Very high temperature HVDC busbar (180 - 240°) with reliable and cost effective technology

Project Information

VILB

Grant agreement ID: 821065

DOI

10.3030/821065

Project closed

EC signature date 30 October 2018

Start date 1 November 2018

End date 31 October 2021

Funded under

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Total cost

€ 668 276,25

EU contribution

€ 497 355,00

Coordinated by

AUXEL
France

Periodic Reporting for period 3 - VILB (Very high temperature HVDC busbar (180 - 240°) with reliable and cost effective technology)

Reporting period: 2020-11-01 to 2021-10-31

Summary of the context and overall objectives of the project

VILB project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 821065. The project took place during 3 years (from November 2018 to October 2021).

The objective of the project has been the design and development a high temperature HVDC busbar (180°C and more).

This is because, "More Electrical Aircraft" power distribution systems are increasingly required to operate in harsh environments and increasing voltage (HVDC), including high temperature. The company Auxel (an industrial leader in laminated busbars) & the LSEE Research Laboratory (Electrotechnical Systems and Environment) will conjointly address this topic by developing a technology able to effectively address the challenges of High Voltage, high operating temperature and controlled lifetime: VILB (Varnished & Isolated Laminated Busbar) technology.

With this technology, we manufactured some electric conversion devices (busbars) for SAFRAN Group.

The resulting busbars meet the primary requirement of temperature resistance (180°C). However, the requirement for partial discharge inception at the very high voltage level (3kV) was not achieved (we obtained only 1,5 kV on the busbars). Nevertheless, we have demonstrated that the principle of additive manufacturing of the insulation around the electrical conductors is a viable solution.

We have also continued our research and demonstrated on models that we can reach 220°C with the use of inorganic nanoscale fillers in the varnish.

The potential VILB impacts are way beyond aeronautical sector: VILB could be duplicated in many other applications such as power modules, converters, automotive Industry, etc.
In particular, we were able to reuse the VILB technology for electrical insulation in planar power transformers. A patent application has been filed.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

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

(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.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Several technological barriers have been removed druing the periods
- ability to apply the varnish in multiple thin and regular layers on individual busbar conductors,
- ability to cover conductor edges, (a key factor for good insulation),
- use of a solvent-free varnish, without volatile organic compound (VOC) release,
- use of coupling agent to promote the adhesion of the varnish on the electrical conductor.
- use of varnish in additive manufacturing (stereolithography) for the production of insulating parts or the encapsulation of flat electrical conductors

The role of adjuvants, their choices, their rates, how to incorporate them is now better known.

In addition, in our laboratory, we have designed, manufactured and validated the means of applying the varnish (thin coating, rapid cross-linking, etc.).

We also have a more accurate view of the costs of the VILB technology. It is competitive compared to conventional laminated busbars based on thermo-glued film and much more economical (20-25%) for busbars with a high technical level (high voltage, high temperature, etc.).

We confirm that the addition of inorganic filler to the varnish significantly improves its resistance.

VILB technology seems universal to us and can potentially address the entire laminated busbar market (USD 1 billion in a few years according to various studies). We therefore focused on the three most promising markets well suited (Electric Vehicles, Power module, Aerospace).

VILB technology can be deployed to improve the electrical isolation of planar power transformers which are increasingly used for aircraft electrification.


PATENTS
The VILB technology is covered by two patents. Co-inventors are the members of the consortium (LSEE -Artois University & AMPHENOL AUXEL) and were able to develop the technology through this European project.
WO2019068969 – Multilayer connector with conductors insulated by enameling
https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2019068969

WO2019068968 – Multilayer connector insulated by impregnation with resin
https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2019068968

In September 2021 we applied for a patent for the use of our VILB technology applied to the insulation of planar power transformers.
MAGNETIC INDUCTION COMPONENT COMPRISING A METAL FOIL CUT AND COATED WITH A DIELECTRIC RESIN AND METHOD OF MANUFACTURING THE SAME

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