JP2008167554A - Control method and controller of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method and a controller of a motor in which sensorless control can be applied without complicating control while increasing the number of revolutions so as to switch to stabilized sensorless control in other system operation. <P>SOLUTION: In the method of controlling a synchronous motor 200 by sensorless driving, an applied voltage vao is determined such that the current of the synchronous motor 200 has a predetermined level in the beginning of start-up for performing forced operation or at low speed, voltages eα and eβ induced through rotation of the synchronous motor 200 are estimated. Furthermore, first voltage vectors vα1 and vβ1 correlated with the applied voltage vao and second voltage vectors vα2 and vβ2 correlated with the induced voltages eα and eβ are synthesized and applied to the synchronous motor 200. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for controlling a synchronous motor for starting a compressor used in, for example, a heat pump cycle.

  Conventionally, many sensorless motor control methods that do not use a position detection sensor have been proposed in synchronous motor control for driving a compressor or the like. In this sensorless control, position information and phase information are detected from the induced voltage and current information and used for control. However, since it is difficult to detect them at the initial stage of startup, the commutation operation (hereinafter referred to as “other control operation”) is forcibly performed. In other words, a method of switching to position detection operation after stable position detection is possible is employed. However, depending on the state of the load and the induced voltage, rotation may become unstable during other braking operations, and startup may fail.

  Here, in order to prevent a start failure due to an unknown load at start-up, for example, as shown in Patent Document 1, there are those having a plurality of start patterns and selecting an optimal start pattern according to ambient temperature conditions and the like. Proposed.

  Further, when shifting from other control operation to position detection operation, in order to prevent a switching failure due to the load state or load fluctuation level at the time of switching, for example, as shown in Patent Document 2, the load is estimated during other control operation, In response to this, there has been proposed a method in which the control gain of the position detection operation is determined and stabilization is achieved.

Also, as means for increasing the limit rotational speed during other braking operation, for example, as shown in Patent Document 3, the phase difference detection means is used to detect the high frequency component of the phase difference between the voltage and current, thereby controlling the voltage phase. What to do has been proposed.
JP 2002-125391 A JP 2003-284377 A JP 2004-343948 A

  However, in the start-up method as described in Patent Document 1, if there is an estimated deviation of the temperature condition or the like, it cannot be said that a start-up pattern selection error occurs and a reliable start-up is not possible. In Patent Document 2, the control gain is changed to stabilize the sensorless control. However, there is no description about a means for continuing the other braking operation until the rotational speed at which stable position detection is possible.

  Furthermore, in the above-mentioned Patent Document 3, when applied to vector control without phase difference detection means, detection means is added, which increases the calculation load and makes control complicated, such as gain adjustment according to the rotation speed. There is a problem.

  In view of the above problems, an object of the present invention is to avoid complicated control when applying sensorless control, and to increase control to a rotational speed at which switching to stable sensorless control can be performed in other control operations. It is an object of the present invention to provide a motor control method and apparatus capable of enabling it.

  In order to achieve the above object, the present invention employs the following technical means.

  According to the first aspect of the present invention, there is provided a motor control method for controlling the synchronous motor (200) by sensorless driving, wherein the current of the synchronous motor (200) becomes a predetermined value at the initial stage of starting the forced operation or at a low speed. The applied voltage (vao) is determined, the induced voltage (eα, eβ) generated by the rotation of the synchronous motor (200) is estimated, and the first voltage vector (vα1, vβ1) correlated with the applied voltage (vao) The second voltage vector (vα2, vβ2) correlated with the induced voltage (eα, eβ) is synthesized and applied to the synchronous motor (200).

  The first voltage vector (vα1, vβ1) is a voltage command for forcibly rotating the synchronous motor (200) in the other control operation, and has no correlation with the rotational position of the synchronous motor (200). On the other hand, the second voltage vectors (vα2, vβ2) are obtained from the induced voltages (eα, eβ) and have a correlation with the rotational position of the synchronous motor (200).

  When the first voltage vector (vα1, vβ1) and the rotational position of the motor (200) are shifted, the phase difference between the first voltage vector (vα1, vβ1) and the second voltage vector (vα2, vβ2) changes. The combined vector (vα, vβ) is adjusted in a direction to suppress the deviation between the first voltage vector (vα1, vβ1) and the rotational position of the motor (200), and passive stabilization is performed.

