The project took place during 3 years (from November 2018 to October 2021)and has been the subject of several separate works.
(1) Development and improvement of the coating formula
We improved and adapted a UV-crosslinked acrylic varnish already used as an electrical insulator to suit our needs. We worked on:
- the IBOA type thinner, to lower the viscosity of the varnish and facilitate its use, also essential for the dispersion of the additives, and which brings a beneficial plasticity to the insulation without too much degradation of the thermal performances
- the photoinitiator. Several were tested, BAPO was selected.
- the coupling agent. We started with mercaptan and ended up with a silane that provides very good adhesion and the ability to disperse nanometric fillers.
- a thixotropic agent which improves the coating of the edges of the conductors with the micro-spray process
- the addition of inorganic fillers to reinforce the thermal resistance of the coating. Several fillers were tested in micrometer and nanometer size (alumina, silica, hexagonal boron nitride, barium sulfate).
(2) Study and deployment of implementation processes
Two processes were studied and deployed. The first one is based on a micro-spraying of the varnish in multiple thin layers. First with a Cartesian micro robot and then with a 6-axis micro robot. The second, at the end of the project, is based on additive manufacturing using SLA LCD stereolithography.
We also worked in parallel on the preparation of the mixtures, degassing (essential) and coating by vacuum impregnation.
(3) Characterisation tests of the VILB electrical insulation
Numerous tests were carried out to characterise the coating and the quality of the resulting electrical coating.
(4) Prototype construction for SAFRAN
We made several busbars according to SAFRAN's drawings and carried out preliminary tests on them.
The 180° temperature resistance criterion is complied. On the other hand, the required partial discharge inception voltage (PDIV) at 3KV has not been reached. The other qualification tests could therefore not be carried out.
Mock-ups meeting the PDIV requirement have been provided. New prototypes with PD compliance will be delivered in 2022.
(5) Communication
We have participated in several events to promote participation in European projects (3 round table conferences, 2 videos and a white paper, all with the regional council "Haut de France"). The official website of the VILB project has been put online :
https://vilb.eu(s’ouvre dans une nouvelle fenêtre)(6) Dissemination
We presented the VILB project at a webinar (NAE NORMANDY), at a conference (APEC USA), at two poster sessions (GDR SEEDS & MEA2021). A 3-year thesis has also been launched in January 2021 with AUXEL and the University of Artois on this subject
We have ALSO identified many avenues of scientific research to improve the technology during and beyond the project, especially with the incorporation of nanometric filler in the varnish
(7) Exploitation
We are developing VILB technology for planar power transformers. A patent application has been filed.
