TW201436448A - Motor control apparatus - Google Patents

Abstract

Implementing broader definite output field. Excitation current instruction exerciser uses torque current command and motor rotational speed to recognize rotational load condition of the motor and calculate excitation current instruction corresponding to the rotational load condition. Motor driving part (q axis current controller, d axis current controller, coordinate transformer, PWM controller, power converter) uses torque current command and calculated excitation current instruction to drive the motor.

Description

Motor control unit Field of invention

The present invention relates to a motor control device that can achieve a wider range of output fields.

Background of the invention

The spindle of the machine tool is expected to combine low speed heavy cutting and high speed cutting. Therefore, high torque and high speed rotation at the time of low speed rotation are achieved using the output control according to field weakening. The motor control device that performs the constant output control is as follows, for example.

Figure 10 is a block diagram of a conventional motor control device. The motor control device performs the following operations.

First, the speed command is compared with the motor rotation speed ωm from the speed calculator 15, and the q-axis current command IqC is obtained by the speed controller 20. The motor rotation speed ωm output from the speed calculator 15 is calculated using the position feedback detected by the encoder 10. The q-axis current command IqC is compared with the q-axis current feedback IqF from the coordinate converter 25, and the q-axis voltage command VqC is obtained by the q-axis current controller 30.

On the other hand, the necessary exciting current is given by the d-axis current command IdC with reference to the motor rotation speed ωm. The d-axis current command IdC comes from The d-axis current feedback IdF of the coordinate converter 25 is compared, and the d-axis current command VdC is obtained by the d-axis current controller 45.

The slip frequency calculator 50 calculates the slip frequency command ωs from the q-axis current command IqC and the d-axis current command IdC. The slip frequency command ωs is added to the motor rotational speed ωm output from the speed calculator 15. The primary frequency command ω1 is obtained by the slip frequency command ωs and the motor rotational speed ωm. The stator position command θmc is obtained by integrating the primary frequency command ω1 with the integrator 55.

The coordinate converter 60 performs coordinate conversion on the q-axis voltage command VqC and the d-axis voltage command VdC based on the stator position command θmc, and obtains three-phase voltage commands Vuc, Vvc, and Vwc. The three-phase voltage commands Vuc, Vvc, and Vwc are supplied to the motor 80 through the PWM controller 65 and the power converter 70, and the motor 80 is driven in response to the three-phase voltage commands Vuc, Vvc, and Vwc.

The q-axis current feedback IqF and the d-axis current feedback IdF are obtained by coordinate conversion of the motor currents Iu and Iv by the coordinate converter 25 based on the stator position command θmc.

The excitation current command IdC is constant in the constant torque field as shown in the figure, and is reduced in inverse proportion to the increase in the rotational speed of the motor 80 in the fixed output field. The field weakening control is performed by reducing the exciting current command IdC in inverse proportion to the increase in the rotational speed of the motor 80.

Incidentally, as a technique similar to the above-described conventional technique, the following Patent Document 1 shows a technique of detecting a DC voltage of an inverter and automatically performing magnetic flux at a balance with a rotational speed of the motor. An example of control.

Advanced technical literature Patent literature

Patent Document 1 Japanese Patent Laid-Open No. 59-149785

Summary of invention

In recent years, it has been demanded to improve both of the characteristics of further high torque at low speed heavy cutting and increased rotational speed at high speed cutting. In order to respond to the request, it is expected to broaden the range of output.

However, in general, if a wide field of output is obtained by weakening the magnetic field, the magnetic flux at the time of high-speed rotation is reduced. The induced voltage of the motor is expressed as the product of the magnetic flux and the rotational speed. Therefore, when a wide range of output fields is obtained, the relative magnetic flux component becomes small at the time of high-speed rotation, and the rotational speed component becomes large, and the induced voltage of the motor is easily affected by the fluctuation of the rotational speed of the motor.

The motor has a core offset of the rotor caused by the bearing that holds the rotating shaft offset from the core of the encoder. When the core offset is large, the induced voltage of the motor fluctuates, and the rotation of the motor is detected as a rotation change, so that the motor current at the time of high-speed light load rotation becomes unstable.

In order to improve this, it is conceivable to increase the magnetic flux when rotating at a high speed. However, when the magnetic flux at the time of high-speed rotation is increased, the induced voltage of the motor becomes high, and when the high-speed heavy load rotates, the output voltage of the inverter that controls the operation of the motor is saturated, and the rotational speed of the motor becomes unstable.

Thus, the conventional motor control device cannot balance the high speed and light weight The stability of the core offset of the motor during rotation and the stability of the core offset of the encoder and the saturation of the output voltage of the inverter at high speed and heavy load cannot broaden the output field of the motor.

In addition, as disclosed in Patent Document 1, a voltage detector for detecting the voltage of the DC power source and a speed detector for detecting the speed of the induction motor can be considered, and the primary current of the induction motor is controlled to be obtained by dividing the voltage signal by the speed signal. The value corresponds to the magnetic flux, which suppresses the saturation of the output voltage of the inverter. However, even if the technique disclosed in Patent Document 1 can optimize the magnetic flux in the case where the voltage of the DC power source changes, it is not possible to simultaneously achieve the improvement of the stability of the motor current at the time of high-speed light load rotation and the high speed weight. Suppression of voltage saturation when the load is rotating.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the conventional motor control device as described above, and an object thereof is to provide a core offset of a motor and a core offset of an encoder when high speed light load rotation can be simultaneously achieved. The stability of the stability, the suppression of the saturation of the output voltage of the inverter during high-speed heavy-duty rotation, and the realization of a motor control device in a wide range of output fields.

In order to achieve the above object, a motor control device according to the present invention includes an excitation current command calculator and a motor drive unit.

The excitation current command calculator recognizes the rotational load state of the motor using the torque current command and the motor rotational speed, and calculates an excitation current command corresponding to the rotational load state. The motor drive unit drives the motor using a torque current command and a calculated excitation current command.

According to the motor control device according to the present invention configured as described above, it is possible to achieve both the improvement of the stability of the core offset of the motor and the core offset of the encoder when the high-speed light load is rotated, and the high-speed heavy load rotation. The suppression of the saturation of the output voltage of the inverter enables a wider range of output fields.

