JP2019205244A - Stator of rotary electric machine - Google Patents

Abstract

To provide a stator of a rotary electric machine that has sufficient insulation property for high voltage, and can maintain insulation property by suppressing breakage of a slot liner with respect to increase in a bending angle of a stator coil rising portion due to a low coil end.SOLUTION: A stator 20 of a rotary electric machine includes: a stator core 21 provided with a plurality of slots 21s; a plurality of segment conductors 28 provided in the plurality of slots 21s; and a slot liner 302 provided in the slot 21s and electrically insulating the segment conductors 28, and connects a conductor end section 28E of the plurality of segment conductors 28 to configure an annular stator coil. The slot liner 302 has a recess 303 recessed from an edge surrounding the segment conductor 28 toward inside of the slot 21S at a portion located between adjacent segment conductors 28 and a portion opposing that portion.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an insulating structure for a stator of a rotating electrical machine.

The rotating electrical machine includes a stator, and this stator ensures a stator core provided with a plurality of slots, a stator coil disposed in the slot, and insulation between the stator core and the stator coil. And a slot liner formed of an insulating sheet. Here, the slot liner is formed and arranged so as to wrap the side surface of the stator coil in the slot, and a portion located inside the slot of the stator coil and a predetermined range of a rising portion that goes out of the slot from the slot are arranged. It is shaped so as to protrude from the slot by a predetermined length so as to cover it. In recent years, in rotating electrical machines used for electric vehicles and hybrid electric vehicles, high voltage (650 Vdc by boosting) for the purpose of high output and high efficiency, and low coil end (small size) for miniaturization. ) Is becoming stronger. In order to reduce the coil end, it is necessary to reduce the protruding amount of the stator coil from the stator core, and it is necessary to increase the bending angle of the stator coil rising portion protruding from the end surface of the stator core. . However, if the bending angle of the rising portion of the stator coil is increased, the protruding portion from the slot of the slot liner is likely to be broken, and there is a concern that the insulation function of the high-voltage rotating electrical machine is deteriorated. As a measure for suppressing the breakage of the slot liner, for example, Japanese Patent Laid-Open No. 2014-100039 (Patent Document 1) includes a stator core provided with a plurality of slots and a stator coil provided in the slots. Each of the slots is provided with N segment conductors (where N is a positive even number), and the stator coil is connected to a plurality of segment conductors via welds provided at the conductor ends of the respective segment conductors. Are connected, and the conductor ends of the segment conductors are annularly arranged in the circumferential direction at one coil end in the axial direction, constitute an N-row annular row, and at least at one coil end in the axial direction, In a stator of a rotating electrical machine in which an insulating member is annularly interposed between a pair of annular rows, the amount of protrusion from the stator end surface of the slot liner is Hmm, and the stator end surface at the coil bending start portion is The distance when the L mm, between the H and L,
H ≧ L ≧ H / 2
The relationship is set.

JP 2014-100039 A

  As described in the background art, the slot liner of the stator in the rotating electric machine is formed of an insulating sheet having high insulating properties, and is formed so as to wrap the side surface of the stator coil in the slot of the stator core. The coil is formed so as to protrude a predetermined length from the slot so as to cover the rising part from the slot of the coil. When the stator coil is composed of a plurality of segment conductors arranged in the radial direction in the slot, not only the insulation between the stator core and the segment conductor, but also in the adjacent part of each segment conductor It is necessary to ensure insulation. In this case, the slot liner is shaped so as to wrap around the entire side surface of each segment conductor, or, for example, in the case of a three-phase alternating current, wraps the entire circumference of the mass by using the same-phase segment conductors arranged in the same slot as a mass. Sometimes it takes a shape. In particular, rotating electric machines composed of segment conductors for electric vehicles and hybrid vehicles are compatible with high voltage (650Vdc by boosting) for the purpose of higher output and higher efficiency. In many cases, the shape surrounding the entire side surface of the conductor is employed to improve the insulation of the segment conductor. On the other hand, as a result of increasing the bending angle of the rising part of the stator coil with respect to the stator core end surface in order to cope with the reduction in coil end for the purpose of downsizing in recent years, breakage occurs at the protruding part from the slot of the slot liner. (Generated due to interference with the stator coil) and insulation function degradation (further degradation due to extension of breakage due to external force) are problems.

