JP2021044879A - Control device for induction motor - Google Patents

Abstract

To provide a control device for an induction motor, with which a secondary resistance fluctuation compensation is accurately effected even in a transient operation state so that a torque error can be reduced.SOLUTION: A control device for an induction motor 10 includes a secondary resistance fluctuation compensation unit 25 which compensates for a secondary resistance component of a slip calculation unit 13 for calculating a slip angle frequency such that a voltage fluctuation component of an output voltage from a current control amplifier becomes zero, has a secondary resistance fluctuation compensation system in which a transient state is not taken into consideration. The control device further includes an acceleration/deceleration torque calculation unit 26 that calculates an acceleration/deceleration torque from a speed detection component ωr obtained for the induction motor 10 by the speed calculator 12, and a gain varying unit 27 that changes a secondary resistance fluctuation compensation varying gain to be multiplied with the output from the secondary resistance fluctuation compensation unit 25 in accordance with the acceleration/deceleration torque calculated by the acceleration/deceleration torque calculation unit 26.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control device for an induction motor, and more particularly to a method for compensating for secondary resistance fluctuations.

Vector control is widely used as a variable speed drive system for induction motors (induction motors). However, although the vector control method requires a secondary time constant of the induction machine, this secondary time constant is not always constant because the secondary resistance fluctuates due to temperature fluctuations and the like. Therefore, various proposals have been made conventionally for a method of estimating and compensating for the fluctuation component of the secondary resistance from the voltage, current, frequency information and the like of the induction machine.

As prior art documents, the present applicant also refers to the vector control device of the induction motor of Patent Documents 1 and 2 that compensates for the fluctuation of the secondary resistance when performing vector control, the variable speed drive device of the induction motor of Patent Document 3, and the like. is suggesting.

^{For example, Patent Document 3 describes a feed-forward voltage component (V1γ *} , V1δ ^* ) obtained by calculating a model voltage on a rotational coordinate system synchronized with a power supply frequency, and a feedback voltage component (ΔV1γ ^* , ΔV1δ ^* ) by a current control amplifier. Correct the secondary resistance component of the slip calculation unit so that ^{a certain feature amount (ΔV1δ *} ) of the output voltage of the current control amplifier and the vector control unit having a current control system that adds and outputs is zero. In the variable speed drive device of the inducer having the secondary resistance compensation function, the phase angle φ ′ that limits the vector phase φ of the current command or the phase angle φ ″ that is the coefficient multiplied by the vector phase φ of the current command is calculated. A function and a function of obtaining a voltage component projected on an axis orthogonal to the phase angle φ'or φ'from the output voltage of the current control amplifier are provided, and the projected voltage component is used in the secondary resistance fluctuation compensation function. It is stated that it will be input.

Japanese Patent No. 27626117 Japanese Patent No. 2940167 Japanese Unexamined Patent Publication No. 11-136999

In the prior art document, the secondary resistance fluctuation compensation amount is calculated by omitting the term of the transient state. Therefore, if the calculation of the secondary resistance fluctuation compensation is performed even in the transient state, there is a problem that the voltage error at the time of the transient becomes a disturbance and the secondary resistance cannot be corrected correctly. If the secondary resistance fluctuation compensation cannot be corrected correctly, the slip frequency will be different from the true value, resulting in a torque error.

The present invention solves the above problems, and an object of the present invention is to provide a control device for an induction motor capable of accurately operating secondary resistance fluctuation compensation even in a transient operation state to further reduce torque error. There is.

The control device for an induction motor according to claim 1 for solving the above problems is
A vector control unit having a current control system that adds and outputs a feed forward voltage component that calculates a model voltage on a rotational coordinate system synchronized with a power supply frequency and a feedback voltage component by a current control amplifier, and the current control amplifier. It is equipped with a secondary resistance fluctuation compensation unit that corrects the secondary resistance component of the slip calculation unit that calculates the slip angle frequency so that the voltage fluctuation component of the output voltage becomes zero, and secondary resistance fluctuation compensation that does not consider the transient state. In the control device of the induction motor having the method
Acceleration / deceleration torque calculation unit that calculates acceleration / deceleration torque from the speed or torque state of the induction motor,
It is characterized by including a gain variable unit that changes the variable gain for secondary resistance fluctuation compensation that is multiplied by the output of the secondary resistance fluctuation compensation unit according to the acceleration / deceleration torque calculated by the acceleration / deceleration torque calculation unit. And.

