Philippe Dessante

Polyimide and FEP charging behavior under multienergetic electron-beam irradiation

Surface and internal charging of dielectric materials is a potential cause of surface discharges and satellite anomalies, due to the fluctuating irradiation levels induced by space environment. Understanding conduction mechanisms and reducing charging levels are therefore important industrial issues for satellite designers and manufacturers. Surface potential measurements under irradiation and after charging (potential decay) are the most significant laboratory tests to qualify and understand the charging and discharging behavior of insulating materials. We present here experimental results obtained using the SIRENE facility at ONERA. Kapton and Teflon FEP films respond differently when subjected to a 20 keV charging electron beam combined with a 400keV ionizing electron beam. The physics underlying these experimental results is discussed. A simple numerical model has been developed. It is shown that different combinations of mobility, trapping and recombination may explain the results on both materials. The complex behavior observed on Teflon FEP may be attributed to the progressive deep trapping of the negative charge, enhancing holes recombination.

Assessing available transfer capacity on a realistic European Network: Impact of assumptions on wind power generation

This paper aims at assessing the impact of massive wind power penetration on the calculation of ATC. Calculations are made for the ATC between France and Belgium and are realized on a realistic European Electricity Network. We find that the German wind power production make this ATC vary depending on the total wind power production and its geographical distribution in Germany. Wind power production and the nodes involved in cross-border exchange must then be forecast precisely so that the cross-border exchange can be maximal without breaching network security.

Optimization of the steady voltage profile in distribution systems by coordinating the controls of distributed generations

Distributed generation (DG) is more and more installed and integrated in the electric power systems, mainly in distribution networks. The conventional method of voltage control with on-load tap changer transformers is not efficient enough to deal with the growth of integration of distributed generators. The DG power regulation will contribute to optimize the steady voltage profile in network and thus to rise the maximal DG installation capacities of network. The work reported in this paper shows that the coordination of DG power regulation can realize a voltage control of distribution network. The coupling between active power and voltage magnitude must be taken into account according to the our results.

Anticipation for efficient electricity transmission network investments

This paper proposes a model and preliminary results to evaluate the efficiency of anticipating the connection of power plants with shorter construction duration than the time needed to obtain the right to upgrade the network and finally to do this reinforcement. This evaluation is made in presence of a cost of anticipation related to the study of the project of network investment and to the administrative procedures needed to obtain the building agreement. This model compares a proactive TSO that anticipates the connection of new generators and then the required network reinforcement, with a reactive one that does not make any anticipation but that may then face greater congestion while the network is being reinforced. The efficiency of these behaviors is measured in terms of social cost. We find out that there exists a limit of probability for the connection of generators beyond which a proactive TSO is more efficient than a reactive one. Evaluated on a realistic case of connection, this limit of probability is found quite low, which indicates that the proactive behavior for a TSO shall generally be the optimal one.

A compact transient electrothermal model for integrated power systems: Automotive application

The paper is about a so-called ”diffusive representation”, a new modeling dynamic systems method and its application to efficient transient thermal modeling of multichip power module taking into account thermal coupling effects. Compact thermal models are required for many analyses during the design of power systems. Generally a RC-ladder model is used and analytical expressions enable to quantify R and C values. Unfortunately the trade-off between complexity, convergence and accuracy is hard to settle. Diffusive approximation of the heat law equation offers an alternative representation. The compact thermal model is a state space model. Parameters identification procedures are given and are validated. The method is applied on an inverter leg, a 400A MOSFET power module manufactured by VALEO for starter-alternator system. Electrothermal measurements have been achieved to develop an electrical model with thermo-sensitive parameters of the MOSFET dies. Electro-thermal measurements and 3D Finite Element thermal simulations have been performed for validations. A compact diffusive model comes as a state space model and may be easily implemented in a ”circuit” simulator.

Optimisation of a Drive System and Its Epicyclic Gear Set

This paper describes the design of a drive consisting of a DC motor, a speed reducer, a lead screw transformation system, a power converter and its associated DC source. The objective is to reduce the mass of the system. Indeed, the volume and weight optimisation of an electrical drive is an important issue for embedded applications. Here, we present an analytical model of the system in a specific application and afterwards an optimisation of the motor and speed reducer main dimensions and the battery voltage in order to reduce the weight.

Progress in the development of the neutron flux monitoring system of the French GEN-IV SFR: Simulations and experimental validations

The neutron flux monitoring system of the French GEN-IV sodium-cooled fast reactor will rely on high-temperature fission chambers installed in the reactor vessel and capable of operating over a wide-range neutron flux. The definition of such a system is presented and the technological solutions are justified with the use of simulation and experimental results.

Electro thermal stochastic optimization of a smart actuator for an automotive application

In this paper, authors present an automated sizing framework able to handle electro-thermal couplings. Our case study is a complex multi-physics system intended for automotive applications. Our aim is to minimize the physical volume of a smart actuator under multiple constraints (power converter efficiency and motor copper windings temperature). A lightweight simulation approach allowing reduced computing time and multi-physics coupling is described. The system model we have developed has been verified against experimental measurements.

Cathode Surface Morphology Effects on Field Emission: Vacuum Breakdown Creation of Field Emitters

The effect of stainless steel cathode surface morphology on field electronic emission in high vacuum (~10-5 Pa) is studied. The surface rugosity is shown to affect the emission intensity; high-aspect ratio surface features lead to locally enhanced electric field, thereby increasing the field electronic emission. A breakdown in the vacuum, caused either by impact of charged dust particles or other impurities, or by overheating and vaporization of field emitters, can lead to cratering on the cathode surface. This cratering drastically changes the local surface rugosity, enhancing the local field and leads to greater emission intensity. Treatment of the cathode surface by glow discharge at higher pressure is known to reduce field emission by ionic bombardment and sputtering of emission sites; an image of such a glow-type discharge in the same apparatus used to study field emission is presented.

Performance comparison of the permanent magnet assisted synchronous reluctance motor and the double magnet synchronous motor

This paper presents a method for the comparison of two kinds of permanent magnet synchronous motors. The study also includes the selection of permanent magnet type: ferrite or NdFeB. The aim is to maximize the performance (average torque and power factor) of these motors at equal cost. The analysis is done using Finite Element Method.