Frenetic Public Documents
In this book you can find all the information related with the Frenetic Online usage and behavior.
- User Guide
- Core Losses
- Fringing Effect Losses
- Leakage Inductance with AI
- Magnetizing Inductance
- Winding Losses
User Guide
In order to become a Master Engineer in Power Electronics, you are going to need to master the science of magnetics. Although we try to make the design experience as easy as possible in Frenetic, we've put together a guide so you don't waste a single minute on your journey to building your sample.
Waveform
Overview
Waveform is the first section or screen of the Simulator. From this screen you will be able to build or upload your own waveforms for a specific operation point.
Suggested designs and simulation results will be generated based on the waveforms set in this screen.
At the top of the section you will see a field showing the file name. At any point you can modify the given name just by typing in the new file name and saving the changes.
Right below, you can find the Generate PDF and Share features.
In the central part of the screen you can find the schematic diagram of the topology that you selected in the previous step. In case that that you selected the custom option, you will see the schematic of the component (transformer or inductor).
Using the + WINDING buttons, you will be able to add either auxiliary or power windings in both primary or secondary sides.
The crossing arrows button in the top right corner of the diagram will allow you to expand the view of the schematic.
Waveform builder
In order to build the waveform, you must fill in the blanks with the parameters from your converter. It is necessary to fill in at least the nominal values for all the parameters. If any nominal value from the input parameters is missing, the waveform builder will show an error message.
Minimum, maximum and tolerance values are optional and will only affect the suggested designs. Results of the simulation will always be calculated from the nominal values.
The list of parameters will vary depending on the selected topology. The common parameters are: Ambient Temperature (T), Magnetizing Inductance (L), Switching Frequency (fsw) and Turn Ratio (m2).
Once all the blanks are filled in (with at least the nominal values), you can click the UPDATE WAVEFORM button. In a few seconds you will be able to see the results and representation of the built waveforms.
Every time you make a change to any input from the waveform builder, you must click the UPDATE WAVEFORM button to see the new results.
You can also do it with the RUN button. By clicking it, you will update the waveform and run the simulation at the same time.
Advanced settings
Above the Results table, you can find the Advanced button that will display a new screen, allowing you to set different requirements and parameters regarding your project.
You can use this section to store information and requirements critical for your design. These settings are not taken into account when simulating or generating designs (except forced convection).
Using the Forced convection mode, under the Cooling conditions section, will allow you to simulate your design using forced convection. Set a value for the speed of the Blowing Forced Air (m/s) and click the RUN button to do this.
For now, forced convection is the only module from the Advanced Settings that will affect your simulation.
Upload your own waveforms
As an alternative to the waveform builder, you can always upload your own waveforms through a CSV file. Simulation results and suggestions will be generated based on your uploaded waveforms.
To use this feature, you must click the UPLOAD CSV button that you will find below the Results Table.
Keep in mind that you will still need to fill in the common parameters (T, Lmag, fsw, m2) in the waveform builder section before uploading your CSV file.
Under the UPLOAD CSV button, you will find a feature to download a CSV file example. Make sure that your CSV file follows the correct format and contains the same headers as in the example file.
Results
Either if you use the waveform builder or upload your own waveforms, you will be able to see the results in the bottom section of the screen. These results are:
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- Results table: Showing the main calculations of voltage and current
- Waveform representation
- Discrete Fourier Transformation representation
These results will be available for both primary and secondary sides.
Suggest design and run
Every time you update the waveforms (either with the waveform builder or with the upload waveform feature), you will be able to generate suggested designs by clicking SUGGEST DESIGN button.
WARNING: If you click SUGGEST DESIGN button the simulator will take you to the List of Designs screen, not allowing you to move to another section until the suggested designs are generated.
Also, the platform will automatically load and simulate the first suggestion from the list of designs, removing any previous design that you could have loaded in the Core and Winding sections.
Keep in mind that, to run a simulation you need to have previously loaded a complete design, using the Core and the Winding sections.
The run button will also update the waveforms from the waveform builder inputs.
Other features
In the bottom part of the screen, you can find additional buttons:
It is important to save the file before exiting the simulator or doing any actions with the file (sharing, requesting Ansys model or ordering a sample).
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- Ansys download: Allows you to download a Maxwell file of the simulation.
- Delete project
- Return to My projects
List of Designs
Overview
Customize Designs
- Core shape and size.
- Weight.
- Temperature (T): This result refers to the maximum temperature reached in the component.
- Total Losses (Pt)
- Dimensions (WxLxH): Width, length and height referred to the whole set.
The aim of these suggestions is to provide a starting point for the design process. With the technology offered by the Frenetic platform you will be able to modify parameters of your design in the Winding and Core sections.
By default the platform will provide 3 suggested designs, but we can change that number up to 10 in the drop-down menu.
In the left part of the screen you will see the drawing of the core , as well as a brief breakdown of the results and the winding arrangement representation of the selected design.
Library Designs
This feature will be available soon in the user guide.
Generate Designs and Load Design
Unlike the Suggest Design feature (from the Waveform screen), when clicking in **Generate Design**, you will still be able to navigate through the rest of the platform while the tool generates the list of designs. Also, the first suggestion will not be automatically loaded.
- Load Design : By clicking here you will load all the information regarding the core and the windings of the selected design in the respective screens. This means loading all the inputs from the suggested design and also running the simulation.
Once you load a design you can access the detailed information and also make any changes, going through the Core and Winding sections.
At any point in the design process, you can reload the original design, erasing all the changes that you made in the Core and Winding sections.
Core
Overview
In the core section you will be able to select and define the parameters of your core, as well as seeing results of the simulation regarding Core losses and magnetic flux density.
At the top of the screen you will find several drop-down menus in blue, from which you will be able to define the parameters in order to characterize your core. These are:
Inductance - Launch Calculator
The Inductance Calculator can be accessed through the Launch Calculator button located in the Inductance section of the screen.
The calculator has two main modes:
Accurate Mode
The default. It computes the Inductance of the magnetic taking into consideration all constructive parameters and the operating conditions.
This mode is set by default once a simulation is created. It will compute the real inductance that the magnetic will show in the operation point once working on the converter.
