JP5490171B2 - Rotor and synchronous motor - Google Patents

Description

  The present invention relates to a rotor and a synchronous motor.

  When using a magnet with high magnetic force for the rotor of a synchronous motor, rare earth magnets are very expensive materials, so in order to reduce the amount of use, they are often used in the form of as thin a wall as possible (for example, See Patent Documents 1 and 2 below). Further, in the case of an electric motor for blower use, since the blade is directly attached to the rotating shaft of the electric motor and used, if pulsation occurs in the torque output from the electric motor, it causes noise through the blade. For this reason, the structure (SPM: Surface Permanent Magnet) which arranges a magnet on a rotor surface is often used rather than the structure of a magnet embedded type (IPM: Interior Permanent Magnet) which is easy to generate torque ripple by reluctance torque. In this case, the rotor generally has a structure in which a soft magnetic material such as iron is used as a back yoke and a thin ring magnet or arc-shaped roof magnet is disposed on the rotor surface.

  In the case of a flat motor in which the outer diameter of the motor is larger than the axial dimension, the part where the rotor does not face the stator core when the axial length of the rotor is larger than the thickness of the stator core The amount of magnetic flux that is fixedly linked to the motor greatly affects the characteristics of the motor. For this reason, in the case of a flat motor, the axial dimension of the permanent magnet of the rotor is often larger than the thickness of the stator core.

  In addition, there is a rotor in which the rotor is composed of a plurality of different structures or magnet materials in the axial direction, and a high-magnetism rare earth sintered magnet and a ferrite sintered magnet are used (for example, Patent Document 3 below, 4). Sintered rare earth magnets are often used in the form of a flat plate in order to reduce the manufacturing cost of the magnet because a large magnet block is sintered and then cut into a predetermined shape from the block. . For this reason, when used in a rotor of a synchronous motor, an IPM is often used in which a magnet insertion hole is provided in a soft magnetic core and a permanent magnet is disposed inside the rotor. Also, in applications where sintered ferrite magnets have a high rotational frequency, in order to prevent scattering of the magnets due to centrifugal force, an IPM structure is often used as well.

  Further, in order to improve the performance of the rotor, a rare earth magnet having a higher magnetic force may be used. Since the material of a rare earth magnet having a high magnetic force is expensive, there is a method of incorporating a rare earth magnet into a part of a rotor composed of a low magnetic force magnet (see, for example, Patent Documents 5 and 6 below).

Japanese Patent Laying-Open No. 2005-312166 JP 2009-142144 A JP-A-2005-304204 JP 2010-68600 A Japanese Utility Model Publication No. 7-3278 JP-A-9-205746

  However, when a rare earth magnet having a reduced thickness is used for the rotor of a synchronous motor as in Patent Documents 1 and 2, if the axial dimension is made larger than that of the stator core, it does not face the stator core. In the portion, there are many nonmagnetic spaces (air) on the magnet surface, the permeance of the magnet is lowered, and the magnetic force generated by the magnet is lowered. Since the permanent magnet of the rare earth magnet is thinly used, the decrease in magnetic force due to the decrease in permeance becomes larger. For this reason, even if the rotor axial length is increased with respect to the stator thickness, there is a problem that the effect is reduced with respect to an increase in material cost.

  In addition, in the case of an IPM structure rotor using a plurality of different structures or magnet materials in the axial direction as in Patent Documents 3 and 4, since a soft magnetic material that is an iron core exists between adjacent magnetic poles, There are many magnetic fluxes that pass through this portion and short-circuit to the adjacent magnetic poles. In the case of a ferrite sintered magnet, since the magnetic force is lower than that of a rare earth sintered magnet, the influence of a short circuit of magnetic flux between magnetic poles is larger than that of a rare earth magnet. When these are arranged at both ends in the rotor axial direction that do not face the stator core, air is outside the rotor surface, so that the magnetic resistance is large, the permeance is reduced, and the magnetic flux generated from the magnet is reduced. The magnetic flux that is short-circuited between the magnetic poles inside the rotor is not greatly affected by the presence or absence of the stator core, so there is little change in the amount of magnetic flux that is short-circuited. There is a problem that the ratio of the amount increases and it becomes difficult to effectively use the magnetic force of the magnet. In addition, when a rare earth sintered magnet is used, there is a problem of high cost.

