HomeResearch - 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
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
- Electrical measurements :
- resistivity, Hall effect, current- voltage relationships, R-L-C characteristics,... on conductor materials, superconducting (bulk or tape) and magnetoresistive ceramics, measurements on dielectric materials,
- Magnetic measurements :
- DC magnetisation, magnetic permeability, AC susceptibility, Hall probe mapping, magneto-optical imaging, magnetic shielding, influence of "crossed" magnetic fields, superconducting levitation force,
- Thermal measurements :
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 |
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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 |
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| Superconducting
samples (YBCO) prepared for magnetic measurements |
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| Experimental
setup for thermal properties measurements (on YBCO samples) |
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| Permanent magnet in levitation above superconductors |
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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) |
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| Permanent magnet in suspension below superconductor |
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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
:
- Study of non-linear potential grading materials used for reducing the partial discharges on end-windings.
- Electrical characterisation of so-called "semi-conducting" varnishes.
- Transient study of charge - discharge currents through the mica-resin insulation.
- Partial discharge measurements under influence of vibrations.
- Expertise in low current measurements.
- Electrical characterisation of ceramic insulating composites and polymer materials.
- Electrical characterization of ceramics obtained by FLASH sintering (ultrafast and low energy densification technology) - ERDF Project..
| Test bar
prepared for measurements on insulation and surface varnishes |
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| Probe of an electrostatic voltmeter for surface potential mapping on stator bars |  |
| Stator end-windings : damage caused by electrical discharges on the anticorona varnish |
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