JP3777943B2 - Control device for vector control inverter for AC motor drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a vector control inverter for driving an AC motor that controls the torque of the AC motor by vector control of the inverter.
[0002]
[Prior art]
FIG. 4 is a block circuit diagram showing a conventional control circuit for controlling the torque of an AC motor by a vector control inverter. In the conventional circuit of FIG. 4, AC power from the AC power source 1 is converted into AC power having a predetermined voltage and frequency by the inverter 2, and the induction motor 3 as an AC motor is operated with a desired torque. Reference numeral 4 denotes a load driven by the induction motor 3, and reference numeral 5 denotes a speed detector that detects the speed of the induction motor 3.
[0003]
The secondary magnetic flux command value φ ₂ ^* set by the secondary magnetic flux setter 14 is converted into an M-axis current command value I _M ^* parallel to the secondary magnetic flux of the primary current of the induction motor 3 by the M-axis current command calculator 15. Converted. Further, the T-axis current setting unit 12 sets a T-axis current command value I _T ^* perpendicular to the M-axis current command value I _M ^* . On the other hand, the first coordinate converter 11 inputs the U-phase current I _U and W-phase current I _W of the induction motor 3 detected by the current detector 6, and detects the M-axis current parallel to the secondary magnetic flux of the primary current. It is converted into I _M and a T-axis current detection value I _T perpendicular thereto. In this conversion, the T-axis current detection value I _T and the M-axis current detection value I _M can be obtained by calculating according to the following equations 1 and 2. Here, θ ₂ is an angle formed by the U-phase winding and the secondary magnetic flux of the induction motor 3.
[0004]
[Expression 1]
I _T = I _U · cos θ ₂ + I _V · cos (θ ₂ -2π / 3) + I _W · cos (θ ₂ + 2π / 3)
[0005]
[Expression 2]
I _M = I _U · sin θ ₂ + I _V · sin (θ ₂ -2π / 3) + I _W · sin (θ ₂ + 2π / 3)
The T-axis current regulator 13 inputs a deviation between the T-axis current command value I _T ^* and the T-axis current detection value I _T, and generates a T-axis voltage command value V _T ^* that makes the input deviation zero by the adjustment operation. Output. The M-axis current regulator 16 inputs a deviation between the M-axis current command value I _M ^* and the M-axis current detection value I _M, and obtains an M-axis voltage command value V _M ^* that makes the input deviation zero by the adjustment operation. Output. The second coordinate converter 17 inputs these T-axis voltage command value V _T ^* and M-axis voltage command value V _M ^* and converts them into three-phase voltage command values V _U ^* , V _V ^* , V _W ^* . However, this conversion is calculated by the following mathematical formulas 3, 4, and 5 where θ ₂ is an angle formed between the U-phase winding and the secondary magnetic flux of the induction motor 3.
[0006]
[Equation 3]
V _U ^* = V _M ^*・ cosθ ₂ + V _T ^*・ sin θ ₂
[0007]
[Expression 4]
V _V ^* = V _M ^* · cos (θ ₂ -2π / 3) + V _T ^* · sin (θ ₂ -2π / 3)
[0008]
[Equation 5]
V _W ^* = V _M ^* · cos (θ ₂ + 2π / 3) + V _T ^* · sin (θ ₂ + 2π / 3)
These three-phase voltage command values V _U ^* , V _V ^* , and V _W ^* are converted into AC power having a predetermined voltage and frequency by the inverter 2 and supplied to the induction motor 3.
[0009]
The slip frequency calculator 18 inputs the T-axis current command value I _T ^* and the secondary magnetic flux command value φ ₂ ^* described above, and calculates the slip frequency ω _sl by the calculation of Equation 6 below. However, R ₂ is the secondary resistance of the induction motor 3.
