Department of Electrical Engineering and Computer Science
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Research - Topics

The purpose of the research carried out in the “Electrical measurements and instrumentation” laboratory of the Department of Electrical Engineering and Computer Science is to apply and to develop sensitive measurement techniques in order to characterize the electrical, thermal, and magnetic properties of various materials.

These include:

1. "Functional" ceramics with non-linear properties

2. Dielectrics et Insulators

These research activities are closely related to the development of electrical engineering applications. The laboratory is equipped with numerous high-sensitivity devices allowing precision measurements to be carried out at room temperature as well as in cryogenic conditions. The developed experimental rigs are based on precision devices required to measure low-level signals, including low-level voltages (i.e. below 1 µV), low-level temperature changes  (i.e. below 1 K) or low-level currents (i.e. below 1 nA).

"Functional" ceramics with non-linear properties

The studied "functional" ceramics are mainly High-Temperature Superconductors (HTS) and Colossal Magneto-Resistive (CMR) manganates. Both of them require experimental conditions involving low temperatures as well as high magnetic fields. In addition to using commercial measurement devices, the laboratory has developed its own data acquisition set-ups in which the materials are characterised through 

resistivity, Hall effect, current- voltage relationships, R-L-C characteristics,... on conductor  materials, superconducting (bulk or tape) and magnetoresistive ceramics, measurements on dielectric materials,
DC magnetisation, magnetic permeability, AC susceptibility, Hall probe mapping, magneto-optical imaging, magnetic shielding, influence of "crossed" magnetic fields, superconducting levitation force,
thermal conductivity, specific heat, thermopower, coupling with magnetic properties.

The final objectives are thus the elucidation of the physical mechanisms involved in the materials, combined with a co-ordinated research effort looking into their use in engineering applications, such as sensors, rotating machines and flywheels.

Superconducting sample (YBCO)
prepared for
transport measurements

Superconducting sample (DyBCO) prepared for transport measurements.
Polarized light photograph to see the grain boundaries

resistivite YBCO2 petite.jpg (5294 bytes)


Experimental setup for magneto-optical imaging

Magneto-optical image of magnetic tracks on credit cards

YBCO  optical image
and magneto-optical image of the remnant magnetization 

Magneto-optical image of the remnant magnetization of a YBCO ring
Manip MO

MO carte1
MO carte2

MO optique


MO trou
Superconducting samples (YBCO)
prepared for
magnetic measurements

magnetique YBCO2 petite.jpg (4410 bytes)

photocrosscoils petite.jpg (1867 octets)

Experimental setup
for thermal properties measurements
(on YBCO samples)

thermal conductivity.jpg (1685 bytes)

thermal diffusivity.jpg (2497 bytes)

Permanent magnet in levitation above superconductors

levitation small.jpg (6787 bytes)

levitation2 small.jpg (3901 bytes)

Mapping of the trapped magnetic induction in a superconducting sample (DyBCO)

Measurement performed at 1mm from the top surface of the sample (1 cm x 1.6 cm) in liquid nitrogen (T = 77 K)
Resize of JPMremn04.jpg (7237 octets)

Permanent magnet in suspension below superconductor

susp2 small.jpg (1175 bytes)

Dielectrics and Insulators

Within this area, the research carried out in the laboratory concerns the predictive maintenance of high-voltage insulating components used in power plants and power cables. The laboratory has acquired some expertise in the electrical characterisation of various insulating materials, including polymer films and potential-grading varnish used on alternator stator bars. The evolution of the properties of the insulation subjected to thermal and / or electrical ageing, as well as the influence of external parameters (temperature, moisture, corrosive gases) are also investigated.

The studied subjects are the following :

Test bar prepared
for measurements
on insulation and surface varnishes

barreau small.jpg (1969 bytes)

Probe of an electrostatic voltmeter for  surface potential mapping on stator bars sonde electrostatique petite.jpg (6145 octets)
Stator end-windings :
damage caused by electrical discharges
on the anticorona varnish
vernis abime small.jpg (9450 bytes)