The control device for an induction motor according to claim 2 is claimed in claim 1.
The gain variable unit is characterized in that the variable gain for compensating for secondary resistance fluctuation is set to 1 when the acceleration / deceleration torque is less than the set threshold value and 0 when the acceleration / deceleration torque is equal to or higher than the set threshold value.

The control device for an induction motor according to claim 3 is claimed in claim 1.
The gain variable portion sets the variable gain for compensation for secondary resistance fluctuation to 1 when the acceleration / deceleration torque is equal to or less than the set first threshold value, and the acceleration / deceleration torque exceeds the first threshold value and becomes the first. In the range up to the second threshold value set larger than the threshold value of 1, the variable gain for compensation for secondary resistance fluctuation is linearly changed between 1 and 0, and the acceleration / deceleration torque is the second. It is characterized in that the variable gain for compensating for secondary resistance fluctuation is set to 0 when the value is equal to or higher than the threshold value.

The control device for an induction motor according to claim 4 is claimed in claim 1.
The gain variable unit has a variable gain lower limit limiter value set between 1 and 0, and when the acceleration / deceleration torque is equal to or less than the set first threshold value, the variable gain for secondary resistance fluctuation compensation is set to 1. Then, when the acceleration / deceleration torque exceeds the first threshold value, the variable gain for compensation for secondary resistance fluctuation is linearly changed from 1 to the lower limit limiter value for variable gain, and the secondary resistance is changed. In the range equal to or larger than the acceleration / deceleration torque when the variable gain for fluctuation compensation is set to the lower limit limiter value for variable gain, the variable gain for secondary resistance fluctuation compensation is set to the lower limit limiter value for variable gain.

The control device for an induction motor according to claim 5 is the device according to any one of claims 1 to 4.
The acceleration / deceleration torque calculation unit is the following equation (9), which is a relational expression between the acceleration / deceleration torque T of the rotating body and the angular velocity ω.

(However, J is the moment of inertia)
Is integrated with an integral constant of 0, and the following equation (10)

The deviation between ω represented by and the speed detection component that detected the speed of the induction motor was taken, the deviation was multiplied by the moment of inertia J to output the calculated acceleration / deceleration torque, and the calculated acceleration / deceleration torque was fed back. It is characterized by having an acceleration / deceleration torque calculation circuit that obtains the angular velocity ω of the above equation (10) by integrating things, multiplying by the inverse of the moment of inertia, and adding the angular velocity command value to the multiplied value. To do.

(1) According to the inventions of claims 1 to 5, the variable gain for compensation for secondary resistance fluctuation can be changed according to the transient state. Therefore, even in the transient operation state, the secondary resistance fluctuation compensation can be operated accurately to further reduce the torque error. (2) According to the invention according to claim 3, the acceleration / deceleration torque is the first. In the range from the threshold value to the second threshold value (in a transient state), the variable gain for secondary resistance fluctuation compensation can be gradually weakened to weaken the effect of secondary resistance fluctuation compensation. As a result, the secondary resistance fluctuation compensation is less likely to become a disturbance.
(3) According to the invention of claim 4, it is possible to operate without losing the effect of the secondary resistance fluctuation compensation in the transient state.
(4) According to the invention of claim 5, the acceleration / deceleration torque can be calculated accurately with a simple configuration.

The block diagram of the control device of the induction motor of the Embodiment of this invention. The characteristic figure which shows the transition of the variable gain for secondary resistance fluctuation compensation in Example 1 of this invention. The characteristic figure which shows the transition of the variable gain for secondary resistance fluctuation compensation in Example 2 of this invention. The characteristic figure which shows the transition of the variable gain for secondary resistance fluctuation compensation in Example 3 of this invention. The block diagram of the acceleration / deceleration torque calculation part of the Example of Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples of embodiments.

In the present embodiment, when the acceleration / deceleration torque value is generated by calculating the acceleration / deceleration torque from the state of speed or torque (for example, from the component that detected the speed, the torque detection value, or the speed estimation value). Is regarded as a transient state, and in the transient state, the secondary resistance fluctuation compensation is operated to perform the secondary resistance fluctuation compensation in consideration of the transient state.

FIG. 1 shows a block diagram of an example in which the present invention is applied to the control device of the secondary resistance fluctuation compensation method described in Patent Document 3. The definition of each symbol in FIG. 1 is as follows.

