JP5957727B2 - Permanent magnet rotating electric machine - Google Patents

Description

  The present invention relates to a permanent magnet type rotating electrical machine. More specifically, the present invention relates to a technology for reducing eddy current loss generated in a rotor of a concentrated-winding large-capacity rotating electric machine, particularly a large permanent magnet generator for wind power generation having a rated output exceeding 1000 kW.

A so-called concentrated winding permanent magnet type rotating electrical machine having a rotor having a plurality of magnetic poles by permanent magnets and a stator having an armature winding wound around the magnetic poles is used in various applications. Yes.
In small motors, concentrated winding is often used because it can be automatically wound by a machine because of the structure of concentrated winding around the magnetic poles of the stator. In such a small motor, copper loss, iron loss, and mechanical loss account for most of the loss, and eddy current loss generated in the rotor is often not a problem.

On the other hand, in large machines, distributed winding stators have been used so far, but concentrated windings with small coil ends are also often used in large machines.
In particular, when a permanent magnet generator is used in a gearless wind power generation system, compared to distributed winding, concentrated winding can reduce the axial length due to the small coil end, and armature winding In many cases, concentrated winding is selected from the viewpoint that high efficiency can be realized because of small copper loss.

As described above, concentrated winding has the advantage that the coil end is small. On the other hand, when concentrated winding is used for armature winding, the number of stator slots is reduced relative to the number of poles. There is a problem that the change in the magnetic flux of the rotor portion becomes larger than that of the rotor, and the eddy current loss of the rotor due to the magnetomotive force of the armature current becomes larger than that of the distributed winding.
Further, when a high-performance magnet having a high residual magnetic flux density and a high coercive force such as a rare earth magnet is adopted as a magnetic pole of a rotor of a large capacity machine, for example, an Nd-Fe-B magnet has a conductivity of the magnet itself. It is high and has the feature that eddy current flows more easily than a ferrite magnet.

For the above reasons, in the case of a concentrated-winding large-capacity rotating electric machine, particularly a large-scale permanent magnet generator for wind power generation with a rated output exceeding 1000 kW, eddy current loss generated in the rotor cannot be ignored. Sometimes.
That is, there is a problem that the efficiency of the generator is significantly lowered due to this eddy current loss, or the temperature of the rotor is increased due to this eddy current loss, leading to demagnetization of the magnet. Moreover, even if it does not reach demagnetization, the residual magnetic flux density decreases due to the temperature rise, and as a result, the magnetic flux generated by the magnet decreases. For this reason, in order to produce the same output as that without temperature rise, it is necessary to flow a large amount of armature current, and there is a problem that copper loss increases and efficiency decreases.

Japanese Utility Model Publication No.4-1448 JP 2010-252448 A

As described above, in the case of a large-scale permanent magnet generator for wind power generation, as a technique for solving the problem that eddy current loss generated in the rotor cannot be ignored, a rotor yoke has been conventionally used as a silicon steel plate, for example. There has been a technique for reducing eddy currents by using a structure in which various electromagnetic steel sheets are laminated.
However, a structure in which electromagnetic steel sheets are laminated as a yoke of a rotor has a problem that the cost is higher than that of a case of a solid (solid) yoke, and as disclosed in Patent Document 1. When magnetic steel sheets are laminated, it is necessary to tighten the laminated magnetic steel sheets with bolts to unite them. When this tightening bolt is made of a ferromagnetic material such as steel, magnetic flux also flows through this tightening bolt. There was a problem that eddy current loss would occur. In patent document 1, in order to solve this subject, it tightens with the insulation nut and the insulation stud.

Moreover, in patent document 2, as a shape of the through-hole provided in the laminated iron core through which a fastening bolt passes, the dimension in the direction orthogonal to the direction of the main magnetic flux passing through the laminated iron core is perpendicular to the direction of the main magnetic flux passing through the laminated iron core. A method of reducing the eddy current loss of the fastening bolt by using a larger shape is disclosed.
Furthermore, since the magnetic flux passes through a massive (solid) spider portion to which the electromagnetic steel plate is attached, there is a problem that an eddy current is also generated in the spider portion.

