3D Modelling of Laminated Parts in Power Transformer Accounting for Eddy-Current Losses KU Leuven University, Department of Electrical Engineering

ESAT-Electa is a division of the Department of Electrical Engineering (ESAT) of the KU Leuven. Its research covers the broad spectrum of electrical energy systems, with the development of the future smart grid at the heart of the matter. 

We aim at strengthening our wide and international recognition as a centre of excellence in these topics, bridging fundamental research and prospectively applicable solutions for industry. Together with two other key actors in Flemish energy research, VITO and imec, all KU Leuven energy research joined forces into EnergyVille, a renowned energy research cooperation.

Main Research topics:

Smart Grids - Transmission and Distribution Systems - Electricity markets - Regulation - Product and service development - Economic Sustainability - Rational use of Energy - Modelling of electrical energy systems - Renewable Energy Sources - Distributed Connected Flexible Components - Motors and Drives - Control for Smart Grids - Multiscale & Multiphysics Modelling

 

Energy efficiency is one of the main pillars to reduce carbon dioxide impacts in our society, i.e. limit greenhouse gas emissions and preserve environment. For instance, even though the efficiency of the transformers in the distribution network is about 97 to 99%, their environmental impact is far from negligible due to intensive use. Besides electrical motors and actuators are more and more present worldwide. Having a precise knowledge of the losses in this kind of equipmentis thus crucial to improve the energy efficiency of both electrical networks and power electronic devices.

 

Losses appear in different parts of the transformers: the windings, the magnetic circuits, the tank, the clamping plates, the shielding plates, the magnetic shunts, the tie rods. The windings can be wires with rectangular section or strips made of copper or aluminum. The latter are called foil windings and are less expensive to manufacture. There is a need for a more accurate model of distribution transformers including foil windings to assess the losses and locate the ensuing hot spots by means of a coupled electromagnetic and thermal model.  

  

This PhD proposal deals with the modeling of foil windings and laminated magnetic circuits. We aim at accurately accounting for the losses in the foil windings and the lamination stacks. The target applications are the power transformers. In order to compute the loss distribution and the resulting heating in these devices, we need to develop and validate ad-hoc models for the foil windings and the laminated cores to be integrated in a finite element approach (2D and3D).

 

The foil windings and the laminated cores exhibit particular difficulties from the modelling point of view, particularly concerning the multiple spatial scales (width of the foil or lamination versus the size of the device) and the complex 3D geometries. Homogenization techniques allow accounting for the foil windingsand laminations without discretizing each foil or lamination separately. Thefoil winding and laminated core are thus considered as a block and meshed as such.

 

Furthermore,the laminations are characterized by nonlinear magnetic constitutive laws, inthe general case anisotropic and hysteretic, that increases considerably the modelling and simulation drawback and constitutes a real challenge.    

 

Software developments will be performed within Flux®. The open-source software suite Onelab(with mesh generator Gmsh and finite element software GetDP) might also be used and help with the required model developments.

 

Three research topics are identified:

• Development of suitable homogenization techniques for accurately accounting for the losses in the foil windings of power transformers. A frequency domain resolution is envisaged (complex formalism).
• Thermal modelling of the foilwindings with heating source due to the electromagnetic losses. The homogenization techniques must provide a sufficiently accurate localdistribution of the losses for succeeding this task.
• Development of homogenization techniques for a precise estimation of the losses in the laminated cores. This research is based on previous research findings. We envisage a time domain resolution, i.e. time-stepping approach.

The candidate should:

• Have a Master in Engineering or Engineering school degree.
• Have an excellent knowledge in electromagnetism and applied mathematics (numerical methods, finite elements, ...).
• Have an excellent English level (speaking, writing, reading and listening). Knowledge of French is an asset.
• Be an independent worker able to take initiatives and paying attention to details (meticulous and precise). 
• Publish research results in international journals.
• Present research results in national/international journals.
• Assist in teaching tasks (mainly exercise sessions and supervising master theses). 

Application should comprise:

• An academic CV.
• Transcripts of bachelor and master degrees.
• Proof of English proficiency (TOEFL/IELTS), level B2 at least, if English is not the candidate's mother tongue.
• Two referees (name, position, affiliation, telephone and email address).

The PhD candidate will enjoy:

• A doctoral scholarship for one year, renewable up to 3 years (joint PhD with France where PhD length shorter).
• A highly specialised doctoral training, hosted by two different European institutions (At least 1 year should be spent in KU Leuven).
• Stimulating research environment with active involvement and collaboration with academia and industry (Altair Engineering).

For more information please contact Prof. dr. ir. Ruth Vazquez Sabariego, tel.: +32 16 32 88 91, mail: ruth.sabariego@kuleuven.be.

The vacancy will be closed as soon as a suitable candidate is found. Do not hesitate in applying.