JP2006304462A - Motor drive system and control method for permanent magnet motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vector control technology for driving a PM motor with a few driving currents. <P>SOLUTION: This motor drive system includes a PM motor 4 equipped with a rotor 8 having a permanent magnet 12 and an inverter 3 for supplying a driving current to the PM motor 4. The inverter 3 performs field weakening control for the PM motor 4 as necessary. In performing the field weakening control, the magnitude of a d-axis current component of a driving current supplied to the PM motor 4 is decreased more as a temperature of the permanent magnet 12 is higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor drive system and a permanent magnet motor control method, and more particularly to a technique for controlling a permanent magnet motor (PM motor) by vector control.

  Vector control is widely known as a technique for operating a PM motor with high efficiency and high rotation speed, and its application to various applications including electric vehicles is being studied.

  In particular, field weakening control performed by vector control is effective as a technique for operating a PM motor at a high rotational speed. One cause for defining the upper limit of the rotation speed of the PM motor is an excessive increase in the induced voltage of the armature winding due to the increase in the rotation speed, and the field weakening control effectively suppresses the excessive increase in the induced voltage. More specifically, in the field weakening control, as shown in FIG. 1, when the PM motor is operated at a high rotational speed, the d-axis current (weakening field) is designed to weaken the magnetic flux generated by the permanent magnet. Magnetic current) is passed through the armature winding. Thereby, the induced voltage of the armature winding is suppressed, and a PM motor at a high rotational speed is enabled.

  What should be taken into consideration in the vector control of the PM motor is that the characteristics of the permanent magnet used as the field change according to its temperature. When the PM motor is operated at a high rotational speed, its temperature rises, and the temperature of the permanent magnet used as the field also rises. Therefore, the characteristics of the permanent magnet also vary with the temperature rise, and affect the PM motor vector control. More specifically, as described below, the temperature dependence of the characteristics of the permanent magnet has various effects on the vector control of the PM motor.

First, when the temperature of the permanent magnet rises, the torque generated by the PM motor decreases due to a decrease in the amount of magnetic flux generated by the permanent magnet. Japanese Patent Laid-Open No. 7-212915 discloses, as a technique for avoiding such a problem, controlling the command value Iq ^* of the q-axis current component of the PM motor according to the amount of magnetic flux (estimated value) generated by the permanent magnet. Is disclosed.

  Second, the coercive force of the permanent magnet (that is, the magnitude of the external magnetic field at which the demagnetization phenomenon of the permanent magnet occurs) has temperature dependence. Japanese Patent Laid-Open Nos. 7-337072 and 9-289799 disclose a technique for determining the allowable maximum value of the d-axis current depending on the temperature in consideration of the temperature dependence of the coercive force. is doing. Specifically, Japanese Patent Laid-Open No. 7-337072 discloses that when a ferrite-based permanent magnet whose coercive force increases with an increase in temperature is used as a field magnet, the d-axis current increases with the increase in the temperature of the permanent magnet. When a rare earth magnet whose coercive force decreases with increasing temperature is used as a field magnet, the allowable maximum value of the d-axis current is decreased with increasing temperature of the permanent magnet. Disclosure. Japanese Patent Laid-Open No. 9-289799 also discloses a similar technique.

  One requirement for PM motor vector control is that the PM motor can be driven with a small drive current. A small drive current is extremely important, particularly when the PM motor is driven by a battery, such as when applied to an electric vehicle. In addition, the small drive current effectively suppresses heat generation due to iron loss of the PM motor. The small heat generation is important when the PM motor is continuously operated; the small heat generation means that the PM motor can be continuously operated at a high rotation speed.

From such a background, it is desired to provide a vector control technique capable of driving a PM motor with a small drive current.
JP 7-212915 A Japanese Patent Laid-Open No. 7-337072 JP-A-9-289799

  An object of the present invention is to provide a vector control technique capable of driving a PM motor with a small drive current.

  The present invention is based on the discovery that an increase in the temperature of the permanent magnet reduces the induced voltage induced in the armature winding of the PM motor. Increasing the temperature of the permanent magnet reduces the amount of magnetic flux generated by the permanent magnet, and thus reduces the induced voltage induced in the armature winding. The present invention reduces the magnitude of the d-axis current component during field-weakening control in response to a decrease in the induced voltage caused by a rise in the temperature of the permanent magnet, thereby reducing the drive current of the PM motor. Achieve reduction.