Torque ^* : Torque command, Lux ^* : Magnetic flux command, ωr: Speed detection component, ωs ^* : Sliding frequency command, ω1: Output frequency, I1d ^* : Excitation current command component, I1q ^* : Torque current command component, I1γ ^* : Current Command component, V1γ ^* , V1δ ^* : Model voltage component (γδ axis component), ΔV1γ ^* , ΔV1δ ^* : Output voltage component of current control unit (γδ axis component), V1γ, V1δ: Output voltage component (γδ axis component), θ: rotation phase angle of d-axis (magnetic flux axis) based on fixed coordinates, _{φ: phase angle of I1 based on d-axis (magnetic flux axis), θ φ: phase angle of I1 based on fixed coordinates,} Kr: Secondary resistance fluctuation compensation coefficient, K: Feedback coefficient for compensating for secondary resistance fluctuation, T: Acceleration / deceleration torque.

In FIG. 1, 1 is ^{a command converter that converts a magnetic flux command Flex *} into an exciting current command I1d ^* , 2 is a command converter that converts a torque command Torque ^* into a torque current command I1q ^* , and 3 is a current command I1d ^* , I1q. ^{This is a polar coordinate converter that converts the combined vector of *} into the phase angle φ of I1 with respect to the current command component (γ component) I1γ * and the d-axis (magnetic flux axis).

Reference numeral 4 denotes a model voltage calculation unit that calculates ^{the terminal voltage component of the inducer as γ, δ-axis component V1γ *} , V1δ ^* from the current command component I1γ ^* , the phase angle φ, the output angular frequency ω1, and the set motor constant. ..

Reference numeral 5 denotes a current control amplifier that feedback-controls the difference between the current command component I1γ ^{* on the} γ-axis and the current detection using the subtractor 5b, and outputs the output voltage component ΔV1γ ^*. Reference numeral 6 denotes a current control amplifier ^{that feedback-controls the difference between the current command I1δ *} (= 0) of the δ-axis component and the current detection using the subtractor 6b ^{and outputs the voltage component V1δ *.}

7 outputs by adding ^{the model voltage components V1γ *} and V1δ ^* of the model voltage calculation unit 4 and the current control output voltage components ΔV1γ ^* and ΔV1δ ^* from the current control amplifiers 5 and 6 for each axis component of γ and δ. This is a PWM control unit that obtains voltage components V1γ and V1δ and outputs a PWM voltage pattern equivalent to this output voltage component (command).

8, the output current detecting sensor of the three-phase (or two-phase), 9 3-phase current components u detected by the output current detecting sensor 8, v, and w, the phase angle theta _phi phase integrator 14 outputs , Γ, δ axis is a coordinate conversion unit that converts into orthogonal two-phase components I1γ, I1δ.

Reference numeral 10 denotes a load induction motor (induction motor) driven by a three-phase output current, 11 is a speed detector, and 12 is a speed calculator that calculates a speed detection component ωr from the measurement results of the speed detector 11.

Reference numeral 13 denotes a slip calculation unit that calculates the slip command ωs ^* (slip angular frequency command) of the inducer 10 from the exciting current command I1d ^* and the torque current command I1q ^*. Reference numeral 14 is an ^{integral of the output frequency ω1 obtained by adding the slip command ωs *} and the speed detection component ωr by the adder 13a, and the rotation phase angle θ of the d-axis (the rotation phase of the d-axis (fog axis) with respect to the fixed coordinates). It is a phase integrator that calculates the angle).

The rotation phase angle θ calculated by the phase integrator 14 is added to the phase angle φ of I1 with respect to the d-axis in the adder 14a, and the phase angle θ _φ of the current command with respect to the fixed coordinates (based on the fixed coordinates). The phase angle of I1) is calculated.

Reference numeral 25 denotes a compensation coefficient Kr (secondary resistance described later) of the _{secondary resistance R 1} ′ component of the slip calculation unit 13 so that the current control output (output voltage component of the current control amplifier 6) ΔV1δ ^{* of the δ axis becomes zero.} This is a secondary resistance fluctuation compensation unit that calculates a secondary resistance fluctuation compensation coefficient) having a fluctuation compensation gain A.

Reference numeral 26 denotes an acceleration / deceleration torque calculation unit that calculates an acceleration / deceleration torque from the speed detection component ωr calculated by the speed calculator 12.

Reference numeral 27 denotes a gain variable unit that changes the variable gain for secondary resistance fluctuation compensation that is multiplied by the output of the secondary resistance fluctuation compensation unit 25 according to the acceleration / deceleration torque calculated by the acceleration / deceleration torque calculation unit 26.

