SYSTEM AND INSTALLATION FOR GENERATING A THREE-PHASE ALTERNATING VOLTAGE

Abstract

A three-phase generator for an installation for generating a three-phase alternating voltage, has a two-pole rotor having two magnetic poles, wherein the magnetic poles are arranged irregularly and offset to one another on the periphery with respect to a rotor rotational axis of the rotor

Claims

1. A system for generating a three-phase AC voltage, comprising: at least one three-phase generator having a two-pole rotor having two magnetic poles, which are arranged, with respect to a rotor axis of rotation of the rotor, in an unevenly circumferentially offset manner with respect to one another, and at least one filter unit, adapted to filter phase voltages of a three-phase AC voltage generated by way of the three-phase generator.

2. The system as claimed in claim 1, wherein a pole angular spacing between the magnetic poles in a direction of rotation of the rotor is 210.

3. The system as claimed in claim 1, further comprising: a stator having at least one fractional-pitch stator winding.

4. The system as claimed in claim 3, wherein the stator is a 60 Hz stator and the rotor is a 50 Hz rotor.

5. The system as claimed in claim 1, wherein the filter unit has one series resonant circuit per phase of the three-phase AC voltage generated by way of the three-phase generator.

6. A plant for generating a three-phase AC voltage, comprising: at least one turbine, and at least one system as claimed in claim 1, wherein a turbine rotor of the turbine is connected to the rotor of the three-phase generator in a rotationally fixed manner, wherein an operating frequency of the turbine rotor is lower than a frequency of the three-phase AC voltage filtered by way of the filter unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The invention is explained by way of example below with reference to the attached figures on the basis of advantageous embodiments, wherein the features depicted below may constitute an aspect of the invention both taken alone and in different combinations with one another. In the figures:

[0022] FIG. 1 shows a schematic illustration of an exemplary embodiment of a three-phase generator according to the invention; and

[0023] FIG. 2 shows a schematic illustration of an exemplary embodiment of a plant according to the invention.

DETAILED DESCRIPTION OF INVENTION

[0024] FIG. 1 shows a schematic cross-sectional illustration of an exemplary embodiment of a three-phase generator 1 according to the invention for a plant (not shown) for generating a three-phase AC voltage.

[0025] The three-phase generator 1 comprises a two-pole rotor 2 having two magnetic poles 3 and 4, wherein the magnetic pole 3 is a magnetic north pole and the magnetic pole 4 is a magnetic south pole. The three-phase generator 1 also comprises a stator 5, which has an, in particular fractional-pitch, stator winding 6, in which a voltage is induced owing to the rotation of the rotor 2 about the rotor axis of rotation 7 thereof. The stator 5 is a 60 Hz stator and the rotor 2 is a 50 Hz rotor.

[0026] The magnetic poles 3 and 4 are arranged, with respect to the rotor axis of rotation 7 of the rotor 2, in an unevenly circumferentially offset manner with respect to one another. In particular, the magnetic poles 3 and 4 are arranged, with respect to the rotor axis of rotation 7 of the rotor 2, in an unevenly circumferentially offset manner with respect to one another in such a way that a pole angular spacing 8 between the magnetic poles 3 and 4 in a direction of rotation (indicated by an arrow 9) of the rotor 2 is greater than 180. In particular, the pole angular spacing 8 in the direction of rotation of the rotor 2 in the exemplary embodiment shown is 210. The magnetic pole 4 of the rotor 2 is thus arranged angled by 30 with respect to an axis 10 running perpendicular to the rotor axis of rotation 7 and on which the magnetic pole 3 of the rotor 2 lies. Therefore, the magnetic pole 4 follows the magnetic pole 3 in the opposite direction of rotation of the rotor 2 as early as at a pole spacing of 150. The first half-wave of a voltage oscillation induced in the stator winding 6 corresponds approximately to a 60 Hz half-wave, whereas the second half-wave of the voltage oscillation corresponds approximately to a 40 Hz half-wave. The first half-wave of the oscillation proceeds faster than the second half-wave. A Fourier decomposition of said induced voltage contains, in addition to other oscillation components, a 40 Hz, a 50 Hz and a 60 Hz oscillation. This configuration of the rotor 2 induces in the stator winding 6 a relatively greatly distorted oscillation compared to a usual, approximately sinusoidal 50 Hz oscillation. In order to be able to supply a 60 Hz three-phase AC voltage to a 60 Hz power grid, all of the oscillation components that are not required, that is to say all of the oscillation components outside of the 60 Hz oscillation, are filtered out of the induced voltage by way of a filter circuit (not shown).

[0027] FIG. 2 shows a schematic illustration of an exemplary embodiment of a plant 11 according to the invention for generating a three-phase AC voltage.

[0028] The plant 11 comprises a turbine 12 in the form of a 50 Hz gas turbine. The plant 11 furthermore comprises a system 13 for generating the three-phase AC voltage. The system 13 is connected to a 60 Hz power grid 14 into which the 60 Hz three-phase AC voltage is intended to be fed.

[0029] The system 13 comprises a three-phase generator 1, which may be configured as per FIG. 1. From the three-phase generator 1, only a stator circuit diagram having three winding resistors 15 representing the stator winding is shown in FIG. 2. A turbine rotor (not shown) of the turbine 12 is connected to the rotor (not shown) of the three-phase generator 1 in a rotationally fixed manner.

[0030] The plant furthermore comprises a filter unit 16, which can be used to filter phase voltages generated by way of the three-phase generator 1. The filter unit 16 comprises one series resonant circuit 17 per phase of the three-phase AC voltage generated by way of the three-phase generator 1. Each series resonant circuit 17 comprises an inductance 18 and a capacitance 19. An operating frequency of the turbine rotor is lower than a frequency of the three-phase AC voltage filtered by way of the filter unit 16.

[0031] Although the invention has been described and illustrated in more detail by way of the advantageous exemplary embodiments, the invention is not restricted by the disclosed examples, and other variations may be derived herefrom by a person skilled in the art without departing from the scope of protection of the invention.