Optimization aspects of common mode chokes are presented. These are based on a behavioral model for common mode chokes and its sensitivity study. Results are used to show the influence of the designable parameters on the final performance of the choke placed in a circuit

Bergsma, H.

Ferreira, B.

Leferink, F.B.J.

Roc'h, A.

Zhao, D.

English

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Performance optimization aspects of common mode chokes

Roc'h, Anne

Bergsma, Hans

Zhao, Dongsheng

Ferreira, Braham

Leferink, Frank

University of Twente Research Information

April 30, 2004 20:45 Research Publishing: Trim Size: 8.50in x 11.00in (IEEE proceedings) emc08:P177Performance Optimization Aspects ofCommon Mode ChokesAnne Roc’h1, Hans Bergsma3, Dongsheng Zhao 2, Braham Ferreira2, Frank Leferink1, 31University of TwenteP.O. Box 217, 7500 AE EnschedeThe Netherlandsa.roch@ewi.utwente.nl2 Technical University DelftP.O. Box 5, 2600 AA DelftThe Netherlands3Thales NetherlandsP.O. Box 42, 7550 GD HengeloThe Netherlandsfrank.leferink@nl.thalesgroup.comAbstract—Optimization aspects of common mode chokes arepresented. These are based on a behavioural model for commonmode chokes and its sensitivity study. Results are used to showthe influence of the designable parameters on the finalperformance of the choke placed in a circuit.I. INTRODUCTIONA proper filtering of the frequency converter is a key aspectin the management of the EMI in the overall motor drives.Frequency converter (FC) components generate a high level ofelectromagnetic interferences on the power lines, motor cablesand via radiated electromagnetic field. It is necessary toprovide a proper filtering of the main supply and cables toreduce their radiation which constitutes the main source ofinterferences. Traditionally filters are designed after theconstruction of the FC. The EMI emission phenomenon iscomplex, and in the case of passive filtering [1], chokes aredesigned in a “cut and try” process with significant issues assize, cost and weight [2], [3] .To avoid the construction ofseveral prototypes, often oversized, designers need ananalytical method to predict performances of filters. In thispaper some sensitivity aspects of designable parameters of thecommon choke are presented.In the following section, the designable parameters and thebehavioural model used as a basis for the sensitivity analysisis presented, this is followed by focuses on the sensitivityanalysis. In the last section theoretical results are compared tomeasurements. A toroid core with 2 windings as illustrated inFigure 1 is considered for the studies.II. BEHAVIOURAL MODEL AND DESIGNABLE PARAMETERSIn this section the designable parameters of the commonmode choke (CMC) are identified. A behavioural model isused to determine the influence of these parameters in the ‘in-situ’ performances of the CMC under consideration.Figure 1: Typical CMC under considerationA. Designable parameters and modellingThe designable parameters of the common mode choke arepresented in table 1. The impedances of the CMC can bemodelled via several formulae available in the literature. Themodelling of the turn to turn capacitance and the inter-winding capacitance is detailed in [4], [5].The value of the CM impedance is strongly related to thevalue of the permeability of the core. As detailed in [6] theferrite core introduces frequency variable impedance in thecircuit. The core will not affect the lower frequency operatingsignals but does block the conduction of EMI. Thepermeability of a ferrite is a complex parameter consisting ofa real part and an imaginary part. The real componentrepresents the reactive component and the imaginary partrepresents the losses. The CM impedance of a CMC can berepresented by the series equivalent circuit of a ferritesuppression core: the loss free inductor (Ls) is in series withthe equivalent loss resistor (Rs). The flowing equation relatesthe series impedance and the complex permeability.20 ..)".'