and permittivity for Mn-Zn ferrites using two toroidal and rectangular-cross-sectioned cores with different dimensions. The apparent complex permeability of ferrite cores with other dimensions can then be predicted from the traced intrinsic values, so will the effective impedance of common-mode chokes made of such cores. The traced intrinsic permeability is in good agreement with the measured apparent complex permeability of a very small toroidal ferrite core, in which dimensional effect can be ignored. The apparent complex permeabilities of ferrite cores with other dimensions are measured experimentally, and are also calculated from the determined intrinsic values. A very good agreement between the measured and calculated values is found.

Modeling of Parasitic Inductive Couplings in a Pi-Shaped Common Mode EMI Filter

This paper analyzes the effects of parasitic inductive couplings among the filter components and printed circuit board traces in a pi-shaped common mode (CM) electromagnetic interference (EMI) filter. The result shows that some parasitic inductive couplings related with CM choke do not affect the CM EMI filter performance. And then, it proposes a high-frequency circuit model for filtration performance evaluation and prediction for pi-shaped CM EMI filter, in which the parasitic inductive coupling between input and output loops of the investigated filter is considered to be the crucial coupling parameter while other parasitic couplings are ignored. The model is simple because only one coupling parameter is involved. A procedure is introduced to extract the inductive coupling between input and output loops in pi-shaped CM EMI filter using Z parameters through virtual prototyping. Simulation and experiment finally validate the model.

Feasibility Study of Adding a Common-Mode Choke in PLC Modem for EMI Suppression

The feasibility of adding a common-mode (CM) choke in the analog front end (AFE) circuit of a power line communication (PLC) modem to reduce the CM noise coupling onto the power line is investigated. Based on a two-current-probe measurement approach, the CM and the differential-mode (DM) equivalent electrical models of a PLC modem are first developed. Both the CM and the DM attenuations due to the addition of a CM choke when the PLC modem is connected onto the power line network are then determined. Besides the CM noise attenuation, the impact of the CM choke on the PLC signal, which is DM in nature, is also studied.

초크코일을 이용한 SPD 조합회로의 잔류전압 저감기법

Gas Discharge Tubes (GDTs) are widely used as surge protectors for communication applications due to their small internal capacitance. In these days, however, they are mostly used in combined configurations, because the sparkover voltage required to initiate the discharge process in the GDTs and the time taken for arc formation process can be large enough to damage to sensitive circuits. For GDTs with a considerably high initial residual voltage, we should limit the peak voltage using a TVS or filter. We made a hybrid SPD circuits of common-mode type and differential-mode type with the filter using common-mode choke. Also, we applied lightning impulse voltage and ring wave voltage which frequency bandwidth are different each other and verified the characteristics of hybrid SPD circuits according to waveshapes. We describe how the applied SPDs operate in protection process steps with the actual data obtained from the residual voltage measurement at each step. The experiment results show that the surge voltage reduction with the choke coil is more effective in differential-mode circuit than in common-mode circuit.

In-Circuit Characterization of Common-Mode Chokes

The two current probes measurement method was employed by other researchers to measure the radio-frequency impedance of AC power mains. In this paper, with a modified measurement setup, the method is extended to measure the common-mode (CM) impedance of a CM choke under in-circuit condition. With a premeasurement characterization process, the effect of the measurement setup can be determined and eliminated. The proposed measurement provides a more realistic assessment of the CM impedance characteristic of any CM choke under actual operating condition.

Visualization of Noise Propagation in Grounding System

This paper develops a probe for measuring the high frequency grounding potential and demonstrates its effectiveness. The developed probe is applied to a motor drive system and measures a potential difference between a grounding terminal and the motor frame connected by a grounding conductor. Moreover, this paper attempts to visualize noise propagation in a grounding system. An experimental system is constructed on a lattice-shaped ground plane. A three-phase cable stretched on the ground plane connects between a common-mode voltage source and a motor, and the motor frame is earthed to the ground plane. In experiment, the developed probes detect 25-point potentials, and reconstructing these 25 waveforms makes it possible to visualize noise propagation. In addition, influence of a common-mode choke upon the noise propagation are shown experimentally.