A feedback coefficient K that compensates for fluctuations in the secondary resistance is output from the gain variable unit 27, and the secondary resistance component of the slip calculation unit 13 is corrected by this coefficient K.

^{Feed-forward voltage components V1γ *} , V1δ ^* and feedback by the command converters 1 and 2, the polar coordinate converter 3, the model voltage calculation unit 4, the current control amplifiers 5 and 6, the subtractors 5b and 6b, and the adders 5a and 6a. It constitutes a vector control unit having a current control system that adds and outputs voltage components ΔV1γ ^* and ΔV1δ ^*.

In the block diagram of FIG. 1, the input to the acceleration / deceleration torque calculation unit 26 is the speed detection component ωr, but the acceleration / deceleration torque may be obtained from the torque detection value, or the acceleration / deceleration torque may be obtained from the speed estimation value. You may. Further, even in other secondary resistance fluctuation compensation methods, the present invention can be applied as long as the control method does not consider the transient state.

Next, the operation of the secondary resistance fluctuation compensation in the block diagram of FIG. 1 will be described. The secondary resistance fluctuation compensation gain in FIG. 1 is defined by the following equation (1).

Secondary resistance fluctuation compensation gain = A × B ... (1)
Here, A: the conventional secondary resistance fluctuation compensation gain (gain by the secondary resistance fluctuation compensation unit 25), B: variable gain for secondary resistance fluctuation compensation by the calculated acceleration / deceleration torque.

The variable gain B (gain of the gain variable unit 27) for compensating for the secondary resistance fluctuation due to the calculated acceleration / deceleration torque in the first embodiment is changed as shown in the characteristic diagram of the calculated acceleration / deceleration torque value vs. gain shown in FIG.

That is, if the acceleration / deceleration torque calculated by the acceleration / deceleration torque calculation unit 26 does not exceed a certain threshold value (set calculated calculation acceleration / deceleration torque threshold value), the value of B is set to 1, and if it exceeds the threshold value, the value of B is set to 0. Although the value of B is set to 0 in this way, the operation is continued with the compensation value in the steady state in order to latch the previous value (output of the secondary resistance fluctuation compensation unit 25) of the secondary resistance fluctuation compensation value. As a result, it is possible to operate with more accurate secondary resistance fluctuation compensation.

Here, the calculated acceleration / deceleration torque threshold value may be a value in consideration of the detection accuracy of speed detection. This is because acceleration / deceleration occurs due to the speed detection accuracy.

In FIG. 1, the operation of the block other than the secondary resistance fluctuation compensation of the slip calculation unit 13 is the same as the operation described in Patent Document 3.

In the second embodiment, the value of the variable gain for compensating for the secondary resistance fluctuation due to the calculated acceleration / deceleration torque is changed linearly, and the effect of compensating for the secondary resistance fluctuation is weakened by weakening the gain at the time of transient. As a result, the secondary resistance fluctuation compensation is effective in a certain transient operation state. Since the gain is weakened, the secondary resistance fluctuation compensation is less likely to cause disturbance.

Hereinafter, the operation of the variable gain for compensating for the secondary resistance fluctuation due to the calculated acceleration / deceleration torque will be described together with FIG. 3, which shows the characteristics of the calculated acceleration / deceleration torque value vs. the gain.

(1) When the calculated acceleration / deceleration torque value (output value of the acceleration / deceleration torque calculation unit 26) ≤ the calculated acceleration / deceleration torque low level (set first threshold value) (range of (1) in the figure), the gain is set to the following. The formula (2) is used.

Variable gain for compensation for secondary resistance fluctuation due to calculated acceleration / deceleration torque = 1.0 ... (2)
(2) When the calculated acceleration / deceleration torque low level <calculated acceleration / deceleration torque value <calculated acceleration / deceleration torque high level (second threshold value set larger than the first threshold value), the calculation is performed (range (2) in the figure). Limit processing is performed according to the acceleration / deceleration torque value, and the gain is given by the following equation (3).

Variable gain for compensation for secondary resistance fluctuation due to calculated acceleration / deceleration torque = 1.0- (Calculated acceleration / deceleration torque value-Calculated acceleration / deceleration torque low level) / (Calculated acceleration / deceleration torque high level-Calculated acceleration / deceleration torque low level) ... ( 3)
That is, the variable gain for compensating for the secondary resistance fluctuation is linearly changed between 1 and 0.

(3) When the calculated acceleration / deceleration torque high level ≤ the calculated acceleration / deceleration torque value (range of (3) in the figure), the gain is given by the following equation (4).