  However, in the case of the configuration as described in Patent Document 5, it is necessary to prevent the magnetic flux from leaking outside the motor by causing the stator back yoke to be magnetically saturated by the permanent magnet having a high magnetic force. I can't. Moreover, when it is set as the said patent document 6, since the one part magnetic force of the circumferential direction becomes strong with a high magnetic force magnet, there exists a problem that the distribution waveform of the magnetic flux density on a rotor surface will be distorted greatly.

  The present invention has been made in view of the above, and even if the amount of expensive high-magnetism magnets (rare earth magnets, etc.) is reduced, a sufficient amount of magnetic flux can be obtained, and the magnetic flux density is partially reduced. A rotor of a synchronous motor that can be suppressed can be realized.

  In order to solve the above-described problems and achieve the object, the present invention provides a rotor that faces a stator having an annular stator core, and has a first magnetically oriented radial orientation arranged on the outer peripheral side. A magnet portion including one permanent magnet and a back yoke made of a soft magnetic material disposed on the inner peripheral side of the first permanent magnet; and a magnetic force lower than that of the first permanent magnet and an anisotropic orientation. Annular second and third permanent magnets, wherein the axial center of the magnet part is the axial center of the range facing the stator core, and the axial thickness of the magnet part is The thickness is equal to or less than the axial thickness of the stator core, and the second and third permanent magnets are disposed so as to be in contact with both end surfaces of the magnet portion in the axial direction.

  According to the present invention, a sufficient amount of magnetic flux can be obtained even if the amount of expensive high-magnetism magnets (rare earth magnets, etc.) used is reduced, and the partial decrease in magnetic flux density can be suppressed.

FIG. 1 is a diagram illustrating a configuration example of the synchronous motor according to the first embodiment. FIG. 2 is a diagram showing a shape example of the permanent magnet and the soft magnetic material back yoke according to the first embodiment. FIG. 3 is a diagram illustrating an example of polar anisotropic orientation in the second permanent magnet. FIG. 4 is a diagram illustrating an arrangement example of the first permanent magnet and the second and third permanent magnets according to the first embodiment. FIG. 5 is a diagram showing a comparison between the induced voltage of the rotor of Embodiment 1 and the induced voltage of the comparative example. FIG. 6 is a diagram illustrating an example of a waveform of an induced voltage of the synchronous motor according to the second embodiment. FIG. 7 is a diagram illustrating an arrangement example of the magnetic poles of the rotor according to the third embodiment. FIG. 8 is a diagram illustrating an example of an induced voltage waveform of the synchronous motor according to the third embodiment.

  Embodiments of a rotor and a synchronous motor according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a first embodiment of a synchronous motor according to the present invention. FIG. 1 shows a cross section of the synchronous motor. The stator 7 has an annular stator core 8, and the rotor 5 is rotatably disposed inside the stator 7. The stator core 8 of the stator 7 has a plurality of protruding teeth with respect to the rotor 5, and windings 6 for applying a current from outside are provided in spaces (slots) between the teeth. Deploy. The winding 6 is intensively wound for each tooth.

  The rotor 5 includes two types of permanent magnets, a permanent magnet 1 (first permanent magnet) and permanent magnets 2-1 and 2-2 (second permanent magnet, third permanent magnet). The axial length is larger than the thickness of the stator 7 (the thickness of the stator core 8). The permanent magnet 1 is a high magnetic force permanent magnet. The permanent magnet 1 is, for example, a bonded magnet in which a rare earth magnet and a resin are mixed. For example, a material such as NdFeB or SmFeN is used for the rare earth magnet. These materials are used. The permanent magnets 2-1 and 2-2 are permanent magnets having a lower magnetic force than the permanent magnet 1, and for example, a bonded magnet in which a ferrite magnet and a resin are mixed is used. The resin material used for this is the same as that of the permanent magnet 1.

  FIG. 2 is a view showing a shape example of the permanent magnet 1 and the soft magnetic material back yoke 3 of the present embodiment. The central portion of the rotor 5 in the axial direction (the portion of the portion facing the stator 7 (stator core 8) from the center in the axial direction to a certain distance on both sides) is a permanent magnet 1 as shown in FIG. And the structure comprised by the soft-magnetic material back yoke 3 is used. The permanent magnet 1 has a thin ring shape and has a so-called radial orientation that spreads radially around the rotation axis 4 of the rotor 5.