  In the present invention, after satisfying sufficient insulation against high voltage, the slot liner is prevented from breaking against the increase in the bending angle of the stator coil rising portion due to the low coil end, and the insulation is maintained. An object of the present invention is to provide a stator of a rotating electrical machine that can be used.

In order to achieve the above object, the stator of the rotating electrical machine of the present invention is:
A stator core provided with a plurality of slots;
A plurality of segment conductors provided in the plurality of slots;
A slot liner provided in the slot to electrically insulate the segment conductor;
With
In the stator of the rotating electrical machine that configures the annular stator coil by connecting the conductor ends of the plurality of segment conductors,
The slot liner has a recess that is recessed from a peripheral edge surrounding the segment conductor toward the inner side of the slot at a portion positioned between adjacent segment conductors and a portion facing the portion.

  ADVANTAGE OF THE INVENTION According to this invention, the stator of the rotary electric machine excellent in insulation can be provided. Problems, configurations, and effects other than those described above will become apparent from the description of the following examples.

Sectional drawing which shows the whole structure of the rotary electric machine containing the stator by the Example of this invention. The perspective view which shows the structure of the stator to which this invention is applied. It is a figure explaining the segment conductor of a stator coil, and is a figure which shows one segment conductor. It is a figure explaining the segment conductor of a stator coil, and the figure explaining coil formation by a segment conductor. It is a figure explaining the segment conductor of a stator coil, and the figure explaining arrangement of the segment conductor in a slot. The perspective view which shows the stator coil of a U phase. The cross-sectional perspective view which shows the welding side coil end part of a stator coil. The top view of the welding side coil end part of a stator coil. The top view of the non-welding side coil end part of a stator coil. The top view of the slot liner which surrounds a segment conductor by B shape. The perspective view of the slot liner which concerns on the Example of this invention which surrounds a segment conductor by B shape. The expanded view which shows the shape of the recessed part of a segment conductor. The top view of the slot liner which surrounds a segment conductor by S shape. The perspective view of the slot liner which concerns on the Example of this invention which surrounds a segment conductor by S shape.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the following description, an electric motor used in a hybrid vehicle will be described as an example of a rotating electric machine. Further, in the following description, “axial direction” refers to a direction along the rotating shaft 13 of the rotating electrical machine. The circumferential direction refers to the direction along the rotational direction of the rotating electrical machine. The “radial direction” refers to a radial direction (radial direction) when the rotational center of the rotor of the rotating electrical machine (the center of the rotating shaft 13) is the center. “Inner circumference side” refers to the radially inner side (inner diameter side), and “outer circumference side” refers to the opposite direction, that is, the radially outer side (outer diameter side).

  FIG. 1 is a cross-sectional view showing a rotating electrical machine including a stator according to the present invention. The rotating electrical machine 10 includes a housing 50, a stator 20, a stator core 21, a stator coil 40, and a rotor 11.

  The stator 20 is fixed to the inner peripheral side of the housing 50. The rotor 11 is rotatably supported on the inner peripheral side of the stator 20. The housing 50 is formed into a cylindrical shape by cutting of an iron-based material such as carbon steel, casting of cast steel or aluminum alloy, or pressing, and constitutes the outer casing of the rotating electrical machine 10. The housing 50 is also referred to as a frame or a frame.

  A liquid cooling jacket 130 is fixed to the outside of the housing 50. The inner surface of the liquid cooling jacket 130 and the outer surface of the housing 50 constitute a refrigerant passage 153 through which a liquid refrigerant RF such as oil flows. The refrigerant passage 153 is formed so as not to leak. The housing 50 houses the bearings 144 and 145 and is also referred to as a bearing bracket.

  In the case of direct liquid cooling, the refrigerant RF passes from the refrigerant storage unit 150 through the refrigerant passage 153 and flows out toward the stator 20 through the refrigerant outlets 154 and 155 to cool the stator 20.

  The stator 20 includes a stator core 21 and a stator coil 40. The stator core 21 is made by laminating thin sheets of silicon steel plates. The stator coil 40 is wound around a plurality of slots 21 </ b> S (see FIG. 2) provided on the inner peripheral portion of the stator core 21. Heat generated from the stator coil 40 is transferred to the liquid cooling jacket 130 via the stator core 21 and is radiated by the refrigerant RF flowing through the liquid cooling jacket 130.

