JPS59201689A - Controlling method of ac motor - Google Patents

Abstract

PURPOSE:To enable to stably control an AC motor by controlling so that a magnetic flux or the amount corresponding to the magnetic flux becomes small when the rate of change of rotating speed is the prescribed value or lower, thereby preventing the resonance. CONSTITUTION:When a speed command omega* outputted from an input limiter 11 is altered to accelerate or decelerate and to operate at a constant speed, the rate of change of speed is detected by a rate-of-change-of-speed detector 12, the rate of change of speed is compared with a set value by a comparator 13, and an output signal S13 is applied from the comparator 13 to a resonance preventing magnetic flux pattern corrector 17 when the rate of change is small. A correction magnetic flux command phi*22 is delivered from this circuit, and the magnetic flux command phi*21 outputted from a magnetic flux pattern circuit 16 is corrected by the command phi*22. Accordingly, the command phi*2 becomes smaller than the command phi*2N, the magnitude of the torque ripple is reduced to prevent the resonace.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an AC 11J driven by a frequency conversion device.
In particular, the present invention relates to a method for controlling an AC motor that prevents resonance in a drive system due to torque ripples that occur during commutation of a frequency converter.

[Technical background of the invention]

As a method for continuously controlling the speed of an AC motor such as a high conductivity motor or a synchronous motor, a frequency converter that can continuously vary the frequency is often used.

Examples of this frequency conversion device include an input/output converter using a transistor or a thyristor, a cycloconverter, and the like. These "fine wave number converters" are 6-phase (6-phase) devices used in small and medium-sized AC motors of approximately 200 to 306 kW or less from the viewpoint of economy.

[Problems with background technology]

The above-mentioned 6-pulse cylinder wave number converter performs commutation every 6'0 electrical degrees, so the operating frequency is 6 kf (however, 1 (=l,
2, 3. ) produces a relatively large kinator ripple. In particular, the swing width of Dorkuri and 2 Guru is the widest when ni = 1.

Here, in FIG. 1, as an example, the waveform of the generated torque torque l of a six-nodeless inverter is shown. 2 indicates the average torque value. Therefore, if the frequency 6kf of such generated torque ripple matches the natural frequency (resonant frequency) of the drive system composed of the AC motor and the load machine,
This causes resonance in the drive system, making it impossible to stably control the AC motor and damaging the machine.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and its purpose is to achieve an operation in which the generated torque ripple frequency of 6 kf of the AC motor driven by the frequency converter matches the natural frequency of the drive system. An object of the present invention is to provide a control method for an AC motor that can relatively easily prevent resonance and stably control even if the resonance occurs.

[Summary of the invention]

The present invention d In order to achieve the above object, a frequency conversion device 1
During operation of the AC motor driven by ffi, including acceleration or deceleration, the rate of change in the rotational speed of the AC motor or the rate of change in an amount corresponding to the rotational speed is detected, and when this rate of change is less than a predetermined value, the AC motor is activated. Controlling the magnetic flux or the amount corresponding to the magnetic flux 1. The control signal is corrected to control the output frequency of the frequency converter so that the magnetic flux of the AC motor becomes smaller.

First, the concept and principle of the present invention will be described.

The present invention has been made in consideration of the characteristics of the resonance phenomenon caused by torque rizzol during operation of an AC motor including acceleration or deceleration.

In a drive system that operates with acceleration or deceleration, it usually starts, accelerates, and when acceleration is completed, operates at a certain set rotation speed (or speed) for a certain period of time, and then accelerates or decelerates to the next set rotation speed. The engine is operated at a reduced speed, and these cycles are repeated.

Depending on the application, these accelerations and decelerations may be rapid accelerations and decelerations of about 1 to 3 seconds from atmospheric speed to maximum speed, or
There are cases where slow acceleration/deceleration takes several tens of seconds to several minutes. When performing rapid acceleration and deceleration during these accelerations and decelerations, since the acceleration and deceleration time is short, a large acceleration and deceleration torque is required, and the required torque of the AC electric motor (J!) is also very large.

