Thèse CIFRE Partial discharges (M/F)

Job Description

Thesis Subject

The electrification of the automotive sector is growing, and it is accompanied by a continuous increase in the performance requirements for electric powertrains. One of the major challenges is reducing battery charging times. To achieve this goal, automakers are moving toward higher-voltage electric architectures. Indeed, at the same power level, increasing the voltage reduces the current flowing through cables and power components, thereby limiting Joule losses and improving the system's overall efficiency. This trend is leading to battery voltages of up to 800 or 900 V, compared to approximately 400 V for the present generation.

In this context, the main risk is the occurrence of localized micro-discharges within the insulation, known as partial discharges (PD). These discharges result from localized ionization of the gas present in defects, cavities, or poorly insulated areas, without immediately causing the system to break down completely. The risk of partial discharges is strongly influenced by environmental conditions.
The Ph.D. research program aims to better characterize the conditions under which partial discharges occur in geometries representative of electric motor insulation systems, accounting for environmental parameters such as pressure and temperature. It also seeks to quantify the impact of discharges on the erosion rate of insulating materials under operating conditions, to establish a link to the constraints imposed by customer use.

Your Work Environment

The overall objective is to develop a predictive model and aging laws that will enable the conversion of partial discharge (PD) events into failure probabilities at 800 V.
The first challenge is that the physical mechanisms governing PDs remain poorly understood, which poses a major obstacle to the acceptance of occasional PD events in insulation systems.
The second challenge is to ensure the robustness of the aging laws under PD conditions, across varying temperatures and pressures.

Indeed, adopting a less conservative approach requires not only predicting the stress at which partial discharges (PDs) occur but also understanding their dynamics, interactions with insulating surfaces, and impact on material aging.
This thesis falls precisely within this scope. It will be based on a multiscale modeling approach.

The thesis is organized into three phases:
1) to familiarize oneself with, refine, and utilize a 2D fluid model previously developed by the Renault Group in order to evaluate the UV fluxes produced by DPs and to study their roles in photoemission mechanisms on insulating surfaces;
2) to derive a simplified 1D model that is computationally faster and compatible with large-scale parametric studies;
3) apply previously established aging laws to evaluate the performance of insulation systems under operating conditions representative of those in a real electric vehicle.

The candidate must hold a Master's degree, with fundamental knowledge in fluid physics and plasmas.
Numerical methods skills will be highly appreciated, as well as data treatment techniques.
In addition, basic knowledge on how to assist the experimental work would be very useful for the thesis research project.

Constraints and risks

The work contract will be made by Renault and the work
will be performed in a ZRR environment.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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