Scientists Create New Polymer Cooling System for EV Motors

Fraunhofer and Karlsruhe researchers are working on a new fiber-reinforced polymer cooling system for EV motors.

Apart from making electric cars lighter, the new cooling concept could help increase the power density and efficiency of a motor.

The collaboration is part of the DEmiL project and it includes Fraunhofer ICT, Institute of Vehicle System Technology (FAST), and Karlsruhe’s Institute of Electrical Engineering (ETI).

DEmiL is a German abbreviation that stands for directly-cooled electric motor with integrated lightweight housing.

There are several parameters that go into making an eco-friendly electric motor.

These include high power density, a compact configuration that fits snugly within the electric vehicle, and high levels of efficiency.

An electric motor consists of a rotating rotor and a static stator.

The stator contains the copper windings that the electricity flows through – and this is where the majority of electrical losses occur.

Drawing light on his team’s invention, ICT researcher Robert Maertens remarked that the novel aspects of their new concept lie in the stator.

The current rule is that a stator’s heat gets conducted through a metal housing to a cooling sleeve filled with cold water.

The DEmiL team has now replaced the traditional round wire with a rectangular flat wire to create more space for the cooling channel.

“In this optimized design, the heat losses can be dissipated through the cooling channel inside the stator, eliminating the need to transport the heat through the metal housing to an exterior cooling sleeve,” says Maertens.

“In fact, you no longer need a cooling sleeve at all in this concept. It offers other benefits, too, including lower thermal inertia and higher continuous output from the motor.”

The new design also incorporates a rotor cooling solution which allows the rotor’s heat loss to be dissipated directly within the motor.

By dissipating the heat close to where it is generated, the project partners were able to construct the entire motor and housing from polymer materials, leading to further advantages.

The team chose to use fiber-reinforced, thermosetting plastics of their project partner SBHPP that offer high temperature resistance and high resistance to aggressive coolants.

According to the researchers, thermosets do not swell when they come into contact with chemicals, and this makes them ideal for next-gen EV motor designs.