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GeckoMAGNETICS – Modeling Inductive Components

GeckoMAGNETICS Getting Started – Inductor Model Tutorial

GeckoMAGNETICS – Modeling Inductive ComponentsGeckoMAGNETICS is a tool that enablesfast, accurate and user-friendly modellingand pareto-optimal design of inductivepower components.

The key modelling features ofGecko-MAGNETICS are:

1) An easy-to-use user interface thatguides the user through the designprocess. Based on the user-specifieddesired inductance, application, andcooling conditions GeckoMAGNETICS findsan optimum design with respect to lossesor volume.

2) Sophisticated and accurate models forloss, thermal and inductance calculation,including:• A very accurate inductance cal-

culation based on a novel air gap reluctance calculation approach.

• Different winding loss effects, such as Skin effect, Proximity effects (including the influence of an air-gap fringing field).

• Many core loss effects such as e.g. a DC premagnetization, relaxation effects, etc. Neglecting for instance a DC premagnetization, may lead to a loss underestimation by a factor of more than two.

3) A link to the circuit simulatorGeckoCIRCUITS, enabling multi-domainmodelling and extraction of waveformsfrom circuit simulations.

4) A material and core database(GeckoDB), which is a part of theGeckoMAGNETICS tool, for accurate coreloss modelling.

This tutorial shows how an inductorcan be modeled and how corematerials and cores can be added tothe above mentioned databaseGeckoDB. This is shown on theexample of the core C055104A2 fromMagnetics (www.mag-inc.com).



After GeckoMAGNETICS is started, the tab“Start” is active.

The user can either model the losses andtemperature of a single pre-definedinductor or the tool can help in finding anoptimum inductor for a particular designproblem. In this tutorial, we would like tomodel the temperature and the losses of apre-defined inductor with help ofGeckoMAGNETICS; accordingly, “ModelInductor” has to be selected.

The considered example is a single-phaseboost-type PFC rectifier with nominalpower 750 W, mains frequency 50 Hz, DCvoltage 400 V, and mains voltage 230 V (cf.figure on the right). The boost inductor ismade of solid round wire (N = 62, diameter2.4 mm) and the core is C055104A2 fromMagnetics. It has an inductance of 1.5 mH.

The material as well as the particulartoroid is not yet available in the database.Accordingly, we have to add it into the DBfirst. Therefore, we press the button“Open Database”.



The database opens as illustrated in thefigure above. The user has the possibilityto add, remove, or change core materials,conductor materials, cores, and windings.In the example at hand, we would like toadd the material MPP 300µ fromMagnetics into our database.

We go to the tab “Magnetic (Core)Materials” and press the button “New”.Now we can enter the basic parametersas:

Name: “MPP 300u”,Manufacturer: “Magnetics Inc.”,Initial relative permeability: “300”,Maximum (saturation) flux density: 0.8 T,Type: “Iron Powder”.Lamination factor: “1.0”

Please note: if you use the trial version ofGeckoMAGNETICS, it is important that thematerial name is exactly as written above.

With “Save Changes” the parameters areconfirmed. The physical meaning of most

of the parameters used above is easy tounderstand. The maximum (saturation)flux density was extracted from the“Normal Magnetization Curves MPP”within the data sheet, as can be seen inthe figure on the next page.

A material has two important non-idealproperties: its non-linear behavior (i.e. thenon-linear B-H curve) and the core lossesthat occur in the material. Both of thesecharacteristics have to be specified for anaccurate loss model.

There are three ways of how to define theB-H curve in GeckoDB: we can specify aninitial B-H curve, a dynamic B-H curve,and a µ-H characteristic. Under “DynamicB-H curve” we understand a measuredB-H loop that is extracted based on analternating core excitation. The “InitialB-H curve” is the statically measuredcurve when the material is magnetized forthe first time. In data sheets often theinitial curve is given; it is recommended touse this curve. If the initial curve isspecified, a dynamic curve is notnecessary (and vice-versa). If both arespecified, GeckoMAGNETICS will use theinitial curve.

Based on the B-H curve, Gecko-MAGNETICS can extract the µ-Hcharacteristic (i.e. the relative µ at acertain DC magnetic field strength H).However, this approach has some inherentinaccuracy. Therefore, often, the materialmanufacturer specifies the µ-H



Initial B-H characteristics (© Magnetics)

µ-H characteristics (© Magnetics)


GeckoMAGNETICS – Modeling Inductive Componentscharacteristic in a separate plot. It isrecommended to add this plot, if available,into GeckoDB. GeckoDB allows thedefinition of different characteristics fordifferent temperatures, which increasesthe model accuracy. However, often thisinformation is not provided. In this case, itis sufficient to use the available curves(mostly measured at room temperature).