10, 110, 210, 310‧‧ ‧ encoder

15, 115, 215, 315‧‧‧ speed calculator

20‧‧‧Speed controller

25, 125, 225, 325‧‧‧ coordinate converters

30, 130, 230, 330‧‧‧q axis current controller

45, 145, 245, 345 ‧ ‧ d axis current controller

50, 150, 250, 350‧‧‧ slip frequency calculator

55, 155, 255, 355‧‧ ‧ integrator

60, 160, 260, 360‧‧‧ coordinate converters

65, 165, 265, 365‧‧‧ PWM controller

70, 170, 270, 370‧‧‧ power converters

80, 180, 280, 380‧ ‧ motor

100, 200, 300‧‧‧ motor control unit

135‧‧‧Excitation current command calculator

157, 257, 357‧‧‧ OSC

220, 320‧‧‧ magnetic flux command calculator

235, 335‧‧ ‧ magnetic flux calculator

240, 340‧‧‧ magnetic flux controller

375‧‧‧Maximum current command calculator

385‧‧‧torque limit value calculator

390‧‧‧Restrictor

395‧‧‧q-axis current calculator

Fig. 1 is a block diagram showing a motor control device according to a first embodiment.

Fig. 2 is a view showing the relationship between the motor rotational speed ωm in the excitation current command calculator of Fig. 1 and the excitation current command IdCB before the magnetic field is weakened.

Fig. 3 is a view showing the relationship between the motor rotational speed ωm and the exciting current command IdC in the exciting current command calculator of Fig. 1.

Fig. 4 is a block diagram showing a motor control device according to a second embodiment.

Fig. 5 is a view showing the relationship between the motor rotational speed ωm in the magnetic flux command calculator of Fig. 4 and the magnetic flux command φ2CB before the magnetic field is weakened.

Fig. 6 is a graph showing the relationship between the motor rotational speed ωm and the magnetic flux command φ2C in the magnetic flux command calculator of Fig. 4.

Fig. 7 is a block diagram showing a motor control device according to a third embodiment.

Fig. 8 is a view showing the relationship between the motor rotational speed ωm in the magnetic flux command calculator of Fig. 7 and the magnetic flux command φ2CB before the magnetic field is weakened.

Fig. 9 is a view showing the relationship between the motor rotational speed ωm and the magnetic flux command φ2C in the magnetic flux command calculator of Fig. 7.

Fig. 10 is a block diagram showing an example of a conventional motor control device.

Form for implementing the invention

The motor control device related to the present invention is capable of taking a wide range of output fields and realizing the stability of the high-speed light load rotation of the motor, the stability of the saturation of the output voltage of the inverter when the high-speed heavy load is rotated, and the low speed. High torque during rotation. That is, the motor control device related to the present invention has both low-speed heavy cutting and high-speed cutting.

Next, an embodiment of the motor control device according to the present invention which exhibits the above-described characteristics will be described with reference to the drawings, and will be described as [Embodiment 1] to [Embodiment 3].

[Embodiment 1]

[Overall Configuration of Motor Control Device 100]

Fig. 1 is a block diagram showing a motor control device 100 according to the first embodiment.

The motor control device 100 has a q-axis current controller 130 as a system for issuing the q-axis voltage command VqC.

The q-axis current controller 130 is a current deviation input obtained by subtracting the q-axis current feedback IqF from the input torque current command IqC, and calculates a q-axis voltage command VqC. The q-axis current feedback IqF is output by the coordinate converter 125. The q-axis current feedback IqF is obtained by coordinate conversion of the motor currents Iu and Iv by the coordinate converter 125 based on the stator position command θmc to be described later. The q-axis current controller 130 is constructed with a proportional integral controller.

In addition, the motor control device 100 has an excitation current command calculator 135 and a d-axis current controller 145 as a system for issuing the d-axis voltage command VdC. System.

The excitation current command calculator 135 inputs the torque current command Iqc and the motor rotation speed ωm, and calculates an optimum excitation current command IdC for widening the output field. The motor rotation speed ωm is output by the speed calculator 115. The speed calculator 115 calculates the motor rotational speed ωm using the position feedback detected by the encoder 110. Incidentally, the detailed action of the exciting current command calculator 135 is described later.

The d-axis current controller 145 is a current deviation input obtained by subtracting the d-axis current feedback IdF from the d-axis current command IdC output from the excitation current command calculator 135, and calculates a d-axis voltage command VdC. The d-axis current feedback IdF is output by the coordinate converter 125. The d-axis current feedback IdF is obtained by coordinate conversion of the motor currents Iu and Iv by the coordinate converter 125 based on the stator position command θmc to be described later. The d-axis current controller 145 is constructed with a proportional integral controller.

Further, the motor control device 100 has a slip frequency calculator 150, an integrator 155, an OSC 157, and coordinate converters 125 and 160 as a system for performing coordinate conversion.

The slip frequency calculator 150 inputs the torque current command IqC and the excitation current command IdC output from the excitation current command calculator 135, and calculates the slip frequency command ωs. Incidentally, the detailed action of the slip frequency calculator 150 is stated later.

The integrator 155 is a primary frequency command ω1 input obtained by adding the slip frequency command ωs outputted by the slip frequency calculator 150 to the motor rotational speed ωm outputted by the speed calculator 115, and sets the primary frequency command ω1. The stator position command θmc is obtained by integration. The stator position command θmc is output to the coordinate converters 125 and 160 through the OSC 157.

The coordinate converter 160 performs coordinate conversion on the q-axis voltage command VqC and the d-axis voltage command VdC based on the input stator position command θmc, and obtains three-phase voltage commands Vuc, Vvc, and Vwc.

The coordinate converter 125 performs coordinate conversion on the motor currents Iu and Iv based on the input stator position command θmc, and obtains the q-axis current feedback IqF and the d-axis current feedback IdF.

Furthermore, the motor control device 100 has a PWM controller 165 and a power converter 170 as a system for driving the motor 180. Incidentally, the motor drive unit is formed by the PWM controller 165, the power converter 170, the q-axis current controller 130, the d-axis current controller 145, and the coordinate converter 160.

The PWM controller 165 inputs the three-phase voltage commands Vuc, Vvc, and Vwc output from the coordinate converter 160, and outputs a PWM signal for switching the power converter 170 based on the input three-phase voltage commands Vuc, Vvc, and Vwc.

The power converter 170 is a PWM signal output from the PWM controller 165, and switches the semiconductor switching element provided therein to drive the motor 180.

[Action of the excitation current command calculator 135]

As described above, the excitation current command calculator 135 is an optimum excitation current command IdC for calculating a wide range of output fields.