  Since the permanent magnet 1 is a thin-walled magnet and is disposed at a position that does not face the stator core 8, the outside of the permanent magnet 1 becomes air, the magnetic resistance increases, the permeance decreases, and the magnetic flux appearing on the surface is greatly reduced. For this reason, when the axial direction dimension of the permanent magnet 1 is made larger than the axial direction dimension of the stator 5, the increase in the size of the permanent magnet 1 causes a small increase in the amount of magnetic flux, resulting in poor cost performance. Therefore, it is desirable to increase the amount of magnetic flux while keeping the axial dimension of the permanent magnet 1 below the axial dimension of the stator 5. In the present embodiment, by disposing the permanent magnets 2-1 and 2-2 above and below the permanent magnet 1, the amount of magnetic flux is increased while keeping the axial dimension of the permanent magnet 1 below the axial dimension of the stator 5. Yes.

  The permanent magnets 2-1 and 2-2 each have a ring shape coaxial with the permanent magnet 1, and are disposed so that the permanent magnet 1 is sandwiched between the permanent magnet 2-1 and the permanent magnet 2-2. As shown in FIG. 1, the outer diameters of the permanent magnets 2-1 and 2-2 and the permanent magnet 1 are substantially the same. The thickness in the radial direction of the permanent magnets 2-1 and 2-2 is larger than the thickness in the radial direction of the permanent magnet 1, and there is a cavity between the inner surface of the permanent magnets 2-1 and 2-2 and the rotary shaft 4. It has become.

  The permanent magnets 2-1 and 2-2 are poled anisotropically in accordance with the magnetic poles of the rotor 5. FIG. 3 is a diagram illustrating an example of polar anisotropic orientation in the permanent magnets 2-1 and 2-2. Due to the anisotropic orientation, the thickness of the magnet constituting the magnetic pole is larger than the dimensional thickness (outer diameter-inner diameter), and even if the distance from the stator core 8 is far, Even when the decrease in permeance is small and the distance from the stator core is increased, the decrease in the amount of magnetic flux is small. Since the magnet of the anisotropic magnet has a large thickness, a relatively large magnetic flux can be generated on the surface of the rotor 5 even at the axial end portion of the rotor that does not face the stator core.

  From the above, in the present embodiment, a magnet portion composed of the permanent magnet 1 and the soft magnetic material back yoke 3 as shown in FIG. Permanent magnets 2-1 and 2-2 are respectively arranged above and below the axial direction of the part to constitute the rotor 5. FIG. 4 is a diagram illustrating an arrangement example of the permanent magnet 1 and the permanent magnets 2-1 and 2-2 according to the present embodiment.

  As described above, in the present embodiment, in the synchronous motor, the high-magnetism permanent magnet 1 is disposed in a portion facing the stator core 8 in the vicinity of the center in the axial direction of the rotor 5 that can take high magnet permeance. In addition, permanent magnets 2-1 and 2-2 having a low magnetic force but having an anisotropic orientation are arranged at end portions in the axial direction including portions that do not face the stator core 8 where permeance tends to be low. I made it. Therefore, a sufficient amount of magnetic flux can be obtained even if the amount of expensive high magnetic permanent magnets used is reduced, and a partial decrease in magnetic flux density can be suppressed.

  Further, a configuration in which a permanent magnet with the same orientation as that of the permanent magnets 2-1 and 2-2 is arranged inside the permanent magnet 1 instead of the soft magnetic material back yoke 3 is also conceivable. In this case, since the back surface of the permanent magnet 1 is made of a non-magnetic material, the permeance is reduced and the amount of magnetic flux generated from the permanent magnet 1 is reduced. A decrease in the amount of magnetic flux can be suppressed. In addition, since the permanent magnet 1 has a large number of magnetic poles, the width of the magnetic pole on the surface of the permanent magnet 1 is narrow, or the thickness of the permanent magnet 1 is increased, the decrease in permeance of the permanent magnet 1 becomes smaller. The difference from the case where the back yoke of the soft magnetic material is arranged inside the permanent magnet 1 becomes small. Further, when the width of the magnetic pole is increased or the thickness of the permanent magnet 1 is reduced, the permeance is greatly reduced, and the present embodiment in which the soft magnetic material back yoke 3 is disposed on the inner side takes out a larger magnetic flux. be able to.

