Stator arrangement and electrical generator

Abstract

A stator arrangement includes a stator extending in a circumferential direction and plural teeth alternating with plural slots arranged along the circumferential direction. A first wire is arranged in a first slot of the plural slots. A second wire is arranged in a second slot of the plural slots, wherein the second slot is circumferentially adjacent to the first slot. A first converter has an input terminal connected to the first wire and a second converter has an input terminal connected to the second wire.

Claims

1. Stator arrangement, comprising: a stator extending in a circumferential direction and having plural teeth alternating with plural slots arranged along the circumferential direction; a first wire arranged in a first slot of the plural slots; a second wire arranged in a second slot of the plural slots, wherein the second slot is circumferentially adjacent to the first slot; a first converter having an input terminal connected to the first wire; a second converter having an input terminal connected to the second wire; wherein a number of slots per stator pole is equal to a number of converters times a number of phases; wherein the first wire is connected in a same inward axial direction to the first converter as the second wire is connected to the second converter, or the first wire is connected in a same outward axial direction to the first converter as the second wire is connected to the second converter; and wherein a first current flowing in the first wire has a same direction as a second current flowing in the second wire but has a different phase than the second current.

2. The arrangement according to claim 1, wherein a tooth of the plural teeth is circumferentially between the first slot and the second slot.

3. The arrangement according to claim 1, wherein the first wire is arranged in the first slot in plural turns forming a first coil, wherein the second wire is arranged in the second slot in plural turns forming a second coil.

4. The arrangement according to claim 1, further comprising: another first wire arranged in another first slot, circumferentially adjacent to the second slot, connected to another input terminal of the first converter; another second wire arranged in another second slot, circumferentially adjacent to the other first slot, connected to another input terminal of the second converter.

5. The arrangement according to claim 1, further comprising: a further first wire arranged in a further first slot, circumferentially adjacent to the other second slot, connected to a further input terminal of the first converter; a further second wire arranged in a further second slot, circumferentially adjacent to the further first slot, connected to a further input terminal of the second converter.

6. The arrangement according to claim 1, further comprising: at least one third wire arranged in at least one third slot, circumferentially adjacent to the second slot, and connected to an input terminal of at least one third converter.

7. The arrangement according to claim 6, further comprising: at least one other third wire arranged in at least one other third slot, circumferentially adjacent to another second slot, and connected to anther input terminal of the third converter.

8. The arrangement according to claim 7, further comprising: at least one further third wire arranged in at least one further third slot, circumferentially adjacent to the further second slot, and connected to a further input terminal of the third converter.

9. The arrangement according to claim 1, wherein the number of phases is equal to a number of input terminals of each converter.

10. Electro mechanical transducer, comprising: a stator arrangement, comprising: a stator extending in a circumferential direction and having plural teeth alternating with plural slots arranged along the circumferential direction, a first wire arranged in a first slot of the plural slots, a second wire arranged in a second slot of the plural slots, wherein the second slot is circumferentially adjacent to the first slot, a first converter having an input terminal connected to the first wire, a second converter having an input terminal connected to the second wire, wherein a number of slots per stator pole is equal to a number of converters times a number of phases; a rotor with plural permanent magnets, wherein, during operation of the transducer, the first wire and the second wire are magnetically isolated; wherein the first wire is connected in a same inward axial direction to the first converter as the second wire is connected to the second converter, or the first wire is connected in a same outward axial direction to the first converter as the second wire is connected to the second converter; and wherein the transducer is configured such that a first current flowing in the first wire has a same direction as a second current flowing in the second wire but has a different phase than the second current.

11. The transducer according to claim 10, wherein the second converter is controlled taking into account a phase shift of the phases of a first current and a second current which is 360/(6*q), wherein q is the number of slots per stator pole.

12. The transducer according to claim 10, wherein the transducer is configured for operation in case of a fault in one of the first wire, the second wire, at least one third wire, the first converter, the second converter, and at least one third converter, wherein in the case of the fault a demagnetization of the plural permanent magnets is avoided.

13. The transducer according to claim 10, wherein the transducer is an electric generator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates an axial view of a portion of an electric generator according to an embodiment of the present invention;

(2) FIG. 2 schematically illustrates another embodiment of a portion of an electric generator according to an embodiment of the present invention;

(3) FIG. 3 illustrates a time course of a minimal magnetic field as observed in an electric generator according to an embodiment of the present invention;

(4) FIG. 4 illustrates a graph illustrating an equivalent of a magnetic motive force as generated in an electric generator according to an embodiment of the present invention;

(5) FIG. 5 illustrates a graph of an average torque as generated in an electric generator according to an embodiment of the present invention, and

(6) FIG. 6 illustrates a ripple of a torque as generated in an electric generator according to an embodiment of the present invention.