For this Inductance computation, not only the geometrical and the electromagnetic properties of the selected core will be taken in to account. The whole system, including the ambient temperature, the current, the temperature on the magnetic produced due to core and winding losses, permeability, gaps distribution and fringing will be taken into consideration so the computed Inductance Value is as accurate as possible in the SOA.
In this mode the system takes all the parameters in the simulation, not only the ones in the core, but in the waveform and in the winding section. However, due to its influence and the common designing flows, the three main inputs are: The N (Primary Turns), N. Gaps (Number of gaps), Gap (Gap length for each gap).
Once these three (within the rest of the parameters in the simulation) are introduced, the new values for the L (Inductance), AL (Inductance Factor), FF (Fringing Factor) can be computed by clicking on the RUN button located on the bottom right corner of the screen.
Once it is clicked, the simulation will run and compute all the outputs of the simulation and the L (Inductance), AL (Inductance Factor), FF (Fringing Factor) that the magnetic will show in the given operating conditions.
The Apply button allows, once the selection and results satisfy the needs, to apply the changes within the rest of the simulation, return to the default mode and compute the simulation of the whole magnetic. If clicked, the simulation will run completely and some of the results may vary between modes.
On the other hand the Cancel button allows to undo all changes during this mode and return with the initial configuration on the Accurate Mode.
Iteration Mode
It allows for fast iterations, changing the degrees of freedom between L (Inductance), N (Primary Turns), N. Gaps (Number of gaps) and Gap (Gap length for each gap).
By selecting different button modes in inductance calculator the degrees of freedom of the Inductance Calculator will change. In the Inductance Tab the main output will be the L, in N turns tab the main output will be N (Primary Turns) , and in Gap tab the main output will be the Gap (mm) length for each gap.
During this mode, no extra computations regarding the winding, losses or temperature will be carried out. Only the outputs of the inductance calculator will be processed, drastically reducing the time required to get the results and allowing fast iterations between different combinations. However, the shape and materials are also considered as inputs in this mode, so different alternatives can be explored.
Once this mode is selected, the desired output is chosen, and any value in the blue boxes is modified, the computations will be automatically triggered just by clicking somewhere else on the screen.
Gap Location
In addition to the above, it is also possible to determine the location of the Gap, wherever it is located in the center leg or in all the legs.
For modifying the location of the gap, the gap location selector is used.
Core Losses
- Amplitude of the B field (Bpkac)
- Maximum working flux (BpkT)
- Core Losses
- Saturation Current at 25ºC and 100ºC
- Plotter: The Plotter is now integrated in the core page and automatically will draw the graph of Inductance against Current so you can see how the magnetic inductance changes in the selected current range. The current range is set automatically between 0 and the maximum current of your design but it can also be changed by hand to whatever range you would like to see.
To help clarify these outputs, a typical B-H curve for a Flyback transformer is shown in the image below:
Core parameters
At the top of this section you will find one or two drop-down menus in blue, from which you will be able to define the parameters in order to characterize your core. These are:
- Shape and size: Select the core shape and size from the list of standard cores available.
- Datasheet: Click to access to the core specifications provided by the manufacturer.
- Customize:The customize feature will allow you to modify any dimensions of the selected core. Click in the button and it will unlock the dimension fields , allowing you to type the new value for the specific dimension. Click anywhere in the screen or press enter to save the changes. To reset the dimensions click again the Customize button. The Core families that you will be able to edit are E, U, T (toroids) and PQ.
If the combination of core shape and material is not listed in the manufacturer's catalogue, a warning message will appear. You will still be able to simulate the design with the previous inputs.
Stacking cores and Custom dimensions features are only available for E and U shaped cores.
Stacking cores will allow to increase the Core area while keeping the same height and width.
Coil Former parameters
At the top of the screen you will find several drop-down menus in blue, from which you will be able to define the parameters in order to characterize your coil former. These are:
- Customize: The customize feature will allow you to modify any dimensions of the selected core. Click in the CUSTOM option and it will unlock the dimension fields , allowing you to type the new value for the specific dimension. Otherwise, you can choose the No coil option if your design does not require it. Toroids have only the "No coil" option.
- Thickness: It is the coil former thickness (the coil former is considered to have the same wall thickness in all its shape). It should be bigger tan 0 mm. In practice a minium 0,5mm or 0,8 mm is recomended.
- Coil Depth: It is the máximum length of the coil former. For custom coil formers it should be always bigger than the space required by the winding.
- Distance to core: Distance between the core and the coil former. It is the air that exist between them. It should be bigger tan 0 mm.
Physical description
In the right half of the screen you will be able to see the following information about your core.
- 3D model
- Plans
Run Core vs Run Core Only
At the bottom right there are two main buttons to trigger the simulation. The two options produce two type os simulations.
- Run Core Only: Triggers a quick simulation that only simulates the core constructive parameters within the given waveforms. No simulations will be done for the winding, impliyng that the results on the winding tab are likely to be outdated. Due to this absence of winding considerations a quicker simulation is provided making it a better simulation for trying out different types of configurations and iterations related with shapes, materials, inductances etc. However, it is important to bare in mind that the results provided; L, Bpkac, BpkT, AL, Core Losses, Total Losses, Temperature are simulated without the influence of the winding. The winding section can deeply determine the real behaviour of the core parameters, mainly through heat transfer, that the magnetic would have on the given operating conditions. This implies that, once the desired iterations in the core are finished, the run button should be clicked so a more accurate simulation is provided.
- Run: Triggers the full Frenetic Online simulation. It requires more time than in the previous case, but now, the output results are given by considering all the system, core and winding, impliying more accurate results. In this case the winding tab will be also updated.
Glossary
- L: Inductance shown on the primary winding of the magnetic.
- N: Number of turns on the primary winding of the magnetic.
- N.gaps: Number of gaps on the magnetic.
- Gap (mm): Length of each gap shown in the magnetic.
- Al: Inductar factor for the given shape, material, and gaps characteristics.
- FF: Fringing Factor that represents the the flux density spread on the gapped sections of the magnetic.