As disclosed in Patent Document 1, in a large rotating electrical machine, when a magnetic steel sheet is laminated on a rotor or stator core, a thin magnetic steel sheet is formed into a single ring shape by a press device. It is difficult to form by punching or stacking. Therefore, a plurality of magnetic steel sheets divided into fan shapes are formed into an annular shape, stacked in the axial direction while being shifted in the circumferential direction, and the entire iron core is tightened with a tightening bolt to form an integrated structure.
Also, in the rotor of an inner rotor type rotating electrical machine, the yoke part of the rotor also serves as a support part of the rotating shaft of the rotating electrical machine. However, there is a problem that it is practically difficult in this respect.

In such a case, the electromagnetic steel plates are laminated as the outer peripheral portion of the rotor, the inner peripheral portion is constituted as a massive spider portion, the eddy current loss of the yoke portion is reduced by the structure of laminating the magnetic steel plates, and A technique is used in which the inner peripheral portion requiring mechanical strength is configured as a massive spider portion.
The present invention relates to a first problem of loss of eddy current generated in a fastening bolt for fastening a laminated electromagnetic steel sheet with a bolt to a rotor core composed of a yoke part and a massive spider part laminated with electromagnetic steel sheets, and an electromagnetic The magnetic flux also passes through the massive spider part to which the steel plate is attached, so that the eddy current is also generated in the spider part. It is an object of the present invention to provide a permanent magnet type rotating electrical machine, particularly a permanent magnet generator for wind power generation, capable of reducing the eddy current loss.

  In addition, in a rotor core composed of a yoke portion laminated with electromagnetic steel plates and a massive spider portion, an electromagnetic contact with the massive spider portion is prevented in order to prevent the rotation between the yoke portion laminated with electromagnetic steel plates and the massive spider portion during rotation. A key groove is formed on the yoke portion side where the steel plates are laminated, and the key inserted into the key groove is fixed to the massive spider portion. As with the tightening bolt, eddy current loss also occurs in the key depending on the material. Therefore, as with the tightening bolt, reduction of eddy current loss is a problem.

The permanent magnet type rotating electrical machine according to claim 1 of the present invention that solves the above-mentioned problems is a state in which a stator having concentrated winding of armature windings and a plurality of circularly shaped and circumferentially displaced positions are formed. A rotor comprising a fan-shaped electromagnetic steel sheet laminated in the axial direction, an outer yoke part having a fastening bolt for integrating the electromagnetic steel sheets laminated in the axial direction, and an inner yoke part as a massive spider part A permanent magnet type rotating electrical machine comprising: a tightening bolt; a through hole into which the tightening bolt is inserted; a key for preventing slippage in the rotational direction of the outer peripheral yoke portion and the inner peripheral yoke portion; And a key groove for inserting the magnetic steel sheet, and a distance as a magnetic path from the outer peripheral portion of the electromagnetic steel plate to the inner peripheral portion of the electromagnetic steel plate in contact with the inner peripheral yoke portion Magnetic flux density There and determines to be equal to or less than 1.5T (Tesla).
The permanent magnet type rotating electrical machine according to claim 2 of the present invention that solves the above-mentioned problem is a distance as a magnetic path from the outer peripheral part of the electromagnetic steel sheet to the inner peripheral part of the electromagnetic steel sheet in contact with the inner peripheral yoke part, It is determined that the magnetic flux density of the electrical steel sheet is 1.5T (Tesla).

The permanent magnet type rotating electrical machine according to claim 3 of the present invention that solves the above-mentioned problems is the permanent magnet type rotating electrical machine according to claim 1 or 2 , wherein the fastening bolt and a through hole into which the fastening bolt is inserted. A layer having a small relative permeability is provided between them.

A permanent magnet type rotating electrical machine according to a fourth aspect of the present invention that solves the above problem is the permanent magnet type rotating electric machine according to the first, second, or third aspect, wherein the outer peripheral yoke portion is in contact with the inner peripheral yoke portion. , the position directly below the permanent magnet, characterized in that he partially take dividing the laminated electromagnetic steel plates.

  The permanent magnet type rotating electrical machine according to claim 5 of the present invention that solves the above problem is applied to the permanent magnet generator for wind power generation in the permanent magnet type rotating electrical machine according to claim 1, 2, 3, or 4. It is characterized by that.

