Toroidal inductors are electronic components constructed from a wire coiled around a magnetic (iron) core. They have a wide range of applications including high frequency coils and transformers. Toroidal inductors can also be used for measurement of magnetic characteristics, as an alternative to the solenoid coil. This case study takes a high resolution scan of a toroidal inductor and builds a finite element mesh of the structure and surrounding air. High frequency magnetic simulations are performed to analyse the current and flux density, as well as distributions, through the inductor which cannot be observed directly. The simulation results are very useful for product verification and redesign, and it will help the development of high accuracy electromagnetic simulation.
The toroidal inductor was scanned using a TUX-3200 Tohken Co.,Ltd. CT x-ray inspection machine, at a resolution of 17µm. The images were imported into ScanIP where the core and wire segmented and reconstructed. In addition, the image was padded to generate an appropriate air boundary for the later analysis. The size of the air region was configured by considering the leakage flux. In cases where magnetic flux has wide leakage it is necessary to expand the air region sufficiently. The wire was then artificially extended to the boundary, through this added layer of air.
A smooth, high quality, conforming multipart volume mesh of the coil was created using the +FE module. Initially the default coarseness slider was used to achieve the required mesh resolution. After this, some parameters were manually adjusted to tune the mesh further. These included the maximum allowed mesh size, the internal change rate, and the number of elements across layers. This allowed meshes to be created ranging from around 100,000 to 1,000,000 elements.