Windings
Overview
In the Winding section you will be able to fully customize the winding arrengement of your design. Also, you can run a simulation and visualize the results from it.
Standard
From this tab you can define the standard used to denote wires size: International (mm) or American (AWG).
Winding Arrangement
It is possible to select a different configuration using the Customize feature.
Once a new winding arrangement is selected, it is necessary to run the simulation in order to apply the changes.
Wires
The wires panel allows you to modify all the parameters referred to the wires. At the top of the panel , select the winding tab to see the wire parameters and simulation results of the corresponding winding.
Parameters in the Wire Menu:
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Group with: Allows you to group multiple windings.
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Wire type: Choose between Litz, Round, Foil and Rectangular (Inductors only)
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Turns
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Width (Foil and Rectangular)
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Thickness (Foil wire)
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Height (Rectangular wire)
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Nº of strands (Litz wire)
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Strand diameter (Round and Litz)
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Grade (Round and Litz)
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Serving (Litz wire): Choose to have unserved or single served wire
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Nº of insulation layers (Round and Litz): You can set none, one (SIW), two (DIW) or three (TIW) insulation layers
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Insulation type (Round wire): Enamel or Plastic
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Margin Tape: Added at top and bottom of the layers.
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Nº of Parallels
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Nº of Layers
Every time you make a change in any of the wires parameters, it is necessary to run the simulation in order to update results and representation of the new winding configuration.
Textile serving in the litz wire act as an optional layer of added mechanical protection for the overall conductor. Serves are particularly effective at protecting the enamel layer on the individual strands of the conductor from abrasion during further processing. On the other hand, it reduces the wire flexibility.
Grouped Windings
Use the Group with tab in the Wires menu to group multiple windings. Basic grouping allows you to have a configuration in which different windings are wounded in the same layer.
The image shows the representation of a winding arrangement with two secondary windings grouped.
In order to successfully set grouped windings:
- Windings must have the same wire: dimensions, number of parallels and insulation.
- Windings must have the same number of layers.
- Windings must have the same margin tape.
WARNING: If you try to group windings that don't satisfy the previous requirements, the parameters from the grouped windings will be automatically modified to match with the configuration of the first grouped winding.
Nº of turns is the only parameter from the Wire menu that can be different within the grouped windings. If the number of turns is the same for all the windings, they will be wounded all together, just like the image below.
Simulation Results
In this section you will find a detailed breakdown of specifications and results from the simulations. These results are referred to the selected winding.
Results provided in this section:
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Wire Dimensions: Width, height and length.
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Current density
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Skin depth
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Breakdown of the losses: Due to Fringing, skin and proximity effects.
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Total losses.
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DC Resistance.
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DC losses.
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Leakage Inductance (Secondary windings): This result is the Llk referred to the primary
General results
In this section you can find more general results:
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Filling factor: Percentage of area of the window which is occupied by the winding.
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AC Resistance
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Total winding losses.
Representation of the windings
This section provides visual information about the winding distribution within the window. It will allow you to check if the windings fit in the bobbin as well. Other than windings, margin tape, gap and isolation layers are represented too.
If the winding configuration that is loaded doesn't fit in the bobbin, a warning message will appear once you run the simulation.
Customize button
Suggest Wire
When clicking in the Suggest wire button, the platform will provide a new solution for the windings, modifying and loading the new parameters in Wires menu, and running the simulation at the same time. This suggestion will provide a commercially available and manufacturable solution. Again, you can use these suggestions as starting points for your winding arrangement.
The wire suggestion will take into account the nº of turns, margin tape (if added) and winding arrangement selection (PS, PSP, PSPS or Two Chamber).
Suggest Wire feature does not support Grouped windings or Custom Winding features
Run
Every time you make a change in the winding section, make sure you click the RUN button in order to update both the results and the windings representation.
If you click Suggest Wire you won't need to click RUN to simulate the new windings. It will be automatically done.
Custom Winding
Custom Winding
This feature allows to totally customize the winding arrangement of the magnetic
To access the custom winding click on: Winding tab
And access the winding screen:
Before using the custom winding, all winding parameters must be determined, it means that all inputs of the windings must be fulfilled, and by clicking on run, the outputs are generated.
Custom winding needs 4 parameters to customize the winding arrangement.
- The windings. Primary, Secondary, Secondary 2, Auxiliary 1 etc
- The number of magnetic turns of each winding
- The number of parallels on each winding
- The number of layers in each winding
Once these 4 parameters are fulfilled the advance customization can be done.
For doing so the “Customize” button has to be clicked.
And the custom winding interface will be opened:
6 actions can be done in this mode:
- Apply Changes so the changes are implemented and the simulation is ran. It returns to the winding screen
How it works?
In the custom winding we have a table and a drawing of the winding. Each column of the table in the left refers to a layer in the drawing on the right.
The headers indicate the winding that conforms the given layer. In the example, the first layer "P" is filled with turns and parallels from the "Primary" winding, the second layer "A1" is filled with turns and parallels from "Auxiliar 1", the third layer, is filled with turns and parallels from the "Auxiliar 2", layer forth and fifth are filled with turns and layers from "Secondary" winding, etc etc.
Each layer has 4 cells in and .
- N parallels. Input selector determine the number of parallels that are wounded on the layer for the given winding(shown on the headers)
- N turns per parallel. Input selector determine the number of turns that are wounded for each of the parallels on the layer.
- N turns per layer. The number of total turns that are located on the given layer. This number is computed automatically. For example; the second layer has two Auxiliar 1 parallels and has three turns wounded on each one of these parallels, therefore the number of total turns is 6, 3 turns per parallel.
- Connection between layers . Shown as small clickable circles. Input to indicate if the parallels on the layer end on the layer, or these are continued to be wounded in another layer. In the example, the second layer which is filled with turns and parallels from
What it is possible to do in this mode?
- Locate the layers of each windings in all possible arrangements
- Manage the number of parallels and turns that are winded per layer
- Manage connections between layers of the same winding
Locate the layers of each windings in all possible arrangements
For adjusting and customizing the layers of the windings it is only required to click and drag the headers of the layers and locate them on the desired position
Manage the number of parallels and turns that are winded per layer
Once the arrangement of all layers is defined, the distribution of parallels and turns per parallel for each layer can be determined.