  FIG. 5 is a diagram showing a comparison between the induced voltage of the rotor of the present embodiment and the induced voltage of the comparative example. The horizontal axis in FIG. 5 indicates the axial length of the permanent magnet 1 of the rotor 5, and the vertical axis indicates the value of the induced voltage when the synchronous motor is configured. FIG. 5 shows the results of a three-dimensional magnetic field analysis when the thickness of the stator core 8 is 15 mm. The induced voltages 11 and 12 indicate the three-dimensional magnetic field analysis in the comparative example, and the induced voltage 13 indicates the three-dimensional magnetic field analysis of the present embodiment.

  The induced voltage 11 indicates an induced voltage obtained by a rotor composed of the permanent magnet 1 having an axial length of 15 mm as a comparative example, and the induced voltage 12 has a total axial length of 19 mm as a comparative example. The induced voltage obtained by the rotor comprised with the permanent magnets 2-1 and 2-2 is shown. An induced voltage 13 indicates an induced voltage generated by the rotor 5 according to the present embodiment in which the permanent magnet 1 and the permanent magnets 2-1 and 2-2 are combined. The permanent magnet 1 and the permanent magnets 2-1 and 2-2 are illustrated in FIG. The induced voltage when the total thickness is fixed to 19 mm and the axial length of the permanent magnet 1 is changed is shown. For example, if the axial length of the permanent magnet 1 is 15 mm, the axial length of the permanent magnets 2-1 and 2-2 is 2 mm ((19-15) / 2 [mm]) at the upper limit of the permanent magnet. The total is 4 mm each.

  In the case where both the induced voltage 11 obtained by the rotor using only the permanent magnet 1 and the induced voltage 13 obtained by the rotor 5 of this embodiment are 15 mm in the axial length of the permanent magnet 1. When compared (comparison at a position of 15 mm on the horizontal axis), the induced voltage 13 obtained by the rotor 5 of the present embodiment is induced more than the induced voltage 11 by combining the permanent magnets 2-1 and 2-2. Voltage is obtained. In the example of the synchronous motor shown in FIG. 5, when the axial length of the permanent magnet 1 is 15 mm, the rotor 5 of the present embodiment can obtain an induced voltage that is about 10% higher than the rotor of the permanent magnet 1 alone. It was.

  Further, when the total thickness of the permanent magnet 1 and the permanent magnets 2-1 and 2-2 is fixed to 19 mm and the axial length of the permanent magnet 1 is gradually reduced, the axial direction of the permanent magnet 1 is increased. As the length decreases, the induced voltage 13 decreases. As shown in FIG. 5, the axial length of the permanent magnet 1 is about 11.5 mm (the total axial length of the permanent magnets 2-1 and 2-2 is 7.5 mm). The value is substantially equivalent to the induced voltage 11 of the rotor composed of only the permanent magnet 1 having a length of 15 mm. From this, when the rotor 5 of the present embodiment is used, the axial length of the permanent magnet 1 can be reduced from 15 mm to 11.5 mm, and a reduction of about 25% is possible. The axial lengths of the permanent magnet 1 and the permanent magnets 2-1 and 2-2 described above are examples, and the axial lengths of the permanent magnet 1 and the permanent magnets 2-1 and 2-2 are the above-described examples. It is not limited to.

  Since the unit price of the rare earth magnet used for the permanent magnet 1 and the ferrite magnet used for the permanent magnets 2-1 and 2-2 is more than 10 times different, the axial length of the rotor 5 becomes longer, and the amount of ferrite magnet used is increased. Even if increases, the reduction effect seen from the whole material cost becomes sufficiently large.

  A soft magnetic material back yoke 3 exists inside the permanent magnet 1. When the axial length of the permanent magnet 1 is increased without using the permanent magnets 2-1 and 2-2, the volume of the soft magnetic material back yoke increases and the weight of the rotor increases. In this embodiment, by combining the permanent magnets 2-1 and 2-2 and reducing the volume of the soft magnetic material back yoke simultaneously with the permanent magnet 1, the weight of the rotor can be reduced.

