ANSYS Maxwell: Wireless Charging Systems with Permanent Magnets
In this video, we explore a workflow for modeling and characterizing wireless charging coils using permanent magnets. The models are created and simulated in ANSYS Maxwell. Permanent magnets are utilized in both receiver and transmitter coils to maintain alignment.
Material Consideration
We use the TDK ferrite core material as an example. The relative permeability of this ferrite material is not constant, which affects the self-inductance of the coil. The inclusion of a permanent magnet introduces a constant magnetic field inside the ferrite, altering its operating point. Improper simulation or design can lead to saturation of the ferrite, reducing efficiency and increasing the magnetic energy (ME) of the system.
Methods for Accurate Results
There are two primary methods to achieve accurate results:
-
Linking Eddy Current Solver and Magnetostatic Solver
- Link the eddy current solver to the magnetostatic solver to obtain the operating point and permeability of the nonlinear ferrous material.
- Derive losses and impedances using the eddy current solver.
- In the magnetostatic solver, consider only fields generated by permanent magnets by solving with zero excitation current.
- Copy the completed model to create another model and select the Eddy Current Solver in ANSYS Maxwell 3D Solution Type.
- Add a solution setup, check "Use Precomputed Permeability Data," and click "Setup link."
- Select the correct source design and source solution, then analyze the model and check the results.
-
Using Eddy Current Solver with DC Fields
- Select the eddy current solver and ensure the "include DC field" box is checked (available in version 2025 R1 and later).
- No need to link to the magnetostatic solver.
- Run the simulation and check the results.
Additional Models
We also demonstrate two additional models:
- Model 3: Uses the eddy current solver only, without linking or including DC fields. The magnetic fields from the magnets are not captured.
- Model 4: A magnetostatic model that captures only DC fields, not the AC excitations from the coils.
Comparison of Results
Here is a comparison of the results from the four different models:
- Models 1 and 2: Correctly consider both AC and DC excitations.
- Model 3: Considers only AC excitations.
- Model 4: Considers only DC excitations.
The results from Models 3 and 4 are not accurate enough.
Conclusion
This concludes the demonstration. For more information, please contact us at Ozen Engineering, Inc..
In this video, one of the possible workflows for modeling and characterizing wireless charging coils with permanent magnets is presented. The models are created and simulated in ANSYS Maxwell. Permanent magnets are used in receiver and transmitter coils to help coils stay aligned.
Here is one example of the TDK ferrite core material. As you can see, the relative permeability of the ferrite material is not constant. This permeability will affect the self-inductance and the coil.
The use of the permanent magnet will introduce a constant magnetic field inside the ferrite that will change the operating point of the ferrite.
If it is not simulated or designed properly, the combination of magnetic fields of the permanent magnet and excitation current can saturate the ferrite and reduce the efficiency and increase the ME of the overall system. There are two ways to get the correct results.
The first way is to link the eddy current solver and magnetostatic solver.
By linking the eddy current solver to the magnetostatic solver, we can obtain the operating point and permeability of the nonlinear ferrous material calculated by the magnetostatic solver and derive the losses and impedances using the eddy current solver.
This is the source model using the magnetostatic solver. To accurately link the operating point, it is important to only consider the fields generated by permanent magnets in the magnetostatic solver. That is why the linked magnetostatic design is solved with zero excitation current.
After the model is completed, we can copy and paste it to create another model. Then we need to go to the ANSYS Maxwell 3D Solution Type to select the Eddy Current Solver. After that, we need to add a solution setup.
Then go to the Solver, check "Use Precomputed Permeability Data," and click "Setup link." Then we just need to check "Use This Project" and select the correct source design and source solution. Check these two boxes as well. The final step is to analyze the model and check the results.
The second way is to use the eddy current solver only but include DC fields. When we select the solver, make sure to check the box "include DC field." This option is available in version 2025 R1 and after. Then we do not need to link it to the magnetostatic solver anymore.
Then we can run it and check the results. Here is a third model that I'm going to show, a model with the eddy current solver only. No model is linked to it, and the "include DC field" box is not checked. So, the field from the magnets will not be captured.
The last model here is the magnetostatic model, which means it only captures DC fields but not the AC excitations from the coils. Here is a comparison of the results from the four different models. Models 1 and 2 are the correct ones as they considered both AC and DC excitations.
Model 3 only considered AC excitations, while model 4 only considered DC excitations. The results from models 3 and 4 are not accurate enough. This concludes this demo. Please contact us at https://ozeninc.com/contact for more information.
