Title of Invention

A SYNCHRONOUS GENERATOR

Abstract

ABSTRACT 1516/MAS/98 SYNCHRONOUS GENERATOR FOR USE IN WIND-DRIVEN POWER PLANTS The present invention relates to a synchronous generator having a generator stator with a stator winding and a generator armature which can move with respect to the stator, has n poles and induces an electric voltage in the stator winding, while a stator current flows through the stator winding, characterized in that the time-dependent profile of the induced voltage in a stator winding or a plurality of stator windings essentialiy approximates the current profile in a stator winding or the sum of at least m partial currents (11.12) in m stator windings.

Full Text

The present invention relates to a synchronous generator for use in wind-driven power plants, having a generator stator and a generator armature which can move relative to the stater and has n poles, and to a wind-driven power plant with a tower, rotor blades arranged on the latter and a generator which can he driven by the rotor blades. Slowly rotating multiphase synchronous generators for use in wind-driven power planes are known. Directly driven generators of the abovemer.tionsd type for wind-driven power plants generally rotate at relatively low rotational speeds in the range from 2G to 40 rpm. For an output of approx. 1 to 2 MW, the rotational speed is even lower still, specifically in the range from about * G to 2 5 rpm. Known multiphase synchronous generators of the abovementicned type are employed in the wmd-driven power plants of type E-4 3 or 2-65 produced by Hnercon Energieanlagen GmbH. In these wind-driven power plants, the multiphase synchronous generator has an annular stator inside which an armature moves, the armature being directly coupled to the rotor blades of the wind-driven power plant without any intermediate gearing. The armature is designed as a salient-pole machine and has a multiplicity of poles with pole shoes, which are also referred to as oole heads. A general aim when designing and configuring the generator is for the latter to eni: as little noise as possible when the wind-driven power plant is in operation, in order to pollute the environment as little as possible and, ultimately, also to increase the overall acceptance of wind-driven power plants. The low noise emission required is not always achieved by the generators used to date, since in operation they are excited strongly into mechanical vibration which may he transmitted to other components of the wind-driven power plant, such as the rotor blades, the machine housing or the tower, leading to undesired r.cise emissions. The noise emission is particularly high if the stater of the generator or other components are excited into vibrations at what is called their natural frequency. The object of the present invention consists in providing a method, a generator and a wind-driven power plant which eliminate the problems cited above. The obj ective set out is achieved by means of a method and a synchronous generator having the features according to Clai~ 1 and Claim 4, respectively. Advantageous refinements are described in the subclaims. The invention is based on the recognition that every torque fluctuation of the generator may cause the generator or another part of the wind-driven power converter to vibrate, all the mere so if, in the case of an annular generator, very high torques are applied. The torque cf the generator is proportional to the direct current through a stator winding after coupling downstream of the rectifier diodes. The following formula applies in this regard: where ? is the effective power, M is the torque, co is the rotational frequency, 13 is the direct current and Ud is the DC voltage. Since UQ is constant (DC voltage intermediate circuit), it follows that: M (t) = 1^ (t} , where Z^[t) is the sum of all the currents. The torque M is thus directly proportional to the time-dependent sum cf all the partial currents. If the profile of a partial current or the time-dependent sum of a plurality ox partial currents is now made to resemble the profile of tne stator-induced voltage, the time-dependent profile of the induced voltage being essentially trapezium-shaped, with rounded sections at the leading and trailing edges and the trapezium upper edges, torque vibrations can be minimised. It has been found that by forming the current and voltage profile described above, not only 13 it possible to drastically reduce the forces occurring on the circumference fror. one stator groove to the next, but that, in addition, the tangential force curve on the circumference from one stator groove to the next is substantially smoothed, which led to a considerable reduction in the vibration excitation and ultimately also considerably reduced the sound output level of the synchronous generator. The desired signal shapes of the current and the vol cage may, for example, be obtained by taking the