Therefore, at this time, the torque ripple frequency 6 kf coincides with the natural frequency range (resonant frequency) of the drive system.
Even if there is a fl, the zero deceleration time is very short,
Since the resonant frequency point is passed very quickly, the torque at the resonant frequency point does not grow significantly. In this case, no resonance phenomenon occurs, so in practice it is not necessary to take countermeasures against resonance.

However, in the case of slow acceleration/deceleration operation, the acceleration/deceleration time becomes long and only a relatively small acceleration/deceleration torque is required.For applications where friction torque is not large, the required torque of the AC motor may be relatively small.

During this slow acceleration/deceleration operation, the torque ripple frequency is 6k.
When f matches the resonant frequency of the drive system, since the time to pass through the resonant frequency point is slow, the torque increases greatly at the resonant point depending on the way the torque resonator is excited, causing resonance.

In addition, in the case of constant speed operation, the required torque of the electric motor is not accelerated or decelerated, so there is no need for acceleration or deceleration torque, and it is sufficient to have enough torque to overcome the frictional torque. In this case, in applications where the friction torque is insignificant, the required torque after AC electric power may be relatively small. During this constant speed operation, if the torque ripple frequency 6kf completely matches the resonance frequency of the drive system, the resonance phenomenon continues.

Next, when a 6-pulse (6-phase) current-source inverter is used as a frequency converter and an induction electric UJ machine is driven as an AC motor, the magnitude of the torque rinnor with an angular frequency of 6 to ω (=6k・2πf) is determined. Ttr is expressed by equation (1).

'l'' t r= K7 ・Φ2・ ...(1) However, Φ2: Magnitude of secondary magnetic flux J2 of visiting motor, fundamental wave amplitude of primary current vector il, KT:) Luke coefficient, θ: Position between secondary magnetic flux φ2 and primary current vector II ωS:
Total frequency of induction motor, T2: Secondary time constant of induction motor (=Lz /R2) L2
'm4 Secondary self-inductance of the motor, R2: Secondary resistance of the induction motor, R61e+, l, R6 -1' High frequency component coefficient (
k==1.2. −・Uω: Fundamental wave angular frequency of 11 (−2
πf) f: Fundamental frequency (operating frequency) of i+ Also,
If the average torque is Tm, it is expressed by equation (2).

Tm == KT ・Φ2・Work 1! +IfIθ
-(2) The vector relationship between the -order' commercial vector 11 and the secondary magnetic flux ψ2 is shown in FIG. If the magnetic flux component current of the in-phase component of ml and φ2 is ild, and the torque component current of the orthogonal component is Ilq, the equations N (3) and (4) hold true.

11d=11cosθ−(3
)i, q=11sinθ−(
4) For a certain value of all 9 angular frequencies ωS, the torque ripple in equation (1) becomes as shown in equation (5).

Ttro(Φ241cosθ=Φ2.1ld-(5) Also, itd = (1+T2 S)Φ2
...(51 However, M: Mutual inductance of the induction motor, S Nilagrass operator, Equation (5) can be transformed into Equation (6).

Therefore, according to equation (6), in order to reduce the torque ripple generated by the electric shock absorber, if Φ2 is made smaller, Φ2'
It is found to be relatively small and very effective.

In the vector control method in which the magnetic flux component current i1d and the torque component current 11q are independently controlled, the amount lid corresponding to Φ2 can be reduced in place of the magnetic flux Φ2 to reduce drooping and gluing. Furthermore, in the V/f constant control method for the primary voltage (■) and primary frequency of the induction motor, V/f is approximately proportional to Φ2, so if V/f is reduced in place of Φ2, the torque ripple can be reduced. I can do it.

