JP3019653B2 - Control device for AC motor and method for measuring constants of AC motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an AC motor including an auto-tuning function for automatically measuring a motor constant and an inertia moment of a load including a motor using an inverter device for controlling an AC motor at a variable speed. Furthermore, the primary of the AC motor to be used as control constants in speed sensorless vector control such self-inductance L ₁ of the measurement method and a control device.

[0002]

2. Description of the Related Art General-purpose inverters for controlling an induction motor at a variable speed are required to have high starting torque at low speeds and to improve speed control characteristics. To address this, without using a speed sensor, and controls the induced voltage E _m of the induction motor constant,
2. Description of the Related Art Sensorless vector control in which a slip frequency proportional to a torque current is given to control a speed is becoming widespread. In such control, for performing induced voltage E _m constant control, it is necessary to determine the primary voltage by compensating for the voltage drop across the primary side impedance, primary resistance r _1, the synthesis leakage inductance (l ₁ + l _2), it is necessary to set the motor constants of the primary self-inductance L _1. In general-purpose inverters, it is also required to operate motors whose motor constants are unknown, such as domestic and foreign motors, as loads. in this case,
Before the normal operation, various motor constants are measured using an inverter, the values are set as control constants, and operation is performed as sensorless vector control. Although no specific example of such a conventional control device is found, for example, Japanese Patent Application Laid-Open No. 60-183953 and a document (automatic measurement of motor constants for speed sensorless vector control: 1992 From the competition No. 619), it is generally considered that immediately after measuring the motor constant, sensorless vector control operation is performed using the measured value as a control constant.

[0003] Next, among various motor identification, the conventional system is automatic measurement literature (speed sensorless vector control for the motor constant as one measure of the measurement item is a primary self-inductance L _1: 1992 Electrical National Conference No.
As described in 619), steady operation is performed with the motor alone (no-load condition), and L is determined from the motor terminal voltage and the no-load current.
₁ is calculated and measured.

On the other hand, a method capable of measuring even under a load condition is described in Japanese Patent Application Laid-Open No. 61-92185. this is,
Equipped with a motor terminal voltage detector, detects the induced voltage vector, controls the primary frequency so that this secondary interlinkage magnetic flux direction becomes zero, and calculates and measures the output of the motor terminal voltage detector and the motor current detection value. ing.

[0005]

In the case where the conventional control device detects a current or voltage including an error due to an abnormality in the motor current detector or the like, the measured motor constant value includes a large error. When the speed sensorless vector control operation is performed, the speed and torque control characteristics are considered to be deteriorated. When various motors are driven, the performance may be better when the motor is operated with the motor constant design value than the motor constant measured value. In such a situation, the conventional control device is considered to pose a problem in terms of improvement in usability and reliability because there is no means for judging an abnormality in the motor constant measurement result and no means for avoiding the abnormality.

[0006] Next, as a conventional method of measuring the primary self-inductance, the method described in the above-mentioned literature is as follows.
There is a problem that measurement cannot be performed under load. For this reason, there is a problem that measurement is difficult in an application to which various loads are connected, such as a general-purpose inverter.

On the other hand, in the conventional example described in Japanese Patent Application Laid-Open No. 61-92185, it can be measured in a load state, but it is necessary to measure in a state in which the secondary flux linkage component of the induced voltage vector is zero. For this reason, it is necessary to detect the motor terminal voltage with an AC amount and convert the three-phase AC amount into a DC amount to measure the magnetic terminal direction component in order to detect the magnetic flux direction component of the induced voltage vector. There is a problem that there is. Therefore, there is a problem that the primary self-inductance cannot be measured in a general-purpose inverter or the like having no voltage detector on the inverter output side.

Accordingly, a first object of the present invention is to provide a control device for performing automatic tuning, which can judge an abnormality in a motor constant measurement result and can easily avoid an abnormal condition, and furthermore, improve the reliability of the control device. Another object of the present invention is to provide a control device for an AC motor that is easy to use.

A second object of the present invention is to provide a method and an apparatus for accurately calculating and measuring the primary self-inductance using a voltage-source inverter without using an inverter output voltage detector, regardless of the size of a load. It is in.