following measures on the armature: a) asymmetric distribution of the individual poles ever the circumference of the disk formed by the poles; b) changing the pole shoe geometry tc the effect that the pole head is essentially in the shape of an arrow when viewed f rorr. above and is in the shape of a trapezium in cross-section. The two measures can be implemented separately or in combination with further measures on the generator, so as to achieve the desired aim of low noise. In previous armatures of multiphase generators, the individual pole shoes have been arranged with a constant spacing from one another. When all the poles are distributed in this way, with an even spacing over the circumference of the arrr.ature, ail the pole edges, front or rear, move past a stator groove arranged opposite them on the stator synchronously and at the same time. The result is that a mechanical impulse is produced at each groove of the stator, which can excite a vibration of the stator. The poles thus excite the stator into vibration, owing to the force of the magnetic field. This excitation freqnencv ?ar = (n/oG x grooves) may exactly hit the natural frequency of the stator, so that the latter generates very high noise levels. According to a preferred embodiment of the invention, the armature is designed with pcles m which the distance between pole centres is not constant. In contrast tc the known arrangements with constant distance between pole centres, varying distances between pcle centres according to the invention mean that a plurality of mechanical impulses, which potentially may induce vibration, are no longer transmitted simultaneously from the armature poles, which are moving past the groove of a stator, to the stator, so that less noise is produced. As an alternative, the plurality of pcles may have pole heads of different widths, so as to achieve the effects according to the invention. Advantageously, the armature is configured with three different distances between pole centres a, b, c (a: Tp; b: Tp - V3 * TN; C: Tp - "-'3 * TN) . 3y applying the measure according to the invention, the excitation frequency for the stator and the armature are increased by a factor of 3. The excitation amplitude is reduced to one third of the normal excitation. It is therefore pcssible, by varying the distance between pole centres, to increase the excitation frequency while simultaneously reducing the amplitude, with the result that vibration excitation cf the generator stator is made decisively and significantly more difficult. This alone already minimises the noise quite considerably. According to a further aspect of the invention, the object is achieved in the case of a synchronous generator of the type mentioned at the outset by the fact that the poles of the armature have at least one edge which is formed on a pole head and which is arranged at an angle to the direction of movement of the armature. In a synchronous generator with the pole head described above, the noise production is likewise minimised considerably, since "he forces which cause the vibration of the stator and act or. the stator while the generator is in operation can be reduced considerably. This is achieved by means of the inclined edge of the pole head. This is because the forces which cause the vibrations are produced essentially during a transition of the magnetic flux from one groove web to the next groove web; the flux passes through two adj acent poles of the armature ana the air gap, as well as part of the stator. During the transition from one groove web to the next groove web, the magnetic flux is displaced suddenly to the next groove web - firstly being interrupted, as it were, for a moment - until the following groove web has reached the position of the groove web which was previously arranged at a specific point and the magnetic circuit is closed again. In the known generators, the front - as seen in the direction of movement of the armature - edge of a groove web is always exactly at right angles to the direction of movement of the armature. The same applies to the rear - as seen in the direction of movement -edges of a pole shoe. Due to this right-angled arrangement, the rotating groove web reaches a specific groove of the stater of the generator suddenly and upon the instant ever its entire width, so that the above-described transition of the magnetic flux from one groove web to the next groove web correspondingly takes place "suddenly " at one instant. This sudden or abrupt transition results in correspondingly high forces causing the mechanical vibrations, so that loud noises are produced. In contrast to this, according to the invention the inclined arrangement cf the front edge of a pole shoe relative to the direction of movement of the armature results in a transition cf the magnetic flux from one groove web to the next which is not abrupt but rather is gradual, since initially the front - as