Miniature Planar Spiral Transformer With Hybrid, Ferrite, and Magnetic Nanofluid Core

This paper focuses on a novel, unconventional, hybrid, multi-layered, miniature planar, spiral transformer (MPST) aimed to equip the fly-back convertor for a photovoltaic (PV), energy harvesting (EH) module. The MPST converts the electric parameters (voltage and current) at which the primary "harvestings" stage provides energy to the secondary, conditioning, storage, and delivery stage of the module. The magnetic circuit of the MPST is hybrid, made of ferrite and a specially designed and produced magnetic nanofluid (MNF). Some considerations concerning the preparation and general characterization of the used MNF are included. Then, mathematical models and numerical simulation results that were used in the design phase of the MPST are presented. The electromagnetic field is analyzed for static, stationary, and harmonic working conditions, and the lumped, electric circuit parameters of the MPST are computed. The heat transfer analysis for steady-state conditions shows the good thermal stability of the MPST. Finally, some experiments conducted on the pulsewidth modulation-controlled MPST evidence a very good electric behavior of the dc/dc conversion stage of the PV, EH module.