U. Rieder:
"Intelligentes Bremskonzept für sensorlos betriebene PSM";
Supervisor: E. Robeischl, M. Schrödl; Elektrische Antriebe und Maschinen, 2001.

This diploma-thesis deals with the realisation of a novel brake concept of VSI-fed sensorless vector-controlled permanent magnet synchronous motors (PMSMs). The term "sensorless" denotes that there is no mechanical sensor for detection of the rotor position. Concerning the rentability for small drives, there is no use for classic braking methods like reversible conversion or brake choppers. The new software-oriented concept deals with the decay of generative work in the stator resistance which provides several advantages compared to the classic concepts.
Due to improvement on magnet materials the permanent magnet synchronous motor has an increasing importance for drives in the lower and medium power range. Since the PMSM requires no commutator, there is less need of maintenance compared to a d.c. motor. The control structure of the vector-oriented control of the PMSM is also easy to handle and allows highly dynamic applications.
The algorithms for the sensorless position detection, the field-oriented control and the brake concept are implemented in a digital signal processor (DSP). It is only required to measure DC-link current, phase currents and DC-link voltage of the new developed voltage source inverter. All other signals like rotor-speed and position, that are necessary for the vector oriented application, are either derived from the DC-link current (at low angular rotor speed) by the INFORM-model, which has been developed at the Institute of Electrical Drives and Machines, or from the phase currents (at high velocities) by an emf-based model.
The main parts of this diploma-thesis were the development and implementation of the brake-concept, especially to ensure the function of the velocity control during braking activity. The advantage of this new concept is that there are no more resources necessary, because of the software-implemented realisation. There are neither extra costs, nor is the specific power weight [W/kg] of the drive decreased in relation to classic methods. The mathematical and electrotechnical basics, the actual idea and the resulting method are extensively explained. A separate chapter is dedicated to the new developed voltage source inverter.