HKA: Ms. Hübner, what did you focus on in your bachelor's thesis?

Lena Hübner (LH): I developed an electric motor with a so-called follower pole rotor. The motor was a permanent-magnet synchronous machine. Put simply, such a motor contains a large number of magnets that are attached to the rotor in alternating polarity. The problem is that the permanent magnets are pretty much the most expensive components on such a motor. It is therefore interesting to investigate the extent to which savings can be made here. In the following-pole rotor I developed, every second magnet was removed and replaced with iron. The remaining magnets were all magnetized in the same direction and the electromagnetic field polarizes the iron in the opposite direction, creating torque.

That sounds good if it saves material. But does the motor have the same performance as the original motor, especially if you only install half as many magnets?

(LH): If you remove half of the magnets, you initially assume that the torque is also half as great. But that was not the case. The follower pole rotor with unchanged geometry was able to achieve around 80 % of the torque of the original rotor. That was an interesting finding. Because from that point on, it was all about optimization. I adapted the shape of the magnets a little more and also increased their height and width. As a result, I was even able to achieve the same torque as the original motor. Of course, a little more than half of the magnet material was used, but it was still possible to reduce the overall torque. However, it has to be said that the motor runs a little less smoothly because variables such as the cogging torque and the torque ripple have changed and the magnetic field is no longer as fluid.