A forming technique developed at Fraunhofer IWU increases the groove fill factor in electric motors to over 80 %. This means that motors can be dimensioned smaller for the same power.
In contrast to the other wire and winding geometries shown, the flexible, position-adapted geometry (left) makes extensive use of the installation space.
Fraunhofer IWU
Today, electric vehicles are mostly driven by permanently excited synchronous motors. A key component of the motors are the stators known as toothed coils, whose teeth are wound with copper wire. However, according to the current state of the art, automated winding processes can only fill about half of the grooves in the toothed coil.
A forming process developed at the Fraunhofer Institute for Machine Tools and Forming Technology IWU is now expected to increase the slot filling factor to over 80 %. With a position-adapted winding geometry, the wire is designed geometrically in such a way that the available space is filled in the best possible way, according to the researchers. For example, at the level of the wider base side in the trapezoidal groove, a flat and wide design of the winding makes sense, while on the short base side a narrow wire geometry ensures the best possible utilization of space. The conductivity of the wire in the respective geometry is also taken into account.
According to Fraunhofer IWU, the new process reduces the electrical resistance in the coils. In addition, the current flow is improved and higher magnetic field strengths are achieved. This means that motors can be made smaller for the same power.
