FI122303B - Rotor segment for a rotor in a permanently magnetized electric machine - Google Patents

Description

FIELD OF THE INVENTION Field of the Invention

The invention relates generally to rotating electrical machines. More particularly, the invention relates to a rotor segment for a rotor of a permanent magnet electrical machine and a permanent magnet electric machine.

Background

Large diameter electrical machines, such as direct-driven wind generators, in which the air gap diameter can be as high as 2000 mm, in many cases comprise a segmented stator and / or a segmented rotor. Typically, rotor segments and / or stator segments are fabricated in one location and transported to another location where the electrical machine is assembled from said segments. The rotor segment of a permanent magnet electrical machine typically comprises a support structure and permanent magnets attached to the support structure. The permanent magnets are arranged to form magnetic poles on the air gap surface of the rotor segment. The air gap surface is the surface of the rotor segment facing the stator of a permanent magnet electrical machine when the rotor segment is used as part of a permanent magnet electrical machine. One of the challenges in assembling a permanent magnet rotor of the kind of rotor segments described above involves attaching adjacent rotor segments together. The fact that the attachment takes place in the vicinity of permanently damaged permanent magnets limits the means and methods used for attachment. Another challenge relates to the transport of rotor segments, because especially with structures equipped with surface mounted permanent magnets, the permanent magnets closest to the sides of the rotor segments may be susceptible to damage during transport.

g Summary

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According to a first aspect of the invention, there is provided a new permanent magnet electrical machine. In the permanent magnet electrical machine S according to the invention, the magnetic terminals of the permanent magnet rotor comprising the rotor segments are placed in a <y> §30 such that the positions of each other in the adjacent rotor segments

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the tangential distance between the magnetic axes of the latching magnetic poles is greater than the mean of the tangential distances between the magnetic axes of adjacent magnetic poles of the same rotor segment. Therefore, the tangential distances from the sides of the rotor segments to the nearest center magnets can be increased, thus providing more space for the arrangements for attaching the rotor segments together. Further, especially in the case of structures with surface mounted electromagnets, the susceptibility to damage during transport is reduced because the permanent magnets are further away from the sides. The positioning of the magnetic poles described above reduces the magnetic coupling between the permanent magnet rotor and the stator windings of a permanent magnet electrical machine, but on the other hand, the torque caused by the toothing can also be reduced.

According to another aspect of the invention, there is provided a new rotor segment for a rotor of a permanent magnet electrical machine. The center angle φ between the first and second flanks of the rotor segment of the invention is at most π radians, or 180 degrees, and the rotor segment comprises a support structure and permanent magnets attached to the support structure. The permanent magnets are arranged to form 15 magnetic poles on the air gap of the rotor segment, which air toward the stator of the centrifuged electrical machine when the rotor segment is used as part of a permanent magnet electrical machine. The magnetic poles are positioned in the air gap such that: ai = φ / 2ρ + B ^ Rag, and α α = φ / 2ρ + B2 / Rag, where: ai is the center angle between the first side of the rotor segment and the magnetic axis of the magnetic pole closest to the first side, ™ cc2 is the central angle between one side of the rotor segment and the magnetic axis of the magnetic hub closest to the other side,

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° p is the number of magnetic poles of the rotor segment, tr

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^ Rag is the air gap radius of the rotor segment, and? B-t and B2 are tangential lengths selected such that a sufficient tangential distance is obtained between the permanent magnets of the rotor segments adjacent to each other when using the rotor segment as part of a permanent magnetized electrical machine. Appropriate values for B 1 - and B 2 are, depending on the case, dependent on the dimensions and mechanical structure of the rotor segment and / or the geometry of the stator windings. In practical cases, the lower limit of B-i and B2 is 5 mm. The terms B1 / Rag and B2 / Rag indicate that the angle in radians is the arc length divided by the radius.

A number of exemplary embodiments of the invention are set forth in the appended claims.

Various embodiments of the invention, both in terms of structures and methods of operation, together with further objects and advantages thereof, will be best understood from the following description of certain exemplary embodiments, read in conjunction with the accompanying drawings.