[0010]
[Formula 6]
ω _sl = R ₂ · I _T ^* / φ ₂ ^*
A value ω ₁ obtained by adding the slip frequency ω _sl obtained by this calculation and the speed detection value ω _R detected by the speed detector 5 is input to the integrator 19 and integrated to obtain the above-described value. Θ ₂ is obtained as an angle formed by the secondary magnetic flux of the U-phase winding and the induction motor 3.
[0011]
The induction motor 3 that is driven by the AC power converted by the vector control inverter 2 and is torque controlled is used for various applications. For example, a winding material for winding a long material such as a thread. The case of applying to a machine will be described below.
FIG. 5 is a block circuit diagram showing an example of a case where a motor controlled in torque by a vector control inverter drives a winder. The induction motor 41 receives a yarn 44 as a long material via a speed reducer 42. The winder 43 for winding is driven. The winding machine 43 is provided with a winding diameter sensor 46, and the winding diameter is converted into a magnetic flux command value φ ₂ ^* by an amplifier 47. That is, assuming that the maximum winding diameter of the winding machine 43 is D ₁₀₀ and the current winding diameter detected by the winding diameter sensor 46 is D, the magnetic flux command value φ ₂ ^* is calculated by the following Equation 7.
[0012]
[Expression 7]
φ ₂ ^* = 100 · D / D ₁₀₀ (%)
The amplifier 47 performs the calculation of Equation 7 and gives the magnetic flux command value φ ₂ ^* as the calculation result to the control device 48. The tension T of the yarn 44 is detected by the tension detector 51. When the tension detection value T and the tension command value T ^* set by the tension setting device 50 are input to the tension adjuster 49, the deviation between the two inputs becomes zero. The T-axis current command value I _T ^* is applied from the tension adjuster 49 to the control device 48. Further, a speed detection value ω _R from a speed detector 45 coupled to the induction motor 41 is also input to the control device 48. The control device 48 corresponds to the entire circuit of the conventional example already described in FIG. 4 (except for the T-axis current setting device 12 and the secondary magnetic flux setting device 14).
The generated torque τ of the winder 43 is the product of the T-axis current I _T and the secondary magnetic flux φ _{2 as} shown in Equation 8 below.
[0013]
[Equation 8]
τ = I _T・ φ ₂
On the other hand, since the tension detection value of the yarn 44 is T, when the winding diameter of the winder 43 is D and the constant is K, the torque τ of the induction motor 41 viewed from the tension can be expressed by Equation 9.
[0014]
[Equation 9]
τ = K ・ T ・ D / 2
Therefore, if the magnetic flux command value φ ₂ ^* is manipulated for the winding diameter D and the T-axis current command value I _T ^* is manipulated for the tension T, the torque of the induction motor 41 can be controlled to control the yarn. It can be seen that the tension of 44 can be controlled.
[0015]
[Problems to be solved by the invention]
The control device 48 shown in FIG. 5 has a built-in current detector (corresponding to the current detector 6 in FIG. 4). This current detector must detect low-frequency alternating current. In consideration of the size, mass, price, etc. of the current detector, a Hall element type current transformer or a shunt resistance type current transformer (with an insulation amplifier) is generally adopted. However, there is an offset in the Hall element type current transformer, and there is an offset in the isolation amplifier even if there is no offset in the main body of the shunt resistance type current transformer. Further, since these offsets vary with temperature change, it is difficult to make them zero, and their values vary depending on ambient conditions. Due to this offset, a torque ripple having the same frequency as the frequency of the voltage output from the control device 48 is generated. This torque ripple has a defect that causes tension fluctuation when the tension of the winder 43 is controlled.
[0016]
In particular, static tension control (when the winding operation is temporarily interrupted during the winding operation of the yarn 44, the rotational speed of the winding machine 43 is made zero while the predetermined tension is applied to the yarn 44. ) If there is a torque ripple, the winder 43, which must be stationary, repeats normal rotation and reverse rotation, causing slack in the yarn 44 to which a predetermined tension should be applied, resulting in a defective product. This causes a malfunction.
