JP5095134B2 - Motor control device and motor control method - Google Patents

Description

  The present invention relates to a control device for a permanent magnet type motor, and more particularly to control for suppressing torque ripple of a magnet embedded type permanent magnet motor in which a permanent magnet is embedded in a rotor core.

  Permanent magnet motors are small and can generate high torque, and have been used in various drive devices including servo motors. However, it is known that a permanent magnet motor generates a cogging torque that is a ripple component of torque. Further, when the motor is energized, torque ripple is generated due to the harmonic component of the magnetic flux or magnetic saturation. Since these ripple components become disturbances, when the motor is used for positioning, undesired phenomena such as a decrease in positioning accuracy and vibration and noise caused by resonance with the load machine occur.

  The conventional permanent magnet motor control method for suppressing such torque ripple is to detect the rotation angle of the magnetic flux axis of the permanent magnet, and based on the detection result, the motor input current is determined by the d-axis current and the torque current component. Convert to a certain q-axis current. Then, the phase is set by an artificial operation so that the q-axis current command value is opposite in phase to the torque ripple generated on the rotating shaft of the motor due to the permanent magnet, and the amplitude is set to the same amplitude as the torque ripple. The torque ripple is canceled by superimposing the set pulsation suppression current value (see, for example, Patent Document 1).

  In the conventional motor control device for reducing the cogging torque, the d-axis current command value calculation unit reads the motor rotation angular velocity output from the motor rotation angular velocity calculation unit, and refers to the d-axis current command value map created in advance. Then, it is determined whether or not the read motor rotation angular velocity is within a predetermined range. If it is within the predetermined range, a predetermined negative d-axis current command value is selected from the d-axis current command value map. Output. Thereby, since an exciting current becomes small, a cogging torque can be reduced (for example, refer patent document 2).

JP 2001-352798 A JP 2001-103783 A

  In the control of the motor as shown in Patent Document 1, in order to reduce the torque ripple, the control is performed such that the harmonic current is applied so as to cancel out the torque ripple sequentially. In such control, it is necessary to detect a high-frequency current other than the fundamental wave with high accuracy, and it is necessary to superimpose and control the ripple suppression current at high speed and high accuracy, resulting in a large control calculation load. The carrier frequency for current control has a practical upper limit, but when the frequency of the current to be controlled increases, the current itself cannot be controlled, and the motor controls to suppress the remarkable sixth-order torque ripple with high accuracy. It was difficult.

  Further, in the motor control as shown in Patent Document 2 described above, the cogging torque is reduced by reducing the magnet magnetic flux by passing a negative d-axis current. However, in a magnet-embedded permanent magnet motor (IPM motor) in which a permanent magnet is embedded in a rotor core, a reluctance torque is generated when a negative d-axis current is caused to flow from the magnetic saliency of the rotor. A new torque ripple is generated. For this reason, the IPM motor has a problem that the entire torque ripple component is not suppressed.

  The present invention has been made to solve the above-described problems, and in a magnet-embedded permanent magnet motor (IPM motor), the torque ripple component is accurately suppressed by a simple control calculation, and the command value is highly accurate. The purpose is to realize motor control that can follow the above.

In the motor control device according to the present invention, a three-phase alternating current flowing through a magnet-embedded permanent magnet motor (IPM motor) in which a permanent magnet is embedded in a rotor core is converted into an excitation current (d-axis current) and a torque current (q-axis current). The reluctance torque component is controlled in accordance with the torque command so that the reluctance torque ripple and the magnet torque ripple cancel each other with respect to the sixth-order torque ripple component. When the motor is energized, a negative d-axis current is always applied, and the negative d-axis current is changed to a variable q-axis current so that the sixth-order torque ripple component obtained by combining the reluctance torque ripple and the magnet torque ripple is minimized. Current components (Id, Iq) determined and generated with respect to the torque value are preset and held in accordance with the torque value, and storage means for holding information on the rotational speed range in accordance with the torque value is provided. Within the allowable voltage range based on the speed range, the current component (Id, Iq) on the dq axis is extracted from the storage means according to the torque command and used for the current command on the dq axis.