seen in the direction cf movement - section of the front edge of a groove web passes into the region of a specific stater groove, and then further sections of the groove web pass continuously into the region of the groove. Tests have correspondingly demonstrated that the forces which cause the vibration noises on the stater are considerably lower than in the case of conventional generators. As a result, the noise emission is reduced accordingly. A further effect cf the inventier. is that the voltages induced in the stator windings can be varied in terms cf their time-dependent profile in accordance with the inclined profile of the edge of the pole head. A particularly preferred embodiment of the invention is characterised in that the front edge (as seen in the direction of movement cf the armature) cf a pole head has two edge sections which are arranged at an angle with respect to one another and run towards one another to form a point. In this way, the forces which produce the noise car. be reduced further, and the pcle heads are of essentially symmetric design. The point faces, by way cf example, in the direction of movement of the armature or in the opposite direction. Preferably, the edge sections are arranged at an angle of approximately 100° to 140°, preferably of 120°, with respect to the direction cf movement of the armature. The width b - Fig. 7 - of an edge section thus essentially corresponds to the groove spacing. It has been found that this geometry makes it possible to achieve a particularly lew-loss transition of the magnetic flux with low noise generation. A further, particularly preferred embodiment is distinguished by the fact that the poles of the armature have at least one rear edge which is formed on a pole head and runs essentially at an angle with respect to the direction of movement of the armature. Expediently, the rear - in the direction of movement of the armature - edge cf a pcle head has two edge sections which are arranged at an angle with respect to one another and run parallel to the edge sections formed on the front edge, so that the pole head, when viewed radially from above, is designed essentially in the shape of an arrow. At the rear - as seen in the direction cf movement -edge, in this embodiment the above-described effects which occur on the front edge also occur on the rear edge, so that noise can be reduced further and is adapted to the voltage profile. Furthermore, this measure allows a close arrangement of adjacent pole heads, since they have congruent shaces and, as it were, "fit into one another". According to a further particularly advantageous aspect of the invention, a pole head is approximately in the shape of a trapezium, in cross-section. In this way, the voltage induced in the stater is, in the time-dependent curve, likewise in the shape of a trapezium. In contrast to this, the pole heads m the conventional generators are formed as sinusoidal curves, so as to produce sinusoidal vol-ages. According to the mventicn, it is possible to induce trapezium-shaped voltages. With a trapezium-shaped voltage profile, the amplitude is constant over a long period, so that it is possible to dispense with expensive DC fil-ers, cr for these filters to be significantly smaller and hence more cost-effective. In accordance with the voltage profile, the generator according to the invention supplies, in accordance with this embodiment, a virtuallv constant torque over the angle of rotation. Furthermore, the so-called harmonic content of the torque is very low for a power converter machine. In conventional pele heads, the harmonics in the torque characteristic are disadvantageous. Furthermore, a trapezium-shaped design of the pole head makes it possible to reduce the szray-field losses, which occur at the transition from one pole head to the next. According to a refinement, the edges of the trapezium-shaped pole head are also rounded. This also allows vibration and stray-field losses to be reduced. It is important that a pole head has a reduction in the cross-section on both sides in the edge region. Accordingly the present invention relates to a synchronous generator having a generator stator and a generator rotor which can move relative to the stator and has n poles, for producing electrical power, with the waveform of the induced voltage in one stator winding or in a number of stator windings corresponding the current waveform in one stator winding or the sum of at least m current elements in m stator windings, characterized in that poles are arranged asymmetrically on the rotor . The invention is explained in more details below with reference to an exemplary embodiment which is illustrated in the accompanying drawings, in which; Fig. 1 shows a diagrammatic depiction of a wind-driven power plant with a synchronous generator; Fig. 2 shows a diagrammatic depiction of an armature of a generator with a varying distance between the pole shoes