The requirements in integration the field of power electronics have been orientated for many years into two axis: one by increasing the power densities and another by the volume reduction of active and passive components. The fast development of the monolithic integration of active components shows the important role of the integration of passive components, especially for inductive components for medium and high power applications.
A strategy to reduce the volume of magnetic components is based on the design of interlaced structures. The key point of the interlaced structures is to reduce the size of magnetic components to share the magnetic flux between different phases of the converter. This component is built from many switching cells using a magnetic core with a specific shape and often extremely complex. The work performed in this thesis concerns the development of technologies for the production of ICT (Intercellular Current Transformer), in order to carry out their integration into multilevel converters.
This work presents a general approach for obtaining complex shapes required for the development of new architectures of multilevel magnetic core.
We aimed medium power range applications hat could benefit from the ICT structures, typically using high frequency wideband gap devices as GaN. Firstly, the magnetic and dielectric properties of the material allowed us to chose a ferrite material of Ni0,30Zn0,57Cu0,15Fe2O4. Various processing methods and parameters were studied, such as: the form of the flexible mold, pressing technique and pressures, time and temperature of sintering, and particularly machining method. Two machining systems allow us to perform complex forms for magnetic cores. The fist system using a diamond wire saw, allowed for 2D machining. 3D machining is also possible trough a numerical milling equipment.
The properties of the Ni-Zn-Cu material and the complete process based on isostatic pressing pressure integrated to a green machining can achieve complex shapes required for the next generation of multicellular converters. |
Current needs in power electronics concern mainly the reliability and the increase in the power density. In both cases, what is called power of integration is proposed as the solution. Reliability issues can be solved by reducing the number of interconnections and by the full design and elaboration of converters; and those related to the power density are addressed by reducing the dimensions and the mutualization of a number of functions: integration of passive components, embedded substrates, coupling components ....
This necessarily involves the choice of a strategy for converting structures. Multilevel converters, interleaved multicellular are an example of structures that reduce the size and volume of magnetic components.
The key point of these structures is the sharing of magnetic flux between the different phases of the converter via an intercellular transformer (ICT). This type of component allows interleaving many switching cells. It consists of a magnetic core of specific shape and often complex.
The work done in this thesis concerns the development of technologies for the realization of ICT type of magnetic components for their integration.
The main material properties (magnetic and dielectric) necessary for the implementation of this type of component oriented us towards a ferrite Ni0,30Zn0,57Cu0,15Fe2O4 able to work at the proposed operating frequencies and power range.
Various elaboration processes (and the parameters associated with them) were studied. It is either forming, through the use of flexible molds or by isostatic pressing, and machining either raw or after sintering. By machining, two separate systems have enabled us obtaining complex magnetic cores either in 2D or in 3D.
The results of this approach in terms of object and component properties are presented. The influence of various parameters used during the production (sintering temperature, pressure, ...) on the final characteristics is also investigated. |