Synchronous generators with permanent magnets for stabilization the output voltage of the power wind mill installations

1. 1 Synchronous generators with permanent magnets for stabilization the output voltage of the power wind mill installationsTudor AmbrosProfessor, Technical University of Moldova

2. 2 1. Introduction At the given stage, the wind power even more often is used as a source of electrical energy. On the open places, on the sea, where speed of a wind is high and rather constant, the main indicators of energy quality, voltage and frequency of a source of a current are constant. In zones as, for example, in Republic of Moldova, which is situated in a pool of the Black Sea, the velocity of a wind is variable and not high. From these reasons, the basic element of transformation of a mechanical wind power in electrical energy - electrical generator is necessary for adapting to the parameters of the electrical motor of low velocity. The mechanical construction of those motors, as generators, should ensure constant frequency and voltage on output at variable velocity of a wind. The maintenance of a constancy of frequency and voltage can be realized by electronic devices. But for independent generators of small capacity used in agriculture, in places remote from electrical networks, the electronic devices are becoming unprofitable because of dearness and complexity of service. The decision of this problem offered in the given paper is based on use the synchronous generators with permanent magnets.

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6. 6  On the unmagnetized sectors a flow

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8. 8 The technology of stacking of a three-phase winding and pre magnetization winding is identical, as these windings are toroidal and together enveloped the yoke of stator and practically they are presenting one winding. The basic advantages of the generator: - the frontal parts of a stator winding are reduced approximately twice; - a plenty of poles reduce frequency of rotation; - big moment of inertia, which smooths frequency of rotation at variable load; - increased surfaces of cooling. For studing the process of magnetization and unmagnetization of the stator's yoke the method of final elements was used.

9. 9 In fig.5 is shown the picture of a magnetic field created by permanent magnets, the magnetic lines of which are closing through poles.

10. 10 At imposing a field of permanent magnets (fig. 6,?) and magnetic field of pre- magnetization current, the common picture of a field considerably changes. In a fig.7 are shown the results of computation of a picture of a magnetic field of the axial generator without slots on a stator with a three-phase toroidal winding stacked on yoke. The forces lines of a magnetic induction are distributed in regular intervals in the yoke of a stator of the generator, which represents one half from common yoke of the generator The curve distributions of a magnetic induction in an air gap (fig.8,?), as well as curve of distribution of an induction in a yoke of the stator, do not contain high harmonics. The absence of high harmonics is caused by absence of teeth on a stator and closeness of the permeability of permanent magnets to the magnetic permeability of air.

11. 11 Having changed a configuration of poles, it is possible to receive a sinusoidal curve of induction distribution in an air gap.

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14. 14 2. Conclusions By magnetizing the stator's yoke of the synchronous generator with permanent magnets it is possible to stabilize the output voltage of the generator. For the generator with a toroidal winding, the frontal parts of a three-phase winding are reduced. The generator with an axial rotor can be executed on small frequencies of rotation