  The rotor 11 includes a rotor iron core 12 and a rotating shaft 13. The rotor core 12 is made by laminating thin sheets of silicon steel plates. The rotating shaft 13 is fixed to the center of the rotor core 12. The rotating shaft 13 is rotatably held by bearings 144 and 145 attached to the housing 50, and rotates at a predetermined position in the stator 20 at a position facing the stator 20. The rotor 11 is provided with a permanent magnet 18 and an end ring (not shown).

  In assembling the rotating electrical machine 10, the stator 20 is inserted into the housing 50 in advance and attached to the inner peripheral wall of the housing 50, and then the rotor 11 is inserted into the stator 20. The rotor 11 is assembled to the housing 50 so as to be fitted to the bearings 144 and 145 of the housing 50.

  The structure of the principal part of the stator 20 used for the rotary electric machine 10 by a present Example is demonstrated using FIG. FIG. 2 is a perspective view showing a configuration of a stator to which the present invention is applied.

  The stator coil 40 can improve the space factor in the slot by using a conductor (copper wire in this embodiment) having a substantially rectangular cross section, and the efficiency of the rotating electrical machine 10 is improved.

  The stator core 21 is formed with, for example, 72 slots 21S opened in the circumferential direction on the inner diameter side (inner circumferential side). A slot liner 302 is disposed in each slot 21S to provide electrical insulation between the stator core 21 and the stator coil 40.

  As will be described later, the slot liner 302 is formed into a B shape or an S shape so as to wrap the copper wire constituting the stator coil 40.

  The winding method of the stator coil 40 will be briefly described with reference to FIG. FIG. 3A is a diagram for explaining a segment conductor of a stator coil, and is a diagram showing one segment conductor. FIG. 3B is a diagram illustrating the segment conductor of the stator coil, and is a diagram illustrating coil formation by the segment conductor. FIG. 3C is a diagram for explaining the segment conductors of the stator coil, and is a diagram for explaining the arrangement of the segment conductors in the slots.

  As shown in FIG. 3A, a copper wire insulated by enamel or the like having a substantially rectangular cross section is formed into a substantially U-shaped segment conductor 28 having the anti-welding side coil end apex 28C as a turning point. In the present embodiment, as shown in FIG. 3A, the segment conductor 28 has a substantially triangular shape when the anti-welding side coil end apex 28C and the anti-welding side coil end conductor skew portion 28F are viewed in the axial direction. It is molded into a simple shape. At this time, the non-welding side coil end apex 28 </ b> C may have a shape that turns the conductor so that the segment conductor 28 has a substantially U shape. The shape of the segment conductor 28 is not limited to a shape in which the anti-welding side coil end apex 28C and the anti-welding side coil end conductor skew portion 28F form a substantially triangular shape, as in this embodiment. For example, in a part of the anti-welding side coil end apex 28C, a shape in which the conductor is substantially parallel to the end surface of the stator core 21 (when viewed from the radial direction or the circumferential direction, the anti-welding side coil end apex 28C and the anti-welding are formed. It may be a shape in which the conductor inclined portion 28F of the side coil end forms a substantially trapezoidal shape).

  The segment conductor 28 is inserted into the status lot 21 </ b> S in the axial direction from one end surface side of the stator core 21. At this time, in the status lot 21S, the slot liner 302 is already arranged in a state of being formed into a B shape or an S shape. The conductor end portion 28E of the segment conductor 28 protruding to the other end surface side of the stator core 21 is bent in the circumferential direction to the opposite side from the anti-welding side coil end apex 28C side. The bent conductor end portion 28E is connected to the conductor end portion 28E of another segment conductor 28 inserted at a predetermined slot distance as shown in FIG. 3B by welding or the like. At this time, the segment conductor 28 is formed with a conductor straight portion 28S that is a portion inserted into the slot 21S and a conductor skew portion 28D that is a portion inclined toward the conductor end portion 28E of the segment conductor to be connected. Is done. 2, 4, 6... (Multiple of 2) segment conductors are inserted into the slot 21S.

