Developments for the high frequency power transformer design and implementation

The thesis considers design and manufacturing of ferrite based high frequency power transformers. The primary aim of the work was to study core and winding losses and in particular thermal modeling of high frequency power transformers and to determine appropriate loss and temperature rise modeling methods for power converter applications. The secondary aim of the work was to study improved, mass manufacturable winding methods for toroidal, tube-type planar and disc-type planar high frequency power transformers. The analytical high frequency power transformer design equations for core and winding losses and transformer temperature rise were reviewed from literature, formulated for spreadsheet type calculations using excitation, material, geometry and winding implementation parameters and validated by in circuit temperature rise comparisons between calculated and measured values using regression analysis. The core and winding loss calculation methods in literature were found to provide appropriate accuracy for the practical design purposes. Thermal test block tests suggested a slight modification for analytical convective heat transfer equation from the literature. The results from in circuit temperature rise comparisons suggest that the transformer total losses can be predicted with the average standard error below 0.2 W with datasheet type information only. Further, if conductive thermal resistance from transformer via printed circuit board substrate to ambient is available the transformer operating temperature could be predicted with appropriate accuracy (5.6 °C) as well. The new manufacturing methods developed for toroidal, tube and disc-type transformer geometries were proved to be suitable for high frequency operation. With a common mode choke with static shield and windings deposited and etched directly on the toroidal NiZn core a transfer loss resonant frequency above 1.2 GHz was achieved. A multilayer foil winding with interleaved primary and secondary layers resulted resulted leakage inductance of 10 % of the value achieved using a wire-wound winding. The new developments for Z-folded inductive components resulted material cost savings, reduction of winding resistance and adjustability of leakage inductance and winding capacitances.reviewe

Automated tool for 3D planar magnetic temperature modelling: application to EE and E/PLT core-based components

International audienceThermal performance of power converters is a key issue for the power integration. Temperatures inside active and passive devices can be determined using thermal models. Modelling the temperature distribution of high frequency magnetic components is quite complex due to diversity of their geometries and used materials. This paper presents a thermal modelling method based on lumped elements thermal network model, applied to planar magnetic components made of EE and E/PLT cores. The 3D model is automatically generated from the component's geometry. The computation enables to obtain 3D temperature distribution inside windings and core of planar transformers or inductors, in steady state or in transient case. The paper details the proposed modelling method as well as the automated tool including the problem definition and the solving process. The obtained temperature distributions are compared with Finite Element simulation results and measurements on different planar transformers

Robust snubberless soft-switching power converter using SiC power MOSFETs and bespoke thermal design

A number of harsh-environment high-reliability applications are undergoing substantial electrification. The converters operating in such systems need to be designed to meet both stringent performance and reliability requirements. Semiconductor devices are central elements of power converters and key enablers of performance and reliability. This paper focuses on a DC–DC converter for novel avionic applications and considers both new semiconductor technologies and the application of design techniques to ensure, at the same time, that robustness is maximized and stress levels minimized. In this respect close attention is paid to the thermal management and an approach for the heatsink design aided by finite element modelling is shown

Design, Simulation and Implementation of Three-Phase Bidirectional DC-DC Dual Active Bridge Converter Using SiC MOSFETs

The use of SiC-based martials in fabricating power semiconductor devices has shown more interest than conventional silicon-based. Its promising abilities to improve the performance of power electronic systems made it a valuable choice in building high power DC-DC converters. This thesis presents the design and implementation of a three-phase bidirectional DC-DC Dual Active Bridge using SiC MOSFETs. The proposed circuit is first built in Matlab for simulation analysis. Then a phase shift modulation controller is designed in Simulink to test the simulation circuit. The controls are then integrated through an FPGA to test the prototype. Simulations and experimental results are evaluated to demonstrate the functionality and performance of the proposed circuit

Input Parallel Output Series Structure of Planar Medium Frequency Transformers for 200 kW Power Converter: Model and Parameters Evaluation

Nowadays, the demand for high power converters for DC applications, such as renewable sources or ultra-fast chargers for electric vehicles, is constantly growing. Galvanic isolation is mandatory in most of these applications. In this context, the Solid State Transformer (SST) converter plays a fundamental role. The adoption of the Medium Frequency Transformers (MFT) guarantees galvanic isolation in addition to high performance in reduced size. In the present paper, a multi MFT structure is proposed as a solution to improve the power density and the modularity of the system. Starting from 20 kW planar transformer model, experimentally validated, a multi- transformer structure is analyzed. After an analytical treatment of the Input Parallel Output Series (IPOS) structure, an equivalent electrical model of a 200 kW IPOS (made by 10 MFTs) is introduced. The model is validated by experimental measurements and tests