According to the invention according to claim 1, 2, arranged beneath the permanent magnet, tightening flows to bolts and keys, the magnetic flux density decreases, less susceptible to flux, it is possible to reduce the eddy current loss Since the magnetic path from the outer peripheral part of the electromagnetic steel sheet to the inner peripheral part of the electromagnetic steel sheet is lengthened so that the magnetic path can be secured only in the electromagnetic steel sheet part, the eddy current in the inner yoke part Loss can be reduced.
According to the invention of claim 3 , since the layer having a small relative permeability is provided between the tightening bolt and the through hole into which the tightening bolt is inserted, the magnetic flux density flowing through the tightening bolt is reduced. Less susceptible to eddy current loss .
According to the invention of 請 Motomeko 4, against the outer circumferential yoke portion of laminated magnetic steel sheets, the smallest position of the magnetic flux density, i.e. the position immediately below the permanent magnet is a position which is not utilized as a magnetic path, a massive spider portion By removing a part of the laminated electrical steel sheets, it is possible to suppress the occurrence of eddy current loss in the removed part.
According to the invention which concerns on Claim 5, the eddy current loss in the large-sized permanent magnet generator for wind power generation whose rated output exceeds 1000 kW is reduced, and efficiency improvement is anticipated.

It is a schematic structure figure of the permanent magnet type rotating machine of the present invention. FIG. 2A is an arrangement diagram showing the arrangement of permanent magnets and tightening bolts, and FIG. 2B is a magnetic flux diagram of a rotor composed of an outer peripheral yoke portion in which electromagnetic steel plates are laminated and a massive spider portion. 1 is a schematic structural diagram of a permanent magnet type rotating machine according to a first embodiment of the present invention. It is a schematic structure figure of the permanent magnet type rotating machine concerning the 2nd example of the present invention. It is a schematic structure figure of the permanent magnet type rotating machine concerning the 3rd example of the present invention. It is a graph which shows the BH curve which shows the relationship between a magnetizing force and magnetic flux density. It is a schematic structure figure of the permanent magnet type rotating machine concerning the 4th example of the present invention.

  Means for solving the two problems of the problem of eddy current loss occurring in the tightening bolt or key of the keyway and the problem of eddy current loss occurring in the massive spider portion will be described.

  First, as means for solving the eddy current loss generated in the tightening bolt or keyway key of the first problem, as shown in FIG. 1, a stator core 2 in which armature windings 1 are concentrated and an electromagnetic An outer yoke portion 4 that is formed by dividing a steel plate into a fan shape, laminating in the circumferential direction, laminating in the axial direction, forming an annular shape with a plurality of pieces, and fastening the whole with a fastening bolt 3 to form an integral structure; A permanent magnet comprising a rotor core 6 composed of an inner circumferential yoke part (hereinafter referred to as a massive spider part) 5 which is a massive spider part, and a permanent magnet 7 arranged on the outer circumferential surface of the outer yoke part 4 at regular intervals. In the rotary electric machine, rotation of the tightening bolt 3 and the through hole 3a into which the tightening bolt 3 is inserted, the outer yoke portion 4 and the massive spider portion 5 are rotated at positions where they are not used as magnetic paths with the least change in magnetic flux. The inserted keyway keys 8 and key 8 to prevent slippage of the direction in which to place the (supporting groove) 8a. Thereby, generation | occurrence | production of an eddy current can be reduced and a loss can also be reduced. More specifically, since the position directly below the permanent magnet 7 is not used as the most magnetic path, the loss can be reduced. The through hole 3a is formed in the laminated electromagnetic steel plates, the key 8 is fixed to the outer peripheral surface of the massive spider portion 5, and the key groove 8a is formed on the inner peripheral surface of the outer yoke portion 4 in contact with the massive spider portion 5. ing.