  More specifically, the present invention employs the means described below. In the description of technical matters constituting the means, in order to clarify the correspondence between the description of [Claims] and the description of [Best Mode for Carrying Out the Invention] Number / symbol used in the best mode for doing this is added. However, the added number / symbol should not be used to limit the technical scope of the invention described in [Claims].

  In one aspect of the present invention, a motor drive system (1) includes a permanent magnet motor (4) including a rotor (8) having a permanent magnet (12), and a drive for supplying a drive current to the permanent magnet motor (4). Current supply means (3, 5). The drive current supply means (3, 5) is configured to be able to execute field weakening control of the permanent magnet motor (4). When field weakening control of the permanent magnet motor (4) is performed, the magnitude of the d-axis current component (Id) of the drive current is reduced as the temperature of the permanent magnet (12) is higher. Thereby, the motor drive system (1) suppresses an excessive increase in the d-axis current component (that is, the field weakening current) of the drive current, and drives the permanent magnet motor (4) with a smaller drive current. Can do.

  Preferably, the d-axis current component of the drive current is preferably controlled in response to an induced voltage induced in the search coil (16) positioned facing the rotor (8). The use of the search coil (16) can more directly detect the influence of the temperature change of the permanent magnet (12) on the induced voltage induced in the armature winding (15) of the permanent magnet motor (4). Enable.

In one embodiment, the drive current supply means (3, 5) receives DC power from the battery (2), generates the drive current from the DC power, and supplies the drive current to the permanent magnet motor (4). And a control device (5) for controlling the inverter (3). The control device (5) responds to the torque command (T ^* ), the rotational speed (N) of the permanent magnet motor (4), and the induced voltage of the search coil (16), the q-axis current command (Iq ^* ) and the d-axis. a current command (Id ^*) and the current command generating means for generating (31), in response to the q-axis current command (Iq ^*) and the d-axis current command (Id ^*), q axis current component of the driving current (Iq ) Becomes the q-axis current command (Iq ^* ), and the inverter control means (3) controls the inverter (3) so that the d-axis current component (Id) of the drive current matches the d-axis current command (Id ^* ). 32 to 34).

  In another aspect of the present invention, an electric vehicle includes a drive wheel (7), a permanent magnet motor (4) including a rotor (8) connected to the drive wheel (7) and having a permanent magnet (12). Drive current supply means (3, 5) for supplying a drive current to the permanent magnet motor (4). The drive current supply means (3, 5) is configured to be able to execute field weakening control of the permanent magnet motor (4). When field weakening control of the permanent magnet motor (4) is performed, the magnitude of the d-axis current component (Id) of the drive current is reduced as the temperature of the permanent magnet (12) is higher.

  In still another aspect of the present invention, an electric vehicle includes a permanent magnet motor (4) including a rotor (8) having a permanent magnet (12), and a search coil (16) positioned facing the rotor (8). Drive current supply means (3, 5) for supplying a drive current to the permanent magnet motor (4). The drive current supply means (3, 5) is configured to be able to perform field weakening control of the permanent magnet motor (4). When field weakening control of the permanent magnet motor (4) is performed, the d-axis current component of the drive current is controlled in response to the induced voltage induced in the search coil (16).

  In still another aspect of the present invention, the method of controlling the permanent magnet motor (4) includes a step of supplying a driving current to the permanent magnet motor (4) so that field weakening control of the permanent magnet motor (4) is performed. . The magnitude of the d-axis current component of the drive current during the field weakening control is made smaller as the temperature of the permanent magnet (12) is higher.

  In still another aspect of the present invention, a method for controlling a permanent magnet motor (4) includes a step of measuring an induced voltage induced in a search coil (16) positioned opposite to a rotor (8), and a permanent magnet motor. And (4) supplying a drive current to the permanent magnet motor (4) so that field weakening control is performed. The d-axis current component of the drive current is controlled in response to the induced voltage induced in the search coil (16). The magnitude of the d-axis current component is reduced as the induced voltage of the search coil (16) is lower.

  The present invention provides a vector control technique capable of driving a PM motor with a small drive current.

