MAGNETIC COMPONENT PART FOR A ROTOR ASSEMBLY

Abstract

An electromechanical transducer includes a stator assembly and a rotor assembly including a rotor shaft having a longitudinal axis, a mounting structure connected to the rotor shaft, and at least one magnetic component part including at least one permanent magnet, wherein a skew angle between the permanent magnet and the stator assembly has a value of 60% to 92% of a cogging torque period, or for an integral machine, wherein the skew angle between the permanent magnet and the stator assembly has a value of 35° to 55° electrical degrees.

Claims

1. An electromechanical transducer comprising a stator assembly and a rotor assembly comprising a rotor shaft having a longitudinal axis, a mounting structure connected to the rotor shaft, and at least one magnetic component part comprising at least one permanent magnet, wherein a skew angle between the permanent magnet and the stator assembly has a value of 60% to 92% of a cogging torque period, or for an integral slot machine, wherein the skew angle between the permanent magnet and the stator assembly has a value of 35° to 55° electrical degrees.

2. The electromechanical transducer as set forth in claim 1, wherein the skew angle is relative to a central axis of the magnetic component part.

3. The electromechanical transducer as set forth in claim 1, wherein the skew angle is between 40° to 45° or the skew angle has a value of 75% to 80% of the cogging torque period.

4. The electromechanical transducer as set forth in claim 1, wherein the skew angle is 45° or the skew angle has a value of 75% of the cogging torque period.

5. The electromechanical transducer as set forth in claim 4, wherein the skew angle is relative to the longitudinal axis of the rotor shaft.

6. The electromechanical transducer as set forth in claim 1, wherein the mounting structure is arranged with an angle relative to the longitudinal axis of the rotor shaft which is equal to the skew angle.

7. The electromechanical transducer (as set forth in claim 6, wherein the skew angle has a value smaller than the maximal or full skew angle and is maximized to the manufacturing tolerances and assembly imperfections and operation deformations.

8. The electromechanical transducer as set forth in claim 7, wherein the electromechanical transducer is a generator.

9. A wind turbine for generating electrical power, the wind turbine comprising a tower, a rotor, which is arranged at a top portion of the tower and which comprises at least one blade, and the electromechanical transducer as set forth in claim 1, wherein the electromechanical transducer is mechanically or directly coupled with the rotor.

10. A method for manufacturing a rotor assembly of an electromechanical transducer, the method comprising mounting at least one magnetic component part having at least one permanent magnet to a mounting structure of the rotor assembly, wherein a skew angle between the permanent magnet and the stator assembly has a value of 60% to 92% of a cogging torque period, or for an integral machine, wherein the skew angle between the permanent magnet and the stator assembly has a value of 35° to 55° electrical degrees.

11. The method as set forth in claim 10, wherein the skew angle is relative to a central axis of the magnetic component part.

Description

BRIEF DESCRIPTION

[0035] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0036] FIG. 1 shows a wind turbine according to an embodiment of the present invention;

[0037] FIG. 2A shows a top view example of a known magnetic component part in a linear machine with a rotor magnet skew angle set to zero;

[0038] FIG. 2B shows a top view example of a known magnetic component part in a linear machine with a rotor magnet skew angle set to maximal or full;

[0039] FIG. 3 shows a top view example of a magnetic component part in a linear machine with an optimized rotor magnet skew angle according to an embodiment of the present invention, wherein the magnetic component part is mounted to a support structure of a rotor assembly as shown in FIG. 1;

[0040] FIG. 4 shows a diagram of torque versus a skew angle ratio of a maximal or full skew angle;

[0041] FIG. 5 shows a diagram of torque change versus an absolute skew angle; and

[0042] FIG. 6 shows a diagram of ripple versus an absolute skew angle.

DETAILED DESCRIPTION

[0043] The illustration in the drawing is schematically. It is noted that in different figures, similar or identical elements are provided with the same reference signs.

[0044] FIG. 1 shows a wind turbine 100 according to an embodiment of the invention. The wind turbine 100 comprises a tower 120, which is mounted on a non-depicted fundament. On top of the tower 120 there is arranged a nacelle 122. In between the tower 120 and the nacelle 122 there is provided a yaw angle adjustment device 121, which is capable of rotating the nacelle 122 around a non-depicted vertical axis, which is aligned with the longitudinal extension of the tower 120. By controlling the yaw angle adjustment device 121 in an appropriate manner it can be made sure, that during a normal operation of the wind turbine 100 the nacelle 122 is always properly aligned with the current wind direction. However, the yaw angle adjustment device 121 can also be used to adjust the yaw angle to a position, wherein the nacelle 122 is intentionally not perfectly aligned with the current wind direction.