[0017]
Since the purpose of the tension adjuster 49 is to control the tension to be constant, such a tension fluctuation must be suppressed. However, a high-frequency tension fluctuation exceeding the response speed of the tension adjuster 49 is required. In this case, it becomes difficult to suppress. By the way, the frequency of torque ripple (tension fluctuation) is proportional to the frequency of the voltage output from the control device 48. Therefore, the frequency increases when the winding diameter is small. When the winder 43 is at zero rotation, the induction motor 41 is also at zero rotation, and the frequency of the voltage output by the control device 48 at that time is represented by the slip frequency ω _sl of Equation 6. If the winding diameter D when the winder 43 is at zero rotation is small, the magnetic flux command value φ ₂ ^* becomes small according to Equation 7, and therefore the slip frequency obtained by substituting this magnetic flux command value φ ₂ ^* into Equation 6 ω _sl becomes large, and the tension fluctuation is likely to occur as described above.
[0018]
Further, in the circuit for controlling the torque of the electric motor for driving the winder shown in FIG. 5 by the vector control inverter, the winding diameter sensor 46 in which a detection error exists or when the winding diameter is converted into the magnetic flux command value φ ₂ ^*. Since the amplifier 47 and the like that may cause an adjustment error are provided, the magnetic flux command value φ ₂ ^* may exceed the desired value due to these errors.
[0019]
By the way, since the back electromotive voltage of the motor is proportional to the product of the magnetic flux and the frequency, if a magnetic flux larger than necessary is generated as the magnetic flux command value φ ₂ ^* becomes excessive as described above, the back electromotive force of the motor The voltage becomes excessive. Since the voltage that can be output by the control device 48 is limited, if the back electromotive voltage increases and the difference voltage between the two decreases, the control device 48 becomes difficult to perform stable current control. As a result, tension fluctuation occurs.
[0020]
If the frequency is low, the back electromotive force does not become excessive even if the magnetic flux increases, so the tension fluctuation described above does not occur. However, if an excessive magnetic flux command value φ ₂ ^* is given, the internal magnetic flux of the motor In order to generate a magnetic flux according to the command value in the motor due to the magnetic saturation, an inconvenience that an excessive M-axis current I _M must flow is caused.
[0021]
Therefore, an object of the present invention is to suppress torque ripple caused by the offset of the current detector and to control the unstable or excessive current control caused by various errors when the AC motor is torque controlled by the vector control inverter. It is to suppress the M-axis current.
[0022]
[Means for Solving the Problems]
In order to achieve the above object, a control device for a vector control inverter for driving an AC motor according to the present invention comprises:
The primary current of the AC motor is separated into an M-axis current component parallel to the secondary magnetic flux and a T-axis current component perpendicular thereto, and control is performed to match these current components with respective current command values set separately. In doing
A separately set value when the rotational speed of the AC motor is zero is set as a lower limit value, and the set value is decreased to a predetermined value as the rotational speed is increased to a lower limit value. Is a lower limit value, a first secondary magnetic flux command value changing circuit that outputs the secondary magnetic flux command value as a new secondary magnetic flux command value with the secondary magnetic flux command value as an input, and at least the T-axis current command And a new secondary magnetic flux command value output from the first secondary magnetic flux command value change circuit, and a value inversely proportional to the new secondary magnetic flux command value is output as a new T-axis current command value. And a T-axis current command value changing circuit.
[0023]
Alternatively, when the rotational speed of the AC motor is equal to or lower than the base speed, the separately set value is set as an upper limit value, and when the base speed is exceeded, the separately set value is reduced in inverse proportion to the rotational speed to be set as the upper limit value. A second secondary magnetic flux command value changing circuit that outputs a value corresponding to the rotation speed as a new secondary magnetic flux command value, and at least the T-axis current command value and the second secondary magnetic flux command value. A T-axis current command value changing circuit that inputs a new secondary magnetic flux command value output from the change circuit and outputs a value inversely proportional to the new secondary magnetic flux command value as a new T-axis current command value; Shall be provided.