First System Configuration Referring to FIG. 2, in one embodiment of the present invention, a motor drive system 1 is applied to drive a drive wheel of an electric vehicle. The motor drive system 1 generally includes a battery 2, an inverter 3, a PM motor 4, and a control device 5. The battery 2 supplies a DC voltage to the inverter 3. The inverter 3 generates three-phase AC power from the DC voltage supplied from the battery 2 and supplies it to the PM motor 4. The PM motor 4 is connected to the drive wheel 7 via the power transmission mechanism 6. The PM motor 4 generates power from the three-phase AC power supplied from the inverter 3 and drives the drive wheels 7. The control device 5 controls the inverter 3 by vector control and operates the PM motor 4 in a desired state.

  As shown in FIG. 3, the PM motor 4 includes a rotor 8 and a stator 9. The rotor 8 includes a rotor iron core 11 and a permanent magnet 12 used as a field magnet. The stator 9 includes a stator iron core 13 and an armature winding 15 wound around the armature teeth 14 of the stator iron core 13.

In addition, a search coil 16 is provided so as to face the rotor 8. The search coil 16 has a role of detecting the amount of magnetic flux generated by the permanent magnet 12; when the rotor 8 rotates, an induced voltage corresponding to the amount of magnetic flux generated by the permanent magnet 12 is induced in the search coil 16. Hereinafter, an induced voltage induced in the search coil 16 is referred to as a search coil induced voltage _VSC . As shown in FIG. 2, the search coil 16 is connected to the voltage sensor 17, the control unit 5 performs a vector control in response to the search coil induced voltage V _SC measured by the voltage sensor 17.

Various other sensors are provided in the motor drive system 1 in order to execute vector control. In the present embodiment, the motor drive system 1 includes a voltage sensor 18 that measures a DC voltage output from the battery 2 (hereinafter referred to as “battery voltage V _BAT ”), and a drive current supplied from the inverter 3 to the PM motor 4. : Current sensors 19u, 19v, and 19w for measuring u-phase current Iu, v-phase current Iv, and w-phase current Iw, and a rotary encoder 21 for detecting the rotor position θ and the motor rotation speed N of PM motor 4 are provided. It has been. The control device 5 performs vector control of the inverter 3 in response to the outputs of the voltage sensor 18, current sensors 19 u, 19 v, 19 w and the rotary encoder 21.

  The control device 5 schematically includes a current command generation unit 31, a current control unit 32, a two-phase to three-phase conversion unit 33, a PWM control unit 34, a three-phase to two-phase conversion unit 35, a position / Rotation speed detector 36.

The current command generator 31 generates a q-axis current command Iq ^* and a d-axis current command Id ^* . The q-axis current command Iq ^* and the d-axis current command Id ^* are the following four parameters: torque command T ^* given from the outside, motor rotation speed N of the PM motor 4, search coil induced voltage V _SC , and battery voltage Generated according to _VBAT . As described later, the d-axis current command Id ^* is generated in response to the search coil induced voltage V _SC is important in the motor driving system 1 of the present embodiment.

More specifically, in one embodiment, the generation of the q-axis current command Iq ^* and the d-axis current command Id ^* is performed by table lookup. In this case, a lookup table describing the relationship between the torque command T ^* , the motor rotation speed N, the search coil induced voltage V _SC , and the battery voltage V _BAT , the q-axis current command Iq ^* and the d-axis current command Id ^* is the current. Prepared in the command generator 31, the current command generator 31 generates a q-axis current command Iq ^* and a d-axis current command Id ^* using the lookup table.

In another embodiment, a relational expression describing the relationship among the torque command T ^* , the motor rotation speed N, the search coil induced voltage V _SC , and the battery voltage V _BAT , the q-axis current command Iq ^*, and the d-axis current command Id ^*. Is prepared in the current command generation unit 31, and the q-axis current command Iq ^* and the d-axis current command Id ^* are generated using the relational expression.

The current control unit 32 is controlled so that the q-axis current component Iq of the drive current supplied to the PM motor 4 becomes the q-axis current command Iq ^* , and the d-axis current component Id is controlled by the d-axis current command Id ^*. Q-axis voltage command Vq ^* and d-axis voltage command Vd ^* are generated and supplied to the two-phase / three-phase conversion unit 33.

The two-phase / three-phase conversion unit 33 performs two-phase / three-phase conversion using the position of the rotor 8 (hereinafter referred to as “rotor position θ”). More specifically, the two-phase to three-phase converter 33 converts the q-axis voltage command Vq ^* and the d-axis voltage command Vd ^* into the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^* , and the w-phase voltage command. Convert to Vw ^* .