[0045] The wind turbine 100 further comprises a rotor 110 having three blades 114. In the perspective of FIG. 1 only two blades 114 are visible. The rotor 110 is rotatable around a rotational axis 110a. The blades 114, which are mounted at a hub 112, extend radially with respect to the rotational axis 110a.

[0046] In between the hub 112 and a blade 114 there is respectively provided a blade adjustment device 116 in order to adjust the blade pitch angle of each blade 114 by rotating the respective blade 114 around a non-depicted axis being aligned substantially parallel with the longitudinal extension of the blade 114. By controlling the blade adjustment device 116 the blade pitch angle of the respective blade 114 can be adjusted in such a manner that at least when the wind is not so strong a maximum wind power can be retrieved from the available wind power. However, the blade pitch angle can also be intentionally adjusted to a position, in which only a reduced wind power can be captured.

[0047] As can be seen from FIG. 1, the rotor 110 is directly coupled with a shaft 125, which is coupled in a known manner to an electromechanical transducer 140. The electromechanical transducer is a generator 140.

[0048] Accordingly, the turbine is a direct drive type, in which the hub is directly connected to the generator 140, i.e., no gearbox is present.

[0049] Further, a brake 126 is provided in order to stop the operation of the wind turbine 100 or to reduce the rotational speed of the rotor 110 for instance (a) in case of an emergency, (b) in case of too strong wind conditions, which might harm the wind turbine 100, and/or (c) in case of an intentional saving of the consumed fatigue life time and/or the fatigue life time consumption rate of at least one structural component of the wind turbine 100.

[0050] The wind turbine 100 further comprises a control system 153 for operating the wind turbine 100 in a highly efficient manner. Apart from controlling for instance the yaw angle adjustment device 121 the depicted control system 153 is also used for adjusting the blade pitch angle of the rotor blades 114 in an optimized manner.

[0051] In accordance with basic principles of electrical engineering the generator 140 comprises a stator assembly 145 and a rotor assembly 150. The generator 140 may include an external rotor 150 which is arranged outside the stator 145.

[0052] The stator assembly 145 comprises a plurality of coils for generating electrical current in response to a time alternating magnetic flux. The rotor assembly comprises a plurality of permanent magnets, which are arranged in rows being aligned with a longitudinal axis of the rotor assembly 150. As will be described below in detail, the permanent magnets are skewed with an optimized skew angle to satisfy the level of noise and vibration and increase the torque at the same time when the generator 140 is in operation.

[0053] FIG. 2A shows in a top view a known electromechanical transducer or generator 140, here, by example as a linear machine. The generator 140 includes the stator assembly 145 and the rotor assembly 150.

[0054] The stator assembly 145 includes at least on stator iron 200 and stator windings or stator coils 202 arranged between teeth of the stator iron 200. The rotor assembly 150 includes a magnetic component part 204 with at least one permanent magnet 206.

[0055] The magnetic component part 204 and the permanent magnets 206, respectively are arranged with a skew angle α set to zero, i.e. machine with no skew. The skew angle α can be defined as an angle between an edge 208 of the permanent magnets 206 and the rotational axis 110a or the axial axis of the stator. The edge 208 is an edge of the permanent magnet 206 which runs parallel or almost parallel to the rotational axis 110a. At least, the edge 208 has a smaller angle towards the rotational axis 110a then a neighboring edge of the respective same permanent magnet 206.

[0056] In the example shown on FIG. 2A, the skew angle is zero. Thus, the generator 140 or the rotor magnets 206 are unskewed. In other words, the permanent magnets 206 are aligned with the rotational axis 110a.

[0057] FIG. 2B shows in a top view a further known electromechanical transducer or generator 140, here, by example as a linear machine. The generator 140 includes the stator assembly 145 and the rotor assembly 150.

[0058] The generator 140 shown in FIG. 2B is similar to the generator 140 shown in FIG. 2A. However, the skew angle α is different.

[0059] According to the example shown in FIG. 2B full skewing is implemented. Thus, the skew angle α.sub.max of the rotor magnet 206 is set to be equal to a tooth pitch angle of the stator assembly 145 (or equal to cogging torque period). This skew angle α.sub.max is named as a maximal or full skew angle as it allows the best or full cancellation of cogging torque or torque ripples.

