Electrical machine with magnetic flux intensifier

Abstract

An electrical machine has a stator-rotor configuration in which the rotor has at least two poles. The poles are configured to rotate in an angle and to electromagnetically interact with one or more teeth that is a part of a stator adjoined in a fixed position to the electrical machine. The configuration forms a gap in the lateral direction between the poles and the teeth. At least one of the poles is formed of a permanent magnet material and a magnetic flux intensifier is arranged relative to at least one of the poles and one of the teeth. The magnetic flux intensifier is configured to concentrate the magnetic field lines between a pole and the teeth.

Claims

1. An electrical machine, comprising: a rotor configured to rotate in a direction relative to a stator, where the rotor comprises one or more poles configured to rotate in an angle relative to a center of the rotor, where the one or more poles are configured to interact with one or more teeth in the stator via an electromagnetic field; wherein the stator is configured to be fixed in a stationary position in the electrical machine, where a gap is provided between the one or more teeth and the one or more poles in a lateral direction; wherein at least one magnetic flux intensifier is arranged relative to at least one of the one or more poles and at least one of the one or more teeth, where the magnetic flux intensifier is configured to concentrate magnetic field lines between said at least one of the one or more poles and said at least one of the one or more teeth during rotation of the rotor, wherein the magnetic flux intensifier comprises a first type layer of a high energy magnetic material with magnetic field lines oriented essentially laterally, and at least a second type layer of a second magnetic material having a magnetic strength that is lower than that of the high energy magnetic material, and wherein the first type layer is located between two second type layers, and wherein the magnetic flux intensifier comprises a predetermined number of successive additional first and second type layers around a central layer defined by the first type layer, wherein a first successive type layer of a high energy magnetic material is located against a second successive type layer of a second magnetic material having magnetic properties that differ from the properties of the high energy magnetic material, and wherein at least one third type layer is located at opposite sides of the successive additional first and second type layers.

2. The electrical machine according to claim 1, wherein the magnetic flux intensifier is configured as a pole in which the first and second type layers, over an arc length, form a sandwich of layers and where the at least one third type layer forms a gap between the second type layer and one of the one or more poles located adjacent to the magnetic flux intensifier.

3. The electrical machine according to claim 2, wherein the magnetic flux intensifier further comprises at least another first type layer which is located between the second type layer and the at least one third type layer and comprises a high energy magnetic material with magnetic field lines oriented essentially laterally.

4. The electrical machine according to claim 3, wherein the magnetic flux intensifier further comprises at least another second type layer which is located between the another first type layer and the at least one third type layer and comprises a second magnetic material having magnetic properties that differ from the properties of the high energy magnetic material.

5. The electrical machine according to claim 1, wherein each successive additional first and second type layer has an arc length that decreases from a central layer towards the at least one third type layer.

6. The electrical machine according to claim 5, wherein the magnetic strength of at least the high energy magnetic material in each successive additional first and second type layer decreases from the central layer towards the at least one third type layer.

7. The electrical machine according to claim 1, wherein the magnetic strength of at least the high energy magnetic material in each successive additional first and second type layer decreases from the central layer towards the at least one third type layer.

8. The electrical machine according to claim 1, wherein at least one of the successive additional first and second type layers located at one side of the central layer has an arc length that differs from the arc length of the same successive layer located at the opposite side of the central layer.

9. The electrical machine according to claim 1, wherein the magnetic flux intensifier has a trapezoidal shape, and wherein the first and second type layers are configured as circles.

10. The electrical machine according to claim 1, wherein the magnetic material of the first type layer is from a group of magnetic materials having a magnetic remanence Br above 0.5 Tesla.

11. The electrical machine according to claim 1, wherein the magnetic material of the second type layer is from a group of magnetic materials having a magnetic remanence Br below 0.5 Tesla.

12. The electrical machine according to claim 1, wherein the electrical machine is one of a generator for generating power and a motor for driving a drivable unit.

13. The electrical machine according to claim 1, wherein the magnetic material of the first type layer is from a group of magnetic materials having a magnetic remanence Br above 1 Tesla.

14. The electrical machine according to claim 1, wherein the magnetic material of the first type layer comprises at least neodymium.

15. The electrical machine according to claim 1, wherein the magnetic material of the second type layer is from a group of magnetic materials having a magnetic remanence Br below 1 Tesla.

16. The electrical machine according to claim 1, wherein the magnetic material of the second type layer is made of iron or a ferrite alloy.