  Accordingly, it is possible to provide a motor control method that enables control by avoiding complication of control and increasing the number of rotations to a level at which switching to stable sensorless control can be performed in other braking operation.

  When calculating the second voltage vector (vα2, vβ2), it is preferable to use an induced voltage observer (170) as in the second aspect of the present invention.

  As a result, not only the phase of the induced voltage but also the voltage amplitude can be appropriately reflected in the second voltage vector (vα2, vβ2).

  The second voltage vector (vα2, vβ2) can be calculated using at least the estimated position (θre) of the synchronous motor (200), as in the third aspect of the invention.

  Thereby, even if it is position detection means other than an induced voltage observer (170), the effect similar to the said Claim 2 can be acquired. Further, when the error of the induced voltage estimated by the induced voltage observer (170) is large, the adverse effect due to the error of the induced voltage amplitude can be avoided and stable control can be performed.

  According to a fourth aspect of the present invention, there is provided a motor control method for controlling the synchronous motor (200) by sensorless driving, wherein the current of the synchronous motor (200) becomes a predetermined value at the initial stage of starting the forced operation or at a low speed. A first voltage vector (vα1, vβ1) that correlates to the applied voltage (vao), detects the vector (iα, iβ) of the current flowing through the synchronous motor (200), and determines the applied voltage (vao) The current vector (iα, iβ) and the second voltage vector (vα2, vβ2) having a reverse phase relationship are synthesized and applied to the synchronous motor (200).

  Thus, the first voltage vector (vα1, vβ1) is obtained as a combined vector (vα, vβ) in the same manner as in the first aspect by using the second voltage vector (vα2, vβ2) obtained from the current vector (iα, iβ). Thus, the same effect as in the first aspect can be obtained by simple control (calculation).

  In the invention described in claim 4, in the invention described in claim 5, the magnitude of the second voltage vector (vα2, vβ2) is changed in accordance with the rotational speed of the synchronous motor (200). .

  Since the second voltage vector (vα2, vβ2) having a reverse phase relationship with the current vector (iα, iβ) does not consider the rotation speed of the synchronous motor (200), the rotation speed is taken into consideration. Stable control is possible.

  In the invention described in claim 5, as in the invention described in claim 6, the second voltage vector (vα2, vβ2) is changed to a larger side as the rotational speed of the synchronous motor (200) is higher. Good to do.

  The seventh aspect of the invention is characterized in that the magnitude of the second voltage vector (vα2, vβ2) is changed in accordance with the temperature of the synchronous motor (200).

  Thereby, the influence by the temperature of a synchronous motor (200) is suppressed, and more stable control is attained.

  In the invention described in claim 7, as in the invention described in claim 8, the induced voltage of the main factor that makes the rotation unstable becomes larger, that is, the lower the temperature of the synchronous motor (200), It is preferable to change the voltage vector (vα2, vβ2) of 2 to the larger side.

  In the ninth aspect of the present invention, the first voltage vector (vα1, vβ1) and the second voltage vector (vα2, vβ2) when the rotational speed of the synchronous motor (200) becomes equal to or higher than a predetermined rotational speed. Is synthesized and applied to the synchronous motor (200).

  As a result, it is possible to avoid the adverse effect in the extremely low rotation region including the error of the second voltage vector (vα2, vβ2), and to perform stable control.

  The invention described in claims 10 to 18 relates to a motor control device that enables the motor control method, and its technical significance is the motor control described in claims 1 to 9. Essentially the same as the method.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows a corresponding relationship with the specific means of embodiment description mentioned later.

(First embodiment)
1st Embodiment is described using drawing shown in FIG. 1, FIG. FIG. 1 is a block diagram showing a motor control device 100, and FIG. 2 is a vector diagram showing a combined state of voltage vectors in two-phase (αβ) fixed axis coordinates.

  As shown in FIG. 1, the motor control device (hereinafter referred to as “control device”) 100 has functional units 110 to 190 described below, and controls the operation of the motor 200. The motor 200 is a three-phase brushless DC synchronous motor, and the counterpart device driven by the motor 200 is a compressor 210 disposed in a heat pump cycle for a water heater (not shown) here. It is said.