In such a motor control device, the reluctance torque ripple and the magnet torque ripple are controlled with respect to the sixth order torque ripple component so that the reluctance torque component is controlled according to the torque command. It can be effectively suppressed. Further, it is not necessary to superimpose a current for suppressing high-frequency torque ripple, the control calculation load can be reduced, and high-speed and high-precision motor control can be realized at low cost using a simple control device.

Embodiment 1 FIG.
Hereinafter, a motor control apparatus according to Embodiment 1 of the present invention will be described.
FIG. 1 shows the structure of the IPM motor. As shown in the figure, the IPM motor 5 includes a rotor 3 in which a permanent magnet 1 is embedded in a rotor core 2 made of a magnetic material, and a stator 4 having a winding (not shown).
Here, the direction of the current component that generates a magnetic flux in the same direction as the magnetic field at the magnetic pole center of the rotor 3 is the d-axis direction, and a positive torque is applied to the rotor 3 between the magnetic poles of the rotor 3 perpendicular to the d-axis direction. The direction of the current component that generates the? Is called the q-axis direction. A current vector (Id, Iq), which is a combination of the d-axis current component and the q-axis current component, is a stationary current vector in a steady state in which the stator current is projected onto the dq axis of the rotor 3. Thus, vector control for controlling the three-phase stator current using the current vector (Id, Iq) is widely used.

The motor control apparatus according to the first embodiment converts a three-phase alternating current flowing through the IPM motor 5 as shown in FIG. 1 into a d-axis current (excitation current) and a q-axis current (torque current) and performs vector control. The configuration is shown in FIG.
As shown in FIG. 2, the motor control device includes a voltage-controlled PWM inverter 10 that supplies power to the IPM motor 5, a torque control unit 11 that outputs a current command on the dq axis from the torque command, a current controller 12, coordinates Conversion units 13 and 14, a position detector 15, a phase detection 16, a speed detection 17, and a current detector 18 are provided.

  The voltage control type PWM inverter 10 has a DC input side connected to a DC power source (not shown) made of a capacitor or a battery, and a current from a diode rectifier (not shown) is input to the DC power source. The AC side of the PWM inverter 10 is connected to the IPM motor 5 and allows a three-phase AC current to flow through the IPM motor 5. The current component of each phase of the motor detected by the current detector 18 is input to the coordinate conversion unit 14. Further, the position detector 15 detects the position of the IPM motor 5, and detects the phase θ by the phase detection 16 and the rotational speed ω by the speed detection 17 based on the detected position. The coordinate conversion unit 14 converts the three-phase currents Iu, Iv, and Iw from the current detector 18 into a three-phase two-phase conversion based on the phase θ and outputs the currents Id and Iq on the dq axis. Here, two-phase currents Iu and Iv out of the three-phase currents are detected, and the remaining current Iw is obtained by calculation.

The torque control unit 11 outputs the current commands Id ^* and Iq ^* on the dq axis with the given torque command T ^* and the rotational speed ω as inputs. At this time, the current commands Id ^* and Iq ^* on the dq axis are determined so that the torque ripple is minimized, and details of the method for determining the current command will be described later.
The current controller 12 receives the current commands Id ^* and Iq ^* on the dq axis and the rotational speed ω from the torque control unit 11, and the detected currents Id and Iq on the dq axis are the current commands Id ^* and Iq ^*. The feedback control is performed so as to follow the voltage, and voltage commands Vd ^* and Vq ^* on the dq axis are output.
The coordinate conversion unit 13 converts the voltage commands Vd ^* and Vq ^* on the dq axis into two-phase and three-phase based on the phase θ, and outputs three-phase voltage commands Vu ^* , Vv ^* and Vw ^*. Is controlled by three-phase voltage commands Vu ^* , Vv ^* , Vw ^* .

By the way, in the IPM motor 5, since the permanent magnet 1 is in the iron core 2 that is a magnetic body and the magnetic pole is a magnetic body, the magnetic resistance in the q-axis direction orthogonal to the d-axis direction that is the magnet axis is smaller. With the pole structure, the q-axis inductance is larger than the d-axis inductance. In such an IPM motor 5, reluctance torque is generated in addition to magnet torque.
The magnet torque is generated by q-axis current, and is generated by attracting and repelling the magnetic field generated by the permanent magnet 1 of the rotor 3 and the rotating magnetic field generated by the winding 4a. Shown in a).
The reluctance torque is generated by a negative d-axis current that is a component that generates a magnetic field at the phase of the magnetic pole and weakens the magnetic flux of the permanent magnet 1, and the salient pole portion 2a of the rotor 3 is caused by the rotating magnetic field generated by the winding 4a. FIG. 3B schematically shows the torque generated by the suction, which is schematically explained. Note that when a negative d-axis current is passed, a q-axis current is also actually flowed, and as a result of combining both, the current phase is controlled so that the magnetic field generation position is shifted in the rotor traveling direction.