Figure 2 is a view showing the horse in the exciting current command calculator 135 of Figure 1. A graph showing the relationship between the rotational speed ωm and the excitation current command IdCB before the magnetic field is weakened. The excitation current command calculator 135 is an excitation current command IdcC before the magnetic field attenuation corresponding to the motor rotation speed ωm. 3 is a diagram showing the relationship between the motor rotational speed ωm and the exciting current command IdC in the exciting current command calculator 135 of FIG. 1. The excitation current command calculator 135 is an excitation current command Idc corresponding to the motor rotation speed ωm.

2 and 3 show the magnetizing current command characteristics with respect to the motor rotational speed ωm when the torque current command IqC is 0 (IqC0), rated (IqCR), and maximum (IqCmax). 2 is a view showing an exciting current command IdCB before the magnetic field is weakened, and FIG. 3 is a view showing an exciting current command IdC.

As shown in FIG. 2, the exciting current command IdCB before the field weakening does not change when the motor rotational speed ωm is from 0 to ω0. When the motor rotation speed exceeds ω0, when the torque current command IqC is 0 (IqC0), the excitation current command IdCB rises from the current I0 with a constant slope. When the torque current command IqC is rated (IqCR), the degree of rise is smaller than when the torque current command IqC is 0 (IqC0). When the torque current command IqC is maximum (IqCmax), regardless of the motor rotation speed ωm, the torque current command IqC is the maintenance current I0.

Further, as shown in FIG. 3, the exciting current command IdC does not change when the motor rotational speed ωm is from 0 to ω0. When the motor rotation speed exceeds ω0, when the torque current command IqC is maximum (IqCmax), the excitation current command IdC is decreased in inverse proportion to the motor rotation speed ωm from the current I0. When the torque current command IqC is rated (IqCR), the degree of decrease is smaller than when the torque current command IqC is maximum (IqCmax). Torque current When the command IqC is 0 (IqC0), the degree of decrease is smaller than when the torque current command IqC is rated (IqCR).

The excitation current command calculator 135 obtains the excitation current command IdCB before the magnetic field is weakened by the following equation.

IdCB=I0(0≦|ωm|≦ω0) IdCB={I0+K0. (1-KIqC.|Iqc|)}. (|ωm|-ω0)(ω0<|ωm|)...(1)

Here, ω0: substrate speed

I0: excitation current at the substrate speed

K0: coefficient of increasing the exciting current when rotating at high speed

KIqC: coefficient of reduction of excitation current in response to torque current command

When the motor rotational speed ωm is substituted into the above equation (1) and the excitation current command IdCB before the magnetic field is weakened is visualized, the graph is as shown in FIG. 2 .

The value of the exciting current command IdCB before the magnetic field is weakened when the high-speed light load is rotated can be increased by the coefficient K0 at which the exciting current is increased at the time of high-speed rotation, and the stability of the motor current at the time of high-speed light load rotation can be improved. The optimal value of K0 can be obtained by experimenting with an error method or by simulation.

In addition, when the torque current command Iqc is increased, the excitation current command IdcC before the magnetic field is weakened is reduced by the coefficient KIqC in which the magnetic flux φ0 is decreased in response to the increase in the torque current command Iqc, and the commutation at the time of high-speed heavy load rotation can be suppressed. The saturation of the output voltage of the device.

The excitation current command calculator 135 obtains the magnetic field subtraction as described above. After the weak excitation current command IdCB, the excitation current command Idc is obtained by the following equation.

IdC=IdCB(0≦|ωm|≦ω0) IdC=IdCB. Ω0/|ωm|(ω0<|ωm|)...(2)

When the motor rotation speed ωm is substituted into the above equation (2) and the excitation current command IdC is visualized, the graph is as shown in FIG.

The excitation current command calculator 135 determines the excitation current command IdcC before the magnetic field is weakened by performing the calculation of the equation (1) in response to the motor rotation speed ωm, and then performs the equation (2) on the excitation current command IdcC before the magnetic field is weakened. In the calculation, the excitation current command IdC is output to the d-axis current controller 145.

[Action of Slip Frequency Calculator 150]

The slip frequency calculator 150 calculates the slip frequency command ωs from the torque current command IqC and the exciting current command Idc as shown in the following equation. The slip frequency command ωs is obtained by the following equation.

Ωs=R2/L2. (IqC/IdC)...(3)

R2: secondary resistance

L2: secondary inductance

[Operation of Motor Control Device 100]

First, the input torque current command IqC is compared with the q-axis current feedback IqF from the coordinate converter 125, and the q-axis voltage command VqC is obtained by the q-axis current controller 130.

On the other hand, the excitation current command calculator 135 uses the above-described equations (1) and (2) to generate the excitation current command IdC and the coordinate converter 125 from the motor rotation speed ωm and the torque current command IqC. The d-axis current feedback IdF is compared, and the d-axis current command 145 is used to obtain the d-axis voltage command VdC.

The slip frequency calculator 150 calculates the slip frequency command ωs from the torque current command IqC and the excitation power flow instruction IdC using the above equation (3). The slip frequency command ωs is added to the motor rotation speed ωm output from the speed calculator 115. The primary frequency command ω1 is obtained by the slip frequency command ωs and the motor rotational speed ωm. The stator position command θmc is obtained by integrating the primary frequency command ω1 with the integrator 155.

The coordinate converter 160 performs coordinate conversion on the q-axis voltage command VqC and the d-axis voltage command VdC based on the stator position command θmc, and obtains three-phase voltage commands Vuc, Vvc, and Vwc. The three-phase voltage commands Vuc, Vvc, and Vwc are supplied to the motor 180 through the PWM controller 165 and the power converter 170, and the motor 180 is driven in response to the three-phase voltage commands Vuc, Vvc, and Vwc.

The q-axis current feedback IqF and the d-axis current feedback IdF are obtained by coordinate conversion of the motor currents Iu and Iv by the coordinate converter 125 based on the stator position command θmc.

As described above, the excitation current command calculator 135 obtains a value that increases the excitation current in proportion to the difference between the motor rotation speed and the base speed, and performs field weakening based on the value. Further, in the field of field weakening, torque is applied. The current command Iqc proportionally reduces the magnetic flux. That is, the excitation current command calculator 135 is a high speed light load when rotating at a low speed and heavy load. The optimum excitation current command Idc is output during rotation and high speed heavy load rotation.