(....NlALwherejLwjLwjRZeeossossμμμ=−=+=N: Number of turnsAe and le: Respectively the effective area and length of thecurrent under consideration2008 Asia-Pacific Sympsoium on Electromagnetic Compatibility &44719th International Zurich Symposium on Electromagnetic Compatibility, 19–22 May 2008, SingaporeApril 30, 2004 20:45 Research Publishing: Trim Size: 8.50in x 11.00in (IEEE proceedings) emc08:P17719th International Zurich Symposium on Electromagnetic Compatibility, 19–22 May 2008, SingaporeThis impedance is usually measured and an approach bypolynomial approximation. In [7] a model is proposed offrequency dispersion of complex permeability in ferrites.Figure 2 presents the simulated CM impedance of a sinteredMnZn ferrite core.Figure 2: Simulated complex CM impedance of a MnZn sintered core(Dimension: 25*10*5 mm, N=20)The value of the DM impedance is related to leakageinductances, and hence to spaces within the wiring system.For a more accurate estimation, formulae are available inliterature [8].An overview of the topology of the model in considerationis presented in Figure 3.Figure 3: Topology of the behavioural model for CMCTABLE 1DESIGNABLE PARAMETERS FOR COMMON MODE CHOKEB. Topology of the behavioural modelThe behavioural model for common mode chokes meetssome major requirements: the frequency dependence of theparameters is taken into account to provide accurate resultseven at higher frequencies.It is also assumed that designers do not have access to aprototype and to experimental values. However otherelectrical information like voltages, currents and otherparameters provided by the manufacturer or commonknowledge available in literature is provided to the designer.Small values of parasitics can be integrated in the simulation.The final model is a ‘black box’ for designers. It requiresseveral tested parameters as inputs and provides output neededin graphs and tables. The software Matlab and Simulink havebeen chosen to develop the presented study.The topology of the model is based on a translation of thecommon choke in its electrical equivalent circuit ‘in situ’.Impedances included are: common mode and differentialmode impedances, parasitics capacitances (turn to turn andintra-windings). The impedances seen from the future place ofthe choke between the two phases and between one phase andthe ground are also included in the network. The designer willhave to provide values of currents and voltages, measured orsimulated, where the CMC will be placed later.These values in addition of the characteristics of thecommon mode choke allow evaluation of performances of theCMC with 4 attenuation coefficients. Figure 4 presents theelectrical setups in the case of a frequency converter withvoltage regulation. The equivalent circuit of the commonmode choke is represented: Z3, Z4 and Z5 are the parasiticcapacitances discussed before. Z1 and Z2 are a combination ofthe common mode impedance Zcm and the differential modeimpedance Zdm:dmcmdmcmZZZZZZ−=+=21Figure 4: Electrical setups in case of a voltage regulation of the frequencycontrollerCurrents i1 and i2 are the current initially flowing at theoutput of the frequency converter. Currents ia and ib representthe current flowing at the output of the frequency converterwhen the common mode choke is placed in the circuit. Thesecurrents can be predicted from the initial setup and the knownimpedances of the common mode choke with the followingrelations. The current ia and ib are predicted via fourattenuation coefficient parameters depending on the commonmode choke and the circuit configuration. The new commonmode current flowing in the circuit can be expressed functionof the former current flowing in the circuit i1 and i2:Impedances ofthe CMCDesignable parametersZcm Material (complex permeability)Dimension of the chokeNumber of turnsEffective lengthZdm Number of turnsDimensions of the chokeAngle of leakage inductanceIntra WindingCapacitanceAndTurn to TurnCapacitanceNumber of turnsDimensions of the chokeWire dimensions and materials(isolation anddiameter)Length of turns448April 30, 2004 20:45 Research Publishing: Trim Size: 8.50in x 11.00in (IEEE proceedings) emc08:P1772008 Asia-Pacific Sympsoium on Electromagnetic Compatibility, 19–22 May 2008, Singapore( )( )21121122211122122121111121221212221122211221222112112221121122212121113224212121114344331443443323321312312311343334445252241411)det()det(1....)1.