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REACTION SPHERES | ARTICLE


Leopoldo Rossini received his BSc. degree in Electrical Engineering from the University of Applied Sciences of Southern Switzerland, Manno, Switzerland, and his MSc. in Electrical and Computer Engineering from Purdue University, West Lafayette, IN, United States. Since then, he has been employed in the Systems Division of the Swiss Center for Electronics and Microtechnology (CSEM) in Neuchâtel, Switzerland, and he is also currently a PhD student at EPFL (Lausanne) working on the reaction sphere project.


<< Figure 6: The author of the article, Leopoldo


Rossini, on the right, sitting next to Senior Project


Manager Ivar Kjelberg. >>


Remove the Iron The ultimate goal is to obtain a specific magnetic flux density within the air gap while minimising rotor mass and maintaining a level of useful inertia. Using COMSOL, we plan to study a different approach taking advantage of an interesting phenomenon. Like electrical circuits, magnetic circuits must be closed. In our current design, the metal of the rotor holding the magnets serves as the return path, similar to the ground in an electric circuit. However, in what is known as one-sided flux, a special arrangement of magnets can augment the magnetic field on one side, while cancelling the field to near zero on the other side.


By taking advantage of this effect, we can possibly replace the rotor’s iron core with a lighter weight material. In this new design, there’s no need for iron to close the magnetic flux circuit inside the rotor because the flux is directed outwards by the magnetised material. Although the magnets and iron have roughly the same amount of mass, for the same volume/mass, replacing the iron with permanent magnets would increase the magnetic field outside the rotor — and allow us to reduce the current in the coils to operate the motor and thus cut power consumption. Here, again, COMSOL will allow us to immediately predict the performance of a particular design in terms of developed forces/torques and power consumption.


33 | commercial micro manufacturing international Vol 7 No.2


THE SMALLTEST BORING HEAD IN THE WORLD


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