As used herein, the “position just below the permanent magnet” refers to the center of the cross section of the magnet passing through the rotating shaft in the sectional view of the permanent magnet 7 disposed on the rotor as seen through from the rotating shaft direction, as shown in FIG. It means the position on the center side of the rotation axis and its vicinity.
Further, another means for solving the first problem is that, for the fastening bolt 3, a layer having a low relative permeability is provided between the through-hole 3a formed in the laminated electromagnetic steel sheet and the fastening bolt 3. It is to pinch. Thereby, generation | occurrence | production of the eddy current can be reduced in the fastening bolt 3.

Next, in order to reduce the magnetic flux density in the massive spider part 5 to which the electromagnetic steel sheet is attached, as a first solution to the eddy current loss generated in the massive spider part 5 of the second problem, That is, it is effective to increase the distance of the magnetic path in the outer yoke part 4.
In addition, as for the magnetic path distance in the electromagnetic steel sheet portion, the magnetic flux leakage to the spider is selected by selecting the maximum magnetic flux density as the magnetic flux density of the magnetic steel sheet portion so that the magnetic saturation is not remarkable in the BH curve. As a result, eddy current loss can be reduced.

  Further, as a second solution, in the outer yoke part 4 in which the electromagnetic steel plates are laminated, the massive spider portion 5 at the position where the magnetic flux density is the smallest, that is, the position just below the permanent magnet 7 which is a position not used as a magnetic path. By removing a part of the laminated electrical steel sheet in contact with the eddy current loss, it is possible to prevent the eddy current loss from occurring in the removed part.

As shown in FIG. 2 (a), in the case of a rotor composed of an outer yoke portion 4 laminated with electromagnetic steel plates and a massive spider portion 5, the outer yoke portion 4 also serves as a base portion of the permanent magnet 7. FIG. 2B shows an example of the result of calculating the magnetic flux lines by simulation when the solving means for the first and second problems of the present invention is applied.
The fastening bolt 3 is arranged at a position where the magnetic flux density is the lowest, the eddy current hardly flows, and the outer peripheral yoke portion 4 in which the electromagnetic steel plates that are also used as the base metal portion of the permanent magnet 7 are laminated is shown in FIG. As shown by the thin line, there is a magnetic flux having a high magnetic flux density, but it can be seen that almost no magnetic flux enters the massive spider portion 5.

  In this embodiment, as shown in FIG. 3, a stator core 2 in which armature windings 1 are concentrated, an outer yoke portion 4 in which electromagnetic steel sheets are stacked and tightened with a tightening bolt 3 and a massive spider portion. 5 and a permanent magnet type rotating electrical machine having permanent magnets 7 arranged at regular intervals on the outer peripheral surface of the outer yoke portion 4, the mounting positions of the tightening bolt 3 and its through hole 3a are as follows: The magnetic flux density is disposed at a position where the magnetic flux density is the lowest, that is, a position directly below the permanent magnet 7 that is not used as a magnetic path.

Although omitted in FIG. 3, the mounting position of the key and the key groove for preventing the outer yoke 4 and the massive spider portion 5 from slipping in the rotational direction is also used as a magnetic path in the same manner as the mounting position of the tightening bolt. By disposing at a position where it is not performed, generation of eddy current can be reduced and loss can be reduced.
As used herein, the “position directly below the permanent magnet” refers to the center line of the cross section of the magnet passing through the rotating shaft in the sectional view of the permanent magnet disposed on the rotor as seen through from the rotating shaft direction, as shown in FIG. Means the position on the rotation axis center side and the vicinity thereof.

As described above, when electromagnetic steel sheets are laminated, it is necessary to tighten the laminated electromagnetic steel sheets with bolts to unite them. When this fastening bolt is made of a ferromagnetic material such as steel, magnetic flux is also applied to this fastening bolt. There is a problem that eddy current loss occurs due to flow.
Therefore, as shown in FIG. 3, the fastening bolt 3 is installed at a position where the magnetic flux density is minimum, that is, a position directly below the permanent magnet, which is a position not used as a magnetic path. Since it becomes difficult, eddy current loss can be reduced.
On the other hand, if the mounting position of the tightening bolt 3 is shifted laterally and disposed at a position that is a magnetic path, a magnetic flux flows through the tightening bolt and a larger eddy current loss occurs. The key groove and the key mounting position were also the same as those of the tightening bolt.

