JPH07245979A - AC motor speed controller - Google Patents

Abstract

(57) [Abstract] [Purpose] To effectively reduce the torque ripple generated in the induction motor to be controlled due to the offset of the current detection means. [Configuration] The average speed calculator 11 sequentially calculates the average speed value ωav from which the speed ripple component is removed by averaging the signals indicating the angular speed ωr of the induction motor 1. The peak value detector 12 sequentially detects the velocity ripple peak value ωpk of the angular velocity ωr. The current offset calculator 13 calculates the difference between the speed ripple peak value ωpk and the speed average value ωav as the amplitude of the speed ripple, and the U-phase offset correction command value Iuoff and the W-phase offset correction command are calculated based on the amplitude. The value Iwoff is calculated and given to the arithmetic units 14a and 14b to correct the offset of the three-phase current converter 9 which is the current detecting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for an AC electric motor, in which the speed of the AC electric motor is feedback-controlled based on the detection outputs of the speed detecting means and the current detecting means.

[0002]

2. Description of the Related Art In FIG. 5, which shows a configuration example of a speed control device of this type, an induction motor 1 which is an AC motor to be controlled.
Is driven at a variable speed by, for example, a current control type PWM inverter 2. The speed detector 3, which is a speed detecting means provided to detect the rotation speed of the induction motor 1, is generally an incremental type rotary encoder. In this case, the speed and position are detected. A phase pulse PA and B phase pulse PB are output for
The one that outputs the Z-phase pulse PZ for mechanical position detection is selected. A-phase pulse PA and B from speed detector 3
The phase pulse PB is rotated by the pulse counter 4 by the rotation angle θr.
Is converted into a signal indicating the angular velocity ωr through the differentiating circuit 5.

The speed PI control unit 6 uses the differential signal between the speed reference value and the angular speed ωr given through the calculator 6a as PI.
By performing (proportional integration) calculation, it is converted into a signal indicating the torque reference. The pole number multiplier 7 rotates the rotation angle θr in order to obtain a current phase reference that matches the magnetic pole position of the induction motor 1.
And the number of poles of the induction motor 1 are multiplied. The sine wave reference current generator 8 generates a signal indicating a sine wave reference value based on the torque reference from the speed PI controller 6 and the current phase reference from the pole number multiplier 7.

Three-phase current converter 9 as current detection means
Is a configuration including current transformers 9a and 9b for detecting respective input currents of the U phase and W phase of the induction motor 1 (output currents of the inverter 2), and U, V, and
A signal indicating the load current FIU, FIV, FIW of each W phase is generated. The current PI control unit 10 calculates the difference signal between the sine wave reference value from the sine wave reference current generator 8 and each phase load current FIU, FIV, FIW with an arithmetic unit (only the arithmetic unit for U phase is designated by reference numeral 10a). The output current command value for each phase to the inverter 2 (only the output current command value Vu for the U phase is shown in FIG. 5) is given to the inverter 2 by performing a PI operation on the difference signal. This occurs, and thereby the closed loop control of the induction motor 1 is performed.

FIG. 4 shows an example of the relationship between the rotor rotation angle θ of the induction motor 1 having the above-described structure, the output current of the inverter 2 (input current of the induction motor 1), the generated torque and the rotation speed. Although shown, for simplification of description, it is assumed that the induction motor 1 is not disturbed and is rotated at a constant speed under a constant load. In this state, with respect to the induction motor 1, a sinusoidal output current (1 in FIG.
The generated torque (for one phase) when an output current Ia for the phase is shown) is applied as a torque constant KT (for one phase) corresponding to the magnetic flux distribution of the rotor of the induction motor 1 shown in FIG. If the sine wave is as shown in FIG. 4), the state shown in FIG. The total torque generated for the three phases is shown in FIG.
The torque is constant as indicated by the solid line in (d). However, note in FIG. 4 that from the inverter 2,
Results when assuming a state in which sinusoidal currents of the same amplitude with different phase differences of 120 ° are output and the generated magnetic flux distribution of the rotor 1 also has sinusoidal flux of the same amplitude with different phase differences only. That is the point.