In general, in motor control, since it becomes impossible to increase the rotational speed due to voltage limitation in the high speed rotational range, the current phase is advanced to reduce the magnetic flux of the permanent magnet to widen the rotational speed range. This is a field weakening control in which a negative d-axis current is passed, and voltage saturation can be mitigated. In the IPM motor 5, a reluctance torque is generated by a negative d-axis current, and this reluctance torque contributes to torque increase, but a reluctance torque ripple that is a torque ripple of the reluctance torque is newly generated.
In this embodiment, the reluctance torque is controlled by using the negative d-axis current that is normally used only in the high-speed rotation range to reduce the voltage saturation even within the allowable voltage range, and the reluctance torque ripple and the magnet torque ripple (magnet torque ripple) are used. ) To offset the overall torque ripple.

It will be described below that the reluctance torque ripple and the magnet torque ripple are canceled in the IPM motor 5.
The d-axis and q-axis are just 90 degrees out of phase in electrical angle. In general, with respect to the sixth-order torque ripple component that becomes noticeable in torque ripple, the ripple component of magnet torque caused by q-axis current (magnet torque ripple) and the ripple component of reluctance torque caused by negative d-axis current (reluctance torque ripple) are: The phase is shifted six times by 540 degrees (-180 degrees). Thus, since the reluctance torque ripple and the magnet torque ripple are in opposite phases with respect to the sixth-order torque ripple component, they can cancel each other.

As shown in FIG. 4, a torque ripple MAP that is a MAP for two current components on the dq axis of the torque ripple is created. The torque ripple is a total torque ripple that is a combination of the reluctance torque ripple and the magnet torque ripple, and is represented by a rated torque ratio here. When the current value upper limit is determined from the capacity of the PWM inverter 10 or the thermal upper limit of the IPM motor 5, 21 is a current limit circle indicating the current value upper limit. In addition, there is an upper limit on the current value that can be output from the voltage limit, which varies depending on the rotation speed. This voltage range is determined on the basis of the magnetic flux and the rotational speed by previously obtaining magnetic fluxes for two current components on the dq axis by magnetic field analysis or actual measurement. 22a indicates a voltage range in the case of relatively medium speed, and 22b indicates a voltage range in the case of relatively high speed.
On this torque ripple MAP, a negative d-axis current value that minimizes the torque ripple is determined for the variable q-axis current, and a locus 20 of the current vector (Id, Iq) is generated. It can be seen from the current vector (Id, Iq) locus 20 when the torque ripple is minimum that the torque ripple at which the torque ripple is minimum changes continuously according to the q-axis current. Further, the torque ripple is minimized when the negative d-axis current is passed and the reluctance torque ripple is generated. Therefore, it can also be seen that the torque ripple is reduced by canceling the reluctance torque ripple and the magnet torque ripple.

In this embodiment, the torque control unit 11 that outputs the current commands Id ^* and Iq ^* includes a storage unit, and the current vector (Id, Iq) is a point on the locus 20 according to the torque value ( Id, Iq) is preset and stored in the storage means. That is, a torque ripple MAP in which a MAP for two current components on the dq axis of the torque ripple is created in advance is used, and a negative d-axis current value at which the torque ripple is minimized on the torque ripple MAP is determined for a variable q-axis current. Thus, the locus 20 of the current vector (Id, Iq) is generated in advance. Then, a current vector (Id, Iq) that is a point on the current vector (Id, Iq) locus 20 is set in advance according to the torque value and is stored in the storage means.

Then, the torque control unit 11 receives the given torque command T ^* and the rotation speed ω, extracts a current vector (Id, Iq) from the storage means, and outputs it as current commands Id ^* and Iq ^* . As shown in FIG. 5, a current vector (Id, Iq) 23 that is a point on the current vector (Id, Iq) locus 20 is extracted based on the torque command T ^* to obtain current commands Id ^* , Iq ^* . At this time, the current vector (Id, Iq) 23 satisfies the voltage range 22 a determined by the rotational speed ω and the range of the current limiting circle 21.
By using the current commands Id ^* and Iq ^* generated in this manner, the reluctance torque ripple and the magnet torque ripple can be canceled and the torque ripple can be minimized.

