emotor diagram

Insulation Demands In Emotors For Electric Vehicles

Emotors For Electric Vehicles

What is an Electric Motor?

Electric motors (or E-motors) convert electrical energy into mechanical energy. When an electrical current is produced by a battery for instance, the current flows into the motor, which in the presence of a magnetic field causes the motor to rotate. The rotational torque of the motor is used to power an electric vehicle. Motor insulation such as slot liner or phase insulation is critical to the proper operation of the motor. This insulation is commonly a laminate consisting of aramid paper and polyimide. For a long service life and safe operation, the motor insulation must meet the demands of electrical, mechanical, thermal and chemical stresses.

Interior of electrical motor system.
Electric Car Engine
Insulation for emotor
Emotor System Diagram

Why is an E-Motor for EV different than an Industrial Motor?

An electric motor for use in an electric vehicle (EV) is different compared to industrial motors. In EV applications the overall weight of the vehicle is even more important than in standard automobiles due to the impact on vehicle range. Therefore, the electric motor must be smaller, requiring more electrically and thermally efficient materials to meet the higher power density demands.

Electric Vehicles also go through more start and stop cycles compared to industrial applications that may run continuously. This stress from “on-off” cycling will require more robust materials.

Another differentiating factor for motors in electric vehicles is increased safety considerations - whether it be flame retardant materials or improved electrical performance to reduce the risk of an electrical short. Comparative Tracking Index (CTI) is used to assess the resistance of insulating materials to electrical tracking in the presence of humidity or contaminated moisture. High CTI is very important in EV e-motor electrical insulation.

Lastly, motors for electric vehicles involve exposure to Automatic Transmission Fluids (ATF) and must offer compatibility to these fluids.

Advantages offered by fluoropolymer films in EV Motors

The addition of fluoropolymer films to slot liner and phase insulation constructions (aramid paper and polyimide) is crucial to meet the rigorous demands in motors for electrical vehicles and long-term reliability requirements.

The most important being CTI, where fluoropolymers offer an advantage over standard materials with values >600 (V). The high CTI of fluoropolymers reduces the risk for an electrical short circuit and the consequential risk of fire.

A wide range of fluoropolymer films can be selected offering excellent thermal properties and superior dielectric strength in thin construction. Fluoropolymers are chemically inert and compatible with most all materials (resins, fluids, etc.). Standard and custom surface treatments are available to tailor the fluoropolymer film for a void free interface with surrounding insulating resins and easy lamination to other complementary insulation materials.


Saint-Gobain offers a variety of fluoropolymer films, polyimide films and complex laminated solutions that solve major challenges in electrical insulation applications such as:

Saint-Gobain combines electrical insulation expertise, resources, technology, a world-class R&D center and flexibility to deliver customized solutions to each customer.

If you would like to learn more about Saint-Gobain Specialty Films electrical insulation solutions, please do not hesitate to contact us directly.