  In this embodiment, since the magnetic flux density flowing through the fastening bolt and the key is reduced because it is arranged directly below the permanent magnet, it is difficult to be affected by the magnetic flux, and eddy current loss can be reduced.

In this embodiment, as shown in FIG. 4, a gap 9 having a small relative permeability is provided between the fastening bolt 3 and the through hole 3a formed in the electromagnetic steel sheet.
The material of the gap 9 having a small relative magnetic permeability is made of any material such as a non-magnetic material such as an insulator, a paramagnetic material such as aluminum or a diamagnetic material such as copper.
In this example, the bolt was covered with a tubular pipe made of aluminum or copper, and the electromagnetic steel sheet was tightened. The same effect can be obtained by using a bolt that is covered with a material having a small relative permeability.

If the magnetic flux density flowing through the fastening bolt 3 is reduced, eddy current loss can be reduced.
Therefore, in order to reduce the magnetic flux density flowing in the fastening bolt 3, a non-magnetic material such as an insulator, or a relative magnetic permeability is provided between the laminated electromagnetic steel sheet serving as a magnetic path and the fastening bolt. Occurrence of eddy current in the fastening bolt 3 can be reduced by sandwiching the small layer.
As a material having such a low relative permeability, a vacuum or air layer is typical, but in the case of a metal material, any material such as a paramagnetic material such as aluminum or a diamagnetic material such as copper may be used. It is clear from the table of relative permeability in Table 1 that it is 1 / 1,000 or less as compared with the electromagnetic steel sheet.
The electromagnetic steel sheet is generally made of a material having a very high relative permeability such as silicon steel.

  In the present embodiment, since the gap 9 having a small relative permeability is provided between the tightening bolt 3 and the through hole 3a formed in the electromagnetic steel plate, the magnetic flux density flowing through the tightening bolt 3 is reduced, and therefore the influence of the magnetic flux. It is difficult to receive and eddy current loss can be reduced.

Even in the massive spider portion 5 to which the electromagnetic steel plate is attached, if there is a change in the magnetic flux, an eddy current is generated and a loss occurs. Therefore, in order to reduce the eddy current loss, in order to reduce the magnetic flux density in the massive spider part 5 to which the electromagnetic steel plate is attached, as shown in FIG. It is effective to increase the distance L as a magnetic path to the inner peripheral portion of the magnetic steel sheet.
In addition, the distance is set to such a dimension that a magnetic path can be secured only at the electromagnetic steel plate portion.
FIG. 6 shows an example of the BH curve of a non-oriented electrical steel sheet generally used for rotating electrical machines. In the example of the BH curve in FIG. 6, the magnetic flux density as shown by the broken line in the figure. Is more than 1.5T (Tesla), saturation becomes significant.

Therefore, in the example of the BH curve in FIG. 6, the distance L of the magnetic path is set so that the maximum magnetic flux density is 1.5 T (Tesla) or less .
Ie, in this embodiment, from the design specifications of the characteristics and the rotating electrical machine of the electromagnetic steel sheets used, the maximum magnetic flux density as the magnetic saturation of B-H curve of the electromagnetic plate is magnetic flux density is not significant 1.5T ( Tesla) select, so that its maximum magnetic flux density 1.5T (Tesla) or less, by determining the length of the distance L as a magnetic path, the spider portion to secure a magnetic path only in the electromagnetic steel plate portion Magnetic flux leakage to the

If the flow of magnetic flux into the massive spider portion 5 is reduced, the eddy current loss that occurs can be reduced. Therefore, in order to reduce the inflow of the magnetic flux to the massive spider portion 5, a magnetic path distance that can secure a magnetic path in the electromagnetic steel plate portion is required.
About the distance of a magnetic path, it is set as the distance from which magnetic saturation is not remarkable in the magnetization BH curve of an electromagnetic steel plate, a magnetic path is ensured only in an electromagnetic steel plate part, and the magnetic flux leakage to the massive spider part 5 is carried out. Since the magnetic flux density in the massive spider portion 5 is reduced and eddy current loss can be reduced. In other words, by giving a margin to the magnetic path of the electromagnetic steel plate portion, almost no eddy current loss occurs in the massive spider portion 5, and the massive spider portion 5 can have a free structure.