[0060] Accordingly, the edge 208 of the magnetic component part 204 and the permanent magnets 206, respectively is arranged with the maximal skew angle α.sub.max relative to the rotational axis 110a. The skew angle α.sub.max of the rotor magnet 206 may for example be 60°.

[0061] FIG. 3 shows in a top view an electromechanical transducer or generator 140 according to an embodiment of the invention. Here, the generator 140 is exemplary depicted as a linear machine. The generator 140 includes the stator assembly 145 and the rotor assembly 150.

[0062] In contrast to the examples shown in FIGS. 2A and 2B, the embodiment of FIG. 3 employs an optimized skew angle α.sub.opt which lies between the skew angle α of zero as shown in FIG. 2A and the maximum skew angle α.sub.max as shown in FIG. 2B. The optimized skew angle α.sub.opt does not include the skew angle α of zero and the maximum skew angle α.sub.max. Thus, the optimized skew angle α.sub.opt lies in an interval between the two skew angles or limits which do not belong to the interval. In other words, the skew angle α.sub.opt of the rotor magnet 206 is set to be smaller than the maximum skew angle α.sub.max and larger than the skew angle α of zero.

[0063] This optimized skew angle α.sub.opt is named as an optimized skew angle as it allows to satisfy the level of noise and vibration and to increase the torque at the same time.

[0064] In addition, the optimal skew angle can also be defined as being smaller than manufacturing tolerances. This could also lead to good cogging torque cancellation as tolerances and imperfections are accounted for.

[0065] According to the embodiment of the invention, the edge 208 of the magnetic component part 204 and the permanent magnets 206, respectively is arranged with the optimized skew angle α.sub.opt relative to the rotational axis 110a. Below, ranges of the optimized skew angle α.sub.opt are given.

[0066] For integral slot machine, the optimized skew angle α.sub.opt of the rotor magnet 206 may for example be 35° to 55°, desirably 40° to 45° and more desirably 45° electrical degrees.

[0067] According to another definition, the optimized skew angle α.sub.opt of the rotor magnet 206 may have a value of 60% to 92%, desirably of 75% to 80% and most desirably of 75% of a maximum skew angle α.sub.max of for example 60° electrical for integral slot machines or is the electrical period of cogging torque of an integral slot machine.

[0068] FIG. 4 shows a diagram of torque versus a skew angle ratio of a maximum skew angle.

[0069] The torque per unit is depicted as a function of the skew angle per unit. A skew angle of 1 equals to the full or maximum skew angle α.sub.max.

[0070] According to the described technology, the skew angle is reduced below the maximum skew angle α.sub.max. It can be seen that the reduction of the skew angle can increase the torque by about 1% to about 5%.

[0071] FIG. 5 shows a diagram of torque change versus an absolute skew angle.

[0072] The torque in percent is depicted as a function of the absolute skew angle in electrical degrees. A skew angle of 60° equals to the full or maximum skew angle α.sub.max.

[0073] According to the described technology, the skew angle is reduced below the maximum skew angle α.sub.max. It can be seen that the reduction of the skew angle can increase the torque by about 1% to about 5%. The increase is valid for all load situations. For a skew angle of about 40° to 59° degrees the torque increase is almost the same for all load situations.

[0074] FIG. 6 shows a diagram of ripple versus an absolute skew angle.

[0075] The ripple in percent is depicted as a function of the absolute skew angle in electrical degrees. A skew angle of 60° equals to the full or maximum skew angle α.sub.max.

[0076] According to the described technology, the skew angle is reduced below the maximum skew angle α.sub.max. It has been found that decreasing or reducing the skew angle is not increasing ripple for all load situations. Further, for certain values or ranges of a decreased or optimized skew angle ripple is not increasing or is even decreasing.

[0077] For an optimized skew angle α.sub.opt of the rotor magnet 206 from 59° to about 40° ripple is decreasing for 100% load. For an optimized skew angle α.sub.opt of the rotor magnet 206 from 59° to about 50° ripple is decreasing for 75% load. For loads of 50% and 25% ripple is not increasing for an optimized skew angle α.sub.opt of the rotor magnet 206 from 59° to about 50°.

[0078] According to the described technology, the findings of the diagrams as shown in FIG. 6 and in FIG. 4 and/or 5 are taken together to achieve an optimized skew angle α.sub.opt of 35° to 50°, desirably of 40° to 45° and most desirably of 45°.

[0079] This has the advantage that the torque can be increased by about 1% to about 5% while cogging torque and torque ripples are almost kept the same or can even be decreased.

[0080] Although the present invention has been disclosed in the form of embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0081] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.