New cooling method for electric motors: Researchers at RWTH Aachen University

Research Cooled waveguides for efficient electric motors

2025-03-06 From Sven Prawitz | Translated by AI 2 min Reading Time

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Researchers at RWTH Aachen University are developing a new cooling method for electric motors. Instead of cooling the laminated core from the outside, coolant is to flow directly through cavities in the copper conductors.

Researchers are working on a method of using waveguides for electric car motors.(Image: hyperdrives GmbH) — Researchers are working on a method of using waveguides for electric car motors.
(Image: hyperdrives GmbH)

The Chair of Production Engineering of E-Mobility Components (PEM) at RWTH Aachen University (Germany) has started a new research project. The Federal Ministry for Economic Affairs and Climate Protection is funding the project for around two years. The project is entitled "Production engineering capability of the hairpin-stator process chain for processing rectangular waveguides for use in traction drives". The researchers want to further develop the manufacturing processes for hairpin stators for electric motors. They are aiming to process rectangular waveguides. The waveguides enable direct cooling of the machine instead of the previous indirect cooling methods.

The hairpin stator significantly determines the performance and efficiency of electric motors. Previous concepts cool the winding head or the laminated core. In this way, they indirectly cool the active part of the winding. Professor Achim Kampker, Head of the Chair, emphasizes: "The thermal design of electric motors is one of the current challenges in e-mobility production." This is particularly true if compactness and performance are to be maintained.

Cooling medium flows directly through the copper conductors

Waveguides, on the other hand, enable direct cooling of the winding. Waveguides are copper conductors with a continuous cavity. The outer cross-section and the cavity can take on different shapes. They can be rectangular, circular or other shapes. With direct cooling, a cooling medium flows through the conductor. This dissipates the heat generated from the active part of the winding. Till Backes, the project manager, says: "Waveguides offer significant potential for increasing the efficiency and performance of electric drive machines."

Manufacturers are already using direct liquid cooling with waveguides in generator construction. There, they cool the machines with an output of up to 1,800 megawatts with hydrogen and pure water. The challenge with electric drive motors lies in the other order of magnitude. The rotor diameters of industrial generators are up to thirteen times larger than those of conventional electric motors. Prof. Kampker explains: "The bending and contacting processes used in generator construction cannot simply be transferred." This is particularly true due to the strict quality requirements and high quantities in the automotive sector.

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Date: 08.12.2025

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