[0024]
Alternatively, the first secondary magnetic flux command value change circuit and the second secondary magnetic flux command value change circuit output a new secondary magnetic flux command value in which the upper and lower sides of the input secondary magnetic flux command value are limited, At least the T-axis current command value and a new secondary magnetic flux command value whose upper and lower limits are restricted by these secondary magnetic flux command value changing circuits are input, and a value inversely proportional to the new secondary magnetic flux command value is set. It is assumed that a T-axis current command value changing circuit that outputs a new T-axis current command value is provided.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block circuit diagram showing a first embodiment of the present invention. This first embodiment circuit is different from the conventional circuit already described in FIG. The shaft current command value changing circuit 22 is added, and the names, uses, and functions of the remaining parts excluding this additional part are the same as those of the conventional circuit shown in FIG. .
[0026]
In the first embodiment circuit of FIG. 1, the first secondary magnetic flux command value changing circuit 21 corresponds the secondary magnetic flux command value φ ₂ ^* set by the secondary magnetic flux setting device 14 to the rotational speed of the induction motor 3. Is converted to a new secondary magnetic flux command value φ ₂₂ ^* that does not fall below the lower limit that changes, and is output to the M-axis current command calculator 15. That is, the first secondary magnetic flux command value changing circuit 21 has a separate set value when the speed detection value ω _R detected by the speed detector 5 is zero (this separate set value is determined by the induction motor 3 at the rated rotational speed). The lower limit value is 100% of the command value of the magnetic flux corresponding to the secondary magnetic flux of the motor when the rated torque is output during operation. This lower limit value decreases as the speed detection value ω _R increases. If the lower limit value decreases to a predetermined value, the speed detection value ω _R thereafter increases, but the predetermined value is the lower limit value, and a new second value output from the first secondary magnetic flux command value changing circuit 21 is obtained. The next magnetic flux command value φ ₂₂ ^* is limited so as not to exceed this lower limit value. The M-axis current command calculator 15 outputs a new M-axis current command value I _MM ^* by inputting a new secondary magnetic flux command value φ ₂₂ ^* limited by this lower limit value.
[0027]
The T-axis current command value changing circuit 22 includes a T-axis current command value I _T ^* set by the T-axis current setting device 12, a secondary magnetic flux command value φ ₂ ^* set by the secondary magnetic flux setting device 14, and A new secondary magnetic flux command value φ ₂₂ ^* output from the first secondary magnetic flux command value changing circuit 21 is input, and a new T-axis current command value I _TT ^* is calculated and output by the calculation of Equation 10 below. .
[0028]
[Expression 10]
^{_{I TT * = I T * ·}} φ 2 * / φ 22 *
The motor torque τ is the product of the T-axis current I _T and the secondary magnetic flux φ ₂ as shown in Equation 8 above. Therefore, for example, when the rotational speed of the induction motor 3 is extremely low, even if the new secondary magnetic flux command value φ ₂₂ ^* is increased, the new T-axis current command value I _TT ^* is reduced according to Equation 10. When the motor is operating at a low speed, even if the new T-axis current command value I _TT ^* is small, the new secondary magnetic flux command value φ ₂₂ ^* becomes large and a predetermined torque can be secured. . The time T-axis current I _T is because it is small, it is possible to suppress the torque ripple.
[0029]
FIG. 2 is a block circuit diagram showing a second embodiment of the present invention. The first secondary magnetic flux command value changing circuit 21 shown in FIG. 1 is replaced with a magnetic flux command lower limit calculator 31 and a secondary magnetic flux lower limit limiter 32. However, the rest of the configuration is the same except that the description of the operation of the circuit of the second embodiment shown in FIG. 2 is omitted.
FIG. 3 is a graph showing an example of input / output characteristics of the magnetic flux command lower limit calculator shown in FIG. 2. The horizontal axis represents the detected rotational speed value ω _R of the induction motor 3, and the vertical axis represents the magnetic flux command lower limit value. Represents.