[0006]

The above-mentioned conventional apparatus has the following problems. That is, firstly, since the output current control unit of the inverter 2, especially the current detection means (three-phase current converter 9) always has offset and adjustment variations, the actual current and the detected current do not match. There are many cases. However, since the control as described above is performed by regarding the detected current as the actual current, there is a possibility that torque ripple may occur when the induction motor 1 is actually driven. Secondly, it is premised that the magnetic flux distribution of the rotor is sinusoidal, and the cogging torque in the induction motor 1 and the characteristic variations that occur during manufacturing of the induction motor 1 are not taken into consideration. This may cause torque ripple.

Incidentally, in FIG. 4, a broken line shows an example of a waveform when an offset is present in the three-phase current converter 9 which is a current detecting means. That is, the broken line in FIG.
This figure shows the actual current waveform for one phase when the offset component (DC component) is superimposed, and the torque generated in this phase includes a negative torque component as shown by the broken line in FIG. As a result, the total torque generated for the three phases is shown in FIG.
The pulsating torque is shown by the broken line.

The present invention has been made in view of the above circumstances, and an object of the present invention is to utilize a speed feedback control system to obtain a torque ripple generated in an AC motor to be controlled due to an offset of a current detecting means. Another object of the present invention is to provide a speed control device for an AC electric motor that can be effectively reduced.

[0009]

In order to achieve the above-mentioned object, the present invention has speed detecting means and current detecting means for detecting the speed and the input current of an AC motor, respectively, and is created based on the detected outputs thereof. In a speed control device for an AC electric motor, which performs speed control by controlling a current applied to the AC electric motor based on the output current command value, in a predetermined unit time based on the speed detection value by the speed detecting means. Average value calculation means for sequentially calculating the speed average value, peak value detection means for sequentially detecting the speed ripple peak value of the speed detection value by the speed detection means in a predetermined unit time, and the average value calculation means The difference between the speed average value and the speed ripple peak value detected by the peak value detecting means is a signal indicating the amplitude of the speed ripple of the AC motor. While calculating Te is obtained by a structure which includes an offset correction means for correcting the offset of the current detector by subtracting the result of the operation from the detected current by said current detecting means (claim 1).

Further, it has speed detecting means and current detecting means for respectively detecting the speed and the input current of the AC motor,
In the speed control device of the AC electric motor, which is configured to perform speed control by controlling the current given to the AC electric motor based on the output current command value created based on those detection outputs, the speed detection value by the speed detection means is A configuration is provided in which a current command value correction unit that calculates a torque ripple estimated value of the same period component as the period of the input current of the AC electric motor by differentiating and adds the antiphase component of the estimated value to the output current command value It can also be set (Claim 2).

Further, it has speed detecting means and current detecting means for respectively detecting the speed and the input current of the AC electric motor, and controls the electric current given to the AC electric motor based on the output current command value created based on the detected outputs thereof. In the speed control device for an AC electric motor, which performs speed control by doing so, a storage unit that sequentially stores a speed detection value by the speed detection unit during a period of one rotation or more of the electric motor as a speed ripple detection value, An anti-phase torque ripple calculation means for calculating the anti-phase torque ripple estimated value by inverting the phase of the torque ripple component obtained by differentiating the stored value by this storage section, and the inverse phase torque ripple calculation means calculated by this torque ripple calculation means. The antiphase torque ripple current value calculated based on the estimated phase torque ripple value is used as the output current command value. It can be configured to provide a current command value correcting means for adding (claim 3).

[0012]

The torque ripple caused by the offset of the current detecting means provided for detecting the input current of the AC motor has a phenomenon that it appears as a speed ripple of the AC motor. Therefore, in the apparatus according to claim 1, the average value calculating means, based on the speed detection value by the speed detecting means,
While sequentially calculating the speed average value in a predetermined unit time,
The peak value detecting means sequentially detects the speed ripple peak value of the speed detection value in a predetermined unit time, and these outputs are used for the speed ripple detection of the AC motor. That is, the offset correction means calculates the difference between the speed average value and the speed ripple peak value calculated as described above as a signal indicating the amplitude of the speed ripple of the AC motor. Then, the offset correction means corrects the offset of the current detection means by subtracting the calculation result from the current detected by the current detection means, and the torque ripple of the AC motor is reduced by such offset automatic correction. It

According to the second aspect of the present invention, the torque ripple of the AC motor is reduced by utilizing the characteristic that the torque ripple is proportional to the differential value of the speed ripple of the AC motor. That is, the current command value correction means calculates the torque ripple estimated value of the same cycle component as the cycle of the input current of the AC electric motor by differentiating the speed detection value by the speed detection means, and calculates the antiphase component of the estimated value. The torque ripple is reduced by adding it to the output current command value of the AC motor.