Embodiment 2. FIG.
Next, a method for orienting the permanent magnets 2-1 and 2-2 according to the second embodiment of the present invention will be described. The configuration of the synchronous motor and the configuration of the rotor 5 of the present embodiment are the same as those of the first embodiment.

  The permanent magnet 1 is a thin ring magnet as shown in FIG. 2, and is a radially oriented magnet. For this reason, the magnetic flux density distribution on the surface of the permanent magnet 1 has a trapezoidal wave shape, and the waveform of the induced voltage of the synchronous motor including the rotor 5 using the permanent magnet 1 has a trapezoidal shape in the vicinity of the peak. It becomes the waveform.

  FIG. 6 is a diagram illustrating an example of a waveform of an induced voltage of the synchronous motor according to the present embodiment. In FIG. 6, when the axial length of the permanent magnet 1 is 11.5 mm and the total axial length of the permanent magnets 2-1 and 2-2 is 7.5 mm, the induced voltage generated by the permanent magnet 1 21, the induced voltage 22 generated by the permanent magnets 2-1 and 2-2, and the induced voltage 23 when the permanent magnet 1 and the permanent magnets 2-1 and 2-2 are combined as in the first embodiment, Is shown.

  The induced voltage 21 generated by the permanent magnet 1 has a trapezoidal shape as described above. On the other hand, if the induced voltage 22 generated by the permanent magnets 2-1 and 2-2 has a pointed shape at the center of the magnetic pole as shown in FIG. The induced voltage 23 generated in the synchronous motor using the rotor 5 in which the 1 and the permanent magnet 2 are combined has a waveform with a slight curve near the peak and less distortion than the waveform of the induced voltage generated only by the permanent magnet 1. .

  This is because the distribution waveform of the surface magnetic flux density of the permanent magnets 2-1 and 2-2 is closer to a sine wave compared to the distribution waveform of the surface magnetic flux density of the permanent magnet 1, and occupies the entire induced voltage by combining the two. This is obtained by reducing the ratio of the harmonic components of the permanent magnet 1.

  In the present embodiment, the induced voltage 22 has a waveform close to a triangular wave by making the shape of the surface magnetic flux density distribution waveform of the permanent magnets 2-1 and 2-2 sharp in the vicinity of the peak. Since the permanent magnets 2-1 and 2-2 are oriented by applying an extremely anisotropic magnetic field from the outside during molding, the waveform of the surface magnetic flux density distribution has a peak at the center of the magnetic pole by controlling this magnetic field. It can be adjusted to be triangular.

  Thus, in this embodiment, the permanent magnets 2-1 and 2-2 are oriented so that the magnetic flux density distribution waveforms of the permanent magnets 2-1 and 2-2 are substantially triangular. For this reason, the same effect as in the first embodiment can be obtained, and the distortion of the waveform of the induced voltage of the rotor 5 in which the permanent magnet 1 and the permanent magnets 2-1 and 2-2 are combined is less than that in the first embodiment. be able to.

  The induced voltage 21 of the rotor using the permanent magnet 1 and the induced voltage 22 of the rotor using the permanent magnets 2-1 and 2-2 both include an odd frequency component (harmonic component). However, because the phases of the frequency components included are different, the waveform of the permanent magnet 1 is distorted in a trapezoidal waveform, and the waveforms of the permanent magnets 2-1 and 2-2 are distorted in a triangular waveform. The waveforms of the permanent magnets 2-1 and 2-2 are just inverted with respect to the waveform of the permanent magnet 1, and the permanent magnet 1 and the permanent magnets 2-1 and 2-2 are combined. As a result, the high-frequency components contained in each cancel each other, so that distortion of the induced voltage can be further reduced. When the distortion of the induced voltage is reduced, the torque pulsation during operation of the synchronous motor is reduced, so that the vibration and noise of the synchronous motor can be reduced.

Embodiment 3 FIG.
FIG. 7 is a diagram illustrating an arrangement example of magnetic poles of the rotor according to the third embodiment of the present invention. The configuration of the synchronous motor and the configuration of the rotor 5 of the present embodiment are the same as those of the first embodiment.

