ZF has advanced the design of electric motors by developing one that does not require magnets. The I2SM (In-Rotor Inductive-Excited Synchronous Motor) transmits the energy for the magnetic field via an inductive exciter inside the rotor shaft. This makes the motor uniquely compact with maximum power and torque density.
Dr Holger Klein, CEO, ZF, mentions that this is ZF’s guiding principle for all new products. And the company sees no competitor that masters this technology this well. Compared to common SESM systems, the inductive exciter can reduce losses for the energy transmission into the rotor by 15%. In addition, the CO2 footprint in production, which arises with PSM e-motors in particular due to magnets, including rare earth materials, can be reduced by up to 50%.
To offer the advantages of separately excited synchronous machines competitively, ZF succeeded in compensating for the design-related disadvantages of common separately excited synchronous machines. Further, the increase in power density in the rotor leads to an improvement in performance.
Stephan von Schuckmann, Member of the Board of Management, ZF Group, stated that the uniquely compact electric motor without magnets is impressive evidence of ZF’s strategy to make e-drives more resource-efficient and sustainable, primarily through efficiency improvements. The I2SM does not require any brush elements or slip rings. Furthermore, there is no longer any need to keep this area dry by means of seals. As with a permanently magnetised synchronous motor, circulating oil efficiently cools the rotor. Compared to a common separately excited synchronous motor, the ZF innovation requires up to 90 millimetres less axial installation space. In terms of power and torque density, however, the ZF innovation operates at the level of a PSM.
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