17. Method of making a pole with a magnetic flux intensifier having a rotor configured to rotate in a direction relative to a stator, the rotor having one or more poles configured to rotate in an angle relative to a center of the rotor, wherein the poles are configured to interact with one or more teeth in a stator via an electromagnetic field and at least one magnetic flux intensifier configured to concentrate the magnetic field lines between the poles and the respective one or more teeth (8) during rotation of the rotor, comprising the steps of: making a planar sandwich of successive first type layers of a high energy magnetic material and second type layers of a second magnetic material having a magnetic strength that is lower than that of the high energy magnetic material, bending the planar sandwich around a center point of a central first type layer into a curvature defined by the curvature of a core of the rotor and the stator, and arranging the magnetic flux intensifier (11) with the first type layer (I.sub.0) of a high energy magnetic material (17) with magnetic field lines oriented essentially laterally, wherein the first type layer is located between two second type layers, and wherein the magnetic flux intensifier comprises a predetermined number of successive additional first and second type layers around a central layer defined by the first type layer, wherein a first successive type layer of a high energy magnetic material is located against a second successive type layer of a second magnetic material having magnetic properties that differ from the properties of the high energy magnetic material, and wherein at least one third type layer is located at opposite sides of the successive additional first and second type layers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a cross section of an electrical machine with a permanent magnet generator (PMG);

(2) FIG. 2 shows the magnetic flux interaction between the teeth and poles with a magnetic flux intensifier configuration;

(3) FIGS. 3A-D show different embodiments of the magnetic intensifier shaped as a pole according to the invention;

(4) FIGS. 4A & 4B show alternative embodiments of the magnetic flux intensifier shaped as a pole; and

(5) FIGS. 5A & 5B show a specific comparative example of the magnetic interaction between stator teeth and rotor poles in a case without and with a magnetic flux intensifier.

DETAILED DESCRIPTION OF THE INVENTION

(6) FIG. 1 shows a cross section of a schematic embodiment of an electrical machine 1 in which a PM (permanent magnet) generator 2 may be located. The generator 2 may comprise a rotor 3 connected to a shaft 4 supported in a shaft support arrangement 5. The electrical machine 1 may further support a stator 6.

(7) The rotor 3 may have one or more poles 7 and the stator 6 may have one or more teeth 8 that are separated from the poles 7 by a gap 9 having a gap distance 10 (in a lateral direction).

(8) FIG. 2 shows a cross section of a schematic embodiment of the generator 2 in which the rotor 3 with the poles 7 may be rotatably arranged inside the electrical machine (not shown). The rotor 3 may be arranged inside the stator 6 so that the poles 7 and the teeth 8 form an electromagnetic coupling extending across the gap 9.

(9) The figure further shows a FEM (finite element method) simulation of an enlarged area where the poles 7 and teeth 8 (and the supporting structures) interact magnetically.

(10) Between the teeth 8 and the poles 7 there is a magnetic flux intensifier 11 or a configuration intensifying, focusing or collecting magnetic flux 12 (represented by the density of flux lines) may be arranged relative to the teeth 8 and the poles 7. The magnetic flux intensifier 11 may be arranged between the teeth 8 and the poles 7.

(11) The magnetic flux intensifier 11 will allow a larger gap distance 10 for the same magnetic interaction and hence performance of the generator 2 thereby allowing for a greater slack.

(12) All things being equal, maintaining the same gap distance 10 will allow for a greater efficiency or a more compact generator 2.

(13) Equally advantageous precious magnetic materials can be saved by using a magnetic flux intensifier 11, whilst maintaining the same gap distance 10 and the same generator power or efficiency.

(14) It is understood that the same or all things equal means a comparison between a rotor 3 without a magnetic flux intensifier 11 and a rotor 3 with a magnetic flux intensifier 11.

(15) FIGS. 3A-3D show different embodiments of the magnetic flux intensifier 11.

(16) FIG. 3A shows an embodiment where the pole 7 may be made of a permanent magnetic material 13 and magnetic material 14, i.e., magnetic guiding material in a sandwich 15 construction. The sandwich construction 15 may comprise three layers 16 (I.sub.0, II.sub.1) of high energy magnetic material 17 placed in a central layer I.sub.0 and a layer II.sub.1 of low energy magnetic materials 18 placed on both sides of the center layer I.sub.0. A gap III may be finally be located at both sides of the outer layers II.sub.1 of the low energy magnetic material 18.