or pole heads; Fig. 3 shows an enlarged section of the armature of Fig. 2; Fig. 4 shows a diagrammatic depiction of a section of an armature and a stator of the synchronous generator; Fig. 5 shows a side view of a pole according to the invention of an armature; Fig. 6 shows a plan view of the pole from Fig. 5; Fig. 6 shows a plan view of a pole according to the invention, as well as an associated stator voltage-time diagram; Fig. 8 shows a further stator voltage-time diagram; Fig. 9 shows a further stator voltage-time diagram; Fig. 10 shows a diagrammatic depiction of the stator winding as a 6-phase winding; Fig. 11 shows a force-displacement diagram illustrating the tangential force curve on the circumference of a stator groove for conventional synchronous generators; Fig. 12 shows a force-displacement diagram illustrating the tangential fores curve on the circumference of a stator groove for a synchronous generator according to the invention; Fig. 13 shows a force-displacement diagram illustrating the tangential force curve on the circumference of a stater groove for a further synchronous. generator according to the invention; Fig. 14 shows a further force-displacement diagram for a synchronous generator according to the invention, in which an arrcwing ever half a groove width and a whole groove width is realised; Fig. 15 shows a further force-displacement diagram for a synchronous generator with arrowing ever one groove width and an asymmetric pole arrangement; Fig. 16 shows a current-time diagram for the generator current; Fig. 17 shows a current-time diagram of a rectified current of a three-phase system; Fig. 18 shows a current-time diagram in accordance with Figure 1 with a 30° phase shift; Fig. 19 shews a current-time diagram in accordance with Figure 18 with a rectified current drawn en; Fig. 2C shews a current-time diagram with individual phase currents and their sum; Fig. 21 shews a further exemplary embodiment of a pole head according to the invention with rounded edges; Fig. 22 shows a voltage-time diagram of the stator winding belonging to Figure 21; Fig. 23 shows a further current-time diagram of a stator phase; Fig. 2 4 shews a further current-time diagram cf a stator phase; and Fig. 2 5 shows a current-time diagran of the sum of the currents shown in Figs. 2 3 and 24. Fig. 1 diagrammatically depicts a wind-driven power plant according to the invention having a multiphase synchronous generator 4 which is directly driven by means of a shaft 2 of rctor blades 3 with the interposition of a transmission and is mounted, in a known manner, inside a gondola on a tcwer. The torque of the generator 4 is determined by the magnetic induction 3, the armature current IA and by the angle between these two parameters, while the magnetic field E is represented by the induced voltage uind- This relationship can be described by the formula M - B T IA sin coT or M - I CN^ * IA sin toT in the case of sinusoidal currents. The synchronous generator, which has 6 phases, is connected to a rectifier circuit 6 with a plurality of rectifier diodes 7 and a capacitor 8, in that, from one of the windings of the stator of the generator 4 in each instance, a line 9 leads between two rectifier diodes 7 in each instance, so that in operation a rectified voltags is present across the terminals 1 0, 1 1 . The capacitor 8 is connected between the terminals 10, 1" and provides voltage and current forms which, following rectification, produce approximately an ideal direct current. The current induced in the windings of the stator, which is described in more detail below, of the generator 4 has essentially a DC component and an AC component, cf. Figs. 23 to 25. The AC component ensures a relatively gentle current rise and fall of a current half-wave cf the output current of one cf the six phases. The so-called cos * oscillation ensures a continuous current transition from one phase to the next. As a result of the addition of all the phase currents which is carried out in the rectifier circuit 6, the voltage present across the terminals 10, 11 and the current drawn will be substantially smoothed. The capacitor 3 also takes care of smoothing. After rectification, the generator 4 according to the invention supplies a direct current of virtually constant amplitude and a virtually constant torque over the angle of rotation, so that DC filters can be dispensed with or can be of significantly smaller design. The harmonics content of the torque is low. Furthermore, the generator 4 according to the invention produces less noise and vibration. It can be seen from Figs. 2 and 3 that the distances TD between the poles 1 4 is not constant over the circumference of the armature 12, but rather can adopt different values a, b and c, namely a first distance between pole centres a! xD, a further distance between pole centres b) t.