Enhancing E-Motor Design and Thermal Efficiency with Advanced Cooling

The trend is shifting towards using automatic transmission fluid or oil-based fluids for direct cooling.

March 1, 2025

Brian Baleno

Automotive coolant lines, integrated exhaust pipes and ventilation tubes are among the most complex and challenging components of modern vehicles. (Syensqo)

The acceleration of 800V permanent magnet radial flux e-motors marks a significant leap in the automotive industry. This motor architecture offers increased power density through smaller, lighter designs that spin at higher RPMs. However, this advancement brings with it the challenge of efficient thermal management, especially in dissipating heat from the magnet wire within the stator.

Syensqo’s coolant line polymers, such as Ryton PPS, address the demanding needs of thermal management in vehicles to maximize the performance capabilities of coolant lines. (Syensqo)

Effective thermal management is crucial for improving e-motor efficiency. The primary heat sources are the copper-insulated magnet wires, with heat spreading to the slot liners. Engineers have explored various cooling methods, including traditional water jackets using ethylene glycol and water. However, the trend is shifting towards using automatic transmission fluid (ATF) or oil-based fluids for direct cooling, driven by its integration convenience with the e-motor gearbox and inverter systems.

ATF can be applied to the stator in several ways, including cooling the exterior components and end windings. Polymer circular stator oil guide rings, which direct the ATF to the end-windings from various angles, are also becoming popular. These rings provide design flexibility and optimized thermal management.

Injection molding of stator rings allows for unique cooling channels, facilitating efficient heat removal from the copper magnet wire and slot liners. This method offers significant advantages over traditional materials like die-cast aluminum, including 25% weight savings, faster manufacturing cycles and reduced need for secondary operations like machining or welding.

Selecting materials for stator oil guide rings and cooling tubes involves considering their performance under high temperatures and exposure to ATF. Syensqo, formerly known as Solvay Specialty Polymers, produces Amodel PPA and Ryton PPS, which could be considered because of their mechanical properties retention at temperatures from 150 to 180 C (302 to 356 F), chemical resistance, and dimensional stability. These materials have been used for over 15 years in gearbox components and maintain performance under harsh conditions.

Sustainability also plays a role in the material decision criteria. Producers work to reduce the global warming potential (GWP) and carbon footprint, and using renewable electricity while reducing water usage and industrial waste helps decrease this number.

In summary, thermal management solutions for electric motors should consider chemical resistance and dimensional stability as part of their overall performance. With the right material, engineers can reduce weight, functionally integrate multiple components and improve durability.

Brian Baleno is head of Marketing Automotive at Syensqo.