Therefore, according to the motor control device 100 according to the first embodiment, the stability of the core of the motor and the core offset of the encoder at the time of high-speed light load rotation can be achieved, and the inverter is derived from the high-speed heavy load rotation. The stability of the output voltage saturation. Therefore, it is possible to achieve both the stability at the time of high-speed light-load rotation and the stability at the time of high-speed heavy-duty rotation, and it is possible to realize a machine tool that realizes a wide range of fixed output fields and combines low-speed heavy cutting and high-speed cutting.

Incidentally, the motor control device 100 according to the first embodiment may be provided with a non-dry controller for the system that outputs the q-axis voltage command VqC and the d-axis voltage command VdC, and controls the d-axis and the q-axis to dry. In addition, the inside of the d-axis and q-axis current control system can also be constructed by a three-phase current control system.

[Embodiment 2]

[Overall Configuration of Motor Control Device 200]

Fig. 4 is a block diagram showing a motor control device 200 according to the second embodiment. The motor control device 200 according to the second embodiment is provided with a magnetic flux controller and a magnetic flux calculator in the configuration of the motor control device 100 according to the first embodiment, and a magnetic flux command calculator is provided instead of the excitation current command calculator 135.

The motor control device 200 has a q-axis current controller 230 as a system for issuing the q-axis voltage command VqC. The q-axis current controller 230 is the same as the q-axis current controller 130 of the first embodiment.

Further, the motor control device 200 has a magnetic flux command calculator 220, a magnetic flux controller 240, and a d-axis current controller 245 as a system for issuing the d-axis voltage command VdC.

The magnetic flux command calculator 220 inputs the input torque current command IqC and the motor rotational speed ωm, and calculates an optimum magnetic flux command φ2C for widening the output field. Incidentally, the detailed operation of the magnetic flux command calculator 220 is described later.

The magnetic flux controller 240 is a magnetic flux deviation input obtained by subtracting the magnetic flux φ2 from the magnetic flux command φ2C output from the magnetic flux command calculator 220, and calculates a d-axis current command Idc. The magnetic flux φ2 is output by the magnetic flux calculator 235. The magnetic flux controller 240 is constructed with a proportional integral controller.

The magnetic flux calculator 235 calculates the magnetic flux φ2 by using the d-axis current feedback IdF output from the coordinate converter 225. The detailed action of the magnetic flux calculator 235 is stated later.

The d-axis current controller 245 is a current deviation input obtained by subtracting the d-axis current feedback IdF from the d-axis current command Id output from the magnetic flux controller 240, and calculates a d-axis voltage command VdC. The d-axis current feedback IdF is output by the coordinate converter 225. The d-axis current feedback IdF is obtained by coordinate conversion of the motor currents Iu and Iv by the coordinate converter 225 based on the stator position command θmc to be described later. The d-axis current controller 245 is constructed with a proportional integral controller.

Further, the motor control device 200 has a slip frequency calculator 250, an integrator 255, an OSC 257, and coordinate converters 225 and 260 as a system for performing coordinate conversion.

Slip frequency calculator 250 is the input torque current command The IqC is input to the magnetic flux φ2 outputted from the magnetic flux calculator 235, and the slip frequency command ωs is calculated. Incidentally, the detailed action of the slip frequency calculator 250 is described later.

The integrator 255, the OSC 257, and the coordinate converters 225 and 260 are the same as the integrator 155, the OSC 157, and the coordinate converters 125 and 160 of the first embodiment.

Furthermore, the motor control device 200 has a PWM controller 265 and a power converter 270 as a system for driving the motor 280. The PWM controller 265 and the power converter 270 are the same as the PWM controller 165 and the power converter 170 of the first embodiment. Incidentally, the motor drive unit is formed by the PWM controller 265, the power converter 270, the q-axis current controller 230, the d-axis current controller 245, and the coordinate converter 260.

[Operation of Magnetic Flux Command Controller 220]

As described above, the magnetic flux command calculator 220 is the best magnetic flux command φ2C for calculating the widened output field.

Fig. 5 is a view showing the relationship between the motor rotational speed ωm in the magnetic flux command calculator 220 of Fig. 4 and the magnetic flux command φ2CB before the magnetic field is weakened. The magnetic flux command calculator 220 is a magnetic flux command φ2CB before the magnetic field weakening corresponding to the motor rotational speed ωm. In addition, FIG. 6 is a view showing a relationship between the motor rotational speed ωm and the magnetic flux command φ2C in the magnetic flux command calculator 220 of FIG. The magnetic flux command calculator 220 is a magnetic flux command φ2C corresponding to the motor rotational speed ωm.

5 and 6 show the torque rotation command ωm with respect to the motor rotation speed ωm when the torque current command IqC is 0 (IqC0), rated (IqCR), and maximum (IqCmax). Magnetic flux command characteristic of magnetic flux φ0. Fig. 5 is a view showing a magnetic flux command φ2CB before the magnetic field is weakened, and Fig. 6 is a view showing a magnetic flux command φ2C.

As shown in FIG. 5, the magnetic flux command φ2CB before the magnetic field is weakened is not changed by the magnetic flux φ0 from 0 to ω0. When the motor rotation speed exceeds ω0, when the torque current command IqC is 0 (IqC0), the magnetic flux command φ2CB rises from the magnetic flux φ0 with a constant slope. When the torque current command IqC is rated (IqCR), the degree of rise is smaller than when the torque current command IqC is 0 (IqC0). When the torque current command IqC is maximum (IqCmax), regardless of the motor rotation speed ωm, the magnetic flux command φ2CB is maintained without changing the magnetic flux φ0.

Further, as shown in FIG. 6, the magnetic flux command φ2C does not change the motor rotational speed ωm from 0 to ω0 while maintaining the magnetic flux φ0. When the motor rotation speed exceeds ω0, when the torque current command IqC is maximum (IqCmax), the magnetic flux command φ2C is decreased in inverse proportion to the motor rotation speed ωm from the magnetic flux φ0. When the torque current command IqC is rated (IqCR), the degree of decrease is smaller than when the torque current command IqC is maximum (IqCmax). When the torque current command IqC is 0 (IqC0), the degree of decrease is smaller than when the torque current command IqC is rated (IqCR).

The magnetic flux command calculator 220 obtains the magnetic flux command φ2CB before the magnetic field is weakened by the following equation.