(17) It is understood that low energy magnetic materials 18 can be replaced by magnetic guiding materials 14, but generally both low energy 18 and high energy 17 magnetic materials are permanent magnetic materials 13.

(18) FIG. 3B shows an embodiment of a magnetic flux intensifier 11 having a sandwich construction 15 with further layers 16 of the same strong 17 and low energy 18 magnetic materials placed between the central layer I.sub.0 and the gap III. A further layer I.sub.2 of the high energy magnetic material 17 may be sided next to the layer II.sub.1 of low energy magnetic material 18. A further layer II.sub.2 of the low energy magnetic material 18 may be sided next to the further layer I.sub.2 of high energy magnetic material 17.

(19) FIG. 3C shows a generic embodiment of a magnetic flux intensifier 11 having a sandwich construction 15 with a predetermined number of successive layers 16 comprising permanent magnetic materials 13. In each direction from the center I.sub.0, the layers 16 extend towards the gap III as I.sub.i, II.sub.i for i=1 to N.

(20) FIG. 3D shows an embodiment where the layers 16 are asymmetric. In this particular embodiment, the two layers II.sub.1 of low energy magnetic material 18 may have different (arc) lengths where the layer II.sub.1 according to a preferred rotational direction 19 of the rotor 3. The (arc) length of the layer II.sub.1 located near the front of the magnetic flux intensifier 11 facing an adjacent pole 7b in the rotation direction 19 may have a greater (arc) length that the same layer II.sub.1 facing an adjacent pole 7a in the opposite direction, or vice versa.

(21) The thickness or the (arc) length of the layers 16 are subject to vary according to design parameters and a person skilled in the art will use either simple experimentation or computational modeling to find the right variations of the layers.

(22) A starting point will be that the layers 16 from the center I.sub.0 towards to the gap III become thinner and thinner.

(23) FIGS. 4A & 4B show alternative embodiments of magnetic flux intensifier 11.

(24) FIG. 4A shows an embodiment, where the pole 7 may be configured with a magnetic flux intensifier 11 having as a trapezoidal cross-sectional shape. The pole 7 may have a sandwich construction 15 of at least three layers 16 where each layer 16 may be configured as a circle.

(25) FIG. 4B shows an embodiment, where the pole 7 may be configured with a magnetic flux intensifier 11 shaped by a single layer 16 of a high energy magnetic material 17 but with less magnetic material in the outer part of the layer 16 facing the teeth 8 of the stator 6 than in the inner part facing the center of the rotor 3. The layer 16 may form a sandwich construction 15 where the outer layers or parts have equivalent magnetic properties compared to the layers of the low energy magnetic material 18.

(26) FIGS. 5A & 5B illustrate comparative examples of magnetic interactions for the electrical machine 1 configured as a wind turbine generator. FIG. 5A shows the generator without a magnetic flux intensifier 11 and FIG. 5B shows the generator with a magnetic flux intensifier 11 configuration.

(27) The permanent magnet height is 10 mm and 2269000 mm3 volume per pole or equivalent to 17.0 kg. The gap distance is 6.6 mm.

(28) A strong magnet material variant of Neodymium is used as the pole 7 in FIG. 5A.

(29) A combination of a mixed Ferrite as a low energy magnetic material 18 and Neodymium as a high energy magnetic material 17 is used in FIG. 5B.

(30) The effect of using a magnetic flux intensifier 11 may be scaled to a particular application, such as a generator for a wind turbine. The values based on reliable scaling of dimensions, resources and costs for a 3.6 MW generator are summarized in the following table:

(31) TABLE-US-00002 Convential Invention Without magnetic flux With magnetic flux intensifier according to intensifier according to FIG. 5A FIG. 5B Wind Turbine Nominal Power [MW] 5.4 5.4 Rotor diameter [m] 140 140 Rotational speed [rpm] 12.6 12.6 Generator Number of poles 112 112 Outer diameter [m] 7.00 7.00 Active materials [t] 52 41 Estimated costs [kEUR] 516 449

(32) Thereby, the advantages of using a magnetic flux intensifier according to the invention are readily apparent.

(33) A person skilled in the art will appreciate, that the above sandwich construction 15 with a I.sub.1, II.sub.1, I.sub.2, II.sub.2-configuration of layers 16 of high energy magnetic materials 17 and low energy magnetic materials 18 around a central layer I.sub.0 of high energy magnetic materials 17 as a starting point. The configuration of the layers 16 in the sandwich construction 15 may be optimized to a particular application, such as adding more layers 16 or altering the (arc) lengths of the layers 16.