(..)1.(**AAAAAiiABBABABABABABABAAiiiiBBBBiiAAAAbBaBZgBZgBPZAPZAZgAZgAZgZgZgZgZgZZgZgPZgZgZgZgZgZZgZgPZZgZeqPZZZgZeqbZZgZeqPZZZgZeqaZZgZgZgPgZZgZgZgPgZZZZZeqZZZZZeqbabaeeabbeaeee−=+−+−−+−==−===−=−===−=++++=++++=+++−=+++=++=++=+=+=C. Sensitivity aspectSensitivity studies provide additional insight into thebehaviour of the choke by understanding of how variations ofparameters, for instance of elements values, influence the finalperformance [9], [10].Sensitivity studies will be performed at two levels. Thelocal approach is based on a first order approximation and isnot suitable for large variations. The local approach will bemainly used to evaluate for instance the effect of the errorrelated to modelling or measurements of impedances. Thenormalized simplest sensitivity will be used; it is thederivative function F with respect to any parameter h:hFFhhFS fh ∂∂=∂∂=lnlnWhen a large change occurs in the system, large changesensitivity will be considered. This study is especially relevantwhen the designer wants to try designs drastically differentfrom each other (change of material, size of choke or numberof turns). The large change sensitivity is based on amodification of the original system (the attenuationcoefficients) by a low rank matrix. Assuming that m elementsare subject to change, an (m+1)*(m+1) matrix, by means ofwhich all the information can be obtained, is formed.III. RESULTSA. ImpedancesMeasurements have been performed on a common modechoke presented in Figure 5. Its characteristics have beenmeasured with an Impedance/Gain-Phase Analyser (HP4194A) between 100Hz and 40 MHz. Results are presented inFigure 6.The core is made of iron powder material (Fe). It may beused as pure inductor up to approximately 200 kHz. Theresistive losses dominate thereafter up to approximately 3MHz as presented in Figure 6. The core is no longer effectivein the frequency range above approximately 10 MHz.The core is bonded with a copper wire with a diameter of0.99 mm. Its insulation in polyurethane has a thickness of 12m. The rated current is 5A and nominal voltage 250Vac.Figure 5: CMC under testFigure 6: Impedances of the choke vs. frequencyTABLE 2: PARAMETERS OF THE CHOKE UNDER TESTImpedances TheoreticalvaluesPractical valueCMC inductance 10mH 9.9mHLeakage inductance 41μH 40uHCap. inter windings Nan 16pFCap. Turn to turn 71pF 49pF449April 30, 2004 20:45 Research Publishing: Trim Size: 8.50in x 11.00in (IEEE proceedings) emc08:P17719th International Zurich Symposium on Electromagnetic Compatibility, 19–22 May 2008, Singapore1 50pF2 60pF3 70pF4 80pF5 90pF6 100pF16ResonanceZcm and Z4(=Z5)ResonanceZdm and Z4 (=Z5)ResonanceZdm and ZcmMax ZcmFigure 7: Attenuation coefficient with variable turn to turn capacitances1 500pF2 1000pF3 1500pF4 2000pF14ResonanceZcm and Z4 (=Z5)ResonanceZdm and Z4 (=Z5)ResonanceZdm and ZcmMax Zcm+ ResonanceZg1 (=Zg2) and ZdmFigure 8: Attenuation coefficient with variable capacitances to groundFigure 9: Local sensitivityThe figure 7 and 8 present the attenuation coefficients withrespectively a variable turn to turn capacitance and a variablecapacitance to ground. The behaviour of these coefficients ismainly driven by three resonances between the threeimpedances: common mode impedance, turn to turnimpedances and differential mode impedances. While theincreasing value of the turn to turn is widening the area ofmaximum