[0030]
In the graph of FIG. 3, when the motor speed is zero, the magnetic flux command lower limit value is the maximum value (100%) of the separately set value described above, but is linear until the motor speed ω _R reaches the base speed from zero. The basal velocity is reduced to 25% of the maximum value. However, the magnetic flux command lower limit value is maintained at 25% of the maximum value even if the speed increases from the base speed. However, this graph shows an example of the change in the magnetic flux command lower limit value with respect to the speed. How much is the maximum value and the minimum value of the magnetic flux command lower limit value, or whether the change is curved, etc. It will be determined according to the circumstances.
[0031]
FIG. 6 is a block circuit diagram showing a third embodiment of the present invention. This third embodiment circuit is different from the conventional circuit already described in FIG. 4 with a second secondary magnetic flux command value changing circuit 61 and a T circuit. The shaft current command value changing circuit 22 is added, and the names, uses, and functions of the remaining parts excluding this additional part are the same as those of the conventional circuit shown in FIG. .
[0032]
In the circuit of the third embodiment of FIG. 6, the second secondary magnetic flux command value changing circuit 61 corresponds the secondary magnetic flux command value φ ₂ ^* set by the secondary magnetic flux setter 14 to the rotational speed of the induction motor 3. Is converted into a new secondary magnetic flux command value φ ₂₃ ^* that does not exceed the changing upper limit value, and is output to the M-axis current command calculator 15. That is, in the second secondary magnetic flux command value changing circuit 61, when the speed detection value ω _R detected by the speed detector 5 is less than or equal to the base rotational speed N ₀ , 100% of the separately set value described above is the upper limit value, In the region where the detected speed value ω _R exceeds the base rotational speed N ₀ , the upper limit value decreases in inverse proportion to the rotational speed, and a new secondary magnetic flux command value output from the second secondary magnetic flux command value changing circuit 61 is obtained. φ ₂₃ ^* is limited so as not to exceed this upper limit. The M-axis current command calculator 15 outputs a new M-axis current command value I _MM ^* by inputting the new secondary magnetic flux command value φ ₂₃ ^* .
[0033]
The T-axis current command value changing circuit 22 includes a T-axis current command value I _T ^* , a secondary magnetic flux command value φ ₂ ^* set by the secondary magnetic flux setting device 14, and a second secondary magnetic flux command value changing circuit 61. The input of the new secondary magnetic flux command value φ ₂₃ ^* to be output and the output of the new T-axis current command value I _TT ^* by the above-described calculation of Equation 10 are the same as in the first embodiment described above with reference to FIG. It is the same.
[0034]
As described above, when the secondary magnetic flux φ ₂ of the motor becomes excessive, the motor back electromotive voltage becomes excessive and stable current control becomes difficult, or a large M-axis current I _M due to magnetic saturation of the internal magnetic flux of the motor. However, the second secondary magnetic flux command value change circuit 61 prevents the new secondary magnetic flux command value φ ₂₃ ^{* from} becoming excessive, and avoids the above-mentioned problems. can do.
[0035]
FIG. 7 is a block circuit diagram showing a fourth embodiment of the present invention. The second secondary magnetic flux command value changing circuit 61 shown in FIG. 6 is replaced with a magnetic flux command upper limit calculator 62 and a secondary magnetic flux upper limit limiter 63. However, the rest of the configuration is the same except that the description of the operation of the circuit of the fourth embodiment shown in FIG. 7 is omitted.
FIG. 8 is a graph showing an example of input / output characteristics of the magnetic flux command upper limit calculator shown in FIG. 7. The horizontal axis represents the detected rotational speed value ω _R of the induction motor 3, and the vertical axis represents the magnetic flux command upper limit value. Represents. In the graph of FIG. 8, in the region where the motor speed is lower than the base rotational speed N ₀ , the magnetic flux command upper limit value is the maximum value (100%) of the separately set value, but the motor speed exceeds the base rotational speed N ₀ . In the region, the upper limit value decreases in inverse proportion to the rotation speed.
