Andreas Hamann, Chairman of the Foundation Board and Head of Human Resources Europe at Schaeffler with the Future Technology Award certificate. Photo: UBT.
Award winner Prof. Dr.-Ing. Stephan Tremmel, University of Bayreuth. Photo: UBT.
Regardless of the design, rolling bearings are essential components in all systems in which things rotates. It is impossible to imagine wind turbine gearboxes or a wide variety of applications in the field of transport without them. However, the increasing electrification of many applications is leading to new challenges. One of these is so-called parasitic electrical voltage, which leads to misdirected current. This can damage a wide variety of components - including rolling bearings. The Schaeffler FAG Foundation is now supporting a research initiative at the University of Bayreuth to the tune of €100,000 awarded as part of the "Future Technology Award". Here, Professor Dr.-Ing. Stephan Tremmel is investigating new ways to protect rolling bearings from this phenomenon.
"We see this idea as a highly innovative research approach," says Andreas Hamann, Chairman of the Foundation Board and Head of Human Resources Europe at Schaeffler. "It is precisely for such projects, whose real-life feasibility can only be tested at very high risk and with unclear prospects of success, that we have created the Future Technology Award."
Unbalanced converters create parasitic currents
"Increasingly, parasitic potential is being created by higher switching frequencies in converters, in conjunction with the cheap power electronic components installed there," says the Bayreuth prize winner. These converters convert alternating voltage into an alternating voltage that differs in frequency and amplitude. This is necessary, for example, to control and regulate variable-speed electric motors. Parasitic potential also end up in the mechanical drive train. "If it are large enough, it will discharge and lead to discharge current - which is very often the case at the rolling bearing," says Tremmel, and explains: "You can imagine it as little flashes - arcs of light - across the lubricant, which gradually damage the surface of the rolling elements." This "electroerosion" can then lead to undesired vibration, an increase in temperature, or even premature failure, among other things. Currently, bearings with ceramic rolling elements are used, or bearings provided with thermal spray coatings supposed to ensure electrical insulation. However, these bearings are very expensive compared to conventional ones, and are therefore not suitable for every application.
Promotion of a creative idea
Up to now, brushes in ring form or sliding contacts attached to the rotating shaft have often been used to dissipate currents in a controlled manner. However, this does not always work, especially due to wear arising at higher speeds. This is precisely the case with electric or hybrid drives, given the imperatives of lightweight construction and energy efficiency in theirdesign. Therefore, a different solution is needed here. Moreover, the sliding contacts generate additional friction. "We asked ourselves the question: How can we get around these disadvantages?", says Tremmel. The basic idea is that current dissipation via a metallic solid-state contact works very well at standstill and at low speeds. In process or precision engineering, there are so-called liquid ring seals. With these, a liquid is thrown outwards at high speed by centrifugal force, and then seals a shaft, for example. "We are seeking to make use of this principle," says Tremmel, who is currently still at the beginning of his award-winning project.
Research at the University of Bayreuth
Tremmel is working on this project as Chair of Design & CAD at the Faculty of Engineering Science. "I am very pleased that the Schaeffler FAG Foundation sees such great potential in the idea that they are supporting our work with the Future Technology Award," says Tremmel. With funding amounting to € 100,000 euros, the idea can now be advanced and concretised. In detail, this means that further calculations and simulations will now be carried out. Tremmel has already put together a team at the research group for this very purpose. "This will be followed by the implementation of prototypes and, in a further step, these will be put to the test in various test procedures," says the award winner.
About the Schaeffler FAG Foundation
The Schaeffler FAG Foundation promotes science, research, and teaching in scientific and technical fields related to bearing technology. The foundation forms a bridge between business and science for the ideas, visions, and goals of people working at universities, in research, and in companies.
Contact for scientific information:
Prof. Dr.-Ing Stephan Tremmel
Chair of Design & CAD
University of Bayreuth
Phone: +49 (0)921 55-7194
E-mail: stephan.tremmel@uni-bayreuth.de
