AbstractMagnetic 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 Award||6 May 2022|
|Supervisor||Farhad Nabhani (Supervisor), Simon N.B. Hodgson (Supervisor), David Hughes (Supervisor), Maher Al-Greer (Supervisor) & Nashwan Dawood (Supervisor)|