10 The verb "" encompasses "is used in this document in the open sense in the sense that it does not exclude or require the existence of features not mentioned. The specific features mentioned in the dependent claims are freely combinable with one another unless explicitly stated otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention and their advantages will now be explained in more detail with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a permanent magnet electrical machine according to one embodiment of the invention;

DESCRIPTION OF THE EMBODIMENTS Fig. 1 is a cross-sectional view of an i ° permanent magnet electrical machine according to an embodiment of the invention. The permanent magnet electric machine shown in Figure 1 is an external rotor machine in which the rotor is arranged to surround the stator.

x 25 The stator comprises a segmented stator core comprised of stator segments 125, 126, 127, and 128. The stator windings are preferably, but not necessarily, arranged such that each stator winding member of the stator resides in only one stator groove within a segment of the stator core. In this case, the static

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The segments can be wound separately and only the ends of the windings of the different stator segments need to be properly connected after assembly of the stator core. In accordance with one embodiment of the invention, the rotor of the permanent magnet electrical machine shown in Figure 1 comprises four rotor segments 101, 102, 103 and 4,104. The rotor segments 101-104 are similar to each other and therefore only rotor segment 101 is described in detail below. the central angle between the second side 108 of the root turret segment 101. Since there are four 5 similar rotor segments, the center angle cp is π / 2 radians, or 90 degrees. It should be noted, however, that depending on the structure and dimensions of the electrical machine, the rotor as well as the stator can be segmented with any suitable number of segments. In some cases, the rotor may comprise, for example, only two rotor segments, in which case the center angle φ would be π 10 radians, or 180 degrees, and in other cases the rotor may comprise three segments or more than four segments.

The rotor segment 101 comprises a support structure 109, which may be laminated and / or massive ferromagnetic material. The rotor segment 101 comprises permanent magnets 110, 111, 112 and 113 attached to the support structure 109. In the case shown in Figure 1, the permanent magnets are attached to the surface of the support structure 109. However, it is also possible to use a support structure with recesses for permanent magnets. The permanent magnets are arranged to form magnetic poles on the air gap surface of the rotor segment. The arrows in the figure representing the permanent magnets indicate the direction of magnetization of each permanent magnet. The magnetic poles 20 are disposed such that the tangential distance between the magnetic axes of adjacent rotor segments adjacent to each other's rotor segments is greater than the tangential distance between the magnetic axes of adjacent magnetic poles belonging to the same rotor segment. In Fig. 1, the center angle γ-ι corresponds to the tangential distance between the magnetic axes 114 and 116 of the respective adjacent magnetic poles of adjacent rotor segments 101 and 104. Similarly, the focal angle γ2 corresponds to the tangential distance between the magnetic axes 115 and 120 of the respective adjacent magnetic poles ja adjacent to the rotor segments 101 and 102. Since the rotor segments 101-104 are similar to each other, γι is equal to γ2. The center angles β-ι, β2 and β3 correspond to the tangential distances between the magnetic axes of adjacent magnetic poles in the rotor segment £ 101. The placement of the magnetic poles is accomplished by proper placement of the permanent magnets S 110-113. Using a support structure with recesses for permanent magnets, magnetic pole placement can be implemented

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35 also for magnetic flux phenomena by the proper design of the ferromagnetic bodies forming the paths. The above arrangement of the magnetic poles increases the tangential distances from the flanks 107 and 108 of the rotor segment 101 to the corresponding closest permanent magnets 110 and 113 and thus provides more space for the arrangements 121 and 122 for attaching the rotor segment 101 to the adjacent rotor segments 104 and mag-5 magnetic coupling between the rotor and stator windings, but on the other hand, the torque caused by the toothing may also decrease.

The above-described property of the permanent magnet electrical machine shown in Figure 1 can be achieved by selecting the center angle α-i shown in Figure 1 greater than φ / 8 = π / 16 radians = 11.25 degrees and the center angle 10 α2 shown in Figure 1 greater than φ / 8. The denominator 8 is due to the fact that the rotor segment 101 has four magnetic poles. The center angle α1 is the angle between the first side 107 of the rotor segment and the magnetic axis 114 of the magnetic hub closest to the first side, and the center angle α2 is the angle 15 between the second side 108 of the rotor segment and the magnetic axis 115 of the magnetic hub. This selection of center angles cc-ι and a2 can typically be represented by the following equations: = φ / 8 + BVRag, and (1) a2 = φ / 8 + B2 / Rag, where Rag is the air gap of the rotor segments as shown in Figure 1. In the case of an external rotor machine such as that shown in Fig. 20, Part 1, the air gap Rag is the radius of the largest circle that the rotor can surround. Bi and B2 are tangential lengths selected so as to provide a sufficient tangential distance between the permanent magnets of adjacent rotor segments. Suitable values for B 1 and B 2 depend, as appropriate, on the dimensions and mechanical structure of the rotor segments and / or the geometry of the stator windings. In practical cases, the lower bound of B-t and B2 is 5 mm.