As described above, in this embodiment, since the reluctance torque is generated so that the reluctance torque ripple and the magnet torque ripple are canceled out, a remarkable sixth-order torque ripple component is easily and effectively canceled out by the motor. Torque ripple components can be suppressed.
In addition, it has storage means for presetting and holding the current vector (Id, Iq) on the dq axis that minimizes the torque ripple according to the torque value, and stores the above according to the torque command T ^* within the allowable voltage range Since current vectors (Id, Iq) on the dq axis are extracted from the means and used for the current commands Id ^* and Iq ^* on the dq axis, current control is performed so that the sixth-order torque ripple component is detected and sequentially suppressed. The control calculation load can be remarkably reduced as compared with the above, and there is no restriction on the calculation speed and position detection speed of the control device, and high-precision torque ripple suppression control can be easily realized even with an inexpensive control device.
Furthermore, the current vector (Id, Iq) on the dq axis held by the storage means uses a torque ripple MAP created in advance, and a negative d-axis current value that minimizes the torque ripple on the torque ripple MAP is variable q-axis. Since it is a point on the current vector (Id, Iq) locus 20 determined and generated for the current, highly accurate torque ripple suppression control can be performed with certainty.

Embodiment 2. FIG.
In the first embodiment, the current vector (Id, Iq) that is a point on the current vector (Id, Iq) locus 20 is set in advance and stored in the storage unit. For example, the table format shown in FIG. 6 may be used.
In this case, the current vector (Id, Iq) data that minimizes the torque ripple according to the generated torque value is stored and held as about 10 to 100 points as point sequence data. Here, the applicable rotational speed ω is stored together as the upper limit of the electrical angle rotational speed.
The torque control unit 11 receives the supplied torque command T ^* and the electrical speed of rotation ω as the rotational speed, and extracts a current vector (Id, Iq) from the storage means. At this time, the current vector (Id, Iq) of the generated torque value closest to the torque command T ^* may be adopted as the current commands Id ^* and Iq ^* as it is, but the current is calculated by interpolating the point sequence data in the table. By generating and using the commands Id ^* and Iq ^* , highly accurate torque ripple suppression control can be performed.

A method for interpolating the point sequence data will be described below.
By numbering the point sequence data from the top (from 0), by sequentially comparing the torque command T ^* and the torque values T ₀ , T ₁ ,... Tmax of the point sequence data,
_Tn > T ^* > _Tn-1
Tn and _Tn-1 are obtained.
_Then, T _n, Iq n corresponding to _{T n-1,} the use of Id _n and _{Iq n-1, Id n-} 1,
_{^{(Iq * -Iq n-1)}} / (Iq n -Iq n-1) = (T * -T n-1) / (T n -T n-1)
Therefore, Iq ^* is obtained by the following equation.
Iq ^* = (T ^* −T _n−1 ) / (T _n −T _n−1 ) × (Iq _n −Iq _n−1 ) + Iq _n−1
The same applies to Id ^*
Id ^* = (T ^* −T _n−1 ) / (T _n −T _n−1 ) × (Id _n −Id _n−1 ) + Id _n−1

Such a torque ripple suppression control, the rotational speed of the motor ω becomes effective in smaller speed range than the rotational speed upper limit corresponding to T _n memory means.

  In this embodiment, since the storage information is held and used in a table in which the data of the current vector (Id, Iq) that minimizes the torque ripple for a plurality of torque values is set as point sequence data, the storage information is created, It is easy to hold and extract and use. Moreover, highly accurate torque ripple suppression control can be performed by using the interpolation calculation as described above.