φ2CB=φ0(0≦|ωm|≦ω0)φ2CB={φ0+K0. (1-KIqC.|Iqc|)}. (|ωm|-ω0)(ω0<|ωm|)...(4)

Here, ω0: substrate speed

Φ0: magnetic flux at the substrate speed

K0: coefficient of increase in magnetic flux when rotating at high speed

KIqC: Coefficient of magnetic flux reduction in response to torque current command

When the motor rotation speed ωm is substituted into the above equation (1) and the magnetic flux command φ2CB is visualized, the graph is as shown in FIG.

The value of the magnetic flux command φ2CB when the high-speed light load is rotated can be increased by the coefficient K0 at which the magnetic flux is increased at the time of high-speed rotation, and the stability of the motor current at the time of high-speed light load rotation can be improved. The optimal value of K0 can be obtained by experimenting with an error method or by simulation.

In addition, when the torque current command Iqc is increased, the magnetic flux command φ2CB is made smaller by the coefficient KIqC in which the magnetic flux φ0 is decreased in response to the increase in the torque current command Iqc, and the saturation of the inverter output voltage during high-speed heavy load rotation can be suppressed. .

The magnetic flux command calculator 220 obtains the magnetic flux command φ2C by the following equation after obtaining the magnetic flux command before the magnetic field weakening as described above.

φ2C=φ2CB (when 0≦|ωm|≦ω0) φ2C=φ2CB. Ω0/|ωm|(ω0<|ωm|)...(5)

When the motor rotation speed ωm is substituted into the above equation (4) and the magnetic flux command φ2C is visualized, the graph is as shown in FIG.

The magnetic flux command calculation unit 220 calculates the magnetic flux command φ2CB before the magnetic field is weakened by performing the calculation of the equation (4) in response to the motor rotation speed ωm, and then calculates the magnetic flux command φ2CB by the equation (5), and the magnetic flux command φ2C. Output to the magnetic flux controller 240.

[The action of the slip frequency calculator 250]

The slip frequency calculator 250 calculates the slip frequency command ωs from the torque current command IqC and the magnetic flux φ2C as shown by the following equation. The slip frequency command ωs is obtained by the following equation.

Ωs=M. R2/L2. (Iqc/φ2)...(6)

R2: secondary resistance

Φ2: secondary magnetic flux

L2: secondary inductance

M: mutual inductance

[Operation of Magnetic Flux Calculator 235]

The magnetic flux calculator 235 obtains the magnetic flux φ2 from the d-axis current feedback IdF as shown by the following equation.

Φ2=1/(1+L2/R2.S). M. IdF...(7)

S: slip

IdF: q-axis current feedback

[Operation of Motor Control Device 200]

First, the input torque current command IqC is compared with the q-axis current feedback IqF from the coordinate converter 225, and the q-axis voltage command VqC is obtained by the q-axis current controller 230.

On the other hand, the magnetic flux command is issued with the magnetic flux command φ2C. The magnetic flux calculated by the motor rotation speed ωm and the torque current command IqC by the calculator 220 using the above equations (4) and (5), and the magnetic flux calculated by the magnetic flux calculator 235 using the above equation (7). The φ2 comparison is obtained by the magnetic flux controller 240 to obtain the d-axis current command IdC. The d-axis current command IdC is compared with the d-axis current feedback IdF from the coordinate converter 225, and the d-axis current command 245 is used to obtain the d-axis voltage command VdC.

The slip frequency calculator 250 calculates the slip frequency command ωs from the torque current command IqC and the magnetic flux φ2 using the above equation (6). The slip frequency command ωs is added to the motor rotational speed ωm output from the speed calculator 215. The primary frequency command ω1 is obtained by the slip frequency command ωs and the motor rotational speed ωm. The stator position command θmc is obtained by integrating the primary frequency command ω1 with the integrator 255.

The coordinate converter 260 performs coordinate conversion on the q-axis voltage command VqC and the d-axis voltage command VdC based on the stator position command θmc, and obtains three-phase voltage commands Vuc, Vvc, and Vwc. The three-phase voltage commands Vuc, Vvc, and Vwc are supplied to the motor 280 through the PWM controller 265 and the power converter 270, and the motor 280 is driven in response to the three-phase voltage commands Vuc, Vvc, and Vwc.

The q-axis current feedback IqF and the d-axis current feedback IdF are obtained by coordinate conversion of the motor currents Iu and Iv by the coordinate converter 225 based on the stator position command θmc.

As described above, the magnetic flux command calculator 220 obtains a value that increases the magnetic flux in proportion to the difference between the motor rotational speed and the base speed, and performs magnetic field weakening based on the value. Further, in the field of magnetic field weakening, the torque current command is used. Iqc proportionally reduces the magnetic flux. That is, the magnetic flux The command calculator 220 outputs an optimum magnetic flux command φ2C at the time of low speed heavy load rotation, high speed light load rotation, and high speed heavy load rotation.

Therefore, according to the motor control device 200 according to the second embodiment, the same effects as those of the motor control device 100 according to the first embodiment can be obtained.

Incidentally, the motor control device 200 according to the second embodiment may be configured to provide a non-dry controller for the system that outputs the q-axis voltage command VqC and the d-axis voltage command VdC, and controls the d-axis and the q-axis to dry. In addition, the inside of the d-axis and q-axis current control system can also be constructed by a three-phase current control system.

[Embodiment 3]

[Overall Configuration of Motor Control Device 300]

Fig. 7 is a block diagram showing a motor control device 300 according to the third embodiment. The motor control device 300 according to the third embodiment is configured by adding a maximum primary current command calculator, a torque limit value calculator, a limiter, and a q-axis current calculator to the configuration of the motor control device 200 according to the second embodiment.

The motor control device 300 has a q-axis current controller 330, a maximum primary current command calculator 375, a torque limit value calculator 385, a limiter 390, and a q-axis current calculator 395 as a system for issuing the q-axis voltage command VqC. The q-axis current controller 330 is the same as the q-axis current controller 230 of the second embodiment.

The maximum primary current command calculator 375 calculates the maximum value of the primary current command supplied to the motor 380, and outputs it to the torque limit value calculator 385 with the maximum primary current command IPC.

The torque limit value calculator 385 is a d-axis current command IdC outputted by the magnetic flux controller 340 and a maximum primary current command IPC calculation torque limit value TLIM. Incidentally, the detailed action of the torque limit value calculator 385 is described later.

The limiter 390 inputs the torque limit value TLIM calculated by the torque limit value calculator 385, and limits the value of the torque command TCB to ±TLIM.

