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 a battery produces an electrical current 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 and life 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.

As batteries transition to 800 Volts enabling longer range, the demand on the e-motor is even more important, requiring improved electrical insulation resistant to Partial Discharge. It is also important that the insulation solution is thinner, allowing more copper fill in the slot.

The higher voltage levels also result in higher temperatures requiring innovative electrical insulation solutions that can allow easier flow of heat.

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.

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

Emotors CTQs and Demands

CTQs and Demands

  • Higher Voltage, partial discharge resistance
  • Thinner Insulation allows for more copper fill in the slot
  • Improved heat transfer and high temp resistance
  • Chemical compatibility

Advantages offered by fluoropolymer films in EV Motors

A unique combination of polyimide and fluoropolymer films can meet all of the rigorous demands summarized above for motors in electrical vehicles.

Higher performing insulation in this case equals a thinner solution and improved dielectric performance.

Saint-Gobain’s PTFE coated PI products offer Dielectric Breakdown (V/mil) 4X that of the standard NKN used in many motor slot liner applications.

This type of solution allows for more room for copper fill in the slot while providing improved dielectric performance needed in EV’s with 800V batteries.

Breakdown Voltage Comparison

Saint-Gobain’s PTFE-coated PI products also offer improved heat flow which is 6X better than NKN. which is critical for the thermal efficiency of the motor.

This increase in thermal conductivity enables improved heat transfer from the windings which is even more important as electric vehicles transition to higher voltage batteries and higher temperatures.

average dielectric breakdown chart
thermal resistance and thickness chart

Chemical Compatibility

A fluoropolymer such as PTFE is designed to not stick and is known for its great release properties. This is beneficial for easy insertion of windings into the slots. Saint-Gobain offers expertise in custom surface treatments that can tailor the fluoropolymer film for a void-free interface with surrounding insulating resins.

Additionally, fluoropolymers are chemically inert offering excellent compatibility with automotive fluids such as ATF.


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

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 Composite Solutions electrical insulation solutions, please do not hesitate to contact us directly.