  The control device 100 includes a current amplitude control unit 110, a current calculation unit 120, a coordinate conversion unit 130, a voltage phase control unit 140, a synthesis unit 150, an inverter 160, an extended induced voltage observer 170, a phase calculation unit 180, and a speed calculation unit 190. Have.

  The current amplitude control unit 110 determines the voltage command (applied voltage) vao so that the current value flowing through the motor 200 becomes the target current value (predetermined value). That is, the current amplitude control unit 110 receives a current command ioo for operating the motor 200 (compressor 210) output from a water heater control unit in a water heater (heat pump cycle) (not shown), and a current calculation unit 120 described later. The voltage command vao is determined using PI control based on the actual current value ia.

  The current calculation unit 120 calculates the actual current value ia as the current magnitude from the current vector on the rectangular coordinate of the current flowing through the motor 200, here the current vectors iα and iβ on the two-phase fixed coordinate axis, and the current amplitude Output to the control unit 110.

  The coordinate conversion unit 130 constitutes a first conversion unit, which uses a voltage command vao from the current amplitude control unit 110 and a voltage phase command θvo from a voltage phase control unit 140 described later, based on polar coordinates. Converted into rectangular coordinates, here, it is generated and output as a first voltage vector converted onto two-phase fixed axis coordinates, that is, first voltage vectors vα1 and vβ1.

  The voltage phase control unit 140 integrates the rotation speed command ωo output from the rotation speed control unit (not shown) and outputs the voltage phase command θvo to the coordinate conversion unit 130.

  The synthesizing unit 150 synthesizes the first voltage vectors vα1 and vβ1 from the coordinate conversion unit 130 and second voltage vectors vα2 and vβ2 from the extended induced voltage observer 170, which will be described later, and generates the synthesized vectors vα and vβ as an inverter. To 160.

  The inverter 160 switches the upper and lower arm switching elements of the three phases (U phase, V phase, W phase) at a predetermined timing based on the combined vectors vα, vβ from the combining unit 150, and causes the motor 200 to generate electric power ( Current).

  An extended induced voltage observer (hereinafter referred to as an observer) 170 constitutes a second conversion unit, and an extended induced voltage vector eα is obtained from the combined vectors vα and vβ and the current vectors iα and iβ supplied to the motor 200. , Eβ is estimated (calculated) and output to the phase calculator 180, and a filter or a gain (not shown) is applied to the extended induced voltage vectors eα and eβ to obtain the second voltage vectors vα2 and vβ2, and the above combining unit 150 is output.

  The phase calculation unit 180 calculates the estimated rotational position (estimated position) θre of the motor 200 from the extended induced voltage vectors eα and eβ observed by the observer 170 and outputs the result to the speed calculation unit 190. Then, the speed calculation unit 190 calculates the estimated rotational speed ω by differentiating the estimated rotational position θre or using an identification unit, and outputs the estimated rotational speed ω to a rotational speed control unit (not shown).

  Next, the operation of the control device 100 based on the above configuration will be described. In this control apparatus 100, since the estimated position cannot be reliably detected when the motor 200 is started or at a low rotation, the motor 200 is driven by constant current control in other braking operation. In the other control operation, the voltage command (applied voltage) vao is controlled by feeding back the actual current value ia from the current calculation unit 120 so that the current value in the motor 200 becomes the target current value, and is applied to the motor 200. By setting the target current value to be larger than the load torque condition assumed at the time of start-up, for example, it is possible to eliminate a start-up failure due to the initial load level such as a high-load start-up due to liquid compression of the compressor 210.

  However, when the rotational position of the motor 200 and the current phase, that is, the phase of the voltage command vao are shifted in other control operation, the torque current component fluctuates, causing pulsation between the load torque and unstable rotation. . This tendency is conspicuous under conditions where the impedance of the motor winding is small (for example, resistance is small) and the induced voltage is large (for example, the rotational speed is relatively high), such as when the ambient temperature of the motor 200 is low. It becomes.

  In the present embodiment, the second voltage vectors vα1 and vβ2 correlated with the rotational position of the motor 200 are estimated by the observer 170 while performing other braking operation using the first voltage vectors vα1 and vβ1. Then, as shown in FIG. 2, the first voltage vectors vα1 and vβ1 and the second voltage vectors vα2 and vβ2 are combined by the combining unit 150 and applied to the motor 200 as combined vectors vα and vβ.

