Configurable Nanocrystalline Flake Ribbon Transformer with Variable Leakage Inductance

Leakage inductance adjustment is vital for optimizing the performance of magnetically integrated dual-active-bridge (DAB) converter. This paper proposes a slidable structure to change the leakage inductance of the toroidal transformer, which will not introduce any extra windings or cores and is comparatively simple. By rotating the secondary winding slider in the transformer's core, the distance between the primary and secondary windings is changed, and thus the leakage inductance can be modified seamlessly. The leakage inductance varies sinusoidally with the rotation angle and linearly over a significant region. To verify the proposed transformer structure, a DAB prototype adopting the nanocrystalline flake ribbon (NFR) core is built. The leakage inductance can be adjusted from 13.63 μH to 41.89 μH, corresponding to a 67.3% change. The suitable leakage inductance for the optimal performance of DAB is found to be between 15.29 μH to 26 μH for full load and 30.47 μH for half load, ensuring high efficiency and low current stress. © 2025 IEEE.