Parametric Design of Magnetics for Modern Power Electronics Applications

  • Kapila Warnakulasuriya

    Student thesis: Doctoral Thesis

    Abstract

    Magnetic components in a power conversion system or in any power electronics application
    are responsible for a major part of the volume, weight, and the cost of the systems that they
    are built in to. It is believed that the size of magnetic components and thereby the cost and the
    size of power electronics systems can be reduced by the increase of operating frequency.
    Achieving low switching losses of the semiconductor devices and realizing magnetic
    components that can operate at high frequencies at high power levels have been identified as
    the two major challenges.
    This research aims to provide a complete set of “parametric solutions” of magnetics for a
    particular application that enables holistic optimization of power electronics systems. At the
    start of the research providing a single solution for the power levels and frequency was a not
    possible. Design variables considered in this study include conductor losses, which included
    the study of skin effect, proximity effect in different constructor geometries, assemblies and
    types, core losses in different core geometries, materials and constructions, thermal
    management of the magnetic components including efficient extraction of heat generated,
    impacts of inductance, leakage inductance, and losses.
    The practical solutions derived from the theoretical studies are evaluated in a number of
    constructions. Several winding configurations were developed which give the advantage of
    mitigating the conductor losses at high frequencies and high currents. This includes folded foil
    windings and transposed wound flat conductor windings which is demonstrated to reduce the
    conductor losses by a factor of >4.
    The effectiveness of different core materials for > 50 kW was evaluated. Suitability of certain
    ferrite grades and nanocrystalline grades were identified for different application areas. Even
    though the findings of the study made it possible achieve theoretically minimum loss levels the
    compactness achieved results in high-power densities making it difficult to have good thermal
    management. Novel methods for heat extraction are developed. These provided a drop in
    hotspot temperature by 10 to 25 degrees. These developments in all the key areas of a
    magnetic design and the provision of complete set of parametric solutions is presented in this
    thesis. The design of a 50kW transformer operating at 20kHz was a challenge before this this
    study. With the findings of this study now the design of even 2500 kW transformer is no longer
    a challenge. The outcome of the research has taken the magnetics industry to the position of
    a technology enabler rather than being a factor that acts as a barrier for the development of
    power electronics industry.
    Date of Award6 May 2022
    Original languageEnglish
    Awarding Institution
    • Teesside University
    SupervisorFarhad Nabhani (Supervisor), Simon N.B. Hodgson (Supervisor), David Hughes (Supervisor), Maher Al-Greer (Supervisor) & Nashwan Dawood (Supervisor)

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