Therefore, in operation including acceleration or deceleration, when the rate of change in the rotational speed of the AC motor or the rate of change in it corresponding to the rotational speed is below a predetermined value, the magnetic flux Φ2 of the AC motor or the amount corresponding to Φ2 is controlled. If the output frequency of the frequency control device is controlled so that the magnetic flux Φ2 is reduced by correcting the control signal for the magnetic flux Φ2, the resonance phenomenon of the drive system can be prevented.

The average torque in equation (2) can be transformed as shown in equation (7) using equation (4).

Tm: KT″71′2″l5Inθ=KT−Φ2″l
lq ”° (7) In the case of slow acceleration/deceleration or constant speed where the rate of change in rotational speed is less than a predetermined value, the magnetic flux Φ2 or the amount corresponding to Φ2 is controlled to be small in order to prevent resonance due to torque ripple. However, as can be seen from equation (7), the torque generated by the motor is smaller than that for the current value during normal operation.However, since it is during MW acceleration/deceleration or constant speed operation, the acceleration/deceleration torque is small. without requiring k
In applications where the friction torque is relatively small, the required torque of m q-t may be small, so a reduction in the generated torque is not a problem in practice.

If you want to maintain the required torque of the motor before reducing Φzf in applications where the proportion of friction torque is large, use the vector control method and reduce the decrease in Φ2 by reducing the torque by the current 11.
It is possible to control the motor torque Tm to be constant by increasing q.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Third
The figure shows an example of a configuration in which an induction motor is used as the AC motor, a constant torque load is applied, and the frequency conversion device is applied to a vector control method of a current source inverter.

In FIG. 3, 3 is a three-phase AC power supply, 4 is an induction motor, and the electric path between these AC power supply 3 and the induction motor 4 includes a 7m converter 5, a DC reactor 6, and an inverter 7 at 71. are installed in series. 8 is a speed detector (for example, a ZOLS oscillator) that detects the rotational speed of the 40-induction motor;
9 is a current detecting current transformer installed in the AC power supply side circuit, l
θ is a current transformer for detecting the current phase installed in the electric circuit on the induction machine side. Also, 1 is a stepwise speed command υ1
12 is an input control circuit which converts the input into an angular velocity command ω1 of the inevitable acceleration/deceleration rate, 12 is a speed change rate detection circuit which outputs the rate of change dω"/at when this angular velocity command ω1 is input, and 13 is a speed change rate detection circuit. When the output of the speed change rate detection circuit 12 is input, it is compared with a speed change rate set value set to a predetermined value, and when the speed change rate is smaller than the set value, the output signal S is output.
This is a comparator that generates 13.

14 is an F/'V conversion circuit that converts the pulse signal ω output from the speed detector 8 into an analog voltage, and 15 is a deviation between the angular velocity command ω1 and the output ω of the F/'V conversion circuit 14, that is, the speed variation. A speed control circuit to which Sω is input, 16 a 5A bundle pattern circuit to which the output ω of the Luhe' conversion circuit 14 is input, and 17 an output ω of the Luhe conversion circuit 14 and the output signal 81B of the comparator 13 are input. This magnetic flux/turn circuit 16 and the magnetic flux/turn correction circuit for resonance prevention
The function of the turn correction circuit 17 will be described in detail later. Furthermore, 18 indicates whether the deviation between the output of the magnetic flux pattern circuit 16 and the output of the magnetic flux/main turn compensator circuit 17 for preventing resonance is the magnetic flux command Φ? This magnetic flux control circuit 18 outputs a magnetic flux fraction % flow command "d"k in phase with the secondary magnetic flux vector Φ2 of the primary current vector 11 of the electric motor 4. Reference numeral 19 indicates a torque component current command orthogonal to the secondary magnetic flux vector Φ2 of the primary current vector 11, that is, the output 11□' of the speed control circuit 15, the output 11♂ of the magnetic flux control circuit 18, and the output from the current transformer lO for detecting the current phase. The current phase θ and the speed signal ω of the motor output from the speed detector 8 are input, and the primary current command II”, magnetic flux Φ2, and phase difference θ9 are obtained.
-θ is output. On the other hand, 2o is a current detection circuit that detects the input current of the forward converter 50 from the output of the current detection current transformer 9, and 2) is a current command I output from the output of this current detection circuit 20 and the vector calculation control circuit 19. , ``22 is a phase i which controls the thyristor f of the forward converter 5 in accordance with the current-controlled output of the current control circuit 21 to control the current. ?
7j control circuit d). Further, 23 is a commutation control circuit to which the phase difference θ-θ of the current outputted from the vector control circuit 9-control circuit 19 is added, and this commutation control circuit 23 is designed so that the phase difference θ1-θ of the current becomes an atmosphere. The thyristor of the reverse control unit 7 is selected to apply ignition and pulse to control the frequency.