[0010]

As means for achieving the first object, there are two or more types including a normal operation mode for performing speed sensorless vector control and an auto tuning mode for performing motor constant measurement and inertia moment measurement. The operation mode selection means for selecting the operation mode is provided so that the operation mode can be arbitrarily set. Further, by turning on the operation start switch in a state where the operation mode is selected, the operation corresponding to various operation modes is performed, and the operation is terminated for each operation mode. Also,
In the auto-tuning operation mode, various motor constants and moments of inertia of the load are measured and displayed, so that it is possible to visually determine whether or not the measured data is correct. Next, there is provided a motor control constant selection means for switching between a motor constant design value and an inertia moment set value set for each application, and a motor constant and a load inertia moment measured value measured in the auto tuning mode. I made it possible. Further, when speed sensorless vector control is performed in the normal operation mode, the motor is operated with the motor constant and the inertia moment set by the motor control constant selection means as control constants.

Next, as means for achieving the second object, first, Japanese Patent Application No. 4-208776 and Japanese Patent Application No.
The method which is described in 46147 JP measures advance primary resistance r ₁ and synthetic leakage inductance Lx. Next, based on the primary angular frequency command value ω ₁ and the primary voltage command value V _1c of the inverter, the inverter is driven to operate the AC motor in a steady state, and the primary angular frequency command at this time is integrated. From the phase and the detected current value of the AC motor, the component of the motor current vector I _{1 in} the inverter primary voltage vector direction is obtained.
(Active power component current Iq) and a direction component delayed by 90 ° from the inverter primary voltage vector direction (reactive power component current Iq).
d), and calculates the electric motor based on the primary angular frequency command value ω ₁ and the primary voltage command value V _1c (or the primary voltage detection value V ₁ ), the active power component current Iq, and the reactive power component current Id. the primary self-inductance L ₁ was set to computed measure. Specifically, calculation and measurement are performed using the following equation as a basic equation.

[0012]

(Equation 2)

Here, r ₁ is a primary resistance measured by DC excitation before L ₁ measurement, and Lx is a combined leakage inductance measured by AC excitation.

[0014]

[Function] When the operation start switch is turned on while the operation mode selection means is set to the auto tuning mode, the Japanese Patent Application No.
As described in Japanese Patent Application Laid-Open No. 4-246147, first, an induction motor is AC-excited by an inverter, and primary and secondary combined resistances (r ₁ + r ₂ ) and a combined leakage inductance Lx are measured. Next, to measure the primary resistance r ₁ by DC excitation as described in Japanese Patent Application No. Hei 4-208776. Thereafter, measuring the primary self-inductance L ₁ by steady operation. Also,
Next, the inertia moment of the load is measured by performing acceleration / deceleration operation. After displaying these measured values, the mode is switched to the normal operation mode, and the motor control constant selection means is set to the measured values, and the operation is terminated. Therefore, it is visually determined whether or not the measured data is correct. If the measured data is correct, the operation start switch is turned on in the normal operation mode, and the speed sensorless vector control is performed using the measured data as a control constant. On the other hand, when it is determined that there is an error in the measurement data, the operation is switched to the design value data by the motor control constant selection means and the operation is started. Thereby, speed sensorless vector control can be performed based on the motor constant design value. As described above, the vector control can be performed by switching to the design value data, for example, when there is an error in the motor constant measured in the auto-tuning mode. In addition, usability is improved.

