| Summary: | This thesis aims to explore innovative methodologies for developing compact high-voltage power supplies tailored for industrial magnetrons with a power rating exceeding 100 kW (RF power). Through a comprehensive review of magnetron load characteristics and existing power supply technologies, the proposed converter aims to achieve size reduction by increasing the operating frequency to 100 kHz. Compared to state of art 20 kHz designs, this has the potential to reduce the magnetic component size by 80%.
The research reviews recent advancements in semiconductor and magnetic materials, particularly focusing on silicon carbide (SiC) semiconductors and nanocrystalline magnetic materials. Utilising these technologies, the proposed converter achieves a fivefold increase in operating frequency compared to state-of-the-art designs while maintaining high efficiency.
Based on the magnetron load requirements and the emerging technologies, a novel converter architecture based on a multi-cell interleaved Single Active Bridge (SAB) is proposed. This architecture enables the assembly of high-power, high-voltage converters using relatively low-power, low-voltage components. The use of SiC devices at high frequencies without resonant topologies overcomes many of the issues with existing resonant approaches. Analytical modelling and simulation studies are conducted to validate the proposed concept, alongside the design of associated control strategies.
Furthermore, an optimisation algorithm is developed to aid in transformer design, which is then applied to both ferrite and nanocrystalline transformers. Experimental validation of the transformers is performed to confirm the effectiveness of the algorithm.
A scaled lab prototype converter is constructed for experimental testing, showing a good correlation between simulation and experimental results. The basic concept of the converter is validated. Solutions to issues that emerged during testing, such as cell imbalance and circulating currents, are proposed, implemented, and verified, ensuring the robustness of the proposed converter design.
The unique contributions of this thesis are:
1. Proposed a new multi-cell SAB converter to use for the next generation magnetron power supply.
2. Proposed a unique transformer optimisation routine to aid the design with various core shapes.
3. Proposed methods to compensate for cell imbalance issues and high frequency circulating current issues in the multi-cell converters.
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