Also in the apparatus of claim 3, the torque ripple of the AC motor is reduced by utilizing the characteristic that the torque ripple is proportional to the differential value of the speed ripple of the AC motor. That is, the speed detection value by the speed detecting means in the period of one rotation of the electric motor or more is sequentially stored in the storage section as the speed ripple detection value, and the antiphase torque ripple calculating means differentiates the storage value by the storage section. The reverse phase torque ripple estimated value is calculated by inverting the phase of the torque ripple component obtained by the above, and the current command value correction means is calculated based on the reverse phase torque ripple estimated value calculated by the torque ripple calculation means. The opposite-phase torque ripple current value is added to the output current command value. As a result, it is possible to reduce the torque ripple component unrelated to the torque fluctuation caused by the load torque fluctuation, such as the offset of the current detection unit and the cogging torque of the AC motor.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. 1 and FIG. However, in this embodiment, the same components as those of the conventional configuration shown in FIG. 5 are present, and therefore, those components will be designated by the same reference numerals and detailed description thereof will be omitted.

In this embodiment, the induction motor 1 is shown in FIG.
Current detection means (three-phase current converter 9) as indicated by the broken line in FIG.
When a torque ripple due to the offset is generated, the phenomenon that the torque ripple appears as a speed ripple as shown by a broken line in FIG. The feature is that the correction for the offset is automatically performed.

That is, when the current detecting means has an offset, the angular velocity ω r of the induction motor 1 is as shown in FIG.
As indicated by the broken line in (e), the waveform has a velocity ripple in the DC component, so this velocity ripple value is detected as a feedback signal for correcting the offset.

Specifically, in FIG. 1, an average speed calculator 11 as an average value calculating means has an angular speed output from the differentiating circuit 5 in a predetermined unit time (for example, a time corresponding to one cycle of the output current). By simply averaging the signals indicating ωr, the velocity average value ωav (corresponding to the DC component in FIG. 4E) from which the velocity ripple component has been removed is sequentially calculated. The peak value detector 12 as the peak value detecting means,
The velocity ripple peak value ωpk (see FIG. 4E) of the angular velocity ωr in the unit time is sequentially detected.

Therefore, the amplitude of the velocity ripple can be detected by subtracting the velocity average value ωav from the velocity ripple peak value ωpk. The current offset calculator 13 corresponds to the offset correction means in the invention of claim 1, detects the amplitude of the velocity ripple by performing the subtraction as described above, and uses the signal indicating the amplitude to detect the current. The offset correction of the detection means is automatically performed, and a configuration therefor and an automatic offset correction procedure in the current offset calculator 13 will be described below.

That is, between the output terminals of the current transformers 9a and 9b provided for detecting the U-phase current and the W-phase current of the induction motor 1 and the three-phase current converter 9, the current flow is concerned. Bowl 9a,
Arithmetic units 14a and 14b are provided for subtracting the command value from the current offset calculator 13 from the detected current value 9b. Then, the current offset calculator 13 sequentially executes the following controls (1) to (6).

(1) U-phase offset correction command value Iuoff
And the W-phase offset correction command value Iwoff is set to an initial value, for example, "0". (2) The speed average value ωav and the speed ripple peak value ωpk are input from the average speed calculator 11 and the peak detector 12.

(3) Iuoff = Iuoff + Ki. (Ωpk−ωav) is calculated. However, Ki is an offset correction coefficient (arbitrary value). Then, the U-phase offset correction command value Iuoff obtained by such calculation is output to the calculator 14a.

(4) The velocity average value ωav and the velocity ripple peak value ωpk are re-input to calculate (ωpk-ωav). If the calculation result is smaller than the previous (ωpk-ωav) calculated value, The process is repeated from the calculation and command value output control in (3) above. In addition, the above calculation result is (ωpk−ωa
If it is equal to or larger than the calculated value of v), the output of the previous U-phase offset correction command value Iuoff is stopped, and the process proceeds to the next control.

(5) Iwoff = Iwoff + Ki.multidot. (. Omega.pk-.omega.av) is calculated, and the W-phase offset correction command value Iwoff obtained by such calculation is output to the calculator 14b.