Strong volume reduction of common mode choke for RFI filters with the help of nanocrystalline cores design and experiments

The design of common mode chokes (CMC) for radio frequency interference filter is considered, explained and applied to the compared magnetic core characterization and computation between ferrite and nanocrystalline materials. The latter shows some better insertion losses at low frequencies when comparison is made with the same component characteristics. The volume of the component can be reduced by 50–80% when an appropriate ferrite is replaced by a well-chosen nanocrystalline core, as a result of its superimposed advantages of high and tailored permeabilitys, high saturation and inductive behavior near CMC resonance.

Parasitic capacitance cancellation in filter inductors

This paper introduces a technique for improving the high-frequency performance of filter inductors and common-mode chokes by cancelling out the effects of parasitic capacitance. This technique uses additional passive components to inject a compensation current that cancels the parasitic current, thereby improving high-frequency filtering performance. Two implementation approaches for this technique are introduced. The first implementation achieves cancellation using an additional small winding on the filter inductor and a small capacitor. This approach is effective where very high coupling of the windings can be achieved or where only moderate performance improvements are required. The second implementation utilizes a small radio frequency transformer in parallel with the filter inductor to inject cancellation currents from the compensation capacitor. This technique requires an additional component (the transformer), but can provide a high degree of cancellation. Experimental results confirm the theory in both implementations.

6.6kV，1MWトランスレスBTB方式ループコントローラ

This paper achieves a feasibility study of a 6.6kV, 1MW loop controller that consists of a transformerless back-to-back configuration using two 5-level diode-clamped converters. However, the loop controller requires reducing the zero-sequence current circulating between the two distribution lines below than 0.2 A in rms, in order to avoid malfunction of line-to-ground fault protection relays. Moreover, all the dc voltages across four capacitors in the dc link have to be controlled equally. This paper presents a solution to these problems. Two common-mode chokes are installed at the ac side of each converter to suppress high-frequency zero-sequence currents, while feedback control is applied to eliminate low-frequency zero-sequence currents. Two bidirectional buck-boost dc-dc converters are employed to keep the four capacitor voltages equal. Simulation results verify viability and effectiveness of the loop controller, along with the developed theoretical analysis.

Applications of nanocrystalline soft magnetic Fe-M-B (M = Zr, Nb) alloys

We have succeeded in the development of new nanocrystalline soft magnetic Fe-M-B (M = Zr, Hf, Nb) alloys with high saturation magnetic flux density (B s) above 1.5T as well as excellent soft magndtic properties. For example, the alloys show high permeability ( μ e ) of 16 x10 4 at 1 kHz, high B s of 1.57 T and zero-magnetostriction, simultaneously. In this paper, we report on the performance of toroidal cores with a gap, common mode choke coils and pulse transformers. The excellent characteristics of the components were found in conjunction with very low core losses, sufficient thermal stability and low stress sensitivity for magnetic properties. The nanocrystalline Fe-M-B based alloys are, therefore, expected to be used for many kinds of magnetic components.

Nanocrystalline soft magnetic Fe-M-B (M = Zr, Hf, Nb) alloys and their applications

This paper reviews our results on the development of a new type of soft magnetic material with high saturation magnetic flux density (Bs) above 1.5 T as well as excellent soft magnetic properties. A mostly single bcc structure composed of α-Fe grains with about 10–20 nm in size surrounded by a small amount of an intergranular amorphous layer was obtained by crystallization of amorphous alloys prepared by melt-spinning technique. The typical nanocrystalline bcc Fe 90Zr 7B 3, Fe 89Hf 7B 4 and Fe 84Nb 7B 9 ternary alloys subjected to the optimum annealing exhibit high Bs above 1.5 T as well as high effective permeability (μe) at 1 kHz above 20000. Excellent soft magnetic properties of the nanocrystalline Fe-M-B based alloys can be obtained by the decrease in the bcc grain size, magnetostriction (λ) and the increase in Tc of the intergranular amorphous phase by optimizing the crystallization process, chemical composition and adding small amounts of elements. For example, the improved FeZrNbBCu alloy shows the high ue of 160000 combined with the high Bs of 1,57 T. This excellent μe is comparable to those of nanocrystalline Fe 73.5Si 13.5B 9Nb 3Cu 1 and the zero-magnetostrictive Co based amorphous alloys, and the high Bs is comparable to those of the Fe based amorphous alloys with rather good soft magnetic properties. The excellent characteristics of a power transformer, a common mode choke coil, a pulse-transformer and a flux gate magnetic detector made of ‘NANOPERM ™’ were found in agreement with its very low core losses, sufficient thermal stability and low stress-sensibility of magnetic properties. The nanocrystalline Fe-M-B based alloys ‘NANOPERM ™’ is therefore expected to be used for many kinds of magnetic parts and devices.