The q-axis current calculator 395 calculates the q-axis current IqC using the torque command TCB input through the limiter 390.

Further, the motor control device 300 has a magnetic flux command calculator 320, a magnetic flux controller 340, and a d-axis current controller 345 as a system for issuing the d-axis voltage command VdC.

The magnetic flux command calculator 320 inputs the torque command ratio TCC and the motor rotational speed ωm obtained by dividing the absolute value of the torque command TCB by the maximum torque TCBm, and calculates the optimum magnetic flux command φ2C for widening the output field. . The maximum torque TCBm is obtained from the motor rotational speed ωm output from the speed calculator 315. The maximum torque TCBm is a torque obtained by reducing the maximum torque Tm in inverse proportion to the rotational speed of the base speed ω0 or more. Incidentally, the detailed operation of the magnetic flux command calculator 320 is described later.

The magnetic flux controller 340 and the d-axis current controller 345 are the same as the magnetic flux controller 240 and the d-axis current controller 245 of the second embodiment.

Furthermore, the motor control device 300 has a slip frequency calculator 350, an integrator 355, an OSC 357, and coordinate converters 325 and 360. For the system of coordinate conversion. The slip frequency calculator 350, the integrator 355, the OSC 357, and the coordinate converters 325 and 360 are the same as the slip frequency calculator 250, the integrator 255, the OSC 257, and the coordinate converters 225 and 260 of the second embodiment.

Furthermore, the motor control device 300 has a PWM controller 365 and a power converter 370 as a system for driving the motor 380. The PWM controller 365 and the power converter 370 are the same as the PWM controller 265 and the power converter 270 of the second embodiment. Incidentally, the motor drive unit is formed by the PWM controller 365, the power converter 370, the q-axis current controller 330, the d-axis current controller 345, and the coordinate converter 360.

[Operation of Magnetic Flux Command Calculator 320]

As described above, the magnetic flux command calculator 320 is the best magnetic flux command φ2C for calculating the wide range of output fields.

Fig. 8 is a view showing the relationship between the motor rotational speed ωm in the magnetic flux command calculator 320 of Fig. 7 and the magnetic flux command φ2CB before the magnetic field is weakened. The magnetic flux command calculator 320 is a magnetic flux command φ2CB before the magnetic field weakening corresponding to the motor rotational speed ωm. In addition, FIG. 9 is a view showing the relationship between the motor rotational speed ωm and the magnetic flux command φ2C in the magnetic flux command calculator 320 of FIG. The magnetic flux command calculator 320 is a magnetic flux command φ2C corresponding to the motor rotational speed ωm.

8 and 9 are magnetic flux command characteristics showing the magnetic flux φ0 with respect to the motor rotational speed ωm when the torque command ratio is 0 (TCC0), rated (TCCR), and maximum (TCCmax). Fig. 8 is a view showing a magnetic flux command φ2CB before the magnetic field is weakened, and Fig. 9 is a view showing a magnetic flux command φ2C.

As shown in Fig. 8, the magnetic flux command φ2CB before the magnetic field is attenuated is maintained at the motor rotational speed ωm from 0 to ω0 while maintaining the magnetic flux φ0. When the motor rotation speed exceeds ω0, when the torque command ratio TCC is 0 (TCC0), the magnetic flux command φ2CB rises from the magnetic flux φ0 with a constant slope. When the torque command ratio TCC is rated (TCCR), the degree of rise is smaller than when the torque command ratio TCC is 0 (TCC0). When the torque command ratio TCC is maximum (TCCmax), the motor rotation speed ωm is not related, and the magnetic flux command φ2CB is maintained without changing the magnetic flux φ0.

Further, as shown in FIG. 9, the magnetic flux command φ2C does not change when the motor rotational speed ωm is from 0 to ω0 while maintaining the magnetic flux φ0. When the motor rotation speed exceeds ω0, when the torque command ratio TCC is maximum (TCCmax), the magnetic flux command φ2C is decreased in inverse proportion to the motor rotation speed ωm from the magnetic flux φ0. When the torque command is rated (TCCR), the degree of decrease is smaller than when the torque command is greater than TCC (TCCmax). When the torque command ratio TCC is 0 (TCC0), the degree of decrease is smaller than when the torque command is TCC rated (TCCR).

First, the torque command input from the magnetic flux command calculator 320 is obtained as follows.

The maximum torque TCBm is obtained using the motor rotational speed ωm output from the speed calculator 315.

TCBm=Tm(0≦|ωm|≦ω0)TCBm=Tm. Ω0/|ωm|(ω0<|ωm|)...(8)

Next, the torque command ratio TCC is obtained.

TCC=|TCB|/TCBm

The magnetic flux command calculator 320 obtains the magnetic flux command φ2CB before the magnetic field is weakened by the following equation.

φ2CB=φ0(0≦|ωm|≦ω0)φ2CB={φ0+K0. (1-KTC.TCC)}. (|ωm|-ω0)(ω0<|ωm|)...(9)

Here, ω0: substrate speed

Φ0: magnetic flux at the substrate speed

K0: coefficient of increase in magnetic flux when rotating at high speed

KTC: coefficient of magnetic flux reduction in response to torque command ratio

When the motor rotation speed ωm is substituted into the above equation (9) and the magnetic flux command φ2CB is visualized, the graph is as shown in FIG.

The value of the magnetic flux command φ2CB when the high-speed light load is rotated can be increased by the coefficient K0 at which the magnetic flux is increased at the time of high-speed rotation, and the stability of the motor current at the time of high-speed light load rotation can be improved. The optimal value of K0 can be obtained by experimenting with an error method or by simulation.

Further, by the coefficient KTC which reduces the magnetic flux φ0 in response to the increase in the torque command ratio TCC, if the torque command becomes larger than the TCC, the magnetic flux command φ2CB is made smaller, and the saturation of the inverter output voltage at the time of high-speed heavy load rotation can be suppressed. .

The magnetic flux command calculator 320 obtains the weakening of the magnetic field as described above. After the previous magnetic flux command, the magnetic flux command φ2C is obtained by the following equation.

φ2C=φ2CB (when 0≦|ωm|≦ω0) φ2C=φ2CB. Ω0/|ωm|(ω0<|ωm|)...(10)

When the motor rotation speed ωm is substituted into the above equation (10) and the magnetic flux command φ2C is visualized, the graph is as shown in FIG.

