Design and fabrication of magnetic cores having permeability gradient using additive manufacturing

As a major technological research institute, the CEA-Liten plays a decisive role in the development of future technologies for the energy transition and the limitation of greenhouse gas emissions. The laboratory develops magnetic components working at high frequency (> 100 kHz) for an integration in compact power electronics converters. Today, the discrete magnetic components are among the most bulky parts in the power converters (~30-40%) and they are responsible of almost 40-50% of the heat losses. The advent of wide band gap semiconductors (SiC or GaN) increases the switching frequency to values above 100 kHz. This strategy helps to reduce, theoretically, the dimensions of the passives but the thermal constraints (due to the losses produced at a higher frequency) and the electromagnetic compatibility (EMC; due to the noise emerging from faster switching commutations) may constitute an issue (in a system approach). In this sense, the developments of new architectures (based on advanced core geometries or clever magnetic materials arrangements) may constitute a breakthrough. The diversity of present cores and fabrication technologies permit small incremental gains on these magnetic components integrations. Additive manufacturing is a very emerging fabrication process that allow not only developing new core geometry but also, the adjustment of core composition (by allowing the deposition of layers containing different ferrite powder composition). The post-doctoral fellow will work on the design of a core having a permeability gradient and on its electrical and thermal characterizations. The post-doctoral fellowship is of 2 years duration located in the city of Grenoble (France) with a minimum wage of 40 k€ per year. If you want to have more detail please use the following link: https://liten.cea.fr/cea-tech/liten/Documents/Postdoc-Carnot-EF/AMbassador.pdf

Modeling of faults on low voltage DC networks in buildings, towards fault detection algorithms

The development of the use of renewable energies and energy storage as well as the progress made by power electronic components are gradually leading to a rethinking of the architectures of low voltage electrical distribution networks in buildings. These developments will allow the development of direct current or mixed alternating-direct current networks supplied by static converters. On this type of network, faults become more difficult to manage due to the power sources used. Indeed, the usual signatures of the short-circuit or the overload are no longer the same and will vary according to the converters used and the architecture of the network. For this, it is necessary to identify, by simulation, the most suitable protection topologies (by neutral systems for example) and to identify the typical fault signatures. Ultimately, these signatures will provide optimum detection devices.

Design and fabrication of the magnetic control of 1.000 qubits arrays

Quantum computing is nowadays a strong field of research at CEA-LETI and in numerous institutes and companies around the world. In particular, RF magnetic fields allow to control the spin of silicon qubits, and pathway for large scale control is a real technological challenge.
The bibliographic analysis and the studies already carried out will able to draw out the pros and cons of the various existing solutions. In collaboration with integration, simulation and design staff, a proof of concept will be develloped and fabricated.

Design for reliability for digital circuits

Flash memories are a key enabler for high-temperature applications such as data acquisition and engine control in aerospace, automotive and drilling industries. Unfortunately, the retention time of flash memories is very sensitive to high temperatures. Even at relatively moderated temperatures, flash memories may be affected by retention-related problems especially if they are set to store more than one bit per cell. This impact can be mitigated by periodically refreshing the stored data. The problem is that, in the presence of a variable operating temperature that could be due to variable environmental and workload conditions, a fixed data-refresh frequency may become disproportionately large with a subsequent impact on response time and cycling endurance.

The first objective of this project is to implement a data-refresh method based on a specially designed counter that is able to (a) track the evolution of the temperature and its impact on the data retention time of Flash memory blocks, (b) trigger warnings against potential retention time hazards and (c) provide timestamps.

The second objective is to find the distribution law that gives the evolution of the number of data retention errors in time. The goal is to implement a methodology able to infer the remaining retention time of flash memory pages based on their data retention age, i.e., the elapsed time since data was stored, and the number of retention and non-retention errors.

The publication of the scientific results in high-ranked conferences and journals is major project objective.

Development of a mechanical energy harvester based on a rotating machine architecture with permanent magnets

This Post-doc offer will be aimed at developing energy harvesters, and more especially electromagnetic energy harvesters with an operation mode close to the one of rotating machines with permanent magnets. The post-doc applicant will have a background in electrical engineering and an experience in rotating machines design, ideally, with permanent magnets.