  In this embodiment, the distance L as the magnetic path from the outer peripheral part of the electromagnetic steel sheet to the inner peripheral part of the magnetic steel sheet in contact with the massive spider part is increased so that the magnetic path can be secured only in the electromagnetic steel sheet part. The eddy current loss in the massive spider portion can be reduced.

  In this embodiment, as shown in FIG. 7, in the outer yoke part 4 in which the electromagnetic steel plates are laminated, the massive spider part at the position where the magnetic flux density is the smallest, that is, the position just below the permanent magnet which is not used as a magnetic path. By removing a part (indicated by hatching in the figure) 10 of the laminated electrical steel sheets in contact with 5, it is possible to prevent the occurrence of eddy current loss in the removed part.

In the outer yoke 4 in which the electromagnetic steel plates are laminated, a part 10 of the part in contact with the massive spider part 5 just below the permanent magnet 7 is removed as shown in FIG. Loss can be prevented from occurring.
Since it is originally a part that is not used as a magnetic path, the effect of reducing eddy current loss is not great, but it is possible to prevent eddy current loss from occurring in the removed part.
Furthermore, as a secondary effect, the weight of the iron core part made of the electromagnetic steel sheet is reduced, and the part from which the electromagnetic steel sheet has been removed becomes an air ventilation path. This also improves the cooling effect of the massive spider part.

  In this embodiment, in the yoke part where the electromagnetic steel sheets are laminated, the eddy current loss in the electromagnetic steel sheet part is reduced by removing a part of the laminated steel sheet in contact with the massive spider part, which is directly under the permanent magnet. Can do.

  The present invention is widely used as a technology for reducing eddy current loss generated in a rotor of a concentrated-winding large-capacity rotating electric machine, particularly a large-scale permanent magnet generator for wind power generation having a rated output exceeding 1000 kW. It is available.

DESCRIPTION OF SYMBOLS 1 Armature winding 2 Stator core 3 Fastening bolt 3a Through hole 4 Outer yoke part 5 Inner yoke part (lumped spider part)
6 Rotor core 7 Permanent magnet 8 Key 8a Key groove 9 Gap 10 Part of electrical steel sheet

Claims (5)

A stator in which armature windings are concentrated, a fan-shaped electrical steel sheet laminated in the axial direction in a state in which a plurality of sheets form an annular shape and are displaced in the circumferential direction, and an electromagnetic steel sheet laminated in the axial direction In a permanent magnet type rotating electrical machine comprising a rotor composed of an outer peripheral yoke part having a fastening bolt for integrating the inner peripheral part and an inner peripheral yoke part that is a massive spider part,
The tightening bolt, a through hole into which the tightening bolt is inserted, a key for preventing slippage in the rotation direction of the outer peripheral yoke portion and the inner peripheral yoke portion, and a key groove into which the key is inserted are directly below the permanent magnet. And the distance as a magnetic path from the outer peripheral portion of the electromagnetic steel sheet to the inner peripheral portion of the electromagnetic steel sheet in contact with the inner yoke portion is set such that the magnetic flux density of the electromagnetic steel sheet is 1.5 T (Tesla) or less. A permanent magnet type rotating electrical machine characterized by being determined to be.   Determining a distance as a magnetic path from the outer peripheral portion of the electromagnetic steel plate to the inner peripheral portion of the electromagnetic steel plate in contact with the inner peripheral yoke portion so that the magnetic flux density of the electromagnetic steel plate is 1.5 T (Tesla). The permanent magnet type rotating electrical machine according to claim 1.   The permanent magnet type rotating electrical machine according to claim 1, wherein a layer having a low relative permeability is provided between the fastening bolt and a through hole into which the fastening bolt is inserted. Contact with the inner circumferential yoke portion, wherein the outer circumferential yoke portion, the position directly below the permanent magnet, the permanent magnet according to claim 1, 2 or 3, characterized in that he partially take dividing of the laminated electromagnetic steel plates Rotary electric machine.   5. The permanent magnet type rotating electrical machine according to claim 1, wherein the permanent magnet type rotating electrical machine is applied to a permanent magnet generator for wind power generation.

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