~ + 1/3 * z^ and a further distance between pole centres Tp - 1/3 * T^, where T^ is the width of one groove (groove width'1 of the s tat or. The result is an asymrr.etric arrangement of the poles . As an alternative, or combined therewith, the distances between pole centres may also realised by displacing a pole 14 by a defined groove width. As a result of an asymrr.etric arrangement of this nature, the excitation frequency for the windings of tne stators, these windings being arranged in the grooves, as a displacement by 1/3 of the groove width, is increased by a factor of 3 by comparison with an unshifted arrangement. However, the amplitude of the excitation force is reduced to 1/3 of the excitation with an arrangement which is not offset. As an alternative, the widths cf the pole heads 20 may be different ever the circumference of the armature 12, in order to achieve an asynunetric arrangement of the poles 14, so as to achieve the effects according to the invention. Fig. 4 illustrates the magnetic flux excited by the poles 14 moves in a circui: indicated by the lines 1 3 through a pole 14, the air gap 18 and the laminated core cf the stater 16, back through the air gap 13 and into an adjacent pole ". 4 cf the armature 12. A stray flux, which reduces the magnetic flux which car. be used to generate current, occurs between r.wo adj acer.c pole heads 2 0. The armature 12 is designed as a salient-pole machine. The shape of the poles 14, in particular cf the pole heads 20, can best be seen from Figs. 5 to 7. The side view cf Fig. 5 illustrates that the pole heads 2C are approximately in the form of a trapezium with roundings at both edges 24, 26 of the pole head 20. In the edge region cf a pole head 20, the cross-section of the pole head 2C reduces on both sides towards its end. The cross-section thus decreases with increasing proximity to the edge on both sides. As can be seen from Fig. 6, the pole head 14, when viewed from above towards the surface facing the air gap 18, is in the form of an arrow. The front - as seen in the direction of movement, which is indicated by an arrow 23 in Figs. 4 to 7, of the armature 12 - edge 26 has two edge sections 32, 34, which are arranged at an angle with respect to one another, run towards one another to form a point 30 and are arranged at an angle with regard to the direction of movement 28 of the armature 1 2 and hence of the pole heads 20. The edge sections 32, 34 are arranged at an angle of about 120° with respect tc the direction of movement 23 of the armature 12. The rear - as seen in the direction of movement 28 of the armature 1 2 - edge 24 of a pole head 20 has two edge sections 36, 38 which are likewise arranged at an angle with respect tc the direction of movement 28 cf the armature 12. The edge section 36 is arranged parallel and offset by the width B (Fig. 6) with respect tc the front edge section 32 and the edge section 38 is arranged parallel and offset by the width B with respect to the edge section 34 cf the front edge 26, so that in the view shown in Fig. 6 the pole head 20 is in the form cf an arrow, which is also referred to as an arrcwing. Fig. 7 shews a further pole 14, in which the pole head 20 is likewise designed in the form of an arrow when viewed from above. 3y comparison with the pole head 20 snown in Fig. 6, however, the edge sections 32, 34, JS, 38 are at different angles with respect to the direction cf movement 28 cf the armature 12. The lower part cf Fig. 7 plots the voltage U induced in a winding of the stator 16 over time t. The curve cf the voltage is approximately trapezium-shaped, a fact which can be attributed to the trapezium-shaped design cf the pole head 2 0 illustrated m Fig. 5 in a side view and in cross-section. The voltage induced is proportional to the magnetic flux * which is excited by the poles 20 and flows through the laminated core of the stator 15. The flux Figs. 8 and 9 shew voltage-time curves for the voltage U induced in the windings of the stator 16. If, for example, in the case of alternative pole heads (not shown), the angle between the inclined edge sections 32, 34, 36, 38 with respect to the direction of mcverr.ent 28 of the armature 12 is greater, and hence cne arrow shape in plan view is more pointed, the result is a voltage section which is longer ir. terms of time with rising vol-age U cr with falling voltage U, while the section of constant, maximum voltage U is shortened in terms of time, as is shown diagrammatically in Fig. 9. Fig. 8 illustrates an exemplary embodiment of a pole head 2C in which the angle of the edge sections 32, 34, 36, 3 8 with respect to the direction of movement 28 is reduced, so that voltage rise and fall sections with shorter times are realised. The voltage shape car, thus be varied in a controlled manner by means of the particular geometry cf the pole heads 2G, specifically their arrow shape. As well as the voltage shape, a tangantially resulting force of the poles can also be varied as a function of the arrow-shaped pole