The student Asier Arruti Romero obtained an EXCELLENT CUM LAUDE grade with mention International Doctorate
The student Asier Arruti Romero obtained an EXCELLENT CUM LAUDE grade with mention International Doctorate
The student Asier Arruti Romero obtained an EXCELLENT CUM LAUDE grade with mention International Doctorate
- Thesis title: Modelling of magnetic devices for high frequency power converters
Court:
- Presidency: Gerard Hurley (National University of Ireland)
- Vocal: Ziwei Ouyang (Technical University of Denmark (DTU)
- Vocal: Guillaume Lefèvre (Mitsubishi Electric R&D Centre Europe)
- Vocal: Carlos Bernal Ruiz (Universidad de Zaragoza)
- Secretary:Jon Anzola Garcia (Mondragon Unibertsitatea)
Abstract:
Magnetic devices are becoming the bottleneck element in many high frequency power converter designs. Although fast switching low resistance power transistors are readily available, due to increased losses and limited heat dissipation capabilities, the design of magnetic devices becomes a challenging task. To enhance the performance of these power converters, both in efficiency and power density, overall improvements to the magnetic devices are needed, which is the aim of this PhD thesis, focusing on the power loss aspect.
The design laws of magnetic devices are first analysed to better understand the influence of several phenomena in the design space. This analysis begins from classical low frequency design approaches, and afterwards the high frequency effects in the winding and core losses are introduced to illustrate their impact. The effect of other potential factors regarding the design of high frequency high performance applications is also discussed. Since the losses of these devices comes from two sources, the core and winding losses, these are studied separately. For the core losses, first a literature review of the existing approaches is presented, pointing out the merits and limitations of the different models. Based on this study, and using extensive experimental core loss data, an improved model is presented, which has been demonstrated to work better than the preexisting solutions in a wide range of frequencies, flux densities, waveforms and materials. With the insights provided by this model, intuitive explanations for the complex temperature dependencies, relaxation losses, and premagnetization can be made, allowing to easily integrate these effects in the model. Similarly, for the winding losses first a study of the existing methods is done, limited to one dimension-based models. Focusing on Litz wires, the existing models and a newly proposed approach are compared against finite element simulations, demonstrating how the new model is capable to more accurately depict the high frequency behaviour of the windings. A magnetic device characterization testbench is designed and used to obtain experimental data. The experimental results further demonstrate the advantages of the proposed core loss model.
The new models and insights presented in this PhD thesis allow for a better understanding of the losses of magnetic devices, enabling to further optimize the devices and improve the overall performance of high frequency power converters. The parameters utilized in this PhD thesis are accordingly tabulated within the document, so that this document can serve as a valuable resource for magnetic device designers.