The magnetic flux command calculation unit 320 calculates the magnetic flux command φ2CB before the magnetic field is weakened by performing the calculation of the equation (9) in response to the motor rotation speed ωm, and then calculates the magnetic flux command φ2CB by the equation (10), and the magnetic flux command φ2C. Output to the magnetic flux controller 340.

[Action of Slip Frequency Calculator 350]

The slip frequency calculator 350 calculates the slip frequency command ωs from the torque current command Iqc and the magnetic flux φ2C using the above equation (6) in the same manner as the slip frequency calculator 250 of the second embodiment.

[Operation of Magnetic Flux Calculator 335]

Similarly to the magnetic flux calculator 235 of the second embodiment, the magnetic flux calculator 335 obtains the magnetic flux φ2 from the d-axis current feedback IdF using the above equation (7).

[Operation of Torque Limit Value Calculator 385]

The torque limit value calculator 385 calculates the torque limit value TLIM from the d-axis current command IdC and the maximum primary current command IPC using the following equation.

TLIM=Pm. M/L2. Φ2. (IPC2-IdC2)1/2...(11)

Here, Pm is the pole number of the motor 380

[Action of q-axis current calculator 395]

The q-axis current calculator 395 obtains the torque command after the torque limit through the limiter 390, and obtains the q-axis current command IqC using the following equation.

IqC=L2/(Pm.M.φ2). (Torque command after torque limitation)...(12)

[Operation of Motor Control Device 300]

The input torque command TCB is limited by the limiter 390 within the torque limit value TLIM and is output to the q-axis current calculator 395. The q-axis current calculator 395 calculates the q-axis current command IqC based on the torque command TCB after the torque limit. The q-axis current command IqC is compared with the q-axis current feedback IqF from the coordinate converter 325, and the q-axis voltage command VqC is obtained by the q-axis current controller 330. Incidentally, the torque limit value TLIM for limiting the value of the torque command TCB by the limiter 390 is calculated by the torque limit value calculator 385 using the above equation (11).

On the other hand, the magnetic flux command φ2C is used to generate the magnetic flux calculated by the motor rotation speed ωm and the torque command ratio TCC using the above equations (9) and (10), and the magnetic flux calculator 335 is used. The magnetic flux controller 340 obtains the d-axis current command IdC by comparing the magnetic flux φ2 calculated by the above equation (7). The d-axis current command IdC is compared with the d-axis current feedback IdF from the coordinate converter 325, and the d-axis current command 345 is used to determine the d-axis voltage command VdC.

The slip frequency calculator 350 is twisted using the above equation (6) The slip current command IqC and the magnetic flux φ2 calculate the slip frequency command ωs. The slip frequency command ωs is added to the motor rotational speed ωm output from the speed calculator 315. The primary frequency command ω1 is obtained by the slip frequency command ωs and the motor rotational speed ωm. The stator position command θmc is obtained by integrating the primary frequency command ω1 with the integrator 355.

The coordinate converter 360 performs coordinate conversion on the q-axis voltage command VqC and the d-axis voltage command VdC based on the stator position command θmc, and obtains three-phase voltage commands Vuc, Vvc, and Vwc. The three-phase voltage commands Vuc, Vvc, and Vwc are supplied to the motor 380 through the PWM controller 365 and the power converter 370, and the motor 380 is driven in response to the three-phase voltage commands Vuc, Vvc, and Vwc.

The q-axis current feedback IqF and the d-axis current feedback IdF are obtained by coordinate conversion of the motor currents Iu and Iv by the coordinate converter 325 based on the stator position command θmc.

As described above, the magnetic flux command calculator 320 obtains a value that increases the magnetic flux in proportion to the difference between the motor rotational speed and the base speed, and performs magnetic field weakening based on the value. Further, in the field of magnetic field weakening, the torque current command is used. Iqc proportionally reduces the magnetic flux. That is, the magnetic flux command calculator 320 outputs the optimum magnetic flux command φ2C at the time of low speed heavy load rotation, high speed light load rotation, and high speed heavy load rotation.

Therefore, according to the motor control device 300 according to the third embodiment, the same effects as those of the motor control device 100 according to the first and second embodiments can be obtained.

Incidentally, the motor control device 300 according to the third embodiment may also output the q-axis voltage command VqC and the d-axis voltage command VdC. Set up a non-dry controller to control the d-axis and q-axis dry. In addition, the inside of the d-axis and q-axis current control system can also be constructed by a three-phase current control system.

100‧‧‧Motor control unit

110‧‧‧Encoder

115‧‧‧Speed Calculator

125‧‧‧Coordinate Converter

130‧‧‧q axis current controller

135‧‧‧Excitation current command calculator

145‧‧‧d axis current controller

150‧‧‧ slip frequency calculator

155‧‧‧ integrator

157‧‧‧OSC

160‧‧‧Coordinate converter

165‧‧‧PWM controller

170‧‧‧Power Converter

180‧‧‧ motor

Claims (18)