Next, the primary self inductance L of the motor
V ₁ for controlling a substantially constant ratio of the inverter primary voltages V ₁ and the primary frequency f ₁ in the means for computing measuring ₁
Accelerates by / f ₁ constant control and performs steady operation near the rated frequency. In this case, based on the phase of the primary voltage vector obtained by integrating the primary frequency command value omega _1, direct inverter PWM
And outputs a signal, is converted into a direct current amount primary current vector I ₁ from the three-phase alternating current on the basis of this phase. In this case, the primary voltage is directly output based on the phase of the primary voltage vector, and from this phase, the primary voltage vector direction component (effective power component current Iq) of the primary current vector I ₁ and the primary voltage vector Since a direction component (reactive power component current Id) delayed by 90 ° from the direction is obtained and is not affected by the internal impedance of the motor, accurate Iq and Id are detected. In addition, the voltage when the induction motor is in steady operation,
From the formula obtained based on a current vector diagram for calculating the primary self-inductance L _1. In this case, Iq,
Id varies, but the exact Iq, since it operational measurement based on Id, accurately L ₁ can be measured regardless of the load.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, an AC power supply 1 is converted to a DC power supply via a rectifier circuit 2 and a smoothing capacitor 3. During normal operation, the inverter input voltage _Vdc is PWM-controlled by the inverter 4 to generate an AC voltage, whereby the induction motor 5 is controlled at a variable speed. The control device 6 using a one-chip microcomputer provides a speed command ω during normal operation.
Speed sensorless vector control processing 7 is performed so as to follow _rf , and a PWM signal is generated in the gate circuit 8. In this case, a motor control constant consisting of various motor constants and a moment of inertia on the load side including the motor and a motor current detector 9 are provided.
Speed and torque control are performed based on the output of. Also, in principle the speed sensorless vector control process 7 speaking, the induced voltage E _m of the induction motor compensates for voltage drop by the primary side impedance to be constant and outputs a primary voltage command of the motor. Further, the primary frequency is controlled by giving a slip frequency proportional to the current contributing to the torque, and the PW is controlled based on the magnitude of the primary voltage vector and the primary frequency command.
Output M signal.

Next, a control device for an induction motor, which is a main part of the present invention, will be described. A motor control constant selection means 10 for switching and selecting design value data and measurement value data as motor control constants including various motor constants and moment of inertia which are input to the speed sensorless vector control processing 7 is provided. This can be arbitrarily switched and selected by operating a control constant selection switch such as a touch panel. The motor constant and inertia moment storage memory 11 stores various motor electric constant design values according to the motor capacity and the number of poles, and approximate load inertia moment according to the motor capacity and the application. By setting the motor capacity, the number of poles, and the application by operation, various types of motor electric constant design value data and load inertia moment are output as design value data from the storage memory 11 correspondingly. Next, the auto-tuning process 12 is operated according to an auto-tuning operation command. The induction motor 5 is AC- or DC-excited by the inverter 4, and is further accelerated / decelerated to perform various electric constants of the induction motor and the moment of inertia of the load. Is measured and output as measured value data. Further, these data are displayed on the display 13. Next, the operation mode selection means 14 switches and selects various operation modes such as a normal operation mode for performing a normal operation such as a speed sensorless vector control and an auto tuning mode for performing an auto tuning operation. When an operation start command is input in a state where the normal operation mode is selected, the normal operation command is output and the speed sensorless vector control is performed. On the other hand, when an operation start command is input in the auto tuning mode, an auto tuning operation command is output, and an auto tuning process is performed.

Next, the software processing of the control device of the present invention is shown in FIG.
Shown in First, when a switch operation in the normal operation mode is input, a mode setting interrupt is input to the microcomputer, and it is determined that the operation mode is set. Further, the normal operation mode is determined from the switch ON / OFF signal (output signal of 1 or 0), and this mode is stored in the nonvolatile memory. On the other hand, when the switch operation of the auto tuning operation mode is entered,
In the operation mode setting, it is determined that the operation mode is the auto tuning operation mode, and this mode is stored in the nonvolatile memory. Further, when the switch operation of the design value data is performed, it is determined that the design value data is set by the motor control constant setting, and the design value data is stored in the nonvolatile memory as the motor control constant. On the other hand, when the switch operation of the measured value data is performed, it is determined that the measured value data is set by the motor control constant setting, and the measured value data is stored in the nonvolatile memory as the motor control constant. Since the data is stored in the non-volatile memory, the data is stored even when the power is turned off, and is not changed unless the mode setting is changed.

Next, when a switch operation of the operation ON is performed, an interruption of the operation ON command occurs, and the operation mode is determined first. Therefore, in the normal operation mode, the speed sensorless vector control operation is performed based on the previously set motor control constant. On the other hand, in the case of auto tuning mode,
The motor constant and the moment of inertia are measured using an inverter, stored in a non-volatile memory, and the measured data is displayed on a display.

