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Design of Variable Air-Core Coupled Co-axial Solenoidal Inductors

Variable inductors find their application in many power electronics circuits. This paper discusses the design and prototype of an air-core coupled co-axial solenoidal inductor as a variable inductor. Analytical modeling and FEA simulations are used to design and optimize a coupled solenoidal variable inductor with a maximum inductance of 18.4 µH at 2 MHz. It is observed that the quality factor of a coupled variable inductor is a function of coupling between the inner and outer windings. It is shown that the quality factor of the variable inductor can be increased by 20% by following the proposed optimization. An experimental inductor prototype is built using 3-D printed support and Litz wire. It is observed that the experimental results closely match the simulation ones.