Applications of nanocrystalline soft magnetic Fe-M-B (M=Zr, Nb) alloys "NANOPERM(R)"

This paper reviews our recent results on some applications of new nanocrystalline soft magnetic Fe-M-B (M=Zr, Hf, Nb) alloy ribbons "NANOPERM(R)". NANOPERM(R) has a structure consisting of nanoscale bcc grains and a small amount of an intergranular amorphous layer. NANOPERM(R) exhibits high saturation magnetic flux density above 1.5 T as well as excellent soft magnetic properties. Furthermore, its remanence ratio can be controlled according to the demands of various applications. Toroidal cores with gap, common mode choke coils, ISDN (integrated service digital network) interface pulse transformers and flux gate magnetic detectors made of "NANOPERM(R) have been developed. The excellent characteristics of the components were confirmed in trial. NANOPERM(R) is therefore expected to be used widely in the magnetic application field.

Modeling and Analysis of High-Frequency Leakage Currents Caused by Voltage-Source PWM Inverters.

This paper deals with the high-frequency leakage current caused by a voltage-source PWM inverter. A nonnegligible amount of leakage current would flow through stray capacitors between stator windings and a motor frame due to a, large step change of the common-mode voltage produced by the PWM inverter. An equivalent circuit for the leakage current is proposed, which is expressed by a series resonant circuit. The analysis applying the equivalent circuit gives us such a conclusion that the connection of a common-mode choke in series between the inverter and motor terminal is not effective to reduce the rms and average value of the leakage current, but effective to reduce the peak value. Furthermore, this paper shows that the modeling and analysis are valid in designing a previously proposed suppression method of the leakage current.

ナノ結晶Fe-Nb-B合金を用いたノイズフィルタ特性

Noise filter characteristics of a common-mode choke coil fabricated from a nanocrystalline Fe84Nb7B9 alloy were investigated with the aim of clarifying its potential for application as a core material. The impulse attenuation characteristics of the choke coil with the nanocrystalline alloy core were found to be superior to those of one with an Mn-Zn ferrite core. The choke coils made from the nanocrystalline alloy and the amorphous alloy cores showed higher attenuation in the frequency f range above 1 MHz. The common-mode attenuation of the choke coil with the nanocrystalline alloy core exhibited attenuation values higher than those of the ones with the other two cores in the frequency f range above 4 MHz. The conducted radio noise characteristics of the choke coil with the nanocrystalline alloy core were confirmed to be superior to those of the one with the amorphous alloy core. The attenuation of the former was 5 dB higher than that of the latter.

Common mode choke cores using the new Fe-based alloys composed of ultrafine grain structure

Common mode choke cores using the new Fe-based alloys called ‘‘FINEMET’’ composed of ultrafine grain structure were developed. These new cores show high attenuation to high-voltage pulse noises and good attenuation characteristics over a wide frequency range. Accordingly, the new cores are expected to be applied in many applications as line filters for electronic devices.

Common-Mode Noise Generation in a DC-to-DC Converter

Analytical and experimental considerations of the common-mode noise in a dc-to-dc connverterare discussed. Analyzing the mechanism of the common-mode noise generation by means of a high-frequency equivalent circuit, we estimate the output noise voltage generated during the transistor's turn-on time. This commonmode noise consists mainly of two frequency components distributed in several megahertz. The effects of parasitic parameters on the noise voltage and frequencies are clarified. In addition, the effect of a common-mode choke on the noise suppression is discussed experimentally.