Fall semester 2021-2023: Teaching for a project-based practicum and presentations from third semester students of materials science about the creation and study of a special type of electric motor
Last update 11 January 2024
Since 2021 the practicum for third semester students of materials science is performed in a new way. There are several project topics which have in common the creation and manufacturing of a device and optimizing and / or studying its properties. The project topic or device should be something which allows many potential types of design and / or control and a creative manufacturing, optimizing, and investigation of one or a few specific variant(s) within the available period, namely one and a half days per week within the semester. The concrete work is performed in the so-called Materials Design Lab which was established and is maintained by Thomas Schweizer and Martin Willeke . Thomas Schweizer and several lab assistants supervise the students when they are working in the Materials Design Lab and Martin Willeke organizes the overall practicum schedule.
So far several project topics were offered and implemented, namely the construction of a
- simple ultraviolet spectrometer
- setup for heat conductivity measurements
- Stirling engine
- special electric motor related to the so-called Keppe Motor
Often several student groups did work simultaneously and independently on the same project topic. Each group comprised around five students. The practicum starts with an introductory event around mid September and ends around mid December with a presentation event where each group of students presents their project and results.
The so-called Keppe Motor as project topic was proposed by Frank Lichtenberg and he supervised the students as tutor / advisor and prepared a draft for this webpage. The Keppe Motor is a special type of a brushless electric motor which is integrated in some commercially available fans. The Keppe Motor website external pagehttps://www.keppemotor.com provides various kinds of information and products including a Keppe Motor kit.
The following picture shows a sketch of principle of the Keppe Motor.
The Keppe Motor concept comprises a turnable permanent magnet which is surrounded by a coil. When an electrical current is flowing through the coil, then a torque is generated which leads to a rotation of the permanent magnet and the shaft. The torque T can be (approximately) described by
T = |B| |H| sin(φ)
whereby B is the so-called magnetic flux density generated by the coil when an electrical current is flowing through it, H is the so-called magnetic field strength generated by the permanent magnet, and φ is the angle between B and H. The torque has the same algebraic sign during the first half of one rotation and the opposite sign during the second half of one rotation. The easiest way to ensure a continuous rotating motion is to interrupt the current through the coil within an angular interval of the second half of one rotation, e.g. around that angular position where the torque with an opposite sign would reach its maximum, i.e. around φ = 270 degrees when the range from φ = 0 to φ = 180 degrees represents the first half of one rotation. Also a flywheel can be used to ensure a continuous rotating motion. The simplest (but not the best) way to interrupt the current is via a reed switch and a small permanent magnet which is attached on the shaft.
The following Portuguese-language video displays the creation of a simple Keppe Motor model in a descriptive and comprehensible way so that it is not necessary to understand the language: external pagehttps://www.youtube.com/watch?v=eZdtuZReufY. Thomas Schweizer discovered this video on the internet.
The Keppe Motor concept offers many mechanical types of design (size, dimensions, materials, weight), plenty electrotechnical variants to control it, and various ways to explore its properties. It can also be used and explored as AC and DC generator (the DC version requires an appropriate circuit).
Thomas Schweizer has created several Keppe Motor models and two of them are shown in the following two pictures. He has also designed, implemented, and explored various kinds of electrical circuits which control the Keppe Motor.
Assembled Keppe Motor kit which was purchased from external pagehttps://www.keppemotor.com and assembled by Thomas Schweizer. The reed switch is not visible in this picture. The picture was taken on 7 September 2021 in the Materials Design Lab.
A Keppe Motor model designed and manufactured by Thomas Schweizer. The reed switch engages a circuit which comprises a transistor that switches the current through the coil. Later another kind of regulation and circuit resulted in an increased efficiency and the flywheel was no longer necessary. Picture taken on 7 Sept 2021 in the Materials Design Lab.
It is also allowed to implement mechanical constructions and / or control variants which deviate significantly from the original Keppe Motor concept. The following two pictures show an example, namely a model of a synchronous motor which is not controlled by the angular position of the rotational axis but by a sequential activation of two opposite coils in an angular array of coils.
A synchronous motor model and associated control electronics designed and manufactured by Thomas Schweizer. This model with 4 coils requires a manual start and a flywheel to ensure a continuous motion. A larger number of coils would allow an automatic start and a continuous motion without using a flywheel. The implementation of a corresponding model represents a potential student project.
Another picture from the synchronous motor model.
Before providing the presentations from the students who have performed the Keppe Motor project it appears appropriate to call attention to safety instructions for working with strong permanent magnets of the type Nd2Fe14B:
DownloadDownload safety instructions in English as pdf (PDF, 57 KB)
DownloadDownload safety instructions in German as pdf (PDF, 58 KB)
DownloadDownload short mp4 type safety video about strong permanent magnets and glass (MP4, 1.8 MB)
Presentations from the students who have performed the Keppe Motor project:
Fall semester 2021: ppsx type PowerPoint show (in German) with 4 embedded short videos from Leonardo Bolliger, Marco Ferretti, Alessandro Bellucci, Vita Augusta Onorina Bianca Rossi, Andrea Mäusli, Camillo Sirvinski, and Maxim Vovk. Title: “Projekt: Keppe Motor“. Date of publication: 19 January 2022.
Fall semester 2022: ppsx type PowerPoint show with 2 embedded short videos by Melody Greminger, Charlotte Kalbermatten, Alessandro Marton, Laura Sironi, Ronja Wyss, Thomas Schweizer, Martin Willeke, Frank Lichtenberg, Christoph Dräyer, Christoph Maier, Maxim Vovk, Karim Bingöl, and Sascha Pucillo. The author list comprises all members of Group 1 as well as others who contributed to this project, see author contributions on pages 23 and 24 in the presentation. Title of the presentation: "Project 3: Keppe Motor". Date of publication: 27 March 2023.
DownloadDownload this presentation as ppsx type PowerPoint show with 2 embedded short videos (PPSX, 18 MB)
Fall semester 2022: pdf presentation (in German) from Jona Ammann, Leonardo Del Gaudio, Oliver Heck, Florent Liechti, and Aaron Locher from Group 2. Title: "Keppe Motor". Date of publication: 3 March 2023.
Comments on the presentation of Group 2 from fall semester 2022: At the second last working day the electric motor of Group 2 did not yet work but there was still hope to put it into operation on the last available working day. Therefore it was decided to perform no practice talk for the presentation event which took place on 20 December 2022. Instead the last possible working day was used for further attempts to put the motor into operation. However, it did not work and the main reason for that was a too large friction of the relatively complex cogwheel system which was part of their design. This outcome should not be considered as a failure but simply as a result without any judgement. If a planned project objective cannot be achieved, then this is important learning experience, especially in the field of research and development and when only a limited period of time is available.
Fall semester 2023: ppsx type PowerPoint show (in German) with 5 embedded videos from Livienne Häusler, Khye-Wen Ho, Dominik Kasper, Luc Heiniger, Leon Brunella, Thomas Schweizer, Martin Willeke, Frank Lichtenberg, and Florent Liechti. Title: “Keppe Motor“. Date of publication: 9 January 2024.
Fall semester 2023: ppsx type PowerPoint show (in German) with 5 embedded videos from Jonathan Amara, Lars Bangerter, Ivo Gmür, David Lindenmann, Samuel Ziegler, Thomas Schweizer, Martin Willeke, Frank Lichtenberg, Cedric Steiner, and Leonardo Del Gaudio. Title: “Keppe Motor“. Date of publication: 11 January 2024.
DownloadDownload this presentation as ppsx type PowerPoint show with 5 embedded videos. (PPSX, 59.4 MB)