head 20. The greater the level of arrowing, the lower the tangentially resulting force produced. If an inclined edge 24, 2 5 (Figure 6 or 7) covers a complete groove of the stater 16, the tangential force becomes very low. However, even a relatively low level of arrowing, with which an mclir.sd edge 24, 26 covers half a groove, ensures that the time-dependent curve of the force becomes considerably mere even. As a result, the noise emitted by the generator also falls, since the amplitude cf the force is the main exciter of the noise. Force curves are illustrated in Figures i 1 to 15. The arrangement of the windings in the stator 16, which has six phases, can be seen from Fig. 10. Phase 1 is arranged on the circumference of the stater 16 (cf. Fig. 4; at 0°, phase 2 at 3C°, phase 3 at 120°, phase 4 at :50°, phase 5 at 240° and phase 6 at 2703. In a manner which is not shown, the stater 16 may be designed with between 60 and 100 poles. The windings mav be arranged m accordance with a known winding method, in which all the poles 1 4 are wound in one ooeraticn, without the formation of contact points, which are often referred to "bridges". The force-displacement diagram illustrated in Fig- 11 illustrates the curve of a tangential force which acts tangentialiy on the circumference of a winding of the stator 16 as a function of the displacement of the armature 12 for a conventional synchronous generator in accordance with the prior art, in which the individual poles are distributed evenly ever the circumference of the armature 12. A relatively high amplitude of the force can be discerned. 3y contrast, Fig. 12 shows the force curve for an asymmetric arrangement according to the invention and shift of the individual poles "4 by half a groove width. The amplitudes cf the force as a function of the displacement (i.e. the rotation cf the armature 12) and hence also as a function of time are clearly lower than in the case of the known generators. Fig. 13 shows a force-displacement diagram for a synchronous generator according to the invention with an asymmetric arrangement of the poles along the circumference of the armature 12 with the poles offset by 1/3 of the groove width. It can also been seen from Fig. 1 3 that the amplitudes of the force on the windings cf the stater 16 are reduced considerably by comparison with the forces produced in known generators. The noise caused by the forces can be reduced considerably according to the invention. It can be seen from the force-displacement diagram illustrated in Fig. 14, which illustrates the tangentially resulting force of the poles 20 over displacement, that the arrowing cf the pole heads 20 according to the invention results in lower forces by comparison with conventional generators. The amplitudes of the forces shown are lowest if the arrowing is designed in sucn a way that an. edge 24, 26, which is at an angle with respect to the direction of movement 23 cf the armature 12, of a pole head 20 extends over an entire groove width, whereas, when the arrowing is such that an inclined edge 24, 26 extends over half a groove width, although reduced forces by comparison with conventional generators are achieved, these forces are higher than those described above. Noise can reduced considerably in this way, since tne amplitude is the main force exciter for sound. A short force impulse contains a very high excitation frequency spectrum. In can be seen from Fig. 15 that the reduction in noise is greatest if the arrowing extends over an entire groove width and an asymr.etric arrangement of the poles 14 on the armature ' 2 is realised according to the invention. .The resultant tangential forces are very low, so that a combination of the two measures according to the invention provides a maximum sound-reducing effect. The asymmetric arrangement cf the poles 14 can be selected in a controlled manner sc that certain excitation frequencies dc not occur. Figures 16 to 20 illustrate phase currents as a function cf time. Figure "6 illustrates the current profile cf a phase without an asymmetric arrangement cf the pedes. Figure 1 7 shows a super-positioning or summing of two currents of a three-phase system with a conducting interval which is greater than 120°. The superpcsitioning is achieved using rectification. It can be seen from Figure 13 that a different current profile is produced in the event of an additional phase shift through 3C°. Figure 19 illustrates the rectification of the phase currents depicted in Figure 18, the result representing a direct current with a low ripple content. In this way, non-sinusoidal voltages are produced in the individual stator phases. Taking into account a highly r.cn-linear load en the rectifier circuit 6 with capacitor 8 (cf. Figure 1), it is possible to generate currents which, giver, a phase shift of 30° in the stater, produce an electric leading with a minimum cf torque fluctuations. Figure 20 also illustrates