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Fluoropolymers as Primary Insulation in Electric Motors

On April 06-07, Tau took part in the Coiltech Deutschland 2022 in Ulm, the fair dedicated to the supply chain of coil winding, electric motors, generators and transformers industry. For this occasion, the company showcased its unparalleled high-performance magnet wire coated with fluoropolymer to enable future electric motor architecture.

Today’s battery-powered electric cars are significantly heavier than combustion vehicles and thus have high energy consumption. This represents the biggest challenge for transport electrification. OEMs and Tier1 companies strive to improve performance and efficiency of their upcoming models.

The move towards 800V technology ensures faster charging and wider range. However, higher voltages stress primary insulation even more and cause partial discharge leading to the motor failure. Modern design concepts use rectangular wires in hairpin or wave windings with a thicker insulating layer.

Fluoropolymers as Primary Insulation in Electric Motors
Photo: Filippo Veglia @ the World Magnetic Conference 2022

Filippo Veglia, Tau’s co-founder and CSO, speaker at the fair’s World Magnetic Conference, pointed out that with increased insulation thickness, made to withstand higher voltage, the slot fill factor has to be reduced. This lowers power density and efficiency of the motor. Since voltage and fill factor are two competing parameters, motor designers must find an optimal equilibrium which depends on the primary insulation resistance to partial discharge.

“The use of special polymers like PEEK and PI, both already highly resistant to partial discharge, allows to increase the voltage without jeopardizing the fill factor of the motor. Nevertheless, fluoropolymers such as PTFE and PFA have the lowest relative permittivity among the insulating polymers and demonstrate superior partial discharge performance compared to commonly used polymers. And this advantage becomes even more evident at the usual operating temperatures of electric powertrains. A wire coated with a fluoropolymer is calculated to work with three times the voltage of the equivalent wire enameled with PAI and almost two times the equivalent wire coated with PEEK”, says Veglia.

This represents a game-changing advantage for systems of 800V and more. However, fluoropolymers are rather soft materials and have relatively poor resistance to abrasion and minor clamping force. They show low adhesion and are difficult to extrude. Therefore, traditional technology of wire enameling and wire extrusion was unable to work with fluoropolymers.

Tau answered these requirements with its self-developed, proprietary DryCycle technology, which guarantees operational peace of mind when coating with PFA, PTFE, ETFE and other fluoropolymers, with no solvents or primers. Based on the recent report by PEM Motion, Tau’s PFA coated wire has a much lower level of partial discharge – 75% less than PAI-coated and 30-40% less than PEEK-coated wire.

Tau will again be displaying its high-performance wire for e-mobility and grid applications at Coiltech Italia 2022 in Pordenone on September 28-29, at Booth 7-A31. Save the date!

About Tau

Tau is a technology and sustainable manufacturing company at the core of the electrification of transport and decarbonization of energy. Its research, development and incubation have resulted in patented technologies that pair environmental responsibility with superior performance and peace-of-mind operating simplicity. Tau focuses on carbon-conscious protective coatings for high-performance and standard copper, aluminium and steel wires. Tau has offices in Turin (Italy) & Berlin (Germany).

Visit or follow Tau on Twitter and LinkedIn.

About Coiltech

Coiltech Italia is an annual international exhibition for the coil and winding industry that gives an excellent opportunity to keep up with the materials and methods innovation for further improvement of efficiency in production, distribution, transformation, and consumption of electrical energy.

For more information visit


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