Next, FIG. 3 shows a T-type equivalent circuit of the induction motor. Here, V ₁ is the primary voltage of the motor r ₁ , r ₂ is 1
Primary and secondary resistances, l ₁ and l ₂ are primary and secondary leakage inductances, and M is a mutual inductance. These values are basically measured as control constants for speed sensorless vector control. There is a need. Note that s is a slip. Next, the specific contents of the auto tuning process are shown in FIG. First, the combined resistance (r ₁ + r ₂ ) and the combined leakage inductance (l ₁ + l ₂ ) are measured by the single-phase AC excitation method described in Japanese Patent Application No. 4-246147. Next, Japanese Patent Application No. 4-2
The primary resistance r ₁ is measured by the DC excitation method described in JP 08776, and the measured value of r ₁ is subtracted from the measured value of (r ₁ + r ₂ ) to obtain a measured value of r ₂ . When measured at room temperature, (r ₁ + r ₂ ) and the measured value of r ₁ should be 10 to ₁ in anticipation of the temperature rise during normal operation.
Increase by 5%.

Next, the self inductance L ₁ (L ₁ = M +
l ₁ ) is measured by steady operation. Next, acceleration / deceleration operation is performed by the method described in JP-A-61-88780, and the moment of inertia of the motor and the load is measured. Finally, these measurement data are stored as control constants in a nonvolatile memory and displayed on a display. Therefore, the operator visually checks the display data to determine whether or not the measurement has been correctly performed. By any chance
If it is determined that there is an error in the measured value data due to an abnormality in the motor current sensor or the like, switching from the motor control constant setting to the design value data and operating can avoid the abnormality. Further, for example, a V / f constant control mode is provided in other operation modes other than the normal operation and the auto tuning mode, and when this mode is switched, the motor can be operated without a motor control constant.
Can be avoided from abnormal times. In addition, the measurement can be performed again by switching to the auto tuning mode and operating again. In addition, when there is some error in the measured value data, the control characteristics may be better when operated with the design value data than when operated with the measured value data. In such a case, the operation can be switched to the design value data. In this embodiment, the motor constant and the moment of inertia are measured continuously. However, the motor constant is measured first, displayed, and the processing is terminated. Thereafter, it may be performed in two steps, such as measuring and displaying the moment of inertia in response to the operation start command again. Alternatively, after displaying the data measured in the auto-tuning mode, the operation mode may be set to the normal operation, and the motor control constant may be selected as the measured value data to end the operation.

Next, a method of measuring the self-inductance L ₁ which is a main part of the present invention will be described. The details of the self-inductance L ₁ assay shown in FIG. 4 is shown in 12a of FIG. First, in the V / f constant processing 15, a primary voltage command V _1c is output in proportion to the primary angular frequency command ω ₁ . Further, ω ₁ is integrated by the integration processing 16 to obtain a phase command θ _v1 of the primary voltage vector. Therefore, in the PWM generation processing 17, a PWM signal is output in accordance with the magnitude command V _1c of the primary voltage and the phase command θ _v1 of the primary voltage vector, and near the rated frequency, the rated magnetic flux (rated frequency and rated frequency) is output. (Ratio of voltage).
In addition, as the size V ₁ of the actual inverter output voltage to 1 in PWM generation process 17 primary voltage command V _1c coincide,
The pulse width is corrected according to the DC voltage _Vdc fluctuation. Further, a voltage error due to a dead time provided so that the inverter positive / negative arm is not short-circuited is also corrected according to the motor current polarity. Next, in the general three-phase AC / two-phase DC conversion processing 18, the operations of Expressions 3 and 4 are performed, and the reactive power component current I
d and the effective power current Iq are determined. Note that θd = θ
_v1− π / 2.

[0023]

Id = iu · sin θd / 1.414− (iu + 2iv) cos θd / 2.45 (Expression 3)

[0024]

Iq = iu · cos θd / 1.414 + (iu + 2iv) sin θd / 2.45 (Equation 4) Therefore, in the self-inductance calculation process 19, this I
d, Iq, the primary angular frequency command value ω ₁ , the primary voltage command value V _1c , the primary resistance r ₁ and the combined leakage inductance Lx (Lx ≒ l ₁ + l ₂ ) previously measured, By L ₁
Seeking.

[0025]

(Equation 5)

Instead of the primary voltage command V _1c , the magnitude V ₁ of the actual inverter output voltage may be detected by a voltage sensor and used.

Next, the calculation of Equation 5 will be described with reference to the voltage and current vector diagrams shown in FIG. Assuming that the primary voltage vector direction is the q axis and the π / 2 delay is the d axis, the q axis component of the primary current vector I ₁ is the effective power component current Iq, and d
The axis component becomes the reactive power component current Id. On the other hand, 2 Tsugikusari flux linkage direction component [pi / 2 delayed from the induced voltage vector E _m is the exciting component current I _m. Therefore, in general, the induced voltage E _m
Is given by Equation 6 where M is the mutual inductance and L ₂ is the secondary self inductance.