In response to the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^* , and the w-phase voltage command Vw ^* , the PWM control unit 34 outputs a PWM signal S _PWM that controls on / off of each switching transistor that constitutes the inverter 3. Generated and supplied to the inverter 3. The inverter 3 is controlled by the PWM signal S _PWM .

The three-phase to two-phase conversion unit 35 performs three-phase to two-phase conversion using the rotor position θ. More specifically, the three-phase to two-phase converter 35 converts the u-phase current Iu, the v-phase current Iv, and the w-phase current Iw measured by the current sensors 19u, 19v, and 19w into q-axis current components Iq and d. Conversion into the shaft current component Id. The obtained q-axis current component Iq and d-axis current component Id are sent to the current control unit 32 and used to generate the q-axis voltage command Vq ^* and the d-axis voltage command Vd ^* .

  The position / rotation speed detection unit 36 detects the rotor position θ and the rotor rotation speed N from the output of the rotary encoder 21. The rotor position θ is sent to the two-phase / three-phase conversion unit 33 and the three-phase / two-phase conversion unit 35, and the rotor rotational speed N is sent to the current command generation unit 31 for use.

  The above-described control blocks: current command generator 31, current controller 32, two-phase to three-phase converter 33, PWM controller 34, three-phase to two-phase converter 35, and position / rotation number detector 36 are software , Hardware, and a combination thereof.

Operation of Second Motor Drive System The most important point of the motor drive system 1 of the present embodiment is that the d-axis current component Id of the drive current supplied to the PM motor 4 is provided in the rotor 8 when field weakening control is performed. The higher the temperature of the permanent magnet 12 is, the more it decreases monotonously. When the motor speed N increases, field weakening control is performed in order to suppress an increase in the induced voltage of the armature winding 15. The magnitude of the d-axis current component Id (field weakening current) during field weakening control is basically controlled to increase as the motor rotation speed N increases. In addition, in the motor drive system 1 of the present embodiment, the magnitude of the field weakening current is monotonously decreased as the temperature of the permanent magnet 12 increases. This is to prevent an unnecessarily large field weakening current from flowing. The increase in the temperature of the permanent magnet 12 decreases the amount of magnetic flux generated by the permanent magnet 12 and decreases the induced voltage of the armature winding 15. This means that when the temperature of the permanent magnet 12 is high, only a relatively small field weakening current is required; as in the prior art, the field weakening current is equal to the temperature of the permanent magnet 12. If it is determined independently, a drive current having a large field weakening current is supplied to the PM motor 4 unnecessarily. In the motor drive system 1 of the present embodiment, the field weakening current is reduced in response to an increase in the temperature of the permanent magnet 12, thereby reducing the drive current supplied to the PM motor 4.

To achieve the control of the response d-axis current component Id in the temperature of the permanent magnet 12, in this embodiment, of determining d-axis current command Id ^* in accordance with the search coils the induced voltage V _SC at the time of the field weakening control Technical means are adopted. d-axis current command Id ^* of the absolute value (i.e., the size of the field weakening current) is induced voltage V _SC of the search coil 16 is increased higher is the lower the smaller. Search coil induced voltage V _SC is, the more the amount of magnetic flux by the permanent magnet 12 is generated is large, i.e., since the temperature of the permanent magnet 12, the higher low, the higher the induced voltage V _SC of the search coil 16 d-axis current command Id Control for increasing the absolute value of ^* is equivalent to control for decreasing the d-axis current component Id as the temperature of the permanent magnet 12 increases.

  Instead of using the search coil 16, it is also possible to detect the temperature of the permanent magnet 12 by providing a temperature sensor in the rotor 8 or the stator 9; however, the use of the search coil 16 is compared with the use of the temperature sensor. It is more preferable. There are two reasons for this. First, it is technically difficult to accurately measure the temperature of the permanent magnet 12 by the temperature sensor. In order to provide a temperature sensor in the rotor 8 which is a rotating body, a complicated mechanism is required to realize an electrical connection between the temperature sensor and the control device 5. On the other hand, the method of estimating the temperature of the permanent magnet 12 from the temperature of the stator 9 by providing a temperature sensor in the stator 9 makes it difficult to estimate the actual temperature of the permanent magnet 12.

