VIDEO: iCARe^® 420 Save Boosting the power density of efficient traction motors

The iCARe^® range already includes three families of electrical steels for different applications: iCARe^® Save, iCARe^® Torque, and iCARe^® Speed. The steels in the iCARe^® Speed family offer the highest mechanical strength, making them ideal for compact, high-speed rotors with higher power density. But to obtain these high mechanical strength values, the magnetic power losses of ArcelorMittal’s iCARe^® Speed grades are slightly impacted. For this reason, iCARe^® Speed grades are only approved for rotor applications in synchronous machines.

To overcome this limitation, a new iCARe^® family was recently launched by ArcelorMittal. Known as iCARe^® 420 Save, the new grades are low loss electrical steels which have an improved guaranteed yield strength of 420 megapascals (MPa).

The iCARe^® 420 Save family offers higher mechanical strength than standard iCARe^® Save grades, but without any detrimental effect on its magnetic properties (such as magnetic power losses). This makes iCARe^® 420 Save the best choice to enhance the magnetic properties of stators, while providing the necessary mechanical properties needed for rotors. Another advantage is that both stators and rotors can be punched from the same grade of iCARe^® 420 Save, which reduces cost.

Popular iCARe^® 420 Save grades include:

• 420 Save 27-15: guaranteed loss level of less than 15 W/kg at 400Hz and 1T at 0.27 mm thick
• 420 Save 30-16: guaranteed loss level of less than 16 W/kg at 400Hz and 1T at 0.30 mm thick.

The improved and guaranteed yield strength (420 MPa) of iCARe^® 420 Save grades allows for rotor design improvements. When combined with the low core losses of the grade (which are particularly useful in the stator), these mechanical rotor design improvements can increase overall performance.

The enhanced mechanical properties of the iCARe^® 420 Save grades are useful in electrical machine topologies where its higher yield strength can be exploited. That may involve optimising the machine’s mechanical design and/or increasing its rotation speed to enhance power density. iCARe^® 420 Save grades are particularly useful for reducing iron losses in high-speed hybrid and electric traction machines.

ArcelorMittal is producing iCARe^® 420 Save at our mill in St-Chély d’Apcher (France). The steels can be shipped almost anywhere in the world.