  When the first voltage vectors vα1 and vβ1 are shifted from the rotational position of the motor 200, the phase difference between the first voltage vectors vα1 and vβ1 and the second voltage vectors vα2 and vβ2 changes, and the combined vectors vα and vβ The vectors vα1 and vβ1 are adjusted so as to suppress the deviation between the rotational position of the motor 200 and passive stabilization is performed. Furthermore, since the second voltage vectors vα2 and vβ2 increase with an increase in the rotational speed, the current amplitude control unit 110 can improve responsiveness by setting a control component other than the voltage component corresponding to the expansion induced voltage. .

  Therefore, it is possible to obtain a control device 100 that can be controlled by avoiding complication of control and increasing the number of rotations to a level at which switching to stable sensorless control can be performed in other braking operation.

  That is, in other control operation, an error largely occurs between the optimum voltage applied to the motor 200 with respect to the rotational position of the motor 200 and the actually applied voltage. In the present embodiment, however, the applied voltage is increased as the rotational speed is increased. The accuracy of can be improved. As the rotational speed increases, the magnitudes of the second voltage vectors vα2 and vβ2 are obtained, and instability factors in other control operations can be suppressed while taking into account the influence of the estimated position error. Further, the target current value in the other control operation can be set low, and for example, the temperature rise of the switching element of the inverter 160 can be suppressed. Furthermore, the vibration of the compressor 210 can be reduced.

(Second Embodiment)
A control device 100A of the second embodiment is shown in FIG. The second embodiment is different from the first embodiment in that the observer 170 as the second conversion unit is changed and the second voltage vectors vα2 and vβ2 are calculated using the estimated position of the motor 200. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and it demonstrates below centering on a changed point.

  Here, the observer 170 and the phase calculation unit 180 are eliminated, and the second conversion unit includes a position estimation unit 171, an induced voltage term calculation unit 172, and a coordinate conversion unit 173.

  The position estimation unit 171 estimates the estimated rotational position (estimated position) θre from the combined vectors vα and vβ and the current vectors iα and iβ supplied to the motor 200. As a position estimation method, a current error method, a power factor angle method, or the like can be used.

  In addition, the induced voltage term calculation unit 172 calculates the electromotive force coefficient ωKE and outputs it to the coordinate conversion unit 173. Then, the coordinate conversion unit 173 calculates the second voltage vectors vα2 and vβ2 converted from the rotation axis coordinates to the two-phase fixed axis coordinates based on the estimated rotation position θre and the electromotive force coefficient ωKE, and combines them. Output to the unit 150.

  In the synthesizing unit 150, as in the first embodiment, the first voltage vectors vα1 and vβ1 and the second voltage vectors vα2 and vβ2 are synthesized, and the voltage phase is adjusted as the synthesized vectors vα and vβ. Apply.

  Thereby, the effect similar to the said 1st Embodiment can be acquired.

(Third embodiment)
A control device 100B of the third embodiment is shown in FIG. The third embodiment is different from the first embodiment in that the observer 170 as the second conversion unit is changed to a calculation unit 174, and the calculation unit 174 uses the current vectors iα and iβ of the motor 200 to change the second voltage vector. vα2 and vβ2 are calculated. In addition, the same code | symbol is attached | subjected to the structure same as 1st Embodiment, and it demonstrates below centering on a changed point.

  As shown in FIG. 5, the calculation unit 174 multiplies the current vectors iα and iβ by predetermined coefficients Kα and Kβ to calculate the second voltage vectors vα2 and vβ2 that have a reverse phase relationship with the current vectors iα and iβ. Like to do. In FIG. 5, in order to make it easy to see the sizes of the vectors (vα1, vβ1, vα2, vβ2, iα, iβ) originally shown on the α axis and β axis, The display is shifted slightly from the axis.

  Then, in the synthesizing unit 150, as in the first embodiment, the first voltage vectors vα1 and vβ1 and the second voltage vectors vα2 and vβ2 are synthesized, and the voltage phase is adjusted as the synthesized vectors vα and vβ, so that the motor 200 applied.

  Thereby, in this 3rd Embodiment, although accuracy is inferior to the control in the said 1st Embodiment, the effect similar to the said 1st Embodiment can be acquired by simple control (calculation).

