Orthogonal Biasing Controllable Inductor using a Commercial Hollow Toroid Core

Controllable magnetic components using orthogonal biasing flux, contrary to the widely researched parallel biasing, offer minimal interaction with the main flux. However, it comes with substantial challenges due to core design constraints. Currently, mostly pot and UR cores are employed, resulting in large discrepancies with mathematical models. Subsequently, more current is required to control the inductance, generating higher losses. This paper analyses a commercial hollow toroid core for an orthogonally biased controllable inductor. A mathematical model is established, and Ansys-Maxwell FEA simulations are employed to analyse its behaviour and the impact of its uneven cross-sectional areas. The characterisation is validated in extensive simulations and an experimental setup, through both small- and large-signal characterisations. The prototype controllable inductor indicates a good match between the simulations and experimental results. Finally, an improved design is suggested to maximise the inductance variation, resulting in a better match with the model and lower losses.