In the permanent magnet electrical machine shown in Figure 1, the magnetic poles are read the number is four per rotor segment. More generally, in the case where the number of magnetic poles per rotor segment is p, the center angles a1 and cc2? 30 are:

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§ cc-ι = φ / 2ρ + BVRag, and (2) cc2 = φ / 2ρ + B2 / Rag.

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In a rotor segment according to an embodiment of the invention, the magnetic axes of the magnetic poles of the rotor segment are uniformly distributed within the rotor segment in the tangential direction. For rotor segment 101 shown in Figure 1, this would mean that βι = β2 = β3 <φ / 4. The fact that βι, β2 and β3 5 are less than φ / 4 is the consequence of equations (1), that is, βι, β2 and β3 are each less than the sum ai + α2 = γ-t = γ2, that is, the magnetic fields of all magnet poles the axes are not uniformly distributed.

In a rotor segment according to one embodiment of the invention, B1 is substantially equal to B2, i.e., the center angle α1 is substantially equal to the center angle 10 α2.

Fig. 2 is a cross-sectional view of a permanent magnet electrical machine according to an embodiment of the invention. The permanent magnet electric machine shown in Figure 2 is an internal rotor machine in which the stator is arranged to surround the rotor. The stator comprises a segmented stator core comprised of stator segments 15,225, 226, 227, 228, 229, and 230. The stator windings are preferably, but not necessarily, arranged such that each stator winding member of the stator is housed in only one stator core segment. In this case, the stator segments can be wound separately from one another and the ends of the coils of the different stator segments need only be properly connected after the co-20 of the stator core has been experienced. The rotor of a permanent magnet electrical machine shown in Fig. 2 comprises six rotor segments 201, 202, 203, 204, 205 and 206 according to an embodiment of the invention. The rotor segments 201-206 are attached to each other and to the axis 250. In FIG. 2, the angle φ represents the central angle between the first side 207 of the rotor segment 201 and the second side 208 of the rotor segment 201. Since 25 have six similar rotor segments, the center angle φ is π / 3 radians ς, or 60 degrees.

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Each of the rotor segments 201-206 comprises a support structure which may be laminated and / or massive ferromagnetic material. Further, each of the rotor segments 201-206 comprises permanent magnets embedded in the surface layer 232. Therefore, single permanent magnets are not shown in Figure 2. The permanent magnets are arranged o to form magnetic poles on the air gap surface of the rotor segments. In Figure 2, the number of magnetic poles per rotor segment is p and the dashed lines 214, 217, 218, 219, 231, and 215 indicate the number of magnetic poles of the rotor segment 201 from the number p of some magnetic axes. The dashed line 216 represents the magnetic axis of one of the two outermost magnetic poles of the rotor 35 segment 206. The magnetic poles are positioned such that the tangential distance between the magnetic axes of adjacent magnetic poles in adjacent rotor segments is greater than the tangential distance between the magnetic axes of adjacent magnetic poles of adjacent magnetic poles in the same rotor segment. In Fig. 2, the center angle γι corresponds to the tangential distance between the respective magnetic axes 214 and 216 of adjacent magnetic poles of adjacent rotation 5 segments 201 and 206. The center angles βι, β2, βρ-2 and βρ-2 correspond to tangential distances between the magnetic axes of adjacent magnetic poles of the rotor segment 201. The arrangement of the magnetic poles described above increases the tangential distances from the sides of the rotor-10 riser segments to the nearest permanent magnets, thus providing more space for arrangements for attaching each rotor segment to its neighboring rotor segments. The above-described arrangement of the magnetic poles reduces the magnetic coupling between the permanent magnet rotor and the stator windings of a permanent magnet electrical machine, but on the other hand, the torque caused by the toothing can also be reduced.

In a permanent magnetized electrical machine according to one embodiment of the invention, the magnetic axes of the magnetic poles are uniformly spaced within each rotor segment and the stator pole segment is different from the uniform spacings.

In a permanent magnet electrical machine according to one embodiment of the invention, the length of the uniform distances, i.e. the rotor pole inside each rotor segment, is substantially: (Ps xp - nx xs) / p where Ps is a stator pole, p is the number of magnetic poles is an integer greater than or equal to 1.

i 0 For illustrative purposes, consider the following example:

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“- number of magnetic poles per rotor segment = p o - stator pole = Ps, σ> 30 - stator slot = xs, o ^ - additional tangential distances Bi and B2, cf. Equations (1) and (2), at each side of the rotor segment, are half of the stator cutoff, that is, B1 = B2 = xs / 2, and - the air gap is Rag.