DETAILED DESCRIPTION

(7) FIG. 1 schematically illustrates a portion 100 of an electric generator according to an embodiment of the present invention.

(8) In particular, the illustration of the stator arrangement 101 comprises two stator poles, wherein the stator pole pitch pp is indicated in FIG. 1.

(9) The portion 100 of the electric generator comprises a stator arrangement 101 and a rotor 103 rotating relative to the stator arrangement 101 around a rotation axis 105 which is oriented along an axial direction. The arrangement 100 is illustrated in FIG. 1 in a rolled-up version in which the circumferential direction 107 is bent from a circular direction to a straight direction for clarity. The axial direction is indicated by reference sign 105 (pointing into the drawing plane) and the radial direction is indicated by reference sign 109.

(10) The stator arrangement 101 comprises a yoke 111 from which plural teeth 113 protrude radially outwards. The yoke 111 and the teeth 113 are manufactured from a magnetically permeable material. The plural teeth 113 alternate with plural slots 115.

(11) In the plural slots plural wires 114 are arranged. For example, in a first slot 117 a first wire 119 is arranged and in a second slot 121 a second wire 123 is arranged. Thereby, the first slot 117 is arranged at a circumferential different position than the second slot 121 such that also the first wire 119 is circumferentially arranged at a different position than the second wire 123. The circumferential difference between the positions of the centers of the first wire 119 and the second wire 123 is indicated as which may result in the property that electric phases of currents flowing in the first wire 119 and the second wire 123 are different.

(12) The stator arrangement 101 further comprises a first converter 125 and a second converter 127 which may be constructed substantially in a same manner. The first converter has an input terminal 129, another input terminal 131 and a further input terminal 133. Also the second converter 127 has an input terminal 130, another input terminal 132 and a further input terminal 134. The first wire 119 is connected to the input terminal 129 of the first converter 125 and the second wire 123 is connected to the input terminal 130 of the second converter 127.

(13) Another first wire 135 (arranged in a slot adjacent to the second slot 121 and thus adjacent to the second wire 123) is connected to the other input terminal 131 of the first converter and another second wire 137 (arranged in a slot adjacent to the other first wire 135) is connected to the other terminal 132 of the second converter 127. A further first wire 139 is connected to the further input terminal 133 of the first converter 125 and a further second wire 141 is connected to the further input terminal 134 of the second converter 127.

(14) In FIG. 1, the first wire 119 is also labeled as a.sub.1 and the second wire 121 is also labeled as a.sub.2, the other first wire 135 is labeled c.sub.1 and the other second wire 137 is labeled c.sub.2, the further first wire 139 is labeled b.sub.1 and the further second wire 141 is labeled b.sub.2. Thereby, unprimed quantities indicate an inward direction and primed quantities indicate an outward direction of the orientation or the current direction, respectively.

(15) Further, the generator portion 100 comprises a rotor 103 which comprises a support structure 143 which holds permanent magnets 145 having a south pole and a north pole as indicated by the letters S and N in FIG. 1. The permanent magnets 145 comprise as a rare earth material Dysprosium but to a smaller amount than in a conventional system and have a radial width d which is also smaller than a radial width of a conventional magnet. In FIG. 1 magnetic field lines 147 produced by some wires 114 are exemplarily indicated which in particular cancel out in the tooth 113 in between the wires 135 and 137. Further, the magnetic flux towards the permanent magnet 145 is reduced compared to a conventional magnetic flux. Thereby, demagnetization of the permanent magnets 145 is reduced or may be even avoided.

(16) If one of the first converter 125 and the second converter 127 fails or a corresponding wire fails, the respective other converter may still operate in order to maintain energy production, albeit to the lesser degree.

(17) The converters 125, 127 generate at output terminals 149 and 151, respectively, a fixed frequency AC power stream (in three phases) which may then be provided, in particular via one or more transformers, to a utility grid.

(18) As is obvious from FIG. 1 three phases (corresponding to the three respective input terminals of the converters) are supported and the number of slots 115 per pole is six, e.g. the number of phases (three phases) multiplied by the number of converters (two converters).

(19) FIG. 2 schematically illustrates a portion 200 of an electric converter according to an embodiment of the present invention. Thereby, elements and components similar in structure and/or function are labeled with the same reference signs as those structures and components illustrated in FIG. 1 except for the first digit. Thereby, explanation of these components can be taken from the respective description of those components as described in FIG. 1.

