As the world accelerates its shift to electric vehicles (EVs), ZF, a prominent German automotive component manufacturer, has unveiled its latest innovation: a compact magnet-free motor. Not only does this new design promise greater efficiency, but it’s also a leap forward in sustainable vehicle technology.
Traditionally, many EVs have employed permanent-magnet synchronous machines (PSMs) in their design. These PSMs demand rare earth materials for their construction. While they’ve been the standard for a while, ZF has dared to think differently.
Enter the In-Rotor Inductive-Excited Synchronous Motor, or I2SM for short. Unlike the PSMs, ZF’s I2SM doesn’t rely on magnets, which translates to a decreased dependence on rare earth elements. This factor alone increases the sustainability quotient of the motor, ensuring a more stable and secure supply chain, given that a vast majority of these rare earth materials are sourced from China.
But it’s not just about sustainability; it’s also about efficiency and design. Traditional magnet-free motors had a catch. They needed additional components like sliding rings or brushes, all essential for transferring electrical current to the rotor windings. This not only increased the motor’s weight and size but also introduced a risk of wear and tear due to friction. Furthermore, these traditional designs demanded a dry installation room which wasn’t conducive to oil cooling and required additional space, complicating model planning for manufacturers.
ZF’s innovative approach changes this narrative. The secret lies in integrating the inductive exciter within the rotor shaft of the I2SM. This setup generates the energy for the magnetic field through coils that create a magnetic pull. The energy is then transferred inductively – a process that takes place without any mechanical contact – into the rotor. The result? No need for brushes, slip rings, or additional seals to keep the area dry. This means that ZF’s motor is incredibly compact, boasting both high power and torque density.
Another benefit of the I2SM is its ability to mitigate drag losses that are commonly seen in conventional PSM e-motors. This makes electric highway driving much more efficient. ZF mentioned in a statement, “The inductive exciter can reduce energy transmission losses in the rotor by 15% compared to traditional SESM systems. Plus, considering the environmental impact, the CO2 footprint, exacerbated by PSM e-motors due to their reliance on rare earth minerals, can be reduced by up to 50%.”
It’s worth noting the geopolitical implications of ZF’s invention. With China controlling over 90% of the global supply of rare earth elements, they’ve had an upper hand in the EV industry. ZF’s magnet-free design could level the playing field a bit, reducing global dependency on a single major supplier.
As for what’s next for the I2SM motor? ZF is committed to refining the technology, ensuring it’s ready for large-scale production. They plan to offer it within their e-drive platform. Customers, whether from the passenger car sector or the commercial vehicle space, will have the flexibility to choose between models with a 400-volt architecture or an advanced 800-volt one, the latter of which will feature power electronics based on silicon carbide chips. This move not only marks an evolution in EV technology but also reinforces ZF’s commitment to driving the future of mobility.