The missions of the Post-doc applicant will be to:
1) Imagine and design small-scale innovative energy harvesters by exploiting the techniques used in rotating machines.
2) Model and optimize the devices
3) Characterize the systems
4) Participate to the industrialization process

Contribution to the development of miniature antennas measuring devices

The generalization of RF links operating at VUHFfrequencies to equip an increasing number of communicating electronic devices helps to intensify research on miniaturization and integration of antennas. As a result, significant progress are regularly carried out to reduce the size of antennas and it is not uncommon to find work describing antenna structures of 1/30 of the wavelength maximum dimension. Increased sensitivity to the operating environment is observable with electrically small antennas. This feature is reflected by problems of measurement of electrical and radiation properties that may be altered with the standard techniques of connecting a measuring cable to the antenna. Accordingly, the subject seeks to develop techniques for electrically small antennas charterization using non-invasive methods, that is to say does not interfere (or few) under test antenna. Two techniques will be investigated based on the work already done in the laboratory. The first technique is based on the far field electromagnetic reflectometry. The second technique involves the use of an RF-optical transducer in the vicinity of the antenna under test for a particular design of miniature optic RF conversion reflectometer for measuring antenna impedance.

Optimal management of a tertiary energy system

In the solution concerning residential or tertiary sites that consume and produce electrical energy , the objective is to optimize the use of energy based on economic criteria or constraints networks (adaptation of the consumption) without introducing perturbations of user comfort. The purpose of this position is to develop a solution for "optimal management of the use of solar energy in a tertiary building integrating EV charging stations and storage." according to three objectives:
- Minimize the cost of consumption based on a dynamic tarif - Maximize the use of solar energy - Minimize the power demand of the network. Taking into account the LCOS (levelised Cost Of Storage) of battery . The Post- Doc will contribute and participate in: - Specification of tertiary system - Development of algorithms for managing a tertiary system - Deploy and test the proposed solution.

Design of integrated photonics modules

Design of next generation optoelectronic transceivers (particularly on-board modules) requires the merging of two advanced technologies: Silicon Photonics and 3D Silicon Packaging, both being developed at Leti.
In order to meet the requirements in term of technical specifications, cost and density, it is needed to achieve a codesign involving mechanical, thermal, optical and mainly RF aspects.
The aim of the work consists in designing such integrated modules by optimizing the RF interconnections of the module (internal and external), and the proper setup of the integrated circuits (ASICs). Modelling of several architectures will be led under HFSS and ADS softwares.
Finally, the integration of the module into its system environnement will be taken in charge, so as its characterization (involving testboard and testbench design).

Reverse engineering of an internal permanent magnet synchronous electrical machine and modelisation of evolutions based on new new magnet technologies developped in CEA

The study aims at studying and modeling a synchronous electric motor with magnet buried in the rotor. This study begins with a preliminary phase of retro engineering and modeling of an existing machine. A second phase will focus on the design and the modeling of a new machine integrating a new technology of magnets developed in the CEA.

In the context of electric transportation, if batteries and energy storage are still the weak point of the energy chain, the electric motor remains a central part that has to be optimized to raise efficiency. For twenty years, all motor structures have been studied and tested: dc motors, synchronous machines with permanent magnets, asynchronous machines and switched reluctance machines. This study will focus on a synchronous machine with magnets buried into the rotor. This type of machine offers a natural ability of delivering at full load a constant power along a wide speed range, associated with a high efficiency. Moreover, power density can be improved by increasing maximal speed range.

The Post doc will be split into three parts:

1st phase:
Testing of an existing commercial electrical synchronous machine with magnets buried in the rotor and characterization of its components. These tests will be done on a motor test bench situated in the CEA

2nd phase:
Modeling of the commercial machine tested on the test bench and comparison of modeling results with experimental measurements from the first phase.

3rd phase:
Design and modeling of evolution of the machine tested and modeled in phases 1 and 2, integrating new technologies of magnets developped by the CEA.

Integrated antenna arrays for 60 GHz high-data rate communications

This post-doctoral offer is in support of our work program on the design of millimetre-wave antennas for high data rate communication systems in the 57-66 GHz frequency band. The realization of smart devices in this frequency band with a high level of integration and a low cost is a challenge accessible today thanks to the recent microelectronic technologies as well as other silicon technologies such as assembly, packaging or micromachining. Some applications in the consumer electronics domain are clearly identified and expected to result in product in a very short term.
After a series of project completed these last years on the design of single antennas built and validated on different technologies, such as silicon or ceramic, the future projects will focus on the demonstration of antenna arrays with electronic beamsteering for long range applications. Several demonstrators will be realized in collaboration with our partners developing the integrated circuits and fabrication/assembly technologies in order to obtain a fully functional system.

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