Siemens Aktiengesellschaft

Marcus Ziegler

Rolf Vollmer

Wilfried Hofmann

The invention relates to a friction brake which can be used for a shaft and a bearing part that can be rotated in relation to each other about a rotational axis (). The friction brake comprises two brake elements: the first brake element has a first friction surface () and has to be mechanically connected to the bearing part, and the second brake element has a second friction surface () and has to be mechanically connected to the shaft. The connectible and disconnectable dynamic effect of an actuation mechanism forces the two brake elements against each other during a braking action or stop in such a manner that the two friction surfaces () rest one on the other and contact each other in the area of a contact surface (). The contact surface () covers only a part of every friction surface () at any point in time during a braking action or stop. The relative position of the contact surface () in relation to any of the two friction surfaces () changes during a braking action.

Friction brake having a contact surface provided between two brake elements

According to the invention, the torque ripple of electrical machines is supposed to be further reduced. For this purpose, it is provided to dispose the magnetic poles, for example, on the surface of a rotor in a plurality of sections (A, A) at different angles. The result are helix angles (&#x3b2;), which have different amounts. Also more than two different helix angles, up to a continuous course of the boundary lines (G) between the poles, can be implemented.

Electrical machine with skew-running magnet pole boundaries

In a method for controlling bi-directional switches in power converters, with separate control signals for both current directions, preferably 3&times;3 matrix converters, a switching process from a base main state, into a secondary main state, and vice versa, occurs after a voltage controlled two-step process or a voltage controlled four-step process, without additional operational current-conducting components. After a first step, all uni-directional switches, apart from those at the interface of reference main state and target main state, are switched off and after a second step, all target main state switches are switched on. The switching processes can thus be carried out, at any time, by an appropriate choice of interval beginning and interval end, whereby a free-wheeling arm for both current directions permanently exists, the only requirement being the creation of a current interval for each phase in multi-phase systems. The method is applicable with practically all supply current frequencies.

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Rasdorf, Germany

Marcus Ziegler