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In the case of an external rotor machine as shown in Figure 1, the air gap Rag is the radius of the largest circle that the rotor is capable of encircling, and in the case of an internal rotor machine like Figure 2, the air gap Rag is the smallest circle radius capable of surrounding the rotor.

5 In the above example case, the central angles cp, ai and a2 shown in Figures 1 and 2 are: φ = (px Ps) / Rag, and αΛ = α2 = φ / 2ρ + xs / (2 χ Rap therefore: 10 φ / 2ρ = Ps / (2 xRag), and cci = α2 = (1 + Ts / Ps) χ (φ / 2ρ).

For example, if the stator section Ps = 150 mm and the stator section xs = 50 mm, the center angles ai = ai = 11/3 χ φ / 2ρ. If the magnetic axes of the magnetic poles of each rotor segment are divided by uniform distances, the length of the uniform intervals, i.e. the rotor pole Pr within each rotor segment, is: (p χ Ps - 2 χ xs / 2) / p = Ps - Xs / p.

For example, if the stator spacing Ps = 150 mm, the stator spacing xs = 50 mm and the number of poles per rotor segment p = 24, the rotor spacing Pr = 147.9 mm.

The specific examples set forth in the above description are not to be construed as limiting. Therefore, the invention is not limited to the embodiments described above, δ

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Claims (10)

A rotor segment (101,201) for a rotor in a permanently magnetized electric machine, in which the rotor segment the central angle φ between the first and second sides (107, 108, 207, 208) is at most π radians and the rotor segment comprises a support structure 5 (109) and permanent magnets (110-113) which are attached to the support structure and arranged to form at least two magnetic poles in the air gap surface of the rotor segment, which air gap surface is against the stator of the permanently magnetized electric machine where the rotor segment is used as part of a permanently magnetized electric machine, characterized in that = φ / 2ρ + Β-ι / Rag, and a2 = φ / 2ρ + B2 / Rag, where: ai is the central angle between the first side of the rotor segment (107, 207) and the magnetic axis (114, 214) of the closest magnetic pole the first side, α2 is the central angle between the second side (108, 208) of the rotor segment and the magnetic axis (115, 215) of the magnetic pole closest to the second side, ___ p is the number of magnetic poles in the root The element segment, δ ^ 20 Rag is the radius of air gap of the rotor segment, which in the case of an external rotor machine is the radius of the largest circle that the machine can surround, and which in the case of an internal rotor machine is the radius of the smallest circle that can surround the rotor, and I 5 and B2 are tangential lengths selected so that a sufficient σ> 0 tangential distance is fixed between the permanent magnets in adjacent rotor segments where the rotor segment is used as part of a permanently magnetized electric machine, where Bi is greater than or as large as 5 millimeters and B2 is greater than or equal to 5 millimeters, the terms Bi / Rag and B2 / Rag expressing a general rule, according to which vinkein in radians is the length of the beaker divided by the radius. The rotor segment of claim 1, wherein the magnetic axes of the magnetic poles are divided at uniform intervals in the tangential direction, the central angle corresponding to each unitary space being less than a 1 + a 2. The rotor segment of claim 1 or 2, wherein Bi is substantially the same as B2. A permanently magnetized electric machine comprising a stator and a rotor comprising at least two rotor segments (101-104, 201-206) according to any of claims 1-3. The permanently magnetized electric machine according to claim 4, wherein the magnetic axes of the magnetic poles are divided at uniform intervals within each rotor segment and the stator pole division is different from the length of the uniform intervals. The permanently magnetized electric machine according to claim 5, wherein the length of the unitary interstices is essentially: (Ps xp - nx xs) / p, where Ps is the stator pole division, p is the number of magnetic poles in each rotor segment, xs is the stator splitting and n is an integer which is greater than or equal to 1. δ ^ 20 The permanently magnetized electric machine according to claim 6, wherein the integer n is 1. ό i A permanently magnetized electric machine according to any of claims 4-7, wherein the permanently magnetized electric machine is an external rotor machine such that the rotor CL surrounds the stator. O The permanently magnetized electric machine according to any of claims 4-7, wherein the permanently magnetized electric machine is an internal rotor machine such that the stator surrounds the rotor. A permanently magnetized electric machine according to any of claims 4-9, wherein the stator comprises a segmented stator core and each stator coil ring is arranged to be placed in the stator coil which belongs to only one segment in the stator core. δ (M o m o X cn CL h- · o δ CD O O {M