[0028]

E _m = ω ₁ M ² · I _m / L ₂ (Equation 6) From FIG. 6, since I _m = (Id · cos δ−Iq · sin δ), Equation 6 becomes Equation 7.

[0029]

Equation 7] ^{_{E m = ω 1 M 2 (}} Id · cosδ-Iq · sinδ) / L 2 ... ( 7) Furthermore, the d-axis component of E _m from the vector diagram of FIG. 6 and H,
q-axis component when the F E _m is next to the number 8, since the number 7 = Number 8, number 9 is established.

[0030]

E _m = F · cos δ + H · sin δ (Equation 8)

[0031]

F · cosδ + H · sinδ = ω ₁ M ² (Id · cosδ−Iq · sinδ) / L ₂ (Equation 9) Next, both sides of Equation 9 are divided by cosδ, and tanδ = H / F is substituted. Then, when it is rearranged, it becomes several tens.

[0032]

F ² + H ² = ω ₁ M ² (Id · F−Iq · H) / L ₂ (Equation 10) Further, since the self-inductance L ₁ = Lx + M ² / L ₂ , M ² / When L ₂ is obtained and substituted into this, L ₁
Becomes the following equation (11).

[0033]

L ₁ = [F ² + H ² + ω ₁ Lx (Id · F−Iq · H)] / [ω ₁ (Id · F−Iq · H)] (Expression 11) = V _1c -ω ₁ Lx · Id-r ₁ · Iq, H
= Ω ₁ Lx · Iq−r ₁ · Id, these are substituted into Equation 11 and rearranged, L ₁ becomes Equation 5. Incidentally, by the load varies Id, Iq also changes but for computing the number 5, which produces the effect of a possible measure L ₁ even when the load without the inverter output voltage sensor.

Further, a PWM signal is output based on the phase θ _v1 obtained by integrating the primary angular frequency command ω ₁ , and the motor current vector I ₁ is calculated from the detected motor current value based on the same phase θ _v1.
Since the next voltage vector direction component Iq and the direction component Id delayed by 90 ° are directly obtained and are not affected by the internal impedance error of the motor, Id and Iq can be accurately calculated.
As a result, precise Id, because calculating the L ₁ based on Iq,
There is an effect to say that can be measured with high accuracy L _1.

[0035]

According to the present invention, any operation can be freely performed by providing the operation mode selection means and the motor control constant selection means, and the display contents of the data measured in the auto tuning mode are visually judged to perform various measurements. If there is an error in the result, measurement can be performed again in the auto-tuning mode, or the operation can be switched to the design value data to operate the system. Furthermore, since the data with the better motor control characteristic among the measured value data and the design value data can be easily set as the motor control constant, the motor control performance is improved and the usability is improved.

Next, regarding the self-inductance L ₁ measuring method, an inverter output voltage is output based on the phase of the primary voltage vector, and the primary current vector is decomposed into primary voltage vector direction components based on the phase. Thus, the accurate effective power component current Iq and the reactive power component current Id are independent of the load.
Is found. Since Iq, it calculates the L ₁ on the basis of Id and primary voltage command value V _1c, etc., without the inverter output voltage sensor, regardless of the size of the load, which produces the effect of a can accurately measure the self-inductance .

[Brief description of the drawings]

FIG. 1 is a control block diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart showing software processing of the one-chip microcomputer shown in FIG. 1;

FIG. 3 is a T-type equivalent circuit diagram of the induction motor shown in FIG.

FIG. 4 is a detailed flowchart of the auto tuning process shown in FIG. 1;

FIG. 5 is a control block diagram showing an embodiment of a self-inductance measuring method according to the present invention.

