Thin Gauge Electrical Steel for EV Applications

07/09/2021

The need for greater electrical efficiency continues to accelerate across markets and applications, mainly driven by rising energy costs and the need to combat global climate change. In electrical vehicle applications, efficiency is inherently critical to maximizing range on a fixed battery energy supply. In order to maximize range, EV manufacturers are constantly improving motor designs to achieve greater and greater efficiencies.

In EV motor/generator applications, core loss due to eddy currents and the resulting excess heat reduces efficiency, lowers motor life expectancy and hinders high frequency operation. Traditional motor design with thicker carbon steel laminations offers lower costs of manufacturing, but doesn’t provide optimal efficiencies for EV’s. 

It is estimated that 5% of total energy loss is due to lamination materials. One answer to increasing motor efficiency is by utilizing thin gauge motor laminations. Typical industrial motor laminations are anywhere from .014” to .025” thick. In contrast, today’s electrical vehicle motor designs are starting to specify motor laminations that are in the .010” range down to .004” thick. While offering greater efficiencies due to reduced eddy current loss, thinner laminations do pose unique challenges of their own in the manufacturing process. 

The thinner the electrical steel, the more challenging it is to stamp, especially when complex geometries are inherent in the lamination design. Flimsiness of thinner materials pose significant challenges in the stamping process. The thinner the material, poses challenges progressing the material through the die, the end result if not addressed properly could create waffling or creasing in the material which can cause irregular gaps between lamination layers or non conforming parts. At these thin gauges, punching is more of a controlled tear that is highly dependent on the quality and regular maintenance of the tooling, integrity of the laminations and removal of parts from the die without damaging laminations also poses certain challenges.

From a processing standpoint, Laser cutting, alternatively, is much better suited to thin gauge material applications. However, issues such as holding the part in place for accuracy during laser cutting require innovative techniques to hold the thinner material in place during the cutting process. Additional challenges could arise from the assist gas vibrating thin gauge material during the laser cutting process. Proper fixturing is required to manage this and maintain required tolerances. 

Laser Technologies Inc. has invested in customized laser cutting cells and developed special manufacturing processes to optimize the production of thin gauge motor laminations. Because of our ability to maintain very high tolerances, while being integrated into an automated manufacturing cell for increased throughput and efficiency, we are able to deliver the electrical properties and highest quality rotor and stator stacks required by today’s demanding electric vehicle applications.