On the previous page, both required datasheet curves are shown. These curves cannow be added to the database. The “InitialB-H Characteristics” and “Initial µ-HCharacteristics” windows have to beopened by pressing the according buttons.The resulting screenshot of GeckoDB aregiven below.

Initial B-H curve µr-H curve


GeckoMAGNETICS – Modeling Inductive ComponentsCore Loss characteristics (© Magnetics)

Above, the core loss characteristics of thematerial MPP 300µ are given. One canspecify the core losses via a LossDatabase or via Steinmetz parameters (cf.according buttons in GeckoDB).

The most accurate way is to set up a coreloss database. The loss database storeslosses per unit volume of a particularmaterial at different operating pointsdefined by the flux density ΔB, frequency f,temperature T, and DC bias HDC at whichthe measurement is made. From thesemeasurements, GeckoMAGNETICSinterpolates the losses for an operatingpoint being simulated by the user. Thebest results are achieved when the coreloss database for a particular material iscomplete. A complete database is onewhich contains a measurement at eachpossible combination of ΔB, f, T, and HDC

stored in the database. For example, iflosses of a particular material weremeasured at flux densities ΔB1, ΔB2,frequencies f1, f2, temperatures T1, T2, andDC pre-magnetizations HDC1, HDC2, acomplete database would contain ameasurement at each combination ofthese values, 16 in total: (ΔB1, f1, T1, HDC1),(ΔB1, f1, T1, HDC2), (ΔB1, f1, T2, HDC1), (ΔB1, f1,T2, HDC2), (ΔB2, f1, T1, HDC1), (ΔB2, f1, T1, HDC2),etc.If a complete set of measurements is notavailable, the next best option is a partiallycomplete database: one which wouldcontain all combinations of measured ΔBand f, but not necessarily all combinationsof measured T and HDC. In the aboveexample, a partially complete databasewould need at least 4 points, covering all(ΔBi, fi) pairs, for example (ΔB1, f1, T2, HDC1),(ΔB2, f1, T1, HDC1), (ΔB1, f2, T2, HDC2), and (ΔB2,f2, T2, HDC2).


GeckoMAGNETICS – Modeling Inductive ComponentsGenerally, a partially complete databasewill most likely yield less accurateaccounting of the effect of temperatureand DC bias on core losses than acomplete database containing the same(ΔBi, fi) pairs. A database satisfying neithercompleteness condition is incomplete, andis likely to yield much less accurateresults when used for core losscalculations.

For all core materials that are markedwith a cross (+), a core loss database hasbeen set up by Gecko-Simulations. In the case at hand, the Steinmetz formula(including the necessary parameters) inorder to calculate core losses is given (cf.the legend of the plot above). The user candirectly set these Steinmetz parametersinto the tool. The parameters are definedas PL = k f

α Bpeakβ, where the units Tesla T,

Hertz Hz, and W/m3 are used.

Here, we set the Steinmetz parameters as:

k = 0.0091 · 37.97 = 0.35α = 1.68β = 2.09

The factor ‘0.0091 = 1000 · 1/(1e3)1.68’ isrequired for a proper unit translation: kHz-> Hz and mW/cm3 -> W/m3.

If a core loss database is available, thishas always priority compared to theSteinmetz parameters. In other words, ifthe Steinmetz parameters are set, they

are used for the core loss calculation onlyif the core loss database is empty.

Furthermore, there is a button “RelaxationParameters”. In most cases relaxationparameters can be neglected and therelaxation parameter is not within thescope of this tutorial. For moreinformation on relaxation effects, thereader is referred to the publication

J. Mühlethaler, J. Biela, J. W. Kolar, A. Ecklebe,Improved Core-Loss Calculation for MagneticComponents Employed in Power ElectronicSystems, IEEE Transactions on PowerElectronics, Vol. 27, No. 2, February 2012.

Now, the core material is fully specifiedand can be used for designing andmodeling of inductors.



Besides the material, the geometricdimensions of the core are not yet definedin database. Accordingly we add a newcore under the tab “Core Dimensions”.

We press the button “New”, define thecore as illustrated in the print screenbelow, and press “Save Changes”.

In GeckoMAGNETICS, toroid cores aremodeled without bobbins; hence the corecharacterization is finished.


GeckoMAGNETICS – Modeling Inductive ComponentsAfter closing GeckoDB, the new core andmaterial are visible in the tab “Core”. Now,the inductor can be modeled inGeckoMAGNETICS.

