Electromagnetic Finite Element Calculations of Permanent Magnet Generators for ECObulb and HYDROMATRIX Applications.

Abstract

Although HYDROMATRIXÔ and ECOBulbÔ technologies are relatively new, they can be considered as a ecologically and economically sound method for the generation of electric energy. With the advent of high energy permanent magnets, several restrictions in geometrical dimensioning have become much less severe. The use of permanent magnets for the excitation of synchronous generators has several beneficial effects such as the improvement of the load factor (compared with asynchronous generators) and the elimination of the ohmic losses in the field coils. Nevertheless, the use of permanent magnets poses several challenges for the design engineer. One of them is the exact prediction of the induced voltage since there is no possibility to re-adjust the voltage by a field current. Second, there is the possibility of de-magnetisation of the magnets in the event of an short circuit which has to be prevented. Additionally, the slot ripple losses in the surface of the rotor parts tends to increase the magnets’ temperature which makes them more vulnerable against de-magnetisation in the case of a short-circuit. The application of modern computation methods to the mentioned problems will be demonstrated in this paper.