For doing so a header of the winding that is deried to be modified is clicked. In the example there are two headers/layers for the Primary winding "P", two headers/layers for the Secondary "S" and one header/layers for each auxiliary "A1", "A2" and "A3".
After clicking a header of a winding:
- All the headers of the same winding will be highlighted.
- The total number of parallels and turns per parallel are shown on the bottom left corner.
- An additional "check" column appears to indicate if the actual selection complies with the requirements.
In this mode the two selectors "N Parallels" and "N turns per parallel" are available to select the desired configuration.
The unique requirement that must be fulfilled for the simulation to run, is that the N of Parallels and number of total turns of the winding are reached. These two values are determined in the winding section.
For ensuring so, the "check" column shows a green check in the rows where the requirement are achieved. And a red cross where any of these requirements are not fulfilled.
As it is seen in the following example, the secondary "S" has a total of 4 parallels, however 6 parallels are selected in the customizer, 4 parallels in the first layer and 2 on the second layer. The red crosses appears on the left indicating the unmatch in the sum of total parallels and total turns on the winding.
In the second example, although the number of parallels are reached, it is not the case for the total turns on the layer having 2 parallels with 2 turns each in one layer and 2 parallels with 4 turns each in the second layer.
Once the "check" column shows both markers in green the "Apply Changes" and "Preview" buttons will be available to click and process the information.
Manage connections between layers of the same winding
Besides the adjustment of the location of the different layers of the windings and the parallels and turns on them, the customization allows to determine when the parallels of the layers finish on the given layer, going to pin, or the parallels continue to be wounded in a different layer before going to pin.
For connecting the paralells on two different layers of the same winding, the node section must be used.
For doing the connections the nodes of the layers must be used. For creating connections, only the nodes of the first and last layer have to be clicked. From left to right.
Once the connection is done, a blue line will unite all the nodes of the layers involved in the connection.
Once the parallels from two or more layers are connected, the "N Parallels" shall show the same number. This will affect the total N Parallels and therefore "check" column.
This effect is seen on the example. For allowing the changes to be applied the N turns per parallel and the N parallels shall be modified.
Preview and Apply Changes
Whenever the "Check" column shows the green check, the system will be able to "Preview" and to "Apply Changes".
- Preview recomputes the winding drawing with the last changes. Cause only the image and the dimensions of the magnetic are simulated, this process allows to do quick checkups to ensure the winding are fitting in the dimensions of the available window. If it is not the case, the software provides a warning besides the preview button.
- Apply Changes applies the changes introduced on the custom winding mode to the simulation. After the system computes all the outputs the rest of the sections of the simulator will be accesible again.
- Undo Changes, located above the check column, undo all changes and restores the last winding configuration that was processed after a "Run" or an "Apply changes".
- Close, located on the top right corner, undos the changes and returns to the simulation.
Datasheet
Overview
The Datasheet page provides all the constructive characteristics and simulation results of a magnetic component design. This section shows a complete overview of the complete design helping you to review and verify the design. The Datasheet is automatically generated and updated everytime you run a simulation, and it can be downloaded in a PDF file.
In the top rectangle you can check the project and file information
Simulation results
This section provides the information about the toplogy chosen , waveforms and performance review .
The performance box will allow you to check the more critical outputs: Temperature, Leakage Inductance, Rac, Total Losses, Core losses and Winding losses.
In the bar graph you can compare the winding and core losses. A well designed component should have similar values for Core and Winding losses.
Mechanical Overview
Schematic
Coming soon
Dimensions and Pinout
Coming soon
Winding window
Here you can see the representation of the windings within the window, in addition to the margin tape and isolation.
Bill of Materials
The bill of materials table will be automatically generated and you can export it into an Excel or PDF file.
The table provides an extended breakdown of all the material needed. The last column can be filled by your assigned engineer after verifying your design, with alternative materials that could replace the original ones.
Assembly instructions
In this section you can fin the necessary instructions and information for correctly manufacturing your magnetic.
Gap
Specifications about the gap that was set using the Inductance Calculator from the Core page.
Isolation
Creepage and clearance requirements.
Finishing and others
Coming soon
Winding distribution
The winding distribution table can also be downloaded as PDF or Excel file. It contains all the information about how to arrange properly the windings. Extra information (grey columns) may also be added by the engineer after reviewing the design. The empty boxes that you can find below the table can be filled with additional comments or pictures in order to clarify or remark a specific step in the assembly proccess.
Validation
The validation section of the overview summarizes the tests and measurements that must be carry out to correctly characterize the magnetic.
Common validation tests are the Inductance measurements of the diferente windings, the DC resistance of the different windings, the leakage inductance shown from the primary and isolation tests like the HI-Pot test between windings and between the windings and the core.
Verification
The verification button located on the bottom right corner allows to initiate the verification process of the design.
The verification process consists on a a review of the design attending the mechanical, constructive and electromagnetical requirements that ensure the design is suitable and manufacturable.
Once the verification process is initiated the simulation will be blocked, it means non constructive modifications on the design will be allowed. Besides, a Frenetic's engineer will receive acces to your design to carry out the review and ensure it is appropiate to go to manufacture.
The verification process goes through different stages, at any moment, the verification button will indicate the status of the verification request.
If it is required, the Frenetic's engineer can propose modifications and improvements on the design. this modifications must be approved by the owner who requested the verification.
Once a design is verified, it is ready to be manufactured, allowing to order samples or to go to mass production.
Core Optimizer
Overview
The Core Optimizer™ is a dedicated tool designed to help you find the most suitable core for your application. You can select and compare many different core shapes and materials simultaneously, allowing you to intuitively find a trade-off between core losses and volume that meets your target specification. We encourage you to make your design process more efficient and take full advantage of this tool.
There are two sections to this tool:
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Ve vs. N turns
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Core Losses vs. N turns
The best section to use will depend upon your goal, see below.
Ve vs. N turns
The main goal of this section is to allow you to quickly compare core shapes, sizes, and materials to find the most suitable core solution for your application.
