Customized electrical steel for drive motors

Which requirements must be met by electrical steel?

The drive motor is by far the strongest of all the electric motors in an electric car. Depending on the motor design, different requirements pertain to the electrical steel used.

High-speed motors require electrical steels in the stator that have low losses at high frequencies, but high strengths are also required in high-speed rotors in order to keep the air gap between the rotor and the stator as small as possible and to place any permanent magnets as far outward as possible in the rotor.

Focus on grades with high polarizations are an interesting alternative. They allow the same torque at low magnetic field strengths, thus reducing conduction losses in the windings.

Ideally two different electrical steel grades with optimized properties should be used in the rotors and stators. Segmentation of the stator makes it possible to increase material utilization from roughly 75% to 95%. This conserves resources and saves costs.

The following solutions are offered by voestalpine:

We specially developed the isovac high perm NO30-15 grade for use in stators. It features extremely low losses at high frequencies and is also suitable for high-speed motors because of its high strength.

Significantly higher polarizations and low losses make isovac high perm NO30-19an interesting alternative in stator applications. Particularly with respect to punching tool wear, the material is excellently workable and weldable. When compared to isovac high perm NO30-15, isovac high perm NO30-19 features higher thermal conductivity and is less expensive.

One of our grades, isovac NO30-28 HS, is especially suitable for use rotors. This grade offers highest strengths as well as good polarization and moderate losses. isovac NO30-28 HS is also suitable for use in stators, especially when the laminations are heat-treated after the stamping process. We use this heat treatment to reduce the stress and deformation introduced to the material during the stamping process. This ensures that isovac NO30-28 HS retains excellent magnetic properties after punching.

Conclusion:

Our wide variety of innovative electrical steels make a valuable contribution to the electrification of the automobile and supplies just the right steel grade for each motor design. The materials range from thin, high-alloy materials and high-strength grades made specially for rotors to thin, highly permeable electrical steels with excellent processing properties.