the levels of the phase currents of a plurality of stator windings in the upper part of the diagram, as well as the sum, achieved by rectification, of the levels cf the phase currents in the lower part of the diagram. Figure 21 illustrates a further exemplary embodiment of a pole 14 according to the invention with an essentially trapezium-shaped pole head 20 with rounded end regions, the cress-section of which is reduced on both sides. Finally, Figure 22 shows a voltage-time diagram which can be generated by a vcltage induced in a stator by using a pole shewn in Figure T- with the aid of a generator 4 according to the invention. The voltage shape has rounded edges. If necessary, it can be varied by means of modified forms of the pole head 20, for example by providing the rounded edges with greater cross-sectional reductions or rour.dmgs. The current-time diagram illustrated in Figure 23 for a stator phase shews a rectangular current profile which shews the DC component of the current, which component is induced ir. the windings of the stator {described in more detail below) of the generator 4. Fig. 24 shows an AC component of the current induced in a stator phase. The AC component ensures a relatively gentle current rise or fall of a current half-wave of the output current of one of the six phases. The cos Fig. 25 shows, in a current-time diagram, the sum - a rectangle with the sixth harmonic - of the currents shewn in Figs. 23 and 24 of a stator phase, as also illustrated in Fig. 20. As a result of the addition of all the phase currents, which is performed in the rectifier circuit 6, the voltage present across the terminals "0, 11 and the current drawn will be substantially smoothed. I CLAIM 1. A synchronous generator having a generator stator (16) and a generator rotor (12) which can move relative to the stator (16) and has n poles (14), for producing electrical power, with the waveform of the induced voltage in one stator winding or in a number of stator windings corresponding the current waveform in one stator winding or the sum of at least m current elements (11,12) in m stator windings, characterized in that poles (14) are disposed asymmetrically on the rotor (12). 2. The synchronous generator according to Claim 1, wherein the poles (14) are asymmetric. 3. The synchronous generator according to Claim 1 or 2, wherein the pitch of the poles (14) is not constant. 4. The synchronous generator according to Claim 3, wherein the poles (14) are arranged with three different poles pitches on the rotor (12). 5. The synchronous generator according to Claim 1, wherein the poles (14) of the rotor (12) have at least one front edge (26), which is formed on a pole head (20) and runs obliquely with respect to the movement direction (28) of the rotor (12). 6. The synchronous generator according to Claim 5, wherein the front edge (26), in the direction (28) of the rotor (12), of a pole head (20) has two edge sections (32, 34), which are arranged at an angle to one another and taper to a point (30). 7. The synchronous generator according to Claim 6, wherein the edge sections (32, 34) of the front edge (26) are arranged at an angle of approximately 100° to 140°, preferably 120°, to the movement direction (28) of the rotor (12). 8. The synchronous generator according to Claim 5 or 6, wherein the poles (14) of the rotor (12) have at least one rear edge (24), which is formed on a pole head (20) and runs obliquely with respect to the movement direction (28) of the rotor (12). 9. The synchronous generator according to Claim 8, wherein the rear edge (24) has two edge sections (36, 38) which are arranged at an angle to one another and run parallel to the edge sections (32, 34) which are formed on the front edge (26), so that, in a radial plan view, the pole head (20) is arrow-shaped. 10,The synchronous generator according to one of the preceding claims, wherein a pole head (20) of a pole (14) has an approximately trapezoidal cross section. 11. The synchronous generator according to Claim 10, wherein the cross section being reduced on both sides in the edge region of the pole head (20). 12. The synchronous generator according to Claim 10, wherein the edges (24, 26) of the trapezoid are rounded. 13. A wind power plant, having a tower, having a rotor arranged on this tower, and having a generator (4), which can be driven by the rotor, wherein the generator (4) is designed according to any one of the preceding claims. 14. A Synchronous generator substantially as herein described with reference to the accompanying drawings.

Documents:

1516-mas-1998 abstract.pdf

1516-mas-1998 claims.pdf

1516-mas-1998 correspondence-others.pdf

1516-mas-1998 correspondence-po.pdf

1516-mas-1998 description (complete).pdf

1516-mas-1998 drawings.pdf

1516-mas-1998 form-19.pdf

1516-mas-1998 form-2.pdf

1516-mas-1998 form-26.pdf

1516-mas-1998 form-4.pdf

1516-mas-1998 form-6.pdf

1516-mas-1998 petition.pdf