[0036]
FIG. 9 is a block circuit diagram showing a fifth embodiment of the present invention, which is a combination of the second embodiment circuit described in FIG. 2 and the fourth embodiment circuit described in FIG. . That is, the magnetic flux command lower limit calculator 31 receives the speed detection value ω _R and outputs the magnetic flux command lower limit value shown in the graph of FIG. 3 to the secondary magnetic flux lower limit limiter 32. The magnetic flux command upper limit calculator 62 also receives the speed detection value ω _R and outputs the magnetic flux command upper limit value shown in the graph of FIG. 8 to the secondary magnetic flux upper limiter 63. The secondary magnetic flux lower limit limiter 32 and the magnetic flux command upper limit limiter 63 are connected in series. For example, the magnetic flux command upper limit limiter 63 inputs the secondary magnetic flux command value φ ₂ ^* and is shown in the graph of FIG. A new secondary magnetic flux command value φ ₂₃ ^* limited so as not to exceed the upper limit value of is output. The secondary magnetic flux lower limit limiter 32 inputs this new secondary magnetic flux command value φ ₂₃ ^*, and generates a new secondary magnetic flux command value φ ₂₂ ^* that is restricted so as not to exceed the lower limit value shown in the graph of FIG. Output.
[0037]
FIG. 10 is a graph showing a first example of a situation in which the upper limit and the lower limit of the secondary magnetic flux command value are limited according to the circuit of the fifth embodiment shown in FIG. 9, and the horizontal axis indicates the rotational speed detection value of the induction motor 3. represents ω _R , and the vertical axis represents the magnetic flux command value. In the circuit of the fifth embodiment described above, the secondary magnetic flux of the motor is not protruded from between the magnetic flux upper limit curve and the magnetic flux lower limit curve shown in this graph. Various problems can be avoided.
[0038]
FIG. 11 is a graph showing a second example of the situation where the upper limit and the lower limit of the secondary magnetic flux command value are limited according to the circuit of the fifth embodiment shown in FIG. 9, and the interval between the upper limit and the lower limit near zero rotation speed. In order to widen, the shape of the magnetic flux lower limit curve is different from the first example graph shown in FIG.
[0039]
【The invention's effect】
When the torque of the motor is controlled by vector control, torque ripple has conventionally occurred due to the offset of the current detector, but there is a problem that a large torque ripple appears and cannot be eliminated, especially when the motor is almost stopped. It was happening. There were also problems such as detection error and adjustment error of detector and amplifier, secondary magnetic flux became excessive, large M-axis current flowed, motor back electromotive voltage increased, and control became unstable. .
[0040]
Since the motor torque is expressed by the product of the T-axis current and the secondary magnetic flux, in the present invention, in order to secure a predetermined torque, the ratio of the T-axis current and the secondary magnetic flux is set corresponding to the motor speed. The lower limit value is determined so that the secondary magnetic flux command value is not too small. In other words, the torque ripple frequency can be reduced by increasing the secondary magnetic flux and decreasing the T-axis current as the motor speed decreases. Therefore, even when torque ripple occurs, the response speed of the control device exceeds the torque ripple fluctuation speed. Torque ripple can be suppressed. As a result, a Hall element type or a shunt resistance type current detector having an offset can be used, so that an effect of achieving downsizing and cost reduction of the device can be obtained, and torque ripple when the motor speed is low can be suppressed. An effect is obtained.
