Water and Energy Abstracts
Year : 2004, Volume : 14, Issue : 1
First page : ( 32) Last page : ( 32)
Print ISSN : 0021-1672.

78. Numerical Investigation of Dynamic Electromagnetic Phenomena in Permanent Magnet Generators

Schlemmer E., Muller F.

(Proceedings, Hydro 2003, Vol. I, Croatia, pp. 531–538).

Abstract

In order to design a permanent magnet generator, several dynamic electromagnetic effects have to be investigated thoroughly. One of these effects is the induction of eddy currents in the conducting parts of the rotor due to the slot ripple and to negative sequence currents. These eddy currents can lead to increased temperatures in the rotor, especially under runaway conditions. Another crucial point is the choice of the right magnet volume since there is no possibility to adjust the excitation. The use of Finite Element solutions is very beneficial in this respect because all effects from iron saturation to leakage are taken into account properly. The danger of demagnetisation of the magnets in the case of a short circuit can be assessed directly by conducting a Finite Element calculation of this fault case. The effects of damper circuits on the field distribution during short circuits and other transient states can also be investigated thus enabling the designer to adjust the dimensions of these elements. In this paper, we will focus mainly on the dynamic aspects of the electromagnetic and electro-mechanical interactions between the rotor and the stator of a permanent magnet machine. In most cases, permanent magnet machines are of moderate size. Therefore, their moment of inertia is rather small thus giving rise to interesting effects in terms of rotor dynamics. During the last years, several important innovations in the field of hydro power generation have been introduced by VA TECH HYDRO, notably in the field of compact hydroelectric power generation. In the development of ECOBulb^TM and HYDROMATRIX® generators, state-of-the-art calculation methods have been applied extensively. In this paper, several problems of the electromagnetic engineering process of permanent magnet excited generators are dealt with. Examples of the evaluation of dynamic electromagnetic phenomena are given, such as start-up, short circuit and synchronisation as well as loss calculations with rotating models in 3D.

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Keywords

Electromagnetic effects, Eddy currents, Finite Element, Damper circuits.

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