(6) Average velocity value ωav and velocity ripple peak value ω from the average velocity calculator 11 and the peak detector 12
When pk is input again and (ωpk−ωav) is calculated, and the calculation result is smaller than the previous calculated value of (ωpk−ωav),
The process is repeated from the calculation and command value output control in (5) above. When the above calculation result is equal to or larger than the previous (ωpk-ωav) calculated value, the output of the previous W-phase offset correction command value Iwoff is stopped and one automatic offset correction is completed.

By performing the automatic offset correction as described above, even if there is an offset in the current detecting means, the offset is automatically corrected, and the torque ripple of the induction motor 1 is thereby corrected. Can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIG. 2 and FIG. However, in this embodiment, since there are the same components as those of the conventional configuration shown in FIG. 5 and the first embodiment shown in FIG. 1, detailed description will be given by attaching the same reference numerals to those components. Is omitted.

That is, the cycle of the torque ripple caused by the offset of the current detecting means has the characteristic of being the same cycle as the cycle of the output current of the inverter 2, as shown by the broken line in FIG. 4 (d). When the inertia J of the induction motor 1 is constant, the generated torque T of the induction motor 1 has a characteristic proportional to the rotor acceleration that is the differential value of the angular velocity ω, as shown in the following equation. T = J · dω / dt ……

That is, the torque ripple is the induction motor 1
In this embodiment, the speed ripple is approximated by a sine wave having the same period as the output current of the inverter 2, and the approximation is performed. It is characterized in that the anti-phase component of the torque ripple estimated by the differential value of the value is directly added to the output current command value to automatically correct the torque ripple caused by the offset amount.

Specifically, in FIG. 2, the peak value and peak value phase detector 15 detects the velocity ripple peak value ωpk of the angular velocity ωr output from the differentiating circuit 5, and the Z value from the velocity detector 3 is detected. A signal indicating the rotation angle θr from the phase pulse PZ and the pulse counter 4 is taken in to obtain the rotation angle of the speed ripple peak value ωpk, and the phase of the speed ripple is determined based on this. However, here, most of the above velocity ripple is occupied by the component due to the offset of the current detecting means, and the inverter 2
It is assumed that the output current of is similar to the sine wave of the same period.

The torque ripple calculator 16 (corresponding to the current command value correcting means in the invention of claim 2) advances the phase of the speed ripple determined by the peak value and peak value phase detector 90 by 90 °, In addition to obtaining the torque ripple phase, the torque ripple estimation value synchronized with the U-phase or W-phase output current phase is calculated based on the current phase reference from the pole number multiplier 7, and the antiphase component thereof is obtained. Therefore, the following controls (1) to (4) are sequentially executed.

(1) The U-phase current ripple correction value Iurip and the W-phase current ripple correction value Iwrip are set to initial values such as "0". (2) The average speed value ωav is input from the average speed calculator 11, and the speed ripple peak value ωpk and the phase difference ψrip between the speed ripple and the U-phase current are input from the peak value and peak value phase detector 15.

(3) Iurip = Iurip−Kt · (ωpk
−ωav) ・ SIN (θ + ψrip) Iwrip = Iwrip−Kt ・ (ωpk−ωav) ・ SIN (θ +
π / 3 + ψrip), where Kt is the current ripple correction coefficient (arbitrary value). Then, the U-phase current ripple correction value Iurip and the W-phase current ripple correction value Iwrip obtained by such calculation are added to the U-phase and W-phase output current command values, respectively. In FIG. 2, the U-phase current ripple correction value Iu
Only the components for adding rip through the arithmetic unit 10a are shown.

(4) Velocity average value ωav, velocity ripple peak value ωpk, and phase difference ψrip between velocity ripple and U-phase current
Is re-input to calculate (ωpk−ωav), and when the calculation result is smaller than the previous calculated value of (ωpk−ωav), the calculation and correction value output control in (3) above are executed again. . If the above calculation result is equal to or larger than the previous (ωpk-ωav) calculation value, the previous U-phase current ripple correction value Iurip and W-phase current ripple correction value I
The wrip is directly used as the U-phase and W-phase current ripple correction command.