To provide the tool with some context about your higher-level goals you must first specify either your target Bpeak Limit (mT) or your total Core Loss Target (W). The quality of your inputs here will have a significant impact on the tool’s outcome, so please take your time to read the specific sections below giving you extended guidance on choosing these inputs.
Once you have set a target value, the next step is to prime the optimizer with relevant core parameters:
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Core Shape Family
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Core Material
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Number of Stacks (if relevant)
Once you have provided this information, you may click ‘PLOT SELECTED CORES’ and this will populate the graph with a set of results. You can experiment with different combinations and simultaneously plot up to ten different results.
If you wish, you can click on the legend to hide/unhide plots from view. The “DELETE” button will remove the last plot added to the Optimizer.
The two axes for the graph shown in this section, as in the title, are Number of Turns (X) and Effective Core Volume (Y). The Optimizer will strive to maintain your limit provided and show you a range of results for each scenario created.
In this example we selected a Flux Density limit of 120mT, and we can see that as the turn count increases the effective volume of the cores can be decreased, hence showing a range of discrete core sizes within the same family. We have also compared several different core families with the same material.
To make the most of this tool, it’s important that you can effectively translate the results provided. Once you click on a point in the graph, important information about that point will appear on the right-hand side, as shown below.
Note that the Core Optimizer™ tool focuses on delivering you optimal results for your core, but this may not necessarily lead to optimal results in your winding strategy, so here are some useful pointers below.
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As the turns increase and the effective volume of the core decreases, the current density in your windings will increase, making it harder to achieve a feasible winding strategy. The further you travel along the x-axis, the more challenges you will face in your winding stage.
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Keep an eye on your inductance, the tool will try its best to maintain your high-level goals set above, this may mean that the inductance strays from the parameter you set as a target in the waveform page.
If you have decided upon an appropriate core for your application and you want to move to the next stage, simply click on the point you like and hit “APPLY” in the results window. This will move your choice to the core configuration page for further fine tuning.
Core Losses vs. N turns
The goal of this section is to provide insight, at a specific core level, about the relationship between turns and core losses. In a similar way to the last section, you will create your initial conditions to prime the optimizer tool. The difference now is that you can only set the Bpeak Limit as a target, and you must choose a specific discrete core size.
The greatest core losses will be seen with the lowest turns, and this will coincide with the Bpeak Limit you set. As the turn count increases, in the results box on the right you will see the inductance increase whilst the core gap remains null.
Once your target inductance is reached, the optimizer will begin appropriately gapping your core options to maintain the target. Naturally, as you increase the turns the flux density will continue to decrease and thus the core losses. When selecting your core, be mindful of the gap and the effects that may have (due to its fringing field) on the winding losses, and once again bear in mind your turns count and current densities.
How to Pick an Appropriate Bpeak Limit
Your choice of Bpeak Limit will depend on the material you are going to choose, both in terms of understanding the relationship between this value and the overall core losses, and how this is impacted by the frequency you are operating at.
The number one rule is to ensure that the core isn’t going to saturate under the operating conditions you have. You can find this information in the material datasheets online, below we have provided a table showing the saturation levels of some of our popular materials. Remember that maximum saturation current decreases with temperature, so you will need to be appropriately conservative with your design.
Material |
Bsat @ 25 oC (mT) |
Bsat @ 100 oC (mT) |
3C90 |
470 |
380 |
3C91 |
470 |
370 |
3C92 |
540 |
460 |
3C92A |
570 |
480 |
3C94 |
470 |
380 |
3C95 |
530 |
410 |
3C95A |
550 |
430 |
3C95F |
550 |
430 |
3C96 |
500 |
440 |
3C97 |
550 |
430 |
3C98 |
530 |
440 |
3C99 |
500 |
450 |
3F4 |
410 |
350 |
3F36 |
520 |
420 |
3F46 |
520 |
430 |
N27 |
500 |
410 |
N41 |
490 |
390 |
N49 |
490 |
400 |
N51 |
480 |
380 |
N72 |
480 |
370 |
N87 |
490 |
390 |
N88 |
500 |
400 |
N92 |
500 |
440 |
N95 |
525 |
410 |
N97 |
510 |
410 |
PC47 |
530 |
420 |
PC200 |
485 |
410 |
The values in the table above are maximum values as a guideline. If you are designing for an application with predominantly DC currents and small AC currents, then you may successfully design with greater Flux Densities closer to these values. In these cases, it is useful to operate with high Flux Density to improve the Power Density of your design.
However, if you are operating with a higher ratio of AC current, such as most transformer applications and AC inductors, you must be mindful that higher operating frequencies will incur greater core losses, so you should operate at with an appropriately lower flux density.
We don’t have a rule of thumb for this, but we recommend you start with a high value and let the Optimizer provide you with a good range of options to analyse. The proof will be in the final core losses and the temperature rise you see in the full design. Alternatively, if you are more interested in the final core losses as a target, follow our guidance below as a starting point.
How to Pick an Appropriate Core Loss Target
This can be quite a subjective value, but the aim here is to give you a little guidance and a starting point. As a rule of thumb, your magnetic can be expected to account for up to 1/6th of your converter’s total losses.
If you have in mind an efficiency for your converter then that’s great, you have a starting point. From our observations through experimentation and online literature, a guiding target for your converter efficiency may be derived from the graph below.
Where:
Total Converter Efficiency, Total Transformer Efficiency, Percentage of Transformer losses to total converter.
From here you can calculate a starting point for your magnetic loss:
Magnetic Loss = (Input Power * (1- Total Converter Efficiency)) * Percentage of Transformer losses to total converter
Input Power is the amount you specified on the Waveform Page and in the graph above, the x-axis.
From here you have a choice to make about the ratio of core to copper losses, this can be highly dependent on your application, topology, and your overall design priorities.
If you are unsure, start with a 50/50 split. You can always quickly adapt to different scenarios once you get more familiar with the tool and your design.
So, to get an initial Core Loss Target value take your Magnetic Loss calculated above and divide it by 2.
What Core Material Should I Pick?