We set the inductor parameters in the tabs“Core” and “Winding”, as given below:

Core: “C055104A2”,Core Material: “MPP 300u”,Nr. of Turns: “62”,Conductor Diameter: “2.4 mm”,

Core Tab Parameters:



Winding Tab Parameters:



The user can select from differentstandard waveforms, such as sinusoidal,triangular, or trapezoidal flux waveforms.However, the highest accuracy is achievedwhen setting up a link betweenGeckoMAGNETICS and GeckoCIRCUITS (orany other circuit simulator).

GeckoCIRCUITS is a powerful circuitsimulator that allows a power electronicsystem to be described on a system level.GeckoCIRCUITS is distributed as an open-source project (for more information,please visit www.gecko-simulations.com).In the tab “Waveform”, we select “FromGeckoCIRCUITS” and then press thebutton “Start GeckoCIRCUITS”.

After GeckoCIRCUITS is started, we openthe model “GeckoMAGNETICS_pfc.ipes”.

In the tab “Waveform”, the inductor aswell as its current and voltage label has tobe specified. For it, it is very important tohave the labels specified properly inGeckoCIRCUITS (including the scope), as itis shown below:

Note: to select more than one inductor inGeckoCIRCUITS, enter e.g. “L.1;L.2;L.3”.


GeckoMAGNETICS – Modeling Inductive ComponentsThe maximum expected current is animportant value in case a non-linearinductance characteristic is transferred toGeckoCIRCUITS, where in GeckoCIRCUITSthe non-linear inductance is thencharacterized up to this current. We select6 A as the maximum expected current. After the button “Send Inductance toGeckoCIRCUITS” has been pressed, thenon-linear inductance characteristic isvisible in GeckoCIRCUITS. It can be foundin the inductor property window under“Define characteristic”:

Now, some parameters that are related tothe GeckoCIRCUITS settings have to bedefined. The tool assumes steady state inthe analyzed operating point (which meansthe average voltage during the analyzedfundamental period should beapproximately zero). Steady state isreached after approximately 0.1 s; hence,we set the simulation time to 0.1 s. Awaveform frequency of 100 Hz should beselected (since twice the mains frequencyis the fundamental flux frequency). Thesimulation time step of 1e-8 s is a goodchoice for this example. If this value is toolow, GeckoMAGNETICS becomes veryslow, if the value is too big,GeckoCIRCUITS might not be accurateenough.

The maximum occurring frequencydefines up to which frequency the tool istaking current harmonics into account forthe winding loss calculation. Themaximum occurring frequency in theexample at hand is set to 144E3 Hz.

The current waveform in the example athand is “Rectified Sinusoidal with HFRipple” and should be selectedaccordingly. After the button “StartSimulation” is pressed, GeckoCIRCUITSsimulates the active circuit model. Thewaveforms can be loaded with “LoadVoltage/Current From GeckoCIRCUITS”.



Another important aspect in the designphase of inductive components is theexpected temperature of the component.This is not only important to avoidoverheating; it also influences the lossmodeling accuracy, since the losses areinfluenced by the temperature. Hence, athermal model is indispensable for anaccurate loss model.

In the tab “Cooling” the thermal boundaryconditions can be defined. The user canselect between natural convection, forcedconvection, and a user specified fixedtemperature. How the component ispositioned in the space (i.e. the gravitydirection) as well as the air streamdirection can be specified too.Furthermore, a fixed Rth can be defined foreach side.

Here, we select “Natural Convection”with inductor orientation “Top-Down”.

Now, all the required information for aproper inductor modeling is defined andthe losses can be calculated.

After pressing the button “EvaluateDesign”, the simulated losses and theloss distribution due to different physicaleffects is shown within the tab “Results”.Additionally, the simulated core andwinding temperatures are displayed.


GeckoMAGNETICS – Modeling Inductive ComponentsIn this tutorial, a step-by-step introductionto the tool GeckoMAGNETICS was given. Ithas been shown how a given inductor caneasily be modeled.

A particular focus was put on how to addmaterials and cores to the databaseGeckoDB. Also, we showed the possiblecoupling between GeckoMAGNETICS andthe circuit simulator GeckoCIRCUITS.

This tutorial example gives a good startingpoint to the reader to GeckoMAGNETICS.Generally, the tool is designed to be asself-explanatory as possible. However, ifquestions arise, or you would like to havea feature which is not available at themoment, please do not hesitate to contactus. Please also consider visiting our bugreporting platform

www.bugs.gecko-simulations.orgContact Information / Feedback

Dr. Jonas Mühlethaler

Gecko-Simulations AGPhysikstrasse 3CH-8092 Zürich, Switzerland

Phone +41-44-632 6576Fax +41-44-632 1212

[email protected]

Document version: March 2014


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