Embodiment 3 FIG.
In the control for suppressing the torque ripple shown in the first and second embodiments, when each of the torque ripple components of the reluctance torque and the magnet torque is extremely large, a harmonic component other than the sixth order that can be canceled appears or cancels each other. May be different, making it difficult to suppress with high accuracy. In this embodiment, the structure of an IPM motor to which the above-described torque ripple suppression control can be effectively applied will be described.
FIG. 7 is a diagram showing the structure of an IPM motor according to Embodiment 5 of the present invention.
As shown in the figure, the IPM motor 35 includes a rotor 33 in which a permanent magnet 31 is embedded in a rotor core 32 made of a magnetic material, and a stator 34 having a winding (not shown). The rotor 33 has a round flower-shaped outer shape 33a in which a plurality of arcs having an arc diameter smaller than the rotor radius are arranged in a direction protruding to the outer periphery, and an arc shape is formed inside the arcs along the plurality of arcs. The permanent magnet 31 is embedded.

With such a structure, the width of the salient pole portion 2a (see FIG. 3) of the rotor 3 between the magnetic poles is reduced, and the gap between the rotor 33 and the stator 34 is reduced in the salient pole portion 2a. The structure can be increased, and the torque ripple component is suppressed by suppressing the saliency.
Although the current vector locus 20 shown in FIG. 4 varies depending on the motor shape, a current vector locus that minimizes the torque ripple is generated in advance by a similar method according to the motor to be used, and the current vector locus (Id, Id, Iq) is preset and stored in the storage means.

Embodiment 4 FIG.
In the motor control, as described above, since it becomes impossible to increase the rotation speed due to the voltage limitation when the high-speed rotation region is reached, control to alleviate voltage saturation is normally performed by field weakening control in which a negative d-axis current flows. In the fourth embodiment, the torque ripple suppression control shown in the first and second embodiments is performed within the allowable voltage range, and when the voltage is out of the allowable range, control by field weakening control is performed. Such control can be achieved by appropriately generating the current commands Id ^* and Iq ^* in the torque control unit 11, and will be described below based on the flowchart shown in FIG. Note that the information of the storage means used by the torque control unit 11 is held in the table format shown in FIG. 6 of the second embodiment.

When the torque command T ^* and the rotational speed ω are input to the torque controller 11 (step S1), the torque command T ^* and the torque values T ₀ , T ₁ ,... Tmax of the point sequence data in the storage means. Are sequentially extracted, and data of the minimum torque value T _n satisfying T _n > T ^* is extracted (steps S2 and S3). It is determined whether or not the rotation speed upper limit ω _n of the extracted data is larger than the rotation speed ω of the motor (step S4). If the rotation speed is larger, the current commands Id ^* and Iq ^* are set as in the second embodiment for torque ripple suppression control. It calculates | requires similarly (step S5). In step S4, if the rotation speed upper limit ω _n of the extracted data is equal to or less than the rotation speed ω of the motor, current commands Id ^* and Iq ^* by field weakening control are calculated and obtained (step S6).

Referring to the torque ripple MAP shown in FIG. 9, when the rotational speed ω is within the applicable range, that is, the voltage is within the allowable range, the current commands Id ^* and Iq ^* that are the first current commands 23a for torque ripple suppression control ^. When the rotational speed of the motor increases and the rotational speed ω is out of the applicable range, that is, the voltage is out of the allowable range, the second current command that is optimal for a predetermined torque value by the known field weakening control The current commands Id ^* and Iq ^* which are 23b are calculated and used.
The current commands Id ^* and Iq ^* in the field weakening control can be calculated by the following formula based on the electrical angular frequency ω, the magnetic flux Ψ, the voltage V, and the motor inductances Ld and Lq, which are rotational speeds, for example, in a motor with a pole pair number Pn. .

  In the IPM motor with suppressed saliency as shown in the third embodiment, it can be regarded that Ld≈Lq, and the calculation becomes easy.

In this embodiment, torque ripple suppression control is performed within the allowable voltage range, and when the voltage is out of the allowable range, control by field weakening control is performed, so that optimal motor control using a negative d-axis current can be performed. High performance motor control can be obtained.
Also, in the storage means, the upper limit of the rotation speed that is the basis of the allowable voltage range is stored together with the data of the current vector (Id, Iq), and whether the voltage is within or outside the allowable voltage range by referring to the upper limit of the rotation speed according to the torque command. Therefore, it is easy to determine whether the voltage is within or outside the allowable voltage range. Only one of torque ripple suppression control and field weakening control can be used by calculating the current commands Id ^* and Iq ^*. Is possible.