Second, by using the search coil 16, the influence on the induced voltage induced in the armature winding 15 can be detected more directly. The parameter of final interest in field weakening control is the induced voltage induced by the linkage of the magnetic flux generated by the permanent magnet 12 to the armature winding 15. Since the search coil induced voltage V _SC has a high correlation with the induced voltage induced in the armature winding 15, it is more appropriate to determine the d-axis current command Id ^* according to the search coil induced voltage V _SC. Field weakening control can be realized.

More specifically, in the present embodiment, the vector control in response to the induced voltage V _SC of the search coil 16 as follows is performed.

When the torque command T ^* , the rotor speed N, the search coil induced voltage V _SC and the battery voltage V _BAT are given, the current command generator 31 responds to these parameters with the q-axis current command Iq ^* and the d-axis current. Command Id ^* is generated. As described above, the q-axis current command Iq ^* and the d-axis current command Id ^* are generated using a lookup table or a function expression.

The current command generator 31 performs field weakening control when necessary. More specifically, field weakening control is not performed in a range where the rotor rotational speed N is low, and the d-axis current command Id ^* remains zero. When the rotor rotational speed N exceeds a predetermined value, the d-axis current command Id ^* is set to a negative value, and the drive current having a d-axis current component Id that weakens the field (that is, field weakening current) is PM. It is supplied to the motor 4. d-axis current command Id ^* of the absolute value (i.e., the size of the field weakening current) is larger the higher the rotor rotational speed N, is greater the larger the search coil induced voltage V _SC.

Whether performing field weakening control it can also be determined in dependence on the rotor in the rotational speed N without search coils the induced voltage V _SC. In this case, field weakening control is not performed in a range where the search coil induced voltage _VSC is low, and the d-axis current command Id ^* remains zero. If search coils the induced voltage V _SC exceeds a predetermined value, the d-axis current command Id ^* is set to a negative value, the drive current having the above weaken the field d-axis current component Id (i.e., field weakening current) Is supplied to the PM motor 4.

Further, the absolute value of the d-axis current command Id ^* increases as the battery voltage V _BAT is lower. This is to prevent the induced voltage of the armature winding 15 from becoming excessively higher than the maximum value of the output voltage that can be output by the inverter 3. When the battery voltage V _BAT is low, the maximum value of the output voltage that the inverter 3 can output also decreases. Therefore, when the battery voltage V _BAT is low, the absolute value of the d-axis current command Id ^* (that is, the magnitude of the field weakening current) is increased, and the induced voltage of the armature winding 15 is output from the inverter 3. An excessive increase compared to the possible output voltage is prevented.

The q-axis current command Iq ^* and the d-axis current command Id ^* thus generated are used for controlling the q-axis current component Iq and the d-axis current component Id of the drive current of the PM motor 4. Specifically, the current control unit 32 generates the q-axis voltage command Vq ^* so that the difference between the q-axis current component Iq and the q-axis current command Iq ^* becomes zero, and the d-axis current component Iq and the d-axis current are generated. The d-axis voltage command Vd ^* is generated so that the difference from the command Iq ^* becomes zero. The q-axis voltage command Vq ^* and the d-axis voltage command Vd ^* are converted into a u-phase voltage command Vu ^* , a v-phase voltage command Vv ^* , and a w-phase voltage command Vw ^* by the two-phase / three-phase converter 33. Further, the u-phase voltage Vu, the v-phase voltage Vv, and the w-phase voltage Vw of the PM motor 4 are matched with the u-phase voltage command Vu ^* , the v-phase voltage command Vv ^* , and the w-phase voltage command Vw ^* by PWM control. PWM signal S _PWM is generated and supplied to the inverter 3. The inverter 3 supplies a drive current to the PM motor 4 in response to the PWM signal S _PWM to drive the PM motor 4.

By the above procedure, the temperature of the permanent magnet 12, i.e., control of the d-axis current component Id in accordance with the search coils the induced voltage V _SC is realized.

Third Summary As described above, in the motor drive system 1 of the present embodiment, the field-weakening current is decreased in response to the temperature increase of the permanent magnet 12, and is thereby supplied to the PM motor 4. Reduction of drive current has been achieved.

FIG. 1 is a graph for explaining field-weakening control. FIG. 2 is a block diagram showing the configuration of the motor drive system according to the embodiment of the present invention. FIG. 3 is a conceptual diagram showing the configuration of the PM motor in the embodiment.

