Coupled Magnetic Field-Circuit Analysis of Inductive Power Transfer in High-Potential Transformers

Abstract

Inductive Power Transfer grew to be a hot topic as reflected by monographs and thousands of papers published mainly last decade. We complement the bulk of research by harnessing power of coupled magnetic field-circuit simulations on examples of virtually air-core high-potential transformers. Circuit analysis, on the base of simplified equivalent circuits is performed. A comparison is made to Tesla transformer. Major impediment here is modeling ferromagnetic parts of the system. Thus, circuit analysis is mostly helpful for a qualitative grasp of the problem. The design is greatly simplified by coupling the magnetic field of the transformer to external circuitry. We do it on a COMSOL platform. Sweeping number of turns, height of the windings, values of resonant capacitors, etc., we can arrive to an optimal design point. Most of the simulations were done in frequency domain. Following this procedure, we built and extensively characterized several 20-kV, 1-kW transformers with high-potential insulation sized to 150 kV in a wide range of switching frequencies centered around 50 kHz. A transformer of choice was tested at high voltage (HV) and nominal power in ambient air. The transformer efficiency was >92 %, with largest overheat of 50° C being on the primary.