  Note that, when the calculation unit 174 calculates the second voltage vectors vα2 and vβ2, the magnitudes of the second voltage vectors vα2 and vβ2 may be changed according to the rotation speed of the motor 200. That is, the second voltage vectors vα2 and vβ2 are calculated so as to increase as the rotation speed of the motor 200 increases. Specifically, the absolute values of the coefficients Kα and Kβ are related in advance so as to increase as the rotational speed increases, the coefficients Kα and Kβ are selected according to the rotational speed, and the selected coefficients Kα and Kβ are used. The second current vectors vα2 and vβ2 are calculated.

  The second voltage vectors vα2 and vβ2, which have a reverse phase relationship with the current vectors iα and iβ, do not take into account the rotational speed of the motor 200. Therefore, more stable control can be achieved by considering the rotational speed as described above. It becomes possible.

(Other embodiments)
In each of the above embodiments, the magnitudes of the second voltage vectors vα2 and vβ2 may be changed according to the operating temperature at a predetermined portion of the motor 200, other temperatures correlated with the motor 200, and estimated temperatures. For example, when the temperature of the motor 200 is low, the resistance of the motor winding is small, and the electromotive force is large, a phase error between the rotational position of the motor 200 and the voltage command vao is likely to occur. It is preferable to increase the adjustment amounts of the first voltage vectors vα1 and vβ1 by changing the second voltage vectors vα2 and vβ2 to the larger side.

  Thereby, the influence by the temperature of the motor 200 is suppressed, and the motor 200 can be controlled more stably.

  In addition, the generation of the combined vectors vα and vβ in the combining unit 150 and the application to the motor 200 in the other control operation are performed when the rotation speed of the motor 200 is equal to or higher than a predetermined rotation speed (for example, 100 rpm or higher). It is good to gradually increase the composition ratio from zero.

  As a result, in the extremely low rotational speed range where a large rotational position estimation error of the motor 200 occurs, it is possible to avoid the adverse effects of the inappropriate second voltage vectors vα2 and vβ2 and to perform stable control. In particular, when the observer 170 is used as in the first embodiment, in the extremely low rotation range where the induced voltage is small, it is possible to avoid the adverse effect due to the error of the induced voltage estimated by the observer 170 and to perform stable control. It becomes.

  Moreover, the compressor 210 which is the other side of the motor 200 is not limited to the one used for the heat pump cycle for the hot water heater, but may be the one used for the refrigeration cycle for the air conditioner. Furthermore, the counterpart device is not limited to the compressor 210 and may be a machine that receives other motor shaft output.

It is a block diagram which shows the control apparatus of the motor in 1st Embodiment. It is a vector diagram which shows the synthetic | combination state of the voltage vector in the two-phase ((alpha) (beta)) fixed axis coordinate in 1st Embodiment. It is a block diagram which shows the control apparatus of the motor in 2nd Embodiment. It is a block diagram which shows the control apparatus of the motor in 3rd Embodiment. It is a vector diagram which shows the synthetic | combination state of the voltage vector in the two-phase ((alpha) (beta)) fixed axis coordinate in 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Control apparatus of motor 110 Current amplitude control part 130 Coordinate conversion part (1st conversion part)
150 Combining Unit 170 Extended Induced Voltage Observer (Second Conversion Unit)
174 Calculation unit 200 Motor

Claims (18)