[0041]
Further, by setting an upper limit value so that the secondary magnetic flux command value does not become excessive, it is possible to prevent the motor back electromotive voltage from being increased due to the excessive secondary magnetic flux and the control from becoming unstable. Further, the disadvantage that a large M-axis current flows due to an excessive secondary magnetic flux is also avoided. Furthermore, by setting the upper and lower limits of the secondary magnetic flux command value and making it possible to maintain the secondary magnetic flux at an appropriate value in the entire rotational speed range of the motor, torque ripple is suppressed and control is unstable and excessive. An effect of avoiding the M-axis current can be obtained.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram illustrating a first embodiment of the present invention. FIG. 2 is a block circuit diagram illustrating a second embodiment of the present invention. FIG. 4 is a block circuit diagram showing a conventional control circuit for controlling the torque of an AC motor using a vector control inverter. FIG. 5 is a diagram showing a motor controlled by the vector control inverter. FIG. 6 is a block circuit diagram showing a third embodiment of the present invention. FIG. 7 is a block circuit diagram showing a fourth embodiment of the present invention. 7 is a graph showing an example of input / output characteristics of the magnetic flux command upper limit calculator shown in FIG. 7. FIG. 9 is a block circuit diagram showing a fifth embodiment of the present invention. FIG. 10 is a fifth embodiment shown in FIG. Limit the upper and lower limits of the secondary magnetic flux command value according to the circuit [EXPLANATION OF SYMBOLS] graph showing a second example of a situation which limits the upper and lower limits of the secondary flux command value in accordance with the fifth embodiment circuit shown in the first graph 11 showing the example 9 of the situation
DESCRIPTION OF SYMBOLS 1 AC power supply 2 Inverter 3,41 Induction motor 5,45 as an AC motor Speed detector 6 Current detector 11 First coordinate converter 12 T-axis current setting device 13 T-axis current setting device 14 Secondary magnetic flux setting device 15 M Axis current command calculator 16 M-axis current regulator 17 Second coordinate converter 18 Slip frequency calculator 19 Integrator 21 First secondary magnetic flux command value change circuit 22 T-axis current command value change circuit 31 Magnetic flux command lower limit calculator 32 Secondary magnetic flux lower limit limiter 42 Reducer 43 Winder 44 Thread 46 as long material 46 Diameter sensor 47 Amplifier 48 Control device 49 Tension adjuster 50 Tension setting device 61 Second secondary magnetic flux command value change circuit 62 Magnetic flux command Upper limit calculator 63 Secondary flux upper limit limiter I _T T-axis current detection value I _T ^* T-axis current command value I _TT ^* New T-axis current command value φ ₂ ^* Secondary flux command value φ ₂₂ ^* , φ ₂₃ ^* New secondary magnetic flux command value ω _R times Rotation speed detection value ω _sl Slip frequency

Claims (6)

The M-axis corresponding to the M-axis current command value calculated from the secondary magnetic flux command value is separated into an M-axis current component parallel to the secondary magnetic flux and a T-axis current component perpendicular to the secondary current. In the AC motor drive vector control inverter that controls the torque of the AC motor by flowing a current and a T-axis current that matches the T-axis current command value,
A magnetic flux command value corresponding to the secondary magnetic flux of the motor when the AC motor outputs a rated torque during operation at the rated rotational speed is set as a separate set value, and is set separately when the rotational speed of the AC motor is zero The lower limit value is set as the lower limit value, and the separately set value is decreased to a predetermined value as the rotational speed is increased to the lower limit value. After the decrease to the predetermined value, the predetermined value is set as the lower limit value, and the secondary magnetic flux command value is input. A first secondary magnetic flux command value changing circuit for outputting a value corresponding to the rotational speed as a new secondary magnetic flux command value;
At least the T-axis current command value and a new secondary magnetic flux command value output from the first secondary magnetic flux command value change circuit are input, and a value inversely proportional to the new secondary magnetic flux command value is set as a new T A T-axis current command value changing circuit that outputs the shaft current command value;
A control device for a vector control inverter for driving an AC motor, comprising: In the control apparatus for the vector control inverter for driving an AC motor according to claim 1,
The first secondary magnetic flux command value changing circuit is
When the rotational speed signal of the AC motor is input and the speed is zero, 100% of the separately set value is output, and when the speed increases, the speed decreases and decreases between 100% and 0% of the separately set value. A magnetic flux command lower limit calculator that outputs a value and outputs the value even when the speed further increases;