As described above, the current ripple correction in which the estimated torque ripple value having the same period component as the period of the U-phase or W-phase output current phase is calculated and the opposite phase component is added to the output current command value Even if there is an offset in the current detection means, the torque ripple due to the offset is automatically corrected by performing the above, and thus the torque ripple of the induction motor 1 can be reduced. .

Next, a third embodiment of the present invention will be described with reference to FIG. 3 and FIG. However, also in this embodiment, since there are the same constituent parts as those of the conventional structure shown in FIG. 5 and the first embodiment shown in FIG. 1, detailed description will be given by attaching the same reference numerals to those constituent parts. Is omitted.

That is, also in this embodiment, the induction motor 1
By utilizing the above-mentioned characteristic that the torque ripple of is proportional to the differential value of the speed ripple, there is no relation to the torque fluctuation caused by the load torque fluctuation such as the offset of the current detection means and the cogging torque of the induction motor 1. A characteristic is that the torque ripple component, in other words, the torque ripple component that always appears with a constant magnitude is corrected regardless of the output current and frequency of the inverter 2.

Specifically, in FIG. 3, the storage unit 17
Is provided for storing the angular velocity ω r from the differentiating circuit 5 which is the speed detection value of the induction motor 1 as a speed ripple detection value, and is output from the speed detector 3 every time the induction motor 1 makes one revolution, for example. Using the Z-phase pulse PZ as a trigger signal, at least the angular velocity ωr of one revolution of the induction motor 1 is sequentially updated and stored with the velocity ripple detection value. Here, the purpose of using the Z-phase pulse PZ as a trigger signal is to clarify the phase relationship between the output current and the speed ripple. For example, when a permanent magnet synchronous motor is used instead of the induction motor 1, Z The prerequisite is that the positional relationship between the phase pulse and the predetermined magnetic pole is clear.

The anti-phase torque ripple reference generator 18 as the anti-phase torque ripple calculation means uses the speed ripple detection value (indicating the speed ripple of at least one revolution of the induction motor 1) stored in the storage unit 17. The signal is converted into a signal showing the torque ripple component by differentiating, and the phase of the signal is inverted and multiplied by an arbitrary constant Ka to calculate the antiphase torque ripple estimated value, and the calculation result is calculated as the antiphase torque ripple. It is given to the command generator 19.

This anti-phase torque ripple command generator 19
Corresponds to the current command value correcting means in the invention of claim 3, and based on the antiphase torque ripple estimated value, the Z-phase pulse PZ is used as a synchronization signal and based on the current phase reference from the pole number multiplier 7. Then, the antiphase torque ripple current value that matches the current phase is obtained, and the current value is added to the U-phase and W-phase output current command values as a current ripple correction value.
The anti-phase torque ripple command generator 19 is supplied with the speed average value ωav from the average speed calculator 11 and the speed ripple peak value ωpk from the peak value detector 12 for the evaluation of the corrected output. It

Hereinafter, in (1) to (5), the storage unit 1 will be described.
7 shows a series of functions of the antiphase torque ripple generator 18 and the antiphase torque ripple command generator 19. (1) The coefficient Ka is set to an initial value, for example, "0".

(2) The angular velocity ωr, the velocity average value ωav, and the velocity ripple peak value ωpk are detected, and (ωav-ωav) indicating the amplitude of the velocity ripple is calculated. (3) The calculation of Ka = Ka + Ko is performed. However, K0 is a current ripple correction coefficient and can be set to an arbitrary value.

(4) Iurip = −Ka · dωr / dt _{( = 0 )} Iwrip = −Ka · dωr / dt _{( = 120 )} is calculated, and the U-phase current ripple correction value Iurip obtained by such calculation is calculated. W-phase current ripple correction value Iwrip
Are respectively added to the output current command values of the U phase and the W phase. It should be noted that FIG. 3 shows only a component part for adding the U-phase current ripple correction value Iurip through the arithmetic unit 10a.

(5) When the angular velocity ωr, the velocity average value ωav, and the velocity ripple peak value ωpk are detected again, (ωpk-ωav) is calculated, and the calculation result is smaller than the previous (ωpk-ωav) calculated value. In order to re-execute, the operation control from (3) above is executed again. When the above calculation result is equal to or larger than the previous (ωpk-ωav) calculated value, the previous U-phase current ripple correction value Iurip and the W-phase current ripple correction value Iwrip are used as they are for the U-phase and the W-phase. Use the current ripple correction command.

