HV eMotor Efficiency Enabled by Utilizing ProPreg E240 Epoxy & Ajedium? PEEK Slot Liners

By DeeDee Smith, Luigi Marino, Qasim Shaikh, Victoria Lee, Brian Baleno—Solvay Materials;?

Kayla Brown, Jeff Southworth—Epic Resins

Next generation of eMotors are moving from 400 Volts to higher voltages greater than 800 Volts. The significant increase in voltage has created opportunities, but also challenges for design engineers to identify magnet wire and slot liner insulation. eMotor Systems that operate at 800 Volts or higher typically require thicker insulation systems for both magnet wire and slot liners. Thicker insulation leads to lower efficiency because the copper slot fill factor decreases. Additionally, thicker insulation creates a challenge to dissipate the heat.?

The incumbent slot liner solution for eMotors is either aramid paper or aramid paper laminates like NKN. Solvay has introduced Ajedium? PEEK slot liner films to address the challenge of slot fill factor and heat dissipation capabilities while getting the right level of electrical insulation to meet the eMotor life and durability requirements.?

Ajedium? PEEK slot liners provide a balance of high temperature electrical insulation and thermal conductivity that is superior to paper laminates which allows for engineers to use thinner slot liners. As shown in Figure 1 below, the 150 and 100 micron PEEK slot liners offer multiple benefits over the 250 micron NKN slot liner including greater copper slot fill, lower in-slot winding temperatures, and reduced magnet and stator yoke temperatures.

These benefits can be translated into more efficient and compact eMotor designs and down-sized battery packs, as extensively shared in previous articles.?

https://www.dhirubhai.net/pulse/ajedium-peek-slot-liners-potentially-reduce-battery-pack-brian-baleno/

Figure 1: Virtual engineering results comparing NKN to PEEK

The remaining challenge for eMotor design engineers is to optimize the adhesion between the secondary insulation, sometimes referred to as “varnish”, and the PEEK magnet wire and the PEEK slot liner insulation materials. Here Epic Resins partnered with Solvay, bringing together their expertise in secondary insulations and Solvay’s expertise in insulation materials.?

Epic Resins developed a single component epoxy resin called ProPreg E240 which was designed to increase the adhesion to PEEK while also being compatible with other common insulation materials such as PE/PAI enamels (polyester/polyamide-imide) MW35 and PI enamels (polyimide) MW20 on both round and shaped conductors. ProPreg E240 provides the highest industry adhesion in a range of applications including: wire to wire, wire to aramid paper, aramid-paper to steel, wire to Ajedium? PEEK slot liners and steel to Ajedium? PEEK slot liners. Figure 2 below shows the relative peel force between KetaSpire? PEEK magnet wire and Ajedium? PEEK slot liner films where the ProPreg E240 was two times higher than the adhesion between PEEK and the industry standard secondary insulation.

Figure 2: ?Industry Standard Secondary Insulation vs ProPreg E240

As shown below in Figure 3, after 2000 hours of ATF exposure the KetaSpire? PEEK magnet wire and ProPreg E240 maintained their adhesion strength.

Figure 3: PEEK coated magnet wire and ProPreg E240 adhesion strength after 2000 hr ATF exposure at 150 C?(Test Method: IEC 61033)

The ProPreg E240 is designed to drop into existing trickle impregnation process equipment and can be used in most other process types. The trickle impregnation process is the most widely used process for liquid cooled EV automotive traction motors. The ProPreg E240 is trickled onto the Ajedium? PEEK slot liners in the “cuff” area and over the PEEK coated wire “end turns”. This is done at a controlled flow rate and at specific dispense positions. The goal is to achieve a resin slot fill of?>95% or better, and in many cases 100% can be achieved, providing the best overall electrical insulation properties and behavior. The image in Figure 4 shows this effect.?

Figure 4: PEEK Insulation with ProPreg E240 Applied using a Trickle Impregnation

Source: Epic Resins (black light picture)

In summary, Ajedium??PEEK slot liners in combination with Epic Resins ProPreg E240 provide the opportunity to improve high voltage eMotor efficiency over incumbent secondary insulations and slot liner materials like paper and paper laminates. PEEK’s high temperature electrical insulation and thermal conductivity allow for utilization of thinner slot liners which leads to great copper slot fill. ProPreg E240 stands out with high bond strength, excellent penetration and high temperature characteristics. Both the Ajedium? PEEK slot liners and Epic Resins ProPreg E240 in combination are well suited for eMotor applications.?

Please contact us to learn more about these eMotor solutions.

About Solvay?

Solvay is a science company whose technologies bring benefits to many aspects of daily life. With more than 22,000 employees in 61 countries, Solvay bonds people, ideas and elements to reinvent progress. The Group seeks to create sustainable shared value for all, notably through its Solvay One Planet roadmap crafted around three pillars: protecting the climate, preserving resources and fostering a better life. The Group’s innovative solutions contribute to safer, cleaner, and more sustainable products found in homes, food and consumer goods, planes, cars, batteries, smart devices, health care applications, water and air purification systems. Founded in 1863, Solvay today ranks among the world’s top three companies for the vast majority of its activities and delivered net sales of €13.4 billion in 2022. Solvay is listed on Euronext Brussels and Paris (SOLB). Learn more at

www.solvay.com.

About Epic Resins

Epic Resins is an established international leader in epoxy and polyurethane resin manufacturing based in Palmyra, WI. Founded in 1958, Epic Resins has formulated, manufactured and supplied resins for a wide range of industries, specializing in potting and encapsulation compounds, secondary insulation and adhesives. Epic Resins is committed to serving our global customers as a trusted partner in superior quality resins and polymers to enhance their profitability and performance. Learn more at?www.epicresins.com.