Variable gain for compensation for secondary resistance fluctuation due to calculated acceleration / deceleration torque = 0.0 ... (4)
The calculated acceleration / deceleration torque low level may be a value in consideration of the detection accuracy of the speed detection, as in the first embodiment. The calculated acceleration / deceleration torque high level may be a value that takes into consideration the maximum acceleration / deceleration torque value that is possible in operation.

In the third embodiment, a limiter is provided for the variable gain. As a result, it is possible to operate without losing the effect of the secondary resistance fluctuation compensation in the transient state.

Hereinafter, the operation of the variable gain for compensating for the secondary resistance fluctuation due to the calculated acceleration / deceleration torque will be described together with FIG. 4, which shows the characteristics of the calculated acceleration / deceleration torque value vs. the gain.

In FIG. 4, the lower limit limiter value for variable gain is set between the gains of 1.0 and 0.
(1) When the calculated acceleration / deceleration torque value ≤ the calculated acceleration / deceleration torque low level (range of (1) in the figure), the gain is given by the following equation (5).

Variable gain for compensation for secondary resistance fluctuation due to calculated acceleration / deceleration torque = 1.0 ... (5)
(2) When the calculated acceleration / deceleration torque low level <calculated acceleration / deceleration torque value <calculated acceleration / deceleration torque high level (range of (2-1) to (2-2) in the figure), depending on the calculated acceleration / deceleration torque value. Limit processing is performed.

(2-1) When the lower limit limiter for variable gain ≤ the variable gain for compensation for secondary resistance fluctuation (range of (2-1) in the figure), the gain is given by the following equation (6).

Variable gain for compensation for secondary resistance fluctuation due to calculated acceleration / deceleration torque = 1.0- (Calculated acceleration / deceleration torque value-Calculated acceleration / deceleration torque low level) / (Calculated acceleration / deceleration torque high level-Calculated acceleration / deceleration torque low level) ... ( 6)
That is, the variable gain for compensation for secondary resistance fluctuation is linearly changed from 1 to the lower limit limiter value for variable gain.

(2-2) Calculated acceleration / deceleration torque value when the variable gain for secondary resistance fluctuation compensation <the lower limit limiter value for variable gain, that is, when the variable gain for secondary resistance fluctuation compensation is set to the lower limit limiter value for variable gain. From to the calculated acceleration / deceleration torque high level (range of (2-2) in the figure), the gain is given by the following equation (7).

Variable gain for compensation for secondary resistance fluctuation due to calculated acceleration / deceleration torque = lower limit limiter value for variable gain ... (7)
(3) When the calculated acceleration / deceleration torque high level ≤ the calculated acceleration / deceleration torque value (range of (3) in the figure), the gain is given by the following equation (8).

Variable gain for compensation for secondary resistance fluctuation due to calculated acceleration / deceleration torque = Lower limit limiter value for variable gain ... (8)
The calculated acceleration / deceleration torque low level and the calculated acceleration / deceleration torque high level may be set to the same values as in the second embodiment.

In the fourth embodiment, the acceleration / deceleration torque calculation unit 26 is shown in the block diagram of FIG. 5 so that the acceleration / deceleration torque for determining the variable gain for secondary resistance fluctuation compensation can be calculated easily and accurately. It was configured like a circuit.

The calculated acceleration / deceleration torque in FIG. 5 is obtained from the following relationship. First, the relationship between the torque of the rotating body and the angular velocity is given by the following equation (9).

When ω in Eq. (9) is transferred to the left side and the integration constant is set to 0 and integrated, the following Eq. (10) is obtained.

Here, we want to obtain only the acceleration / deceleration torque. The difference between the angular velocity (ω) obtained by Eq. (10) and the angular velocity detection value is taken by the subtractor 51 in FIG. 5, and the deviation output is multiplied by the adjustment gain term 52 in which the moment of inertia J (gain 2) is set. Since the torque corresponding to the fluctuation of the angular velocity can be calculated, it becomes the acceleration / deceleration torque (T).

Here, T: acceleration / deceleration torque, ω: angular velocity, J: moment of inertia, and the angular velocity is substituted by speed detection (output ωr of the speed calculator 12 in FIG. 1).

The calculated acceleration / deceleration torque (T) is fed back and integrated by the integrator 53, and further multiplied by the reciprocal of the moment of inertia J in the multiplication term 54 to output the angular velocity component.