attenuation in the figure 7, the increasing value ofcapacitance to ground is affecting the level of attenuationitself in figure 8.The local sensitivity presented in figure 9 is helpful inpredicting where the sensitivity is the highest and can be forinstance used to design a filter whose attenuation coefficientsare more independent of environment of the filter.A toolbox has been developed in Simulink. The designerprovides as input the value of the designable parametersdetailed in the table 1 and get as output the sensitivity curve aswell as the attenuation coefficient.Some work is carried on large change sensitivity to allowthe designer to test designs presenting designable parameterswith a wider range of values (different size of chokes,material…)CONCLUSIONOptimization aspects of common mode chokes arepresented. There are based on a behavioural model forcommon mode chokes which model accurately theimpedances of the choke using its designable parameters.Sensitivity studies are carried on. Results are used to evaluatethe influence of the designable parameters on the finalperformance of the choke placed in a circuit.REFERENCES[1] Kempski, A.; Smolenski, R.; Kot, E.; Fedyczak, Z.; “Active andpassive series compensation of common mode voltage in adjustablespeed drive system Industry Applications Conference”, 2004. 39th IASAnnual Meeting. Conference Record of the 2004 IEEE, Volume 4, 3-7Oct. 2004 Page(s):2665 - 2671 vol.4[2] A. Roc’h, H. Bergsma, F.B.J. Leferink, D. Zhao, H. Polinder, and J. A.Ferreira, “Design of an EMI Output Filter For Frequency Converters”,in Proc. EMC Europe International Symposium on EMC, Barcelona,Spain, 2006[3] Frank Leferink, Hans Bergsma, Braham Ferreira, Wim van Etten,“High Performance EMI Filter for Frequency Converters”, EMCEurope 2004, Eindhoven[4] A.Massarini, M.K.Kazimierczuk, “Self-capacitance of inductors”,IEEE Transactions on Power Electronics, Volume 12, Issue 4, July1997 Page(s):671 – 676[5] G. Grandii, Kazimiercmk and A. Massarini, “Lumped. Parameter formodels for single- and Multiple-layer Inductor”, IEEE PESC ‘96[6] Fairites, Technical Information, “How to choose Ferrite Componentsfor EMI suppression”, www.fair-rite.com[7] Takanori Tsutaoka, “Frequency dispersion of complex permeability inMn–Zn and Ni–Zn spinel ferrites and their composite materials”,Journal of Applied Physics, March, 2003, Volume 93, Issue 5, pp.2789-2796[8] M.J.Nave, Technol Sverdrup, AL Huntsville,, “On modelling thecommon mode inductor Electromagnetic Compatibility”, 1991.Symposium Record. IEEE 1991 International Symposium on, 12-16Aug 1991 on page(s): 452-457[9] Saltelli, Tarantola, Campolongo, Ratto, “Sensitivity Analysis inPractice_ A Guide to Assessing Scientific Models”, 2004[10] Vlach, Singhal, “Computer methods for circuit analysis and design”,19833 4)450

A .R o c ’ h ,H .B e r g s m a ,F . B . J .L e f e r i n k ,D .Z h a o ,H .P o l i n d e r ,a n dJ .A . Ferreira, “Design of an EMI Output Filter For Frequency Converters”, in

Computer methods for circuit analysis and design”,

Frequency dispersion of complex permeability in Mn–Zn and Ni–Zn spinel ferrites and their composite materials”,

Information, “How to choose Ferrite Components for EMI suppression”, www.fair-rite.com

K e m p s k i ,A . ;S m o l e n s k i ,R . ;K o t ,E . ;F e d y c z a k ,Z . ;“ A c t i v ea n d passive series compensation of common mode voltage in adjustable speed drive system Industry Applications Conference”,

On modelling the common mode inductor Electromagnetic Compatibility”,

Parameter for models for single- and Multiple-layer Inductor”,

Self-capacitance of inductors”,

Sensitivity Analysis in Practice_ A Guide to Assessing Scientific Models”,

Wim van Etten, “High Performance EMI Filter for Frequency Converters”,

https://doi.org/10.1109/APEMC.2008.4559906

Performance optimization aspects of common mode chokes

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