High-temperature, Electrically-insulating Coating for Magnet Wires
Funded by U.S. Army Research Laboratory, WMRD
Project Summary
In this research program, Aegis Technology is to develop and demonstrate a novel class of ceramic coating technology to generate high-temperature, electrically-insulating (HTEI) coating for copper magnet wires, which would enable the power conversion systems to operate at higher power densities, high temperatures and high frequencies. This coating technology based on the pyrolysis of polyceramic precursors is expected to offer advantages such as high efficiency, small size and light weight for resultant power electronic components and power conversion systems in both military and commercial applications. The processes developed will also be scalable for large-quantity production and applicable for copper wires with different diameters.
In the previous Phase I, we successfully carried out the technical feasibility studies of the proposed concept through process design, prototyping and characterization. The objective of this Phase II project is to further identify the underlying technical issues governing fabrication and performance of ceramic coated Cu wires, and address the issues related with process optimization and scale up. The primary research activities and results of the Phase II study included: 1) Process development and optimization of ceramic coatings on Cu wires using different precursors; 2) Microstructure characterization and measurement of electrical insulation performance and thermal endurance performance for ceramic coatings; 3) Investigation and design for production scale up of ceramic coated Cu wires; 4) Testing of ceramic coated Cu wires in real motors, and 5) Pilot-scale production of ceramic coated Cu wires for prototype demonstration and for future performance testing.
In this Phase II, we systematically investigated ceramic coatings on Cu wires with different precursors. Both small-scale laboratory coating processes and scaled-up batch production were explored in detail. Different precursor-solvent-catalyst ratios, different catalysts, different dipping and pyrolysis times, and different heating profiles were investigated. Smooth, uniform and nearly microcrack-free ceramic coatings have been successfully generated around Cu wires, which were characterized by SEM and EDX in detail. Electrical property and thermal endurance measurements have shown that the ceramic coatings have good electrical insulation. The ceramic coatings can provide efficient protection against oxidation in air at temperature of 300 °C for a period of 96 hrs. Particularly, the ceramic coatings synthesized demonstrated good flexibility. For the best ceramic coatings, nearly none cracks and peeling-offs were observed when the coated Cu wires were bent to a curvature radius as small as 3 mm. When the coated Cu wires were bent to a curvature radius of less than 1 mm, cracks and peeling-offs of ceramic coating were not avoidable. The coating process was also scaled-up to coat tens of grams of Cu wires in one batch. In addition, ceramic coated Cu wires were wrapped on rotors and tested in motors at high temperatures. The motors using ceramic coated Cu wires were able to function well and survive at working temperatures up to 300 °C or more.
The accomplished Phase II work has established a solid basis for future Phase III of this project, which will lead to commercially available ceramic coated magnet wires for high temperature applications.