  FIG. 3C shows an example in which four segment conductors D1 to D4 are inserted in one slot. However, since the cross section is a substantially rectangular conductor, the space factor in the slot 21S can be improved. Efficiency is improved. 21T is a tooth configured in the rotor core 21, and a slot 21S is formed between two adjacent teeth 21T. The segment conductors arranged in each slot are arranged at radial positions indicated by approximately 28R1 to 28R4.

  FIG. 4 is a perspective view showing a U-phase stator coil 40. FIG. 4 is a diagram when the connection operation of FIG. 3B is repeated until the segment conductor 28 becomes annular, and the coil 40 for one phase (for example, U phase) is formed. In FIG. 4, the description of the stator core 21 is omitted.

  The coil 40 for one phase is configured such that the conductor end 28E gathers in one axial direction, and forms a welding side coil end 62 and an anti-welding side coil end 61 where the conductor end 28E gathers. In the coil 40 for one phase, a terminal for each phase (U-phase terminal 42U in the example of FIG. 4) is formed at one end, and a neutral wire 41 is formed at the other end. The terminals 42U, 42V, 42W of each phase are collected at one place in the circumferential direction as shown in FIG.

  The detailed configuration of the welded portion (welding side coil end 62) of the stator 20 used in the rotating electrical machine 10 will be described with reference to FIG. FIG. 5 is a cross-sectional perspective view showing a welding-side coil end portion of the stator coil.

  The conductor end portions 28E of the segment conductors 28 are annularly arranged in the circumferential direction at one coil end in the axial direction of the rotating electrical machine 10, and constitute an N-row annular row.

  In the stator coil 40, insulating paper 300 is arranged in an annular shape for insulation between the coils, and insulating paper 301 is arranged in an annular shape for insulation between welds.

  After the insulating paper is disposed, the entire stator coil 40 is covered with a resin member to enhance insulation. Alternatively, the first resin member (for example, polyester or epoxy liquid varnish) is dropped on the whole or a part of the stator coil 40 and cured. In order to reinforce the insulation of the welded portion, the vicinity of the welded portion may be covered with a second resin member (for example, an epoxy powder varnish).

  FIG. 6 is a plan view of a welding-side coil end portion of the stator coil.

  FIG. 6 shows a protrusion L302 from the stator end surface 21A of the slot liner 302 at the welding side coil end 62 and a distance L28G from the stator end surface 21A of the coil bending start portion 28G. In order to insulate between the stator end surface 21A and the stator coil 40, it is desirable that the slot liner 302 protrudes to some extent from the stator end surface 21A. The shorter the distance L28G from the stator end surface 21A of the coil bending start portion 28G, the shorter the coil end and the smaller the stator. However, when the distance L28G is short, the end of the slot liner 302 is deformed and widened greatly. Is formed. If the amount of deformation of this part is within the range of the extension amount of the insulating paper, the insulation is maintained, but if the allowable value is exceeded, the insulating paper is torn and the insulating property is lowered.

  The inventors twisted the coil by forming a recess 303 in a portion between adjacent segment conductors at the end of the slot liner 302 and also forming a recess in the opposite surface (opposite surface). It has been found that the slot liner 302 becomes easy to expand (easily spread) and is not easily broken. The recess 303 is configured as a recess that is recessed from the peripheral edge 302K surrounding the segment conductor 28 toward the inside of the slot 21S. In other words, the recessed portion 303 is configured as a recessed portion that is recessed from the peripheral edge 302K of the slot liner 302 in the protruding direction from the slot 21S in the direction opposite to the protruding direction.

  FIG. 7 is a plan view of an anti-welding side coil end portion of the stator coil.

  FIG. 7 shows the anti-welding side coil end 61 side, but since the conductor skewing portion 28F is also provided on the anti-welding side coil end 61 side, the conductor is inserted when the segment conductor 28 is inserted into the slot 21S. When the segment conductor 28 is further inserted into the slot 21S from the position where the boundary portion 28H between the inclined portion 28F and the conductor straight portion 28S reaches the slot liner 302, the end portion of the slot liner 302 is deformed and greatly expanded.

  For this reason, also at the end portion of the slot liner 302 on the side opposite to the welding end coil end 61, the recess 303 is formed in the portion between the adjacent segment conductors, and the recess is also formed on the opposite surface (opposite surface). As a result, the slot liner 302 can be made difficult to break.