(20) The portion 200 of the electric generator illustrated in FIG. 2 shows similarities to the portion 100 of the electric generator illustrated in FIG. 1. Differing from the electric generator portion illustrated in FIG. 1 the electric generator portion 200 illustrated in FIG. 2 comprises not only two but three converters 225, 227 and 253. The connections of the first wire 219, the other first wire 235 and the further first wire 239 to the first converter 225 correspond to the connections as explained with reference to FIG. 1. Further, the connections of the second wire 223, the other second wire 237 and the further second wire 241 to the second converter 227 correspond to those as illustrated and explained in FIG. 1.

(21) Additionally, a third wire 255 (arranged in a slot adjacent to the other first wire 223) is connected to an input terminal 257 of the third converter 253, another third wire 259 (arranged in a slot adjacent to the other second wire 237) is connected to another input terminal 261 of the second converter and a further third wire 263 (arranged in a slot adjacent to the other third wire 241) is connected to a further input terminal 265 of the third converter 253. Thereby, if one of the converters 225, 227, 253 or two of those converters brake or fail, still the electric generator may provide electric energy via the corresponding output terminals 249, 251 and/or 252 or the unimpaired converters to a utility grid.

(22) Further, the pole pitch pp and the magnet pitch mp are indicated in FIG. 2, as well as the radial width d of the permanent magnets 245. In particular, in FIGS. 1 and 2 the parallel phases (i.e. the phases carried by the wires 219, 223 and 255, also labeled as a.sub.1, a.sub.2 and a.sub.3 are disposed circumferentially adjacent to each other having a circumferential distance which depends on the pole pitch, the number of converters and the number of phases.

(23) The short circuit MMF generated when currents are flowing through the wires opposing one of the magnets 245 is given as
MMF=M/m.Math.(k.Math..Math.I.sub.n+I.sub.n+I.sub.n+ . . . ).

(24) Thereby, M is the number of series half turns per slot, k is the ratio of the short circuit current to the nominal full-load current, m is the number of parallel converters, is the modulation factor to mutual inductance between the two parallel phases. In the present situation is approximately one indicating an at least approximately complete isolation between adjacent wires.

(25) FIG. 3 illustrates a graph, wherein on an abscissa 301 the time is indicated in seconds (sec), while on an ordinate 303 the minimal magnetic field in Tesla (T) is indicated. Thereby, the curve 305 illustrates a conventional electric generator, while the curve 307 illustrates the behavior of an electric generator according to an embodiment of the present invention, such as a generator illustrated in one of the FIG. 1 or 2.

(26) As can be appreciated from FIG. 3, the minimal magnetic field of the generator according to an embodiment of the present invention (curve 307) does not fall below the threshold line 309 below of which a demagnetization of the permanent magnet 245 or 145 would occur, as in the conventional case (curve 305). Thus, according to this embodiment demagnetization of the permanent magnet 145, 245 is reduced or even avoided.

(27) As is apparent from FIG. 3, the minimum flux density or minimal magnetic field Bmin is in a significantly safer zone compared to a conventional generator.

(28) FIG. 4 illustrates a graph wherein on an abscissa 401 the time and seconds is indicated while on an ordinate 403 the normalized Ampere turn as experienced by the magnet 145, 245 is indicated in Ampere (A). Thereby, the normalized Ampere turn is proportional to the magneto motive force (MMF) experienced by the magnets 145, 245. While the curves 405, 407 illustrate conventional systems, the curve 409 illustrates the normalized Ampere turn as observed in an electric generator according to an embodiment of the present invention, such as generators 100 or 200 illustrated in FIG. 1 or 2. As is apparent from FIG. 4 the normalized Ampere turn of the generator according to an embodiment of the present invention (curve 409) is lower than those of conventional systems (curves 405, 407). Thus, demagnetization of the permanent magnets 145, 245 is reduced or even avoided.

(29) FIGS. 5 and 6 illustrate graphs depicting the average torque (FIG. 5) and ripple torque (FIG. 6) as observed in an electric generator according to an embodiment of the present invention. In FIG. 5, the first few cycles correspond to the normal operating conditions, and the following cycles correspond to when the short circuit occurs. Thereby, abscissas 501 and 601 indicate the time in seconds, while ordinates 503 and 603 indicate the torque at 100% load at a temperature of the magnets 145, 245 of high temperature in Newton*m (Nm). Thereby, the curve 605 in FIG. 6 illustrates the ripple torque in a generator according to an embodiment of the present invention which substantially corresponds to a conventional ripple torque. Thereby, the curve 607 corresponds to a behavior of a conventional system.

(30) As is indicated as curve 505 in FIG. 5 the average torque according to a generator according to an embodiment of the present invention substantially corresponds to a conventional average torque. Thereby, the curves 507 and 509 correspond to a behavior of a conventional system.

(31) It should be noted that the term comprising does not exclude other elements or steps and a or an does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.