It is a figure which shows the structure of the IPM motor by Embodiment 1 of this invention. It is the figure which showed the structure of the motor control apparatus by Embodiment 1 of this invention. It is the figure which demonstrated typically the magnet torque and reluctance torque of the IPM motor by Embodiment 1 of this invention. It is a figure explaining the current command generation by Embodiment 1 of this invention on torque ripple MAP. It is a figure explaining the current command generation by Embodiment 1 of this invention on torque ripple MAP. It is a figure which shows the information hold | maintained at the memory | storage means by Embodiment 2 of this invention. It is a figure which shows the structure of the IPM motor by Embodiment 3 of this invention. It is a flowchart which shows the electric current command generation by Embodiment 4 of this invention. It is a figure explaining the current command generation by Embodiment 4 of this invention on torque ripple MAP.

Explanation of symbols

1 permanent magnet, 2 rotor core, 3 rotor, 4 stator, 5 IPM motor,
11 Torque controller, 12 Current controller, 20 Current vector locus,
22a voltage range (medium speed), 22b voltage range (high speed),
23 current command (current vector), 23a first current command (current vector),
23b Second current command (current vector), 31 permanent magnet, 32 rotor core,
33 rotor, 34 stator, 35 IPM motor.

Claims (7)

In a motor control device that converts and controls a three-phase alternating current flowing in a magnet-embedded permanent magnet motor in which a permanent magnet is embedded in a rotor core into an excitation current (d-axis current) and a torque current (q-axis current) ,
The reluctance torque component is controlled according to the torque command so that the reluctance torque ripple and the magnet torque ripple are canceled out with respect to the sixth-order torque ripple component,
When the motor is energized, a negative d-axis current is always applied, and the negative d-axis current is set to a variable q-axis current so that the sixth-order torque ripple component obtained by combining the reluctance torque ripple and the magnet torque ripple is minimized. Storing and storing the current components (Id, Iq) determined and generated in advance according to the torque value and holding information on the rotational speed range according to the torque value;
The current component (Id, Iq) on the dq axis is extracted from the storage means in accordance with the torque command within the allowable voltage range based on the rotation speed range, and is used for the current command on the dq axis. Motor control device. The current component (Id, Iq) on the dq axis held by the storage means is generated by using a torque ripple MAP prepared in advance as a MAP for the two current components on the dq axis of the sixth-order torque ripple component. The motor control device according to claim 1. The storage means holds stored information in a table in which the current components (Id, Iq) are respectively set for a plurality of the torque values.
Information on torque values and current components (Id, Iq) is extracted from the table in accordance with the torque command, and the current command on the dq axis is generated directly or interpolated based on the extracted information. The motor control device according to claim 1 . Outside of allowable voltage range, a motor control apparatus according to any one of claims 1 to 3, characterized in that to increase the value of the negative d-axis current. The rotation speed range in the storage means is referred to in accordance with the torque command, and the rotation speed range and the rotation speed of the rotor are compared to determine whether the voltage is within the allowable range or not. The motor control device according to claim 4. The rotor of the magnet-embedded permanent magnet motor has a round flower-shaped outer shape in which a plurality of arcs having an arc diameter smaller than the rotor radius are arranged in a direction protruding to the outer periphery, and follows the plurality of arcs. the motor control device according to any one of claims 1 to 5, characterized in that it is formed by embedding arc of the permanent magnet on the inside of the arc-like. In a motor control method for controlling by converting a three-phase alternating current flowing in a magnet-embedded permanent magnet motor in which a permanent magnet is embedded in a rotor core into an excitation current (d-axis current) and a torque current (q-axis current) ,
The reluctance torque component is controlled according to the torque command so that the reluctance torque ripple and the magnet torque ripple are canceled out with respect to the sixth-order torque ripple component,
When a motor is energized, a negative d-axis current is always energized, and a torque ripple MAP in which a MAP is created for two current components on the dq axis of a sixth-order torque ripple obtained by combining the reluctance torque ripple and the magnet torque ripple is used. The locus of the current component (Id, Iq) is generated by determining the negative d-axis current value that minimizes the sixth-order torque ripple component on the MAP with respect to the variable q-axis current, and the rotation of the rotor A motor control method characterized by extracting a current component (Id, Iq) on the locus in accordance with the torque command within a voltage allowable range according to speed and using the extracted current component on the dq axis.

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