**Appendix A**

In Figure A1, two example views of the ferrite core assembly are presented where the perpendicular and longitudinal parasitic air gaps can be observed up to about 0.5 mm. In each assembly, 4 randomly selected I-cores are aligned along a calliper on a flat surface. The I-cores are assembled tight together so that even if there is an air gap on the visible surface then there is somewhere a direct contact between the neighbour I-cores. In the 3-phase MFT core assembly, composed of tens of I-cores, the air gaps are even larger due to the cumulating I-core misalignments.

**Figure A1.** Two assemblies of 4 randomly selected 3C90 ferrite I-cores showing the perpendicular parasitic air gap and the longitudinal parasitic air gap measuring up to about 0.5 mm.

#### **Appendix B**

The core assemblies of the single-phase multi air gap MFTs are presented in Figure A2. The MAG4 has 4 and the MAG6 has 6 perpendicular parasitic air gaps along the magnetic flux path. The MAG4 is detailed in [58].

**Figure A2.** Single-phase multi air gap MFT core assembly: MFT4 with 4 air gaps (**left**) and MFT6 with 6 air gaps (**right**).

#### **References**


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