  FIG. 8 is a plan view of a slot liner that surrounds the segment conductors in a B shape. FIG. 9 is a perspective view of a slot liner according to an embodiment of the present invention that encloses a segment conductor in a B shape. 8 and 9, AR1 indicates the circumferential direction, and AR2 indicates the radial direction.

  FIG. 8 is a view of the B-shaped slot liner 302 formed in the slot 21 </ b> S as viewed from the axial direction (insertion direction of the segment conductor 28). The slot liner 302 is provided on each side of the rectangular cross section of the segment conductor 28. Along the side, there are sides 302A to 302H. 8 and 9 show a case where two segment conductors 28 are inserted into the slot 21S in order to simplify the description.

  The side 302A and the side 302H are portions located between adjacent segment conductors in the slot liner 302. The side 302C and the side 302F are portions (opposing surfaces) that face portions between adjacent segment conductors. The side 302B, the side 302D, the side 302E, and the side 302G are portions located in the bending direction (skew direction) of the segment conductor 28 or in the opposite direction.

  As shown in FIG. 9, a recess 303 is formed in the side 302A, the side 302C, the side 302F, and the side 302H. In particular, in this embodiment, the side 302A, the side 302C, the side 302F, and the side 302H are formed such that the whole side is lower than the other sides 302B, 302D, 302E, and 302G, thereby forming the recess 303. . That is, in the slot liner 302, the protruding amount L302 (see FIG. 6) from the stator core 21 is switched for each rectangular side in the cross section of the segment conductor 28, and the recesses 303 are formed on the sides 302A, 302C, 302F, and 302H having a small protruding amount. Form.

  The side 302A, the side 302C, the side 302F, and the side 302H are formed with a recess 303 lower than the sides 302B, 302D, 302E, and 302G, so that the sides 302B, 302D, 302E, and 302G are easily spread. In addition, since the sides 302B, 302D, 302E, and 302G can cover a wide area of the segment conductor 28 in the height direction, the reliability of insulation is improved.

  FIG. 10 is a development view showing the shape of the concave portion of the segment conductor. FIG. 10 shows a side 302A where the recess 303 is provided and a side 302B which is adjacent to the side 302A and where the recess 303 is not provided. As shown in FIG. 10, it is preferable to provide an arc portion at a connection portion 302X between the side 302A and the side 302B. That is, the stepped portion 302Y descending from the side 302B toward the side 302A and the side 302A may be connected by a smooth curve (arc) 302X. Thereby, when the part of the side 302B is expanded, the connection part 302X is not easily broken.

  The configuration in which the side 302A and the side 302B are connected by the arc portion 302X can be provided between any two sides of the side where the concave portion 303 is provided and the side where the concave portion 303 is not provided adjacent to the side.

  FIG. 11 is a plan view of a slot liner that surrounds the segment conductors in an S shape. FIG. 12 is a perspective view of the slot liner according to the embodiment of the present invention in which the segment conductor is surrounded by an S shape. 8 and 9, AR1 indicates the circumferential direction, and AR2 indicates the radial direction.

  FIG. 11 is a view of an S-shaped slot liner 302 formed in the slot 21 </ b> S as viewed from the axial direction (insertion direction of the segment conductor 28). The slot liner 302 is formed on each side of the rectangular cross section of the segment conductor 28. Along the side, there are sides 302a to 302g. 11 and 12 show a case where two segment conductors 28 are inserted into the slot 21S for the sake of simplicity.

  The side 302d is a portion located between adjacent segment conductors in the slot liner 302. The side 302b and the side 302f are portions (opposite surfaces) that face portions between adjacent segment conductors. The side 302a, the side 302c, the side 302e, and the side 302g are portions located in the bending direction (skew direction) of the segment conductor 28 or in the opposite direction.

  As shown in FIG. 12, a recess 303 is formed in the side 302b, the side 302d, and the side 302f. In particular, in this embodiment, the side 302b, the side 302d, and the side 302f are formed such that the whole side is lower than the other side 302a, side 302c, side 302e, and side 302g, thereby forming the recess 303. . That is, the slot liner 302 switches the protruding amount L302 (see FIG. 6) from the stator core 21 for each rectangular side in the cross section of the segment conductor 28, and forms a recess 303 on the sides 302b, 302d, and 302f with a small protruding amount. To do.