The angular velocity output of the multiplication term 54 and the angular velocity command value of the angular velocity command value setting unit 55 are added by the adder 56, the output of the adder 57 provided on the output side of the adder 56 is integrated by the integrator 58, and the integrator 58 is used. By adding the integrator output of the above and the output of the adder 56 with the adder 57, the angular velocity ω (negative side input of the subtractor 51) of the above equation (10) is obtained.

The gain 2 of the adjustment gain term 52 is an adjustment gain in consideration of an error of the moment of inertia (J) and an error of the speed detection accuracy, and the adjustment gain may be set when there is an error.

1, 2 ... Command converter 3 ... Polar coordinate converter 4 ... Model voltage calculation unit 5, 6 ... Current control amplifier 5a, 6a, 13a, 14a, 56, 57 ... Adder 5b, 6b, 51 ... Subtractor 7 ... PWM Control unit 8 ... Output current detection sensor 9 ... Coordinate conversion unit 10 ... Load induction motor 11 ... Speed detector 12 ... Speed calculator 13 ... Sliding calculation unit 14 ... Phase integrator 25 ... Secondary resistance fluctuation compensation unit 26 ... Acceleration / deceleration Torque calculation unit 27 ... Gain variable unit 52 ... Adjustment gain term 53, 58 ... Integrator 54 ... Multiplication term 55 ... Angle speed command value setting section

Claims (5)

A vector control unit having a current control system that adds and outputs a feed forward voltage component that calculates a model voltage on a rotational coordinate system synchronized with a power supply frequency and a feedback voltage component by a current control amplifier, and the current control amplifier. It is equipped with a secondary resistance fluctuation compensation unit that corrects the secondary resistance component of the slip calculation unit that calculates the slip angle frequency so that the voltage fluctuation component of the output voltage becomes zero, and secondary resistance fluctuation compensation that does not consider the transient state. In the control device of the induction motor having the method
Acceleration / deceleration torque calculation unit that calculates acceleration / deceleration torque from the speed or torque state of the induction motor,
It is characterized by including a gain variable unit that changes the variable gain for secondary resistance fluctuation compensation that is multiplied by the output of the secondary resistance fluctuation compensation unit according to the acceleration / deceleration torque calculated by the acceleration / deceleration torque calculation unit. The control device for the induction motor. The variable gain unit according to claim 1, wherein the variable gain for compensation for secondary resistance fluctuation is set to 1 when the acceleration / deceleration torque is less than the set threshold value and 0 when the acceleration / deceleration torque is equal to or higher than the set threshold value. The control device for the induction motor described. When the acceleration / deceleration torque is equal to or less than the set first threshold value, the gain variable unit sets the variable gain for compensation for secondary resistance fluctuation to 1, and the acceleration / deceleration torque exceeds the first threshold value and becomes the first. In the range up to the second threshold value set larger than the threshold value of 1, the variable gain for compensation for secondary resistance fluctuation is linearly changed between 1 and 0, and the acceleration / deceleration torque is the second. The control device for an induction motor according to claim 1, wherein the variable gain for compensating for secondary resistance fluctuation is set to 0 when the value is equal to or higher than a threshold value. The gain variable unit has a variable gain lower limit limiter value set between 1 and 0, and when the acceleration / deceleration torque is equal to or less than the set first threshold value, the variable gain for secondary resistance fluctuation compensation is set to 1. Then, when the acceleration / deceleration torque exceeds the first threshold value, the variable gain for compensation for secondary resistance fluctuation is linearly changed from 1 to the lower limit limiter value for variable gain, and the secondary resistance is changed. The claim is characterized in that the variable gain for secondary resistance fluctuation compensation is set to the lower limit limiter value for variable gain in the range equal to or larger than the acceleration / deceleration torque when the variable gain for fluctuation compensation is set to the lower limit limiter value for variable gain. The control device for the induction motor according to 1. The acceleration / deceleration torque calculation unit is the following equation (9), which is a relational expression between the acceleration / deceleration torque T of the rotating body and the angular velocity ω.

(However, J is the moment of inertia)
Is integrated with an integral constant of 0, and the following equation (10)

The deviation between ω represented by and the speed detection component that detected the speed of the induction motor was taken, the deviation was multiplied by the moment of inertia J to output the calculated acceleration / deceleration torque, and the calculated acceleration / deceleration torque was fed back. It is characterized by having an acceleration / deceleration torque calculation circuit that obtains the angular velocity ω of the above equation (10) by integrating things, multiplying by the inverse of the moment of inertia, and adding the angular velocity command value to the multiplied value. The control device for the induction motor according to any one of claims 1 to 4.

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