Manufacturers often give recommendations on the frequency ranges of their materials. These recommendations will consider the relationship between frequency and core losses.
For guidance, please see the table below with some recommendations. Remember, these are not definitive as the proof is always in the outcome, we are supplying you with this information as a little help to kickstart your Core Optimizer™ experience.
Material |
Fmin (kHz) |
Fmax (kHz) |
3C90 |
10 |
200 |
3C91 |
10 |
300 |
3C92 |
10 |
200 |
3C92A |
10 |
200 |
3C94 |
10 |
300 |
3C95 |
100 |
500 |
3C95A |
100 |
500 |
3C95F |
200 |
500 |
3C96 |
200 |
400 |
3C97 |
100 |
500 |
3C98 |
200 |
400 |
3C99 |
10 |
300 |
3F4 |
1000 |
2000 |
3F36 |
500 |
1000 |
3F46 |
1000 |
3000 |
N27 |
25 |
150 |
N41 |
25 |
150 |
N49 |
300 |
1000 |
N51 |
25 |
150 |
N72 |
25 |
300 |
N87 |
25 |
500 |
N88 |
25 |
500 |
N92 |
25 |
500 |
N95 |
25 |
500 |
N97 |
25 |
500 |
PC47 |
25 |
500 |
PC200 |
700 |
4000 |
Core Losses
The core losses are a bulk term used to include the losses due to the different effects happening inside a ferromagnetic core when an alternating magnetic field runs through it. In the literature these effects are usually listed as three: hysteresis losses, eddy current losses, and excess eddy current losses.
When a magnetic field (H field) is applied to a ferromagnetic material, some of its grains change the orientation and align themselves to the applied field, creating a magnetic flux inside the material. If the magnetic field strength is increased, more grains will align with the direction of the field, incrementing the magnetic flux. This conversion ratio is called the material permeability, and it is not constant: as the magnetic field increases more and more, less and less grains are left to align, and the conversion gain, the permeability, decreases; until a point of saturation is reached in which a non-negligible increment of magnetic field strength produces a negligible increment in the magnetic flux.
If now, after applying a given magnetic field strength, we reverse the direction of the field, some of the already aligned grains will realign with the new direction, but less quantity than before for the same increment of field: some of the grains that were aligned for a given increasing value of H field, will remain unchanged for the same decreasing value of H field. If the H field is now decreased constantly, the ratio of alignment of grains, the permeability, will be similar to the previous iteration, but the net number of turns grains will be lesser than in the previous iteration for the same absolute H field value.
This process will repeat iteratively, and in each loop the number grains that were aligned as we got further from zero magnetic flux will be greater than the number align on the way back when the magnetic flux approaches zero; producing a hysteresis effect and drawing a closed loop, if we were to draw a graph with the magnetic field strength on one axis and the magnetic flux on the other axis.
This extra energy needed to align the extra grains on the way back to zero is lost in material resistance and dissipated as heat. The total amount of energy can be obtained by calculating the area surrounded by the hysteresis loop and is fundamentally independent of the frequency of the field switching; although for some materials the permeability might be influenced by this switching frequency.
Finally, the losses due to hysteresis effect can be obtained by integrating the product of the energy and the frequency over the whole volume of the magnetic material subjected to the magnetic field.
A side effect of the magnetic field circulating through the magnetic material is that, due to the fact that the magnetic materials do not have an infinite resistivity, electrical eddy currents will be induced along the core volume. The boundaries between the grains that realize the ferromagnetic material have a capacitance effect, so at low switching frequencies these induced eddy currents will circulate only inside the grains, which restricts the losses produced by them (eddy current losses are proportional to the area in which they circulate). These losses inside the grains are called excess eddy current losses, and are heavily dependent on the grain size of the ferromagnetic material, its resistivity, and the switching frequency.
As we increase the switching frequency of the magnetic field, the frequency of the induced eddy currents also increases, and the capacitance effects of the grain boundaries start preventing their circulation. Longer eddy currents start appearing through the whole dimension of the magnetic core, ignoring the grains, and generating increasing resistance losses, and therefore heat. These losses are called bulk eddy current losses, or just eddy current losses, and depend heavily on the cross section of the magnetic core, the frequency, and the resistivity of the material. The problem with the latter is that, for ferromagnetic cores, the resistivity is not a fixed value depending only on the temperature (as happens for diamagnetic materials, e.g., copper) but its resistivity depends also on the frequency and magnetic flux in the material, making it really difficult to properly estimate.
The total sum of these losses is what is generally called core losses, though as has been explained it includes really different effects. In order to make an estimation of these total losses, Charles Proteus Steinmetz, in the 19th century, proposed an analytical equation that consists of an exponential curve fit to empirical data measured for each material, resulting in a series of power coefficients that scale the effects of the magnetic flux density, frequency and temperature in total core losses, abstracting them from the physical effects and just using measured data.
The biggest problem with Steinmetz approach is that these measurements and curve fits are usually done in small cores, where the eddy currents are negligible. But as the core sizes grow, the eddy currents losses start gaining a weight that Steinmetz’s model cannot predict.
Steinmetz developed his equation for the then only existing sinusoidal magnetic field, but as electronics developed, the magnetizing currents, and therefore the magnetic fields and fluxes, became triangular in nature, with varying duty cycles.
To account for the effect of these triangular waveforms, many models derived from Steinmetz were proposed, being the most extended the Improved Generalized Steinmetz Equation (iGSE) [1]. This method tries to break down the magnetic flux waveform into small chunks, and then scaling with the switching frequency, which highly improves the accuracy for non-sinusoidal waveforms.
The current analytical model implemented in our platform is the iGSE with a very fine resolution, although other models are being implemented that take into account the losses of both eddy currents [2].
Additionally, these models are used to generate a dataset, that, by being mixed and trained with the measured data taken in our laboratory by means of the TPT method [3], produces an AI model able to improve any analytical data. Refer to the leakage inductance section for more information.
[1] K. Venkatachalam, C. R. Sullivan, T. Abdallah and H. Tacca, "Accurate prediction of ferrite core loss with non-sinusoidal waveforms using only Steinmetz parameters," 2002 IEEE Workshop on Computers in Power Electronics, 2002. Proceedings., 2002, pp. 36-41, doi: 10.1109/CIPE.2002.1196712.).