  In the present embodiment, as in the first embodiment, the permanent magnet 1 (the magnet portion composed of the permanent magnet 1 and the soft magnetic material back yoke 3) and the permanent magnets 2-1 and 2-2 shown in FIG. When combining, the positions of the magnetic poles are shifted as shown in FIG. 7 and combined as if skewed.

  In the present embodiment, the surface magnetic flux density distribution of the permanent magnets 2-1 and 2-2 has a trapezoidal waveform. The permanent magnets 2-1 and 2-2 are oriented by applying an extremely anisotropic magnetic field from the outside during molding. Therefore, by controlling this magnetic field, the waveform of the surface magnetic flux density distribution is near the peak at the magnetic pole center. It can be adjusted to a flat trapezoidal shape. Further, the position of the magnetic pole is adjusted so that the phase of the induced voltage generated by the permanent magnets 2-1 and 2-2 is shifted forward and backward from the phase of the induced voltage generated by the permanent magnet 1, respectively.

  FIG. 8 is a diagram illustrating an example of a waveform of an induced voltage of the synchronous motor according to the present embodiment. For example, the induced voltage 21 generated by the permanent magnet 1 having an axial length of 11.5 mm is trapezoidal as shown in FIG. The induced voltage 24 in FIG. 8 is an induced voltage generated by the permanent magnet 2-1 having an axial length of 3.75 mm (a total axial length of the permanent magnets 2-1 and 2-2 of 7.5 mm). The voltage 25 is an induced voltage generated by the permanent magnet 2-2 having an axial length of 3.75 mm. In contrast to the waveform of the induced voltage 21, the induced voltage 24 and the induced voltage 25 are trapezoidal waveforms whose phases are shifted forward and backward. As shown in FIG. 8, the induced voltage 26 generated in the synchronous motor using the rotor 5 in which the permanent magnet 1 that generates such an induced voltage and the permanent magnets 2-1 and 2-2 is combined is generated by the permanent magnet 1. The waveform near the peak has a slight curve and less distortion than the waveform of the induced voltage generated.

  Although the induced voltage of the rotor using the permanent magnet 1 and the permanent magnets 2-1 and 2-2 both includes an odd frequency component (harmonic component), the phase of the induced voltage to be synthesized is shifted. Thus, since the frequency components included in each cancel each other, distortion of the induced voltage can be further reduced.

  When the distortion of the induced voltage is reduced, the torque pulsation during operation of the synchronous motor is reduced, so that the vibration and noise of the synchronous motor can be reduced.

  As described above, the rotor and the synchronous motor according to the present invention are useful for a synchronous motor that is required to increase cost and obtain a large magnetic flux.

1, 2-1, 2-2 Permanent magnet 3 Soft magnetic material back yoke 4 Rotating shaft 5 Rotor 6 Winding 7 Stator 8 Stator iron core 11-13, 21-26 Induced voltage

Claims (6)

A rotor facing a stator having an annular stator core,
A magnet unit comprising a first permanent magnet of high magnetic force radial orientation disposed on the outer peripheral side and a back yoke of soft magnetic material disposed on the inner peripheral side of the first permanent magnet;
Annular second and third permanent magnets having a magnetic force lower than that of the first permanent magnet and having an anisotropic orientation;
With
The axial center of the magnet part is the axial center of the range facing the stator core, and the axial thickness of the magnet part is equal to or less than the axial thickness of the stator core,
The rotor according to claim 1, wherein the second and third permanent magnets are arranged so as to be in contact with both axial end surfaces of the magnet portion.   2. The rotor according to claim 1, wherein the second and third permanent magnets are oriented so that an induced voltage generated by the second and third permanent magnets has a substantially triangular shape.   The second and third permanent magnets are oriented such that the induced voltage generated by the second and third permanent magnets is trapezoidal, and the second and third permanent magnets are the second and third permanent magnets. The first permanent magnet and the magnetic pole are shifted from each other so that the phase of the induced voltage generated by the third permanent magnet is shifted in a direction different from the phase of the induced voltage generated by the first permanent magnet. The rotor according to claim 1.   4. The rotor according to claim 1, wherein the first permanent magnet is made of a rare earth magnet. 5.   The rotor according to any one of claims 1 to 4, wherein the second and third permanent magnets are composed of ferrite magnets. A stator having an annular stator core;
The rotor according to any one of claims 1 to 5, which faces the stator,
A synchronous motor comprising:

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