A motor control device includes: an excitation current command calculator that recognizes a rotational load state of a motor using a torque current command and a motor rotational speed, calculates an excitation current command corresponding to the rotational load state; and a motor drive unit that uses the torque current command The motor is driven by a calculated excitation current command. The motor control device of claim 1, wherein the excitation current command calculator has a magnetic field weakening function that is inversely proportional to an increase in a rotational speed of the motor to reduce an excitation current command, and the motor is commanded to rotate at a high speed with a small torque current. The excitation current command is greater than the excitation current command under the magnetic field weakening function. On the other hand, when the motor is rotated at a high torque with a large torque current command, the excitation current command is equivalent to the excitation current command under the magnetic field attenuation function. . The motor control device according to claim 1 or 2 further includes a coordinate converter that obtains q-axis current feedback and d-axis current feedback by coordinate conversion of a current supplied to the motor, wherein the motor drive unit is used from the foregoing The torque current command subtracts the value of the q-axis current feedback and subtracts the value of the d-axis current feedback from the excitation current command to determine the power for driving the motor. The motor control device of claim 3, further comprising a slip frequency calculator for calculating a slip frequency command by the torque current command and the excitation current command calculated by the excitation current command calculator, wherein the coordinates are rotated The converter performs coordinate conversion on the current supplied to the motor using the slip frequency command calculated by the slip frequency calculator. The motor control device according to claim 4, wherein the excitation current command calculator first obtains an excitation current command IdCB before the magnetic field is weakened by the following formula: IdCB=I0 (when 0≦|ωm|≦ω0) IdcB ={I0+K0‧(1-KIqC‧|Iqc|)}‧(|ωm|-ω0)(ω0<|ωm|) Here, ω0: substrate speed I0: excitation current K0 at the base speed: Coefficient of increase in excitation current during high-speed rotation KIqC: Coefficient of reduction of excitation current in response to torque current command. Next, after obtaining the excitation current command IdCB before the magnetic field is weakened, the excitation current command Idc is obtained by the following equation: IdC=IdCB (when 0 ≦|ωm|≦ω0) IdC=IdCB‧ω00/|ωm|(ω0<|ωm|) The excitation current command IdC is obtained by performing the above calculation. A motor control device includes: a magnetic flux command calculator that recognizes a rotational load state of a motor using a torque current command and a motor rotational speed, and calculates a magnetic flux command corresponding to the rotational load state; The magnetic flux controller obtains an excitation current command using a magnetic flux calculated from a current supplied to the motor and a magnetic flux command calculated by the magnetic flux command calculator, and the motor drive unit uses the torque current command and the obtained excitation current. The aforementioned motor is driven by an instruction. The motor control device of claim 6, wherein the magnetic flux command calculator has a magnetic field weakening function that is inversely proportional to an increase in a rotational speed of the motor to reduce a magnetic flux command, and the motor is caused to rotate at a high speed with a small torque current command. The magnetic flux command is larger than the magnetic flux command under the magnetic field weakening function. On the other hand, when the motor is rotated at a high speed with a large torque current command, the magnetic flux command is equivalent to the magnetic flux command under the magnetic field weakening function. The motor control device according to claim 6 or 7, wherein the magnetic flux obtained by the current supplied to the motor is obtained by a magnetic flux calculator that returns a d-axis current obtained by coordinate-converting a current supplied to the motor. The motor control device of claim 8 further includes a slip frequency calculator for calculating a slip frequency command by the torque current command and the magnetic flux calculated by the magnetic flux calculator. A motor control device according to claim 8, wherein said d-axis current feedback is obtained by a coordinate converter that performs coordinate conversion on a current supplied to said motor, said coordinate converter performing coordinate conversion on a current supplied to said motor The q-axis current feedback is also obtained. The motor control device of claim 10, wherein the motor drive unit is The power for driving the motor is obtained by subtracting the value of the q-axis current feedback from the torque current command and subtracting the value of the d-axis current feedback from the excitation current command. The motor control device according to claim 11, wherein the magnetic flux command calculator first obtains a magnetic flux command φ2CB before the magnetic field is weakened by the following formula: φ2CB=φ0 (when 0≦|ωm|≦ω0) φ2CB={ Φ0+K0‧(1-KIqC‧|Iqc|)}‧(|ωm|-ω0)(ω0<|ωm|) Here, ω0: base velocity φ0: magnetic flux K0 at the base speed: when rotating at high speed The coefficient of the magnetic flux increase KIqC: the coefficient of the magnetic flux reduction in response to the torque current command. Then, after obtaining the magnetic flux command φ2CB before the magnetic field is weakened, the magnetic flux command φ2C is obtained by the following equation: φ2C=φ2CB (0≦| Ωm|≦ω0) φ2C=φ2CB. When ω0/|ωm|(ω0<|ωm|), the magnetic flux command φ2C is obtained by performing the above calculation. A motor control device having a magnetic flux command calculator obtained by dividing a torque torque command issued by a maximum torque obtained by using a motor rotational speed a torque command ratio, a rotational speed of the motor, a rotational load state of the motor, and a magnetic flux command corresponding to the rotational load state; and a magnetic flux controller that uses a magnetic flux obtained from a current supplied to the motor and the magnetic flux command calculator The excitation current command is obtained from the calculated magnetic flux command, and the motor drive unit drives the motor using the torque current command and the obtained excitation current command. The motor control device of claim 13, wherein the magnetic flux command calculator has a magnetic field weakening function that is inversely proportional to an increase in a rotational speed of the motor to reduce a magnetic flux command, and the motor is caused to rotate at a high speed with a small torque current command. The magnetic flux command is larger than the magnetic flux command under the magnetic field weakening function. On the other hand, when the motor is rotated at a high speed with a large torque current command, the magnetic flux command is equivalent to the magnetic flux command under the magnetic field weakening function. The motor control device according to claim 13 or 14, wherein the magnetic flux obtained by the current supplied to the motor is obtained by a magnetic flux calculator that returns a d-axis current obtained by coordinate-converting a current supplied to the motor. The motor control device according to claim 15 further comprising: a limiter that limits the torque command to a predetermined value; and a q-axis current calculator that inputs the torque command limited by the limiter and outputs the q-axis current command. The motor driving unit obtains a value obtained by subtracting the q-axis current feedback from a q-axis current command output from the q-axis current calculator and subtracting the value of the d-axis current feedback from the excitation current command. The power of the aforementioned motor. The motor control device according to claim 16 further includes the excitation current command outputted by the magnetic flux controller, the maximum primary current command outputted by the maximum primary current command calculator, and the magnetic flux output from the magnetic flux calculator, thereby calculating the limiter setting. A torque limit value calculator for torque limit value, wherein the limiter limits a torque command input to the q-axis current calculator to a constant value using a torque limit value output by the torque limit value calculator. The motor control device according to claim 17, wherein the torque command input TTC of the magnetic flux command calculator is obtained as follows: TCBm = Tm (0 ≦ | ωm | ≦ ω 0) TCBm = Tm. Ω0/|ωm|(ω0<|ωm|) Next, the torque command ratio TCC:TCC=|TCB|/TCBm is obtained. The magnetic flux command calculator obtains the magnetic flux command before the magnetic field weakening by the following equation. φ2CB: φ2CB=φ0 (when 0≦|ωm|≦ω0) φ2CB={φ0+K0. (1-KTC.TCC)}. (|ωm|-ω0)(ω0<|ωm|) Here, ω0: substrate velocity φ0: magnetic flux at the substrate speed K0: coefficient KTC for increasing the magnetic flux at the time of high-speed rotation: a coefficient for reducing the magnetic flux in response to the torque command ratio. Then, after obtaining the magnetic flux command φ2CB before the magnetic field is weakened, the magnetic flux command φ2C: φ2C is obtained by the following equation. =φ2CB(0≦|ωm|≦ω0)φ2C=φ2CB. When ω0/|ωm|(ω0<|ωm|), the magnetic flux command φ2C is obtained by performing the above calculation.