[2] W. A. Roshen, "A Practical, Accurate and Very General Core Loss Model for Nonsinusoidal Waveforms," in IEEE Transactions on Power Electronics, vol. 22, no. 1, pp. 30-40, Jan. 2007, doi: 10.1109/TPEL.2006.886608.
[3] Triple Pulse Test (TPT) for Characterizing Power Loss in Magnetic Components in Analogous to Double Pulse Test (DPT) for Power Electronics Devices," IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society, 2020, pp. 4717-4724, doi: 10.1109/IECON43393.2020.9255039.
Fringing Effect Losses
The fringing effect is a phenomenon in which the magnetic field circulating inside a magnetic core is deformed when it reaches a discontinuity in the material, which usually results from the insertion of air gaps along the magnetic path,
This deformation is represented as a swollen volume which increments the stores energy in the air gap, and it provokes an increment in the magnetizing inductance due to this extra energy storage.
More accurately, this discontinuity provokes a leakage of part of the H field circulating through the magnetic core, with the whole gap creating a residual H field that expands to the whole winding window and whose strength is inversely proportional to the distance from the source, the air gap.
This H field, which can be quite strong in the vicinity of the gap, when it crosses a conductive volume, induces eddy currents at the switching frequency of the magnetic field, proportional to the perpendicular conductive area, which in turn generates ohmic losses and heat in the conductive materials.
In a magnetic component, these conductive materials near the air gap are usually the wires of the windings, which will have increased winding losses in all the turns, although for turns that are not close to the air gap these losses will be negligible. There are several rules of thumb in the literature about the distance for which the losses start to be negligible, but the reality is that this distance depends on the strength of the H field inside the core (which in turn depends on the number of turns and the current through them), the gap length and the relative orientation of the wires in respect to the air gap
The calculations of these effect are done following the model proposed by Waseem Roshen [1]. In his paper, Roshen derives the magnetic field horizontal and vertical component produced by the air gap in each point of the window, and then applies Snelling's eddy-current losses formula [2] to calculate the induced power losses in each conductor based on its coordinates inside the winding window. The author expands his work to round conductors in a posterior paper [3]
[1] (W. A. Roshen, "Fringing Field Formulas and Winding Loss Due to an Air Gap," in IEEE Transactions on Magnetics, vol. 43, no. 8, pp. 3387-3394, Aug. 2007, doi: 10.1109/TMAG.2007.898908.).
[2] E. C. Snelling, Soft Ferrites: Properties and Applications, U.K., London:Butterworth, 1988.
[3] W. A. Roshen, "High-Frequency Fringing Fields Loss in Thick Rectangular and Round Wire Windings," in IEEE Transactions on Magnetics, vol. 44, no. 10, pp. 2396-2401, Oct. 2008, doi: 10.1109/TMAG.2008.2002302.
Leakage Inductance with AI
The leakage inductance is a measure of how many magnetic flux lines are not coupled due to the imperfect coupling existing between two windings. It appears as an inductance in series with the magnetizing inductance, and it is proportional to the total inductance and inversely to the square of the coupling factor between the coupled windings, which depends uniquely on geometric factors (e.g., the level of interleaving or the isolation between the windings).
As generally it is difficult to calculate the coupling between two given windings, the classical methods for calculating the leakage inductance rely on calculating the energy stored in the virtual series inductance and equating it to the energy stored due to the present H field in the interstices between the wires.
In order to obtain this energy, the H field is calculated horizontally along the concentric layers [1, 2], and vertically between different windows (in the case of top-down designs) of a winding window [2]. This H field distribution generates a storage of energy that depends on the relative permeability of the interstitial material, which usually is air or insulation.
A special case is considered regarding the Litz wires, which in reality is comprised of tens, hundreds or thousands of individual strands, isolated between them, so there is a large quantity of energy stored in this insulation. Additionally, not all strands have the same coupling factor from a given source. These two effects must be taken into account in order to properly obtain the leakage inductance for a Litz wire.
A proprietary model for leakage inductance has been derived from the aforementioned principles. This implementation alone can provide leakage inductance values that are on par with those calculated with 3D Finite Elements Analysis, in a thousandth of the time.
To be able to improve these results, an AI-based data architecture was developed. From the introduced model we sampled values varying all the affecting geometrical parameters (number of turns, number of parallels, core shapes, wires, etc.) and created a dataset of analytical values. This dataset is them mixed together with another dataset of measurements taken in our Laboratory in Madrid (Spain), sampling the same input parameters and obtaining its measured leakage inductance.
The mixed dataset is given different weights, depending on the provenance (measured data is much more important than calculated data) and a Machine Learning model is trained, which is able to incorporate the principles and tendencies of the analytical data and correct the model’s shortcoming with real measured data.
This full data architecture is completely parameter-agnostic (it can be used for calculating other parameters, like the core or winding losses) and it will be presented in "Improved Prediction of a Transformer Design using Machine Learning alongside Analytical Methods" in EPE'22.
Additionally, the leakage inductance measurements are done following a new holistic method that will also be presented in Epe’22, as "Transformer inductances: rationale and experimental determination"
[1] Z. Ouyang, J. Zhang and W. G. Hurley, "Calculation of Leakage Inductance for High-Frequency Transformers," in IEEE Transactions on Power Electronics, vol. 30, no. 10, pp. 5769-5775, Oct. 2015, doi: 10.1109/TPEL.2014.2382175.
[2] M. S. Sanjari Nia, P. Shamsi and M. Ferdowsi, "Investigation of Various Transformer Topologies for HF Isolation Applications," in IEEE Transactions on Plasma Science, vol. 48, no. 2, pp. 512-521, Feb. 2020, doi: 10.1109/TPS.2020.2967412.
Magnetizing Inductance
The inductance of a magnetic is a parameter that depends on the total reluctance of the magnetic core, and the number of turns wound around it. As the number of turns is usually a known value, this documentation will focus on the calculation of the reluctance of the magnetic core.
