As wireless power transfer (WPT) systems evolve in sophistication and ubiquity—from smartphones to electric vehicles—precision in modeling magnetic interactions becomes more critical than ever. One area gaining traction is the integration of permanent magnets for coil alignment and improved efficiency. However, their nonlinear impact on ferrite materials presents simulation challenges. This blog explores a practical workflow using ANSYS Maxwell.
Permanent magnets provide a passive method to stabilize receiver coil positioning. This boosts performance consistency and minimizes misalignment losses. Yet these benefits come with trade-offs: the permanent magnets can saturate the ferrite on the back of the coils and impact the efficiency of the wireless charging.
Ferrite material TDK_PC47 is a common material in WPT devices. The relative permeability of the material is not constant (shown below) and depending on its operating point can be anywhere between 1 and 20000. The use of permanent magnet will introduce a constant magnetic field (H) inside the ferrite material that will change the operating point of the ferrite.
This blog outlines two distinct simulation workflows using ANSYS Maxwell.
Approach #1: linked solvers (Magnetostatic + Eddy Current solvers)
This approach requires two models to be created and linked together: one magnetostatic model to solve the DC fields from permanent magnets and another eddy current model to solve the AC fields from the coils.
Step 1: The complete model is created in ANSYS Maxwell. It includes TX coil/ferrite, RX coil/ferrite and TX/RX magnets.
Step 2: select the Magnetostatic solver to solve the DC magnetic fields from permanent magnets. Make sure the current in the Excitation is zero as we are only modeling the magnets.
Step 3: create another model which will use the eddy current solver. This can be done by copying and pasting the Magnetostatic model.
The solver needs to be changed to Eddy Current. Since the AC field from the coil will be modeled, the windings need to be modified (assign # of conductors and current).
Step 4: link the two models together and solve the model.
This can be done by adding a solution setup in the Eddy Current model.
Approach #2: use the Eddy Current solver and Include DC Fields
This option is available starting from version 2025R1. With the "Include DC Fields" enabled, users do not need to create two separate models and link them together anymore.
Now, both the DC and AC fields can be solved with one single model which simplifies the modeling process.
The modeled relative permeabilities from 4 different approaches are compared below.
The results from #1 and #2 are very close and both results are correct. The results from #3 and #4 are not accurate enough as the models only considered either AC fields or DC fields.
Approach #1: Magnetostatic solver linked with Eddy Current solver
Approach #2: Eddy Current solver only (include DC Fields)
Approach #3: Eddy Current solver standalone (without including DC Fields)
Approach #4: Magnetostatic solver standalone
The video below walks through these steps in detail.
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