There’s no doubt about it: modern e-drives will be among the drive systems of the future. Which is why manufacturers and developers are absolutely committed to further optimizing electric drive units, tweaking everything from torque and power density to efficiency, weight and above all: production costs.
All aspects are being fine-tuned, including the rotor design, where there are a wide variety of different optimization approaches. Besides increasing the pole count, designers are also investigating different geometries for the configuration of the magnets.
Limits are increasingly being reached in terms of producibility or mechanical robustness, especially – but not entirely – due to ever increasing speeds. This is why the CONNACTIVE partners have also turned to Soft Magnetic Composites (SMC) for the rotor, because the strengths of this material can be fully leveraged at all stages, from design and manufacture to subsequent operation.
A GROUNDBREAKING MATERIAL
The rotor manufacturing process on the basis of SMC opens up entirely new possibilities for electromagnetic design. It’s essentially a molding process – and offers exactly the same freedoms. During the manufacturing process an SMC density of around 5.8g/cm3 is achieved. As the magnetic characteristics of the rotor core become less and less significant at higher speeds and the corresponding pole counts, this is a very good compromise – especially as this process allows the true separation of magnetic and reluctance torques.
Right from the start, during the production of the rotor, the use of SMC in combination with epoxy offers a distinct advantage over conventional sheet metal punching, as the material is not punched, but cast in a mold, thus providing maximum design freedom.
All parts of the rotor are cast in a corresponding mould at the same time.
FILLING THE SMC
In the first step the Soft Magnetic Composite is filled into the mould.
POSITIONING OF THE MAGNETS
In the second step the magnets are placed in their final position.
FILLING OF THE CASTING MATERIAL
An epoxy resin is then added as casting material.
CONNECTION VIA NEGATIVE PRESSURE
The epoxy is pulled through the SMC powder by means of negative pressure.
In this way, a rotor is produced from a single cast in a short time - with many advantages.
PROPULSION FROM A SINGLE MOLD
In our innovative procedure all parts of the rotor are assembled simultaneously, placed in their final position, bonded with epoxy resin and cast.
During the process the SMC is placed in a mold and the magnets positioned directly in their designated place. The resin material is then added and drawn through the powder by means of vacuum.
The result is a compact solution “from a single mold”.
This production process opens up a whole spectrum of new opportunities, not limited to freedom of design, but also including improvement potential for electromagnetic design, production time savings with related cost reductions and improved mechanical characteristics for the rotor. As described above, instead of being inserted right at the end during final assembly, the magnets are cast with identical material. This gives increased stability and allows safe, efficient operation, even at high speeds.
And this is irrespective of rotor topology, because it goes without saying that, in addition to the straight magnet configuration in the CONNACTIVE eDrive, the process also permits the arrangement of magnets in V-shape, double-V-shape or delta-shape.
EXPERIENCE THE FUTURE
With this SMC process CONNACTIVE is taking a revolutionary new approach to rotor production and opening up new rotor design opportunities for developers, manufacturers and OEMs. One more step towards the mobility of the future.
Director R&D, MOTEG
“If you want to develop new solutions you have to tread new paths. Using modern materials and innovative production processes we were able to do precisely that when we designed the ConnActive eDrive. A true milestone on the way to finding the drive of the future.”