Figure 4 shows a circuit that controls the pattern of the secondary magnetic flux command Φ2* with respect to the angular velocity ω of the induction motor 4.
In the figure, a magnetic flux pattern circuit 16, a magnetic flux pattern correction circuit 17 for preventing resonance, and these magnetic flux/turn circuits 1
6 and a circuit that obtains the secondary magnetic flux command Φ2* from the deviation of the output of the magnetic flux no.f-turn sleeve correction circuit 17.

The magnetic flux/mother turn circuit 16 provides a secondary magnetic flux command curve for the angular velocity ω, and shows the case where the rated magnetic flux Φ2N is at a constant strength value. In addition, the resonance prevention magnetic flux pattern correction circuit 17 is connected to the output number 813 of the comparator J3 (shown in FIG. 3).
When it is detected that the rate of change in the angular velocity command ω corresponding to the speed has become less than a predetermined value, the correction magnetic flux command Φ221
This outputs the following. The finally issued magnetic flux command Φ2* is obtained by taking the difference between the magnetic flux command Φ21'' based on the normal magnetic flux setting and the corrected magnetic flux command Φ22*. Figure 5 shows this final magnetic flux command Φ2* and Φ21*, Φ22
This shows the relationship with *. Incidentally, in FIG. 4, the turns drawn by the magnetic flux pattern circuit 17 for preventing resonance are shown by the 1C line for the sake of simplicity, but the present invention is not limited to this.

Next, the operation of the embodiment configured as described above will be described. Now, in FIG. 3, the box-flow type inverter is started, and the speed command ω9 inputted to input 1b is changed to perform acceleration/deceleration and constant speed 1. When performing two rotations, the speed command ω゜ and the actual angular velocity ω of the motor
When a speed deviation occurs between the speed control circuit 15 and the command % of the average torque output from the speed control circuit 15, KT is a torque coefficient. Further, when the speed change rate detection circuit 12 receives the speed command ω' of the motor, it detects the speed change rate and supplies it to the comparator 13. The comparator 13 compares this speed change rate with a set value, and when the speed change rate is greater than the set value, an output signal 81B is output.
will not be sent. Therefore, at this time, the output signal S1 from the comparator 13 is sent to the resonance prevention magnetic flux pattern correction circuit J7.
3 is not input, the output of this magnetic flux pattern circuit 17 is blank, and the magnetic flux command Φt is the magnetic flux command Φ2N output from the magnetic flux pattern circuit 16. Further, when the magnetic flux change rate is smaller than the set value, an output signal SI3 is applied from the comparator 13 to the resonance prevention magnetic flux pattern correction circuit 17. Then, a correction magnetic flux command Φ2□' is sent out from the resonance prevention magnetic flux pattern correction circuit 17, and the magnetic flux command Φ21* output from the magnetic flux pattern circuit 16 is corrected by this correction magnetic flux command Φ221. Therefore, the magnetic flux command Φ29 becomes smaller than the magnetic flux command Φ2N* due to the normal magnetic flux setting as shown in FIG. 5, and acts to reduce the magnitude of the torque ripple and prevent resonance. When the magnetic flux command 2* is input to the magnetic flux control circuit 18, the magnetic flux control circuit 18 outputs a current command L+d for the magnetic flux of the primary current.
Output. In this case, the magnetic flux current command 11d* is an inductance. The output 11♂ of the speed control circuit 15, the output 11♂ of the magnetic flux control circuit 18, the current phase θ output from the current phase detection current transformer 10, and the speed signal ω output from the speed detector 8 are vector calculation controlled. When input to the circuit 19, the vector calculation control circuit 19 processes the sequential current command I11 through calculation control.
ld")"+(ilQ")', and the current phase command θ* is obtained from the current phase command θ* to output the phase difference θ9−θ, respectively.

Next, the current command 11'' output from the vector calculation control circuit 19 is compared with the actual current detected by the current detection circuit 20, and the deviation signal is added to the current control circuit 21. The phase control circuit 22 controls the phase of the thyristor of the forward converter 5 according to the output of The commutation control circuit 23 selects the timing of the inverse converter 7 so that this phase difference becomes negative, applies an ignition pulse, and controls the output frequency.

In this way, when the speed of the induction motor 4 becomes smaller than a predetermined value, the magnetic flux command Φ2* is controlled to become smaller, thereby controlling the output frequency of the current source inverter, thereby preventing resonance in the drive system due to torque ripple. I can do it. In this case, if the magnetic flux command Φ2* is made smaller, the average torque Tm is automatically determined according to Φ21, so the torque does not become smaller.

Next, another embodiment of the present invention will be described. FIG. 6 shows a configuration example in which the present invention is applied to V/f control of a current source inverter. In Figure 6, 3 is a three-phase AC power supply,
4 is an induction motor, and a forward converter 5 and a DC reactor 6 are connected to the AC power source 3 and the induction motor 4.
, an inverter 7 are provided in series in sequence.

Reference numeral 9 denotes a current detecting current transformer provided in the AC power supply side circuit. Further, 11 is an input limiting circuit to which the speed command υ'' is input, 26 is a speed change rate detection circuit to which the '8 coffin number command f1 output from the input limit circuit 11 is applied, and 27 is from this speed change rate detection circuit 26. Output speed change rate df*/
This comparator 2-7 compares the speed change rate df''/dt with the speed change rate set value, and outputs a time delay output signal S27 where the speed change rate is smaller than the set value. 28 is a voltage/two-voltage circuit to which the frequency command f*' outputted from the input limiting circuit 11 is applied;
29 also indicates the frequency command f* and the output signal S of the comparator 27.
27 is the input voltage/(turn correction circuit, these voltage pattern generation circuit 2B and voltage pattern correction circuit 2
The function of 9 will be described in detail later. 30 is a voltage detection circuit into which the electric IJJ@voltage is input via a transformer 31 connected to the induction motor side electric circuit, and 32 is a deviation between the output of the voltage/thousand turn circuit 28 and the output of the voltage pattern correction circuit 29. This is a voltage control circuit to which the deviation between the voltage command V* obtained from the voltage command V* and the detected voltage ■ output from the voltage detection circuit 30 is input. 20 is a current detection circuit that detects the input current of the forward converter 5 from the output of the current detection current transformer 9; 21 is the input of the deviation between the output of this current detection circuit 20 and the current command output from the voltage control circuit 32; The current control circuit 22 is a phase control circuit that controls the dart of the thyristor of the forward converter 5 to control the current according to the output subjected to the stain flow control by the current control circuit 21 of the fan. Furthermore, 33 is an oscillator that outputs a pulse according to the frequency command f* input from the input limiting circuit 1, and 34 is an oscillator that outputs a pulse according to the frequency command f* inputted from the input limiting circuit 1.The pulse output from this oscillator 33 is added to determine the firing order of the cyrisk of the inverter 7. The frequency divider circuit 35 is a pulse amplifier to which the output of the frequency divider circuit 34 is added to trigger the sirisk of the inverter 7.

Figure 7 shows a circuit that controls the pattern of the voltage command ■'' for the frequency command f' given to the induction motor.
is a constant) The output is sent out when the speed change rate df''/dt detected by the voltage pattern circuit 28 that generates the voltage given by (constant) and the speed change rate detection circuit 26 is smaller than the speed change rate set value. Voltage pattern correction circuit 29 that generates a voltage/setan of ■2* according to the signal 827
, and a circuit that obtains a voltage command v1 from the deviation of the outputs of the voltage pattern circuit 28 and the voltage/interference correction circuit 29. FIG. 8 shows the relationship between this voltage command V" and the voltage/mother turn V!" Turn v2* is shown as a straight line for simplicity, but it is not limited to this.

Next, the operation of the embodiment configured as described above will be described. Now, in Fig. 6, the speed command υ is applied to the input limiting circuit 1).
”, this speed command V* becomes the frequency command f*
is converted to When this frequency command f9 is applied to the voltage pattern circuit 28 and the voltage pattern correction circuit 29, the voltage command y* obtained as the output deviation of the voltage pattern circuit 28 and the voltage pattern correction circuit 29 is on the line shown in FIG. It is given by taking the value of That is, when the speed change rate df''/dt detected by the speed change rate detection circuit 26 is larger than the speed change rate setting value, the comparator 27 outputs a signal 82γ to the voltage pattern correction circuit 29.
is not input, the output of the voltage pattern correction circuit 29 is in the atmosphere, and therefore the voltage command (1) is the normal V.
Take the value on the solid line due to νTK. However, speed change rate df*
When /dt is smaller than the speed change rate setting value, the comparator 27
Since the output signal 827 is input to the voltage pattern correction circuit 27, the voltage command is controlled to a small value as shown by the dotted line. The voltage command (1) obtained in the above manner is compared with the motor voltage V detected by the voltage detection circuit 30, and the deviation signal thereof is input to the voltage control circuit 28.

This voltage control circuit 28 sends out the output (S) to be controlled as a current command t so that the deviation signal becomes ambience. It is compared with the input current, and the current deviation is input to the current control circuit 21.The current control circuit 21 then inputs an output signal to be controlled to the phase control circuit 22 so that the current deviation becomes equal to the current deviation. Additionally, this phase control circuit 22 controls darting of the thyristor of the forward converter 5 in accordance with the output signal of the current control circuit 21.

On the other hand, the frequency command f* output from the input limiting circuit 1)
is added to the oscillator 33, this oscillator 33 generates a signal corresponding to the frequency command f*, and this signal is applied to the frequency dividing circuit 34, thereby generating the inverter 7.
At the same time, the ignition timing is determined. The output signal of this frequency dividing circuit 34 is amplified by a pulse amplifier 35, and the output frequency of the inverter 7 is controlled by applying the output signal to the thyristor of the inverter 7.

In this way, when the speed of the induction motor 4 is slow acceleration/deceleration or constant speed, the voltage command is controlled to be smaller than the normal voltage command, and the output frequency of the current source inverter is controlled. The generated torque crinol is reduced, and resonance of the drive system can be prevented. Further, during rapid acceleration/deceleration, the current source inverter can be operated by frequency control based on the normal voltage command V1*.

As is clear from the above-mentioned examples,
When the rate of change in the rotational speed of the induction motor or the rate of change in the amount corresponding to the rotational speed is less than a predetermined value, the magnetic flux of the induction motor or the amount corresponding to the magnetic flux is controlled to be small, so that the motor and load Resonance due to torque ripples can be prevented without using an expensive elastic force or 7-knot ring between the two. In addition, since the generated torque rizzol can be reduced, if a 6-phase (6-phase) frequency converter is sufficient in terms of capacity as a frequency converter for controlling the load motor, it is possible to use it, or 12-phase (6-phase) frequency converter.
There is no need to use a frequency converter with a large capacity such as 12-phase) or 18-Prus (18-phase). Furthermore, there is no need to detect the resonance frequency of the drive system, and resonance of the drive system can be prevented with a simple circuit.

In addition, if a vector control method is used as the control method, only the torque ripple can be reduced without reducing the required average torque, and it can be used without problems even with loads that require sudden acceleration and deceleration with constant torque. .

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications without changing the gist thereof. That is, in each of the above embodiments, the speed change rate was obtained based on the angular speed concealment command ω1 and the frequency command f*, but it is also possible to use a value obtained by detecting an actual measured value ω, etc. Although a current source thyristor inverter is used as the embodiment, it goes without saying that a voltage source thyristor inverter, a trannostern converter, a square wave cycloconverter, etc. may also be used. Furthermore, although an induction motor has been described as an example of the motor, it goes without saying that a synchronous motor may also be used.

However, in each of the above-mentioned embodiments, the resonance frequency ωr.

fr is set as one point, but this is to reduce Φ2'' p v2111 near the primary resonance frequency, which has the greatest influence, but when higher-order resonance frequencies such as secondary and tertiary become a problem, Φ2'' e v2* may be made small near the resonance frequency corresponding thereto.

〔Effect of the invention〕

As described above, according to the present invention, an amount corresponding to the rate of change in the rotational speed of the AC motor, or the rotational speed, of the AC motor driven by the frequency conversion device, is applied to the operation including acceleration or deceleration of the AC motor. By controlling the magnetic flux of the AC motor or the amount corresponding to the magnetic flux to be small when the rate of change of is less than a predetermined value,
Even when there is an operation where kf matches the natural frequency of the drive system, it is possible to provide a control method for an AC motor that can relatively easily prevent resonance and provide stable control.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram of the generated torque rizzol when an induction motor is driven by a current source inverter, Figure 2 is a diagram showing the vector relationship between the induction motor's primary current vector i+ and secondary magnetic flux Φ2, and Figure 3 is a diagram showing the vector relationship between the induction motor's primary current vector i+ and secondary magnetic flux Φ2. FIGS. 4 and 5 are circuit configuration diagrams showing an embodiment of the invention;
FIG. 6 is a circuit configuration diagram showing another embodiment of the present invention, and FIGS. 7 and 8 are explanatory diagrams of how to give a voltage command v1 to a frequency command f* to the electric motor in the same embodiment. 3... AC power supply, 4... Induction motor, 5... Forward converter, 6... DC reactor, 7... Inverse converter, 8
...Speed detector, 9.10...Current transformer, 1...
Tachi limit circuit, 12... Speed change rate detector, 13...
Comparator, 14...F bar detector, 15 River speed control circuit, 16...Magnetic flux pattern circuit, 17...Resonance prevention magnetic flux/turn correction circuit, 18...Magnetic flux correction circuit, 1
9... Vector calculation control circuit, 20... Current detection circuit, 2... Current control circuit, 22... Phase control circuit, 23... Commutation circuit, 26... Speed change rate detection Circuit, 27... Comparator, 28... Voltage pattern circuit, 2
9... Resonance prevention voltage/turn correction circuit, 30...
・Voltage detection circuit, 3... Transformer, 32... Voltage control circuit, 33... Oscillator, 34... Frequency dividing circuit, 35
...Pulse amplifier. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] When an AC motor driven by a frequency conversion device is operated including acceleration or deceleration, a rate of change in the speed of the AC motor or a rate of change in an amount corresponding to the speed is detected. When controlling the magnetic flux of the AC motor or the frequency corresponding to the magnetic flux, the output frequency of the frequency converter is controlled so that the magnetic flux of the AC motor is reduced by correcting the control signal. I
J1] Machine control method.