By performing the above control,
It is possible to reduce the torque ripple component unrelated to the torque fluctuation caused by the load torque fluctuation, such as the offset of the current detection means and the cogging torque of the induction motor 1.

In each of the above embodiments, the induction motor 1
I tried to detect each input current of U phase and W phase of
The current detection phase can be set arbitrarily. Also, the circuit components for feedback control can be obtained by a program of a microcomputer.

[0047]

As is apparent from the above description, according to the invention of claim 1, the offset of the current detecting means is automatically corrected by utilizing the speed ripple of the AC motor to be speed controlled. The torque ripple caused by the offset can be effectively reduced by utilizing the speed feedback control system. In addition, claim 2
According to the invention, since the torque ripple is proportional to the differential value of the speed ripple of the AC electric motor, the output current command value for the AC electric motor is directly corrected. It is possible to effectively reduce the torque ripple generated due to this. Further, according to the invention of claim 3, the antiphase torque ripple current value calculated by utilizing the above characteristics is added to the output current command value for the AC electric motor. Therefore, the offset of the current detecting means and the AC electric motor It is possible to reduce the entire torque ripple component such as cogging torque that is unrelated to the torque fluctuation caused by the load torque fluctuation.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an electrical configuration of a first embodiment of the present invention.

FIG. 2 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 3 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 4 is a timing chart for explaining the operation of the first to third embodiments of the present invention and the conventional example.

FIG. 5 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

In the drawing, 1 is an induction motor (AC motor), 2 is an inverter, 3 is a speed detector (speed detecting means), 4 is a pulse counter, 5 is a differentiating circuit, 8 is a sine wave reference current generator, and 9 is three-phase. Current converter (current detecting means), 10 current PI control unit, 11 average speed calculator (average value calculating means), 12 peak value detector (peak value detecting means), 13 current offset calculator (offset) (Correction means), 15 is a peak value and peak value phase detector, 16 is a torque ripple calculator (current command value correction means), 17 is a storage unit, 18 is an antiphase torque ripple reference generator (antiphase torque ripple calculation means). ) And 19 are anti-phase torque ripple command generators (current command value correcting means).

Claims (3)

[Claims] 1. A speed detecting means and a current detecting means for respectively detecting a speed and an input current of an AC electric motor are provided, and a current given to the AC electric motor is controlled on the basis of an output current command value created based on the detected outputs thereof. In the speed control device for an AC electric motor, which is configured to perform speed control, an average value calculation means for sequentially calculating a speed average value in a predetermined unit time based on the speed detection value by the speed detection means, and the speed Peak value detecting means for sequentially detecting the speed ripple peak value in a predetermined unit time of the speed detection value by the detecting means, speed average value calculated by the average value calculating means and speed detected by the peak value detecting means The difference from the ripple peak value is calculated as a signal indicating the amplitude of the speed ripple of the AC motor, and the calculation result is calculated as the current detection value. A speed control device for an AC electric motor, comprising: an offset correction unit that corrects an offset of the current detection unit by subtracting the current detected by the stage. 2. A speed detection means and a current detection means for detecting the speed and the input current of the AC electric motor, respectively, are provided, and the current supplied to the AC electric motor is controlled based on an output current command value created based on the detected outputs. In the speed control device for an AC motor configured to perform speed control, a torque ripple estimated value of the same period component as the cycle of the input current of the AC motor is calculated by differentiating the speed detection value by the speed detection means. In addition, the speed control device for an AC motor is provided with a current command value correction means for adding the antiphase component of the estimated value to the output current command value. 3. A speed detecting means and a current detecting means for respectively detecting a speed and an input current of the AC electric motor are provided, and the electric current given to the AC electric motor is controlled based on an output current command value created on the basis of the detected outputs. In the speed control device for an AC electric motor configured to perform speed control, a storage unit that sequentially stores a speed detection value by the speed detection unit in a period of one rotation or more of the electric motor as a speed ripple detection value, Anti-phase torque ripple calculation means for calculating the anti-phase torque ripple estimated value by inverting the phase of the torque ripple component obtained by differentiating the stored value by this storage section, and the inverse phase torque ripple calculation means calculated by this torque ripple calculation means. Add the anti-phase torque ripple current value calculated based on the estimated phase torque ripple value to the output current command value. A speed control device for an AC electric motor, comprising: