Electric vehicle motors developed in China, Europe and the United States share broadly similar designs, but differ in material choices, component construction and cooling technologies, according to a study by Germany’s RWTH Aachen University.
Researchers from the university’s Chair of Production Engineering of E-Mobility Components (PEM) examined 115 electric motors from 80 vehicles covering model years 2019 to 2025. Published in the journal Energies, the study, titled Review and Benchmarking of Electric Motor Product Design and Manufacturing Technologies from the Chinese Market, focused on Chinese drivetrains and compared them with European and US designs.
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The researchers found few fundamental differences in motor architecture, including housing structures, rotor and stator geometries, and cooling concepts. More significant variations emerged in the materials and construction of individual components.
Differences in Materials and Motor Design
Chinese manufacturers increasingly use magnesium alloys for motor housings, while European automakers more commonly rely on aluminium.
The study also identified differences in electrical power distribution components. Chinese manufacturers predominantly use powder-coated busbars, whereas European designs more frequently incorporate multiple copper bars embedded in polymer components.
Across all three markets, manufacturers are moving towards more compact and integrated drivetrain systems. Since 2022, designs combining the motor, transmission and power electronics into more closely integrated units have become dominant in the examined sample.
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The study found that average peak power density for permanent magnet synchronous motors increased from 1.68 kW/kg in 2019 to 2.43 kW/kg in 2024 and 2025 models, representing an increase of nearly 45%.
Higher rotational speeds have contributed to this improvement. While motors produced between 2020 and 2022 generally operated at maximum speeds of 8,000 to 17,000 rpm, newer designs increasingly reach 20,000 rpm or more. Some examples recorded speeds of up to 30,500 rpm.
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Average drivetrain gear ratios also increased by approximately 21.5% over the period examined.
Higher motor speeds allow manufacturers to use smaller rotor and stator diameters, potentially reducing material requirements. However, the researchers noted that increased rotational speed does not always result in a smaller motor, as it can also support higher vehicle speeds.
Direct Oil Cooling Gains Ground
Cooling technology is another area of development. Older electric motors predominantly relied on conventional water-jacket cooling, while newer designs increasingly combine direct oil cooling for the rotor and stator.
This approach can support higher operating performance but creates additional requirements for sealing systems and manufacturing precision.
Overall, the findings suggest that Chinese manufacturers are contributing significantly to electric drivetrain development, but their fundamental engineering direction remains broadly aligned with European and US competitors. Differences are more apparent in material selection, component implementation and specific manufacturing approaches than in basic motor architecture.