  The side 302b, the side 302d, and the side 302f are formed lower than the side 302a, the side 302c, the side 302e, and the side 302g by forming the recess 303, so that the side 302a, the side 302c, the side 302e, and the side 302g are expanded. In addition, since the sides 302a, 302c, 302e, and 302g can cover a wide range of the segment conductors 28 in the height direction, the reliability of insulation is improved.

  The rotating electrical machine 10 according to the present embodiment includes a stator 20 and a rotor 11 that is disposed inside the stator 20 so as to be rotatable. The stator 20 ensures electrical insulation between the stator core 21 provided with a plurality of slots 21S, the stator coil 40 disposed in the slot 21S, and the stator core 21 and the stator coil 40. A slot liner 302 formed of an insulating sheet. The stator coil 40 is configured to be connected via welds provided at end portions 28E of the plurality of segment conductors 28 arranged in the radial direction in the slot 21S. The slot liner 302 is shaped so as to project a predetermined length L302 from the slot 21S so as to cover the rising portion from the slot 21S of the stator coil 40. When the cross-sectional shape of the slot liner 302 is a shape that wraps around the entire side surface of each segment conductor 28 or a current-voltage waveform is a shape that wraps the segment conductors 28 of the same phase as a lump, with respect to the end protruding from the slot 21S By forming the recess 303 between the adjacent segment conductors and forming the recess 303 on the opposite surface, when the coil 40 is twisted, the slot liner 302 is easily stretched and is not easily broken. The insulation as the stator 20 is improved.

  With the configuration of the above-described embodiment, the slot liner 302 is not broken, so that a rotating electrical machine that satisfies the insulating properties required for an electric vehicle or a hybrid electric vehicle can be obtained.

  In the above description, the permanent magnet type rotating electric machine has been described. However, since the feature of the present invention relates to the coil end welded portion of the stator, the rotor is not a permanent magnet type, but an induction type or synchronous type. It can also be applied to reluctance, claw pole type, and the like. Further, in the winding method, the embodiment of the wave winding method has been described, but any winding method having the same characteristics can be applied. Further, although the explanation is made with the inner rotation type, the same applies to the outer rotation type.

  As described above, according to the present invention, it is possible to provide a stator for a rotating electrical machine that has excellent insulation properties despite its small size and high output.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of the embodiment.

  DESCRIPTION OF SYMBOLS 10 ... Rotary electric machine, 20 ... Stator, 21 ... Stator iron core, 21S ... Slot, 28 ... Segment conductor, 28E ... Conductor end of segment conductor, 40 ... Stator coil, 61 ... Anti-weld side coil end, 62 ... Weld-side coil end, 302... Slot liner, 303.

Claims (4)

A stator core provided with a plurality of slots;
A plurality of segment conductors provided in the plurality of slots;
A slot liner provided in the slot to electrically insulate the segment conductor;
With
In the stator of the rotating electrical machine that configures the annular stator coil by connecting the conductor ends of the plurality of segment conductors,
The slot liner has a recess recessed from a peripheral edge surrounding the segment conductor toward the inner side of the slot in a portion located between adjacent segment conductors and in a portion facing the portion. Electric stator. The stator of the rotating electrical machine according to claim 1,
The segment conductors are provided with N even numbers that are positive even numbers in one slot,
A conductor end of the segment conductor is a stator of a rotating electrical machine that is arranged in an annular shape in the circumferential direction at one coil end in the axial direction of the rotating electrical machine, and constitutes an N-row annular row. The stator of the rotating electrical machine according to claim 2,
Conductor ends of the plurality of segment conductors have welds connected by welding,
The slot liner is a stator of a rotating electrical machine, wherein the recess is formed in both the coil end on the welding side and the coil end on the anti-welding side. In the stator of the rotating electrical machine according to claim 3,
The segment conductor has a rectangular cross section,
The slot liner is a stator of a rotating electrical machine wherein the amount of protrusion from the stator core is switched for each rectangular side in the cross section of the segment conductor, and the recess is formed at a side where the amount of protrusion is small.

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