A motor control method for controlling a synchronous motor (200) by sensorless driving,
At the beginning of startup or low speed for forced operation
The applied voltage (vao) is determined so that the current of the synchronous motor (200) becomes a predetermined value,
Inferring induced voltages (eα, eβ) generated by the rotation of the synchronous motor (200),
The first voltage vector (vα1, vβ1) correlated with the applied voltage (vao) and the second voltage vector (vα2, vβ2) correlated with the induced voltage (eα, eβ) are combined to generate the synchronization. A method for controlling a motor, the method comprising applying to a motor (200).   The method for controlling a motor according to claim 1, wherein an induced voltage observer (170) is used when calculating the second voltage vector (vα2, vβ2).   The motor control method according to claim 1, wherein at least the estimated position (θre) of the synchronous motor (200) is used when calculating the second voltage vector (vα2, vβ2). A motor control method for controlling a synchronous motor (200) by sensorless driving,
At the beginning of startup or low speed for forced operation
The applied voltage (vao) is determined so that the current of the synchronous motor (200) becomes a predetermined value,
Detecting a vector (iα, iβ) of current flowing through the synchronous motor (200);
A first voltage vector (vα1, vβ1) correlated with the applied voltage (vao) and a second voltage vector (vα2, vβ2) having a reverse phase relationship with the current vector (iα, iβ) are synthesized. The method for controlling the motor, wherein the motor is applied to the synchronous motor (200).   5. The motor control method according to claim 4, wherein the magnitude of the second voltage vector (vα2, vβ2) is changed according to the rotational speed of the synchronous motor (200).   The motor control method according to claim 5, wherein the second voltage vector (vα2, vβ2) is changed to a larger side as the rotational speed of the synchronous motor (200) is higher.   The motor according to any one of claims 1 to 6, wherein the magnitude of the second voltage vector (vα2, vβ2) is changed according to the temperature of the synchronous motor (200). Control method.   The motor control method according to claim 7, wherein the second voltage vector (vα2, vβ2) is changed to a larger side as the temperature of the synchronous motor (200) is lower.   When the rotational speed of the synchronous motor (200) becomes equal to or higher than a predetermined rotational speed, the first voltage vector (vα1, vβ1) and the second voltage vector (vα2, vβ2) are combined, The motor control method according to claim 1, wherein the motor control method is applied to a synchronous motor (200). In a motor control device that controls a synchronous motor (200) by sensorless driving,
A current amplitude controller (110) for controlling the applied voltage (vao) so that the current of the synchronous motor (200) becomes a predetermined value;
A first converter (130) for converting the applied voltage (vao) into a first voltage vector (vα1, vβ1) correlated with the applied voltage (vao);
A second voltage vector (vα2) correlating the induced voltage (eα, eβ) with the induced voltage (eα, eβ) while estimating the induced voltage (eα, eβ) generated by the rotation of the synchronous motor (200). , Vβ2), a second conversion unit (170),
A synthesizing unit that synthesizes the first voltage vectors (vα1, vβ1) and the second voltage vectors (vα2, vβ2) and applies them to the synchronous motor (200) at the initial start or low speed for performing forced operation. (150). The motor control apparatus characterized by the above-mentioned.   The motor control device according to claim 10, wherein the second conversion unit (170) is an induced voltage observer (170).   The second conversion unit (170) calculates the second voltage vector (vα2, vβ2) using at least the estimated position (θre) of the synchronous motor (200). Motor control device. In a motor control device that controls a synchronous motor (200) by sensorless driving,
A current amplitude controller (110) for controlling the applied voltage (vao) so that the current of the synchronous motor (200) becomes a predetermined value;
A first converter (130) for converting the applied voltage (vao) into a first voltage vector (vα1, vβ1) correlated with the applied voltage (vao);
A calculation unit for detecting a vector (iα, iβ) of the current flowing through the synchronous motor (200) and calculating a second voltage vector (vα2, vβ2) having a reverse phase relationship with the current vector (iα, iβ). (174),
A synthesizing unit that synthesizes the first voltage vectors (vα1, vβ1) and the second voltage vectors (vα2, vβ2) and applies them to the synchronous motor (200) at the initial start or low speed for performing forced operation. (150). The motor control apparatus characterized by the above-mentioned.   The motor according to claim 13, wherein the calculation unit (174) changes the magnitude of the second voltage vector (vα2, vβ2) according to the number of rotations of the synchronous motor (200). Control device.   The motor according to claim 14, wherein the calculation unit (174) changes the second voltage vector (vα2, vβ2) to a larger side as the rotational speed of the synchronous motor (200) is higher. Control device.   The second conversion unit (170) or the calculation unit (174) changes the magnitude of the second voltage vector (vα2, vβ2) according to the temperature of the synchronous motor (200). The motor control device according to any one of claims 10 to 15.   The second conversion unit (170) or the calculation unit (174) changes the second voltage vector (vα2, vβ2) to a larger side as the temperature of the synchronous motor (200) is lower. The motor control device according to claim 16.   The synthesizing unit (150), when the rotational speed of the synchronous motor (200) becomes equal to or higher than a predetermined rotational speed, the first voltage vector (vα1, vβ1) and the second voltage vector (vα2, vβ2). The motor control device according to any one of claims 10 to 17, wherein the motor control device is combined and applied to the synchronous motor (200).

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