FIG. 6 is a voltage and current vector diagram of the induction motor under a steady load.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 3 ... Smoothing capacitor, 4 ... Inverter, 5 ... Induction motor, 6 ... Control device, 7 ... Speed sensorless vector control processing, 9 ... Current detector, 10 ... Motor control constant selection means,
11 ... motor constant, moment of inertia storage memory, 12 ...
Auto-tuning processing, 13 display, 14 operation mode selection means, 15 constant V / f processing, 16 integration processing, 17 PWM signal generation processing, 18 three-phase AC / two-phase DC conversion processing, 19 Self inductance calculation processing.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Fujii 7-1-1, Higashi Narashino, Narashino City, Chiba Prefecture Hitachi, Ltd. Narashino Plant (56) References JP-A-61-92185 (JP, A) 62-79380 (JP, A) JP-A-2-17887 (JP, A) JP-A 62-42076 (JP, A) JP-A 1-217279 (JP, A) JP-A 5-297080 (JP) JP-A-5-297079 (JP, A) JP-A-5-264677 (JP, A) JP-A-5-276779 (JP, A) JP-A-61-231891 (JP, A) JP-A-sho 59-63998 (JP, A) JP-A-62-181488 (JP, A) JP-A-62-42075 (JP, A) JP-A-2-304380 (JP, A) JP-A-60-183953 (JP, A A) JP-A-62-1114487 (JP, A) JP-A-6-98595 (JP, A) JP-A-6-5 9000 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 31/34 H02P 7/63 H02P 21/00

Claims (4)

(57) [Claims] 1. An AC motor control device comprising: an inverter for converting a DC voltage V _dc into AC or DC and supplying it to an AC motor; and a control device for controlling the magnitude and frequency of the output voltage of the inverter. In the above, two or more types of operation modes including a normal operation mode and an auto tuning mode are provided, and an operation mode selection means for selecting one of the operation modes and an inverter operation start means are provided. by starting operation, the supply power of an arbitrary frequency to the AC motor by the inverter, the motor current and the like when this, the electric constant of the motor is calculated measured, and stored into the memory, stored into the pre-memory Motor capacity and number of poles
The electric constant design value of the motor
The motor power calculated and measured in the
Motor control constant selection means for switching and selecting air constant
In the normal operation mode, the motor control
Based on the electric constant of the motor selected by the constant selection means,
A control device for an AC motor, which performs vector control of a flow motor . 2. A converting direct current into alternating current voltage V _dc, and an inverter for supplying to the AC motor, the AC in the controller for an AC motor comprising a controller for controlling the magnitude and frequency of the output voltage of the inverter How to measure motor constants
In the method, the inverter is driven based on the primary angular frequency command value ω ₁ and the primary voltage command value V _1c of the inverter to operate the AC motor in a steady state, and the primary angular frequency command From the integrated phase of the AC motor and the detected current value of the AC motor, a component Iq of the motor current vector I _{1 in} the same direction as the inverter primary voltage vector direction, and a direction delayed by 90 ° from the same direction as the inverter primary voltage vector direction. Same as
The primary angular frequency command value ω ₁ and the primary voltage command value V _1c or the primary voltage detection value V _1, and
The primary of the motor based on the Iq and Id self-inductance L ₁ or the constant measuring method of the AC motor which is characterized by calculating measuring the mutual inductance M. 3. A process according to claim 2 primary angular frequency command value omega ₁ and described, the primary voltage command value V _1c (or primary voltage detection value V ₁₎
And an arithmetic expression of the primary self-inductance L ₁ based on the Iq and Id , the primary resistance of the motor is r ₁ ,
Assuming that the combined primary and secondary leakage inductance is Lx,
The following equation A constant measuring method for an AC motor, characterized by calculating and measuring using a basic formula. 4. An AC motor control device comprising an inverter for converting a DC voltage V _dc into AC and supplying the AC voltage to an AC motor, and a control device for controlling the magnitude and frequency of the output voltage of the inverter. Based on the primary angular frequency command value ω ₁ and the primary voltage command value V _1c of the inverter,
Means for operating an inverter to control the AC motor at a variable speed; and a motor current vector I _{1 based} on a phase obtained by integrating the primary angular frequency command value ω ₁ and a detected current value of the AC motor.
Component in the same direction as the inverter primary voltage vector direction
Means for calculating Iq , a component Id in the same direction as the direction delayed by 90 ° from the same direction as the inverter primary voltage vector, and the primary angular frequency command value ω ₁ and primary voltage command value V _1c (or Primary voltage detection value V ₁ ), and the Iq and Id
Based on the primary self inductance L _{1 of the} motor
Alternatively, a control device for an AC motor, comprising means for calculating and measuring the mutual inductance M.