The reluctance of a magnetic circuit is a measure of how reluctant the magnetic flux lines are to circulate through a volume, equivalently to the resistance for electricity. The higher the reluctance of a volume compared to its surroundings; the smaller number of magnetic flux lines will go through that volume.
The total reluctance of most magnetic components is calculated by the series connection of the reluctance of the magnetic core with the reluctance of the air gap(s). The reluctance for more complex magnetic components, like coupled inductors or mergences, can be obtained by applying circuit solving methods to the magnetic circuit, but they are out of the scope of this article.
The reluctance of the magnetic core depends on its geometrical parameters, especially the length and the cross-sectional area, and on the relative permeability of the material; while the reluctance of an air gap depends on the perimeter and shape of the magnetic core that defines the gap, the gap length, and the distance to the closest perpendicular surface of the core (in most cases this is equal to half the height of the winding window).
For both reluctance calculations it is vital to use the correct geometrical values of each shape. It is a common mistake to use the effective area of the magnetic core to calculate the reluctance of the air gap in a central column, when the geometric area should be used. This is especially important when modelling a gap in all the legs of the core, because, except the case of common Es and Us, the lateral legs perimeters and areas are completely unrelated with their counter values in the central column. The different lengths and areas of each magnetic shape are calculated according to EN 60205.
As mentioned above, the permeability of the magnetic material es vital in order to calculate the reluctance of the ungapped core. This permeability has a dependence on the working temperature, switching frequency and DC bias of the magnetizing current. To obtain it we use a simple multidimensional interpolation from data measured with a Power Choke Tester DPG10 B. This interpolation is used iteratively in design loop, in order to ascertain that the correct permeability is used at each operation point, as the permeability can change the operation point itself.
Continuing with the other reluctance of our magnetic circuit, in order to obtain the reluctance of the air gap, we use the model proposed by Zhang [1]. He proposes that the reluctance of the gap can be calculated by transforming the air-gap fringing magnetic field into a current source that produces the equivalent magnetic field, which can be easily solved and calculated. Alternatively, other air gap reluctance models [2, 3, 4] were implemented and evaluated for both cases, gap in the central column and gaps in all legs, but Zhang's model was found to have the lowest error when compared with our measured validation data.
Finally, to obtain the final reluctance of our magnetic core, we add the reluctance of the core together with the reluctance of the air gap(s), for the case of the gap existing only in the central column. For the case of gaps in all legs, as is common in prototyping by using spacers, to the previous addition must be added the parallel calculation of the reluctance in the lateral legs, as the magnetic flux divides and runs in parallel for any lateral legs
[1] X. Zhang, F. Xiao, R. Wang, X. Fan and H. Wang, "Improved Calculation Method for Inductance Value of the Air-Gap Inductor," 2020 IEEE 1st China International Youth Conference on Electrical Engineering (CIYCEE), 2020, pp. 1-6, doi: 10.1109/CIYCEE49808.2020.9332553.). The other evaluated models were:
[2] J. Muhlethaler, J. W. Kolar and A. Ecklebe, "A novel approach for 3d air gap reluctance calculations," 8th International Conference on Power Electronics - ECCE Asia, 2011, pp. 446-452, doi: 10.1109/ICPE.2011.5944575.
[3] E. Stenglein and M. Albach, "The reluctance of large air gaps in ferrite cores," 2016 18th European Conference on Power Electronics and Applications (EPE'16 ECCE Europe), 2016, pp. 1-8, doi: 10.1109/EPE.2016.7695271.
[4] McLyman C. Transformer and inductor design handbook (Fourth ed.), CRC Press (2011)
Winding Losses
The calculation of winding losses is done using an algorithm that takes in the current waveform and spits out the total losses.
The first step is to detect and define the conduction modes inside one period: for example, in a flyback we will have two conduction modes: when only the primary is conducting, where we will have skin and proximity losses on the primary, but only proximity losses on the secondaries; and when only the secondaries are conducting, where we will have skin and proximity losses on the secondaries, but only proximity losses on the primary.
As the existing models and equations are developed for sinusoidal waveforms, we must break down the corresponding waveform and extract its harmonics using a Discrete Fourier Transform. With these harmonics we are now able to apply the models to calculate the losses for each harmonic, adding them in the end to have the total losses.
Depending on the magnetic configuration we use different models to calculate the harmonic losses, including DC, skin, external and internal proximity losses:
- Wojda’s model [1] in the case winding windows with only one winding on them (e.g., inductors or top-down transformers) made of solid sound, foil or Litz wires, as it is derived from Dowell’s and Ferreira’s work and has good accuracy with non-interleaved windings.
- Albach’s model [2] in the case of winding windows with more than one winding on them (e.g,, interleaved transformer). Albach’s model is able to calculate the H field distribution along the radial component for any combination of layers, even with different windings and currents, making it ideal for interleaved designs.
- Alternatively to Wojda’s model, we use Payne’s model [3] for edge-wound inductors, as he has empirically investigated the losses mechanisms in this kind of windings.
Once the losses of each harmonic and conducting mode has been calculated, we add them up together to obtain the ditribution of total losses.
Finally, once we have the total losses, the AC resistance is obtained by calculating the equivalent resistance that, for our primary RMS current, would give us the total losses obtained before.
[1] R. P. Wojda and M. K. Kazimierczuk, "Winding Resistance and Power Loss of Inductors With Litz and Solid-Round Wires," in IEEE Transactions on Industry Applications, vol. 54, no. 4, pp. 3548- 3557, July-Aug. 2018, doi: 10.1109/TIA.2018.2821647.
[2] M. Albach, "Two-dimensional calculation of winding losses in transformers," 2000 IEEE 31st Annual Power Electronics Specialists Conference. Conference Proceedings (Cat. No.00CH37018), 2000, pp. 1639-1644 vol.3, doi: 10.1109/PESC.2000.880550. It presents a calculation of the winding losses based on the field distribution in the winding area, with which the skin and proximity losses in each turn are analytically calculated.
[3] Payne, Alan 2021/05/04 - THE AC RESISTANCE OF RECTANGULAR CONDUCTORS