A secondary magnetic flux lower limit limiter that outputs the secondary magnetic flux command value that is input and limited to a new secondary magnetic flux command value that does not fall below the output value of the magnetic flux command lower limit calculator;
A control device for a vector control inverter for driving an AC motor, comprising: The M-axis corresponding to the M-axis current command value calculated from the secondary magnetic flux command value is separated into an M-axis current component parallel to the secondary magnetic flux and a T-axis current component perpendicular to the secondary current. In the AC motor drive vector control inverter that controls the torque of the AC motor by flowing a current and a T-axis current that matches the T-axis current command value,
A magnetic flux command value corresponding to the secondary magnetic flux of the motor when the AC motor outputs a rated torque during operation at the rated rotational speed is set as a separate setting value, and the rotational speed of the AC motor is set separately when the rotational speed is lower than the base speed. If the value exceeds the base speed, the separately set value is reduced in inverse proportion to the rotational speed to be the upper limit value, and the secondary magnetic flux command value is input and a value corresponding to the rotational speed is newly set. A second secondary magnetic flux command value changing circuit that outputs the secondary magnetic flux command value;
At least the T-axis current command value and a new secondary magnetic flux command value output from the second secondary magnetic flux command value change circuit are input, and a value inversely proportional to the new secondary magnetic flux command value is set as a new T A T-axis current command value changing circuit that outputs the shaft current command value;
A control device for a vector control inverter for driving an AC motor, comprising: In the control device for the AC motor driving vector control inverter according to claim 3,
The second secondary magnetic flux command value changing circuit is
When the rotational speed signal of the AC motor is input and the rotational speed is lower than the base speed, 100% of the separately set value is output. If the base speed is exceeded, the separately set value is inversely proportional to the increase in the rotational speed. A magnetic flux command upper limit calculator that outputs a value that is less than 100% of
A secondary magnetic flux upper limiter that limits the input secondary magnetic flux command value to a new secondary magnetic flux command value that does not exceed the output value of the magnetic flux command upper limit calculator;
A control device for a vector control inverter for driving an AC motor, comprising: The M-axis corresponding to the M-axis current command value calculated from the secondary magnetic flux command value is separated into an M-axis current component parallel to the secondary magnetic flux and a T-axis current component perpendicular to the secondary current. In the AC motor drive vector control inverter that controls the torque of the AC motor by flowing a current and a T-axis current that matches the T-axis current command value,
A magnetic flux command value corresponding to the secondary magnetic flux of the motor when the AC motor outputs a rated torque during operation at the rated rotational speed is set as a separate set value, and the rotational speed signal of the AC motor is input to determine the speed. When the value is zero, 100% of the separately set value is output. When the speed is increased, the value is decreased to output a value between 100% and 0% of the separately set value. A magnetic flux command lower limit calculator that outputs a value;
A secondary magnetic flux lower limit limiter that outputs an input value by limiting it to a value that does not fall below the output value of the magnetic flux command lower limit calculator;
When the rotational speed signal of the AC motor is input and the rotational speed is lower than the base speed, 100% of the separately set value is output. If the base speed is exceeded, the separately set value is inversely proportional to the increase in the rotational speed. A magnetic flux command upper limit calculator that outputs a value that is less than 100% of
A secondary magnetic flux upper limiter that outputs an input value by limiting it to a value that does not exceed the output value of the magnetic flux command upper limit calculator;
A series circuit that outputs a new secondary flux command value when the secondary flux command value is input by connecting the secondary flux upper limit limiter and the secondary flux lower limit limiter in series,
At least the T-axis current command value and a new secondary magnetic flux command value output from the series circuit are input, and a value inversely proportional to the new secondary magnetic flux command value is output as a new T-axis current command value. A T-axis current command value changing circuit;
A control device for a vector control inverter for driving an AC motor, comprising: In the control apparatus of the AC motor driving vector control inverter according to claim 5,
The magnetic flux command lower limit calculator reduces the lower limit value when the rotational speed of the AC motor is zero to 100% of the separately set value, and controls the AC motor driving vector control inverter.

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