Explanation of symbols

1: Motor drive system 2: Battery 3: Inverter 4: PM motor (permanent magnet motor)
5: Control device 6: Power transmission mechanism 7: Drive wheel 8: Rotor 9: Stator 11: Rotor core 12: Permanent magnet 13: Stator iron core 14: Armature teeth 15: Armature winding 16: Search coils 17, 18: Voltage sensor 19u, 19v, 19w: Current sensor 21: Rotary encoder 31: Current command generator 32: Current controller 33: Two-phase to three-phase converter 34: PWM controller 35: Three-phase to two-phase converter 36: Position / rotation speed detector

Claims (10)

A permanent magnet motor comprising a rotor having a permanent magnet;
Drive current supply means for supplying a drive current to the permanent magnet motor,
The drive current supply means is configured to execute field-weakening control of the permanent magnet motor,
When field-weakening control of the permanent magnet motor is performed, the magnitude of the d-axis current component of the drive current is reduced as the temperature of the permanent magnet is increased. The motor system according to claim 1,
The drive current supply means includes
Current command generating means for generating a d-axis current command in response to the torque command, the rotational speed of the permanent magnet motor, and the temperature of the permanent magnet;
In response to the d-axis current command, inverter control means for controlling the inverter so that the d-axis current component of the drive current matches the d-axis current command,
When field-weakening control of the permanent magnet motor is performed, the magnitude of the d-axis current command is made smaller as the temperature of the permanent magnet is higher. A permanent magnet motor comprising a rotor having a permanent magnet;
A search coil located opposite the rotor;
Drive current supply means for supplying a drive current to the permanent magnet motor,
The drive current supply means is configured to be able to perform field weakening control of the permanent magnet motor,
When field-weakening control of the permanent magnet motor is performed, the d-axis current component of the drive current is controlled in response to an induced voltage induced in the search coil. The motor drive system according to claim 3,
When field-weakening control of the permanent magnet motor is performed, the magnitude of the d-axis current component is reduced as the induced voltage is lower. The motor drive system according to claim 3, wherein the drive current supply means is
An inverter that receives DC power from a battery, generates the drive current from the DC power, and supplies the drive current to the permanent magnet motor;
A control device for controlling the inverter,
The control device includes:
Current command generating means for generating a q-axis current command and a d-axis current command in response to the torque command, the rotational speed of the permanent magnet motor, and the induced voltage;
In response to the q-axis current command and the d-axis current command, the q-axis current component of the drive current matches the q-axis current command, and the d-axis current component of the drive current is a motor drive system including inverter control means for controlling the inverter so as to coincide with a d-axis current command. Driving wheels,
A permanent magnet motor comprising a rotor connected to the drive wheel and having a permanent magnet;
Battery,
Drive current supply means for receiving DC power from the battery, generating the drive current from the DC power, and supplying the drive current to the permanent magnet motor;
The drive current supply means is configured to execute field-weakening control of the permanent magnet motor,
When the field-weakening control of the permanent magnet motor is performed, the magnitude of the d-axis current component of the drive current is reduced as the temperature of the permanent magnet is higher. Driving wheels,
A permanent magnet motor comprising a rotor connected to the drive wheel and having a permanent magnet;
A search coil located opposite the rotor;
Battery,
Drive current supply means for receiving DC power from the battery, generating the drive current from the DC power, and supplying the drive current to the permanent magnet motor;
The drive current supply means is configured to be able to perform field weakening control of the permanent magnet motor,
When the field-weakening control of the permanent magnet motor is performed, the d-axis current component of the drive current is controlled in response to an induced voltage induced in the search coil. A method for controlling a permanent magnet motor comprising a rotor having a permanent magnet,
Supplying a driving current to the permanent magnet motor so that field weakening control of the permanent magnet motor is performed,
The magnitude of the d-axis current component of the drive current is made smaller as the temperature of the permanent magnet is higher. A method for controlling a permanent magnet motor comprising a rotor having a permanent magnet,
Measuring an induced voltage induced in a search coil located opposite the rotor;
Supplying a driving current to the permanent magnet motor so that field weakening control of the permanent magnet motor is performed,
The d-axis current component of the drive current is controlled in response to an induced voltage induced in the search coil. The permanent magnet motor control method according to claim 9,
The magnitude of the d-axis current component is made smaller as the induced voltage is lower. A permanent magnet motor control method.

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