JPH0627790B2 - Induction motor constant measurement method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for measuring constants of an induction motor, and more particularly to a method for automatically measuring constants of an induction motor to which an inverter is connected.

B. Summary of the Invention The present invention is an induction motor to which a voltage-type non-interference vector control inverter is connected as a drive power source, generates a pulse voltage at the output of the inverter, and measures the primary input current and voltage of the induction motor at this time. By obtaining the equivalent leakage inductance of the induction machine from the above, the automatic constant measurement of the induction motor can be performed reliably and easily.

C. Conventional technology For variable speed control of a conductive motor, a slip frequency control method with good responsiveness and accuracy is known, and recently, the primary current of a motor is divided into an exciting current and a secondary current, and controlled. A vector control method that obtains a response equivalent to that of a DC machine by always making the secondary magnetic flux and the secondary current vector orthogonal to each other (for example, Japanese Patent Laid-Open No. 59-
165982 publication) has been implemented.

For such slip frequency control or vector control, the slip frequency, the primary frequency is calculated by a calculation or a function generator from the constants (for example, primary resistance, secondary resistance, primary inductance, secondary inductance, exciting inductance) of the induction motor as the controlled object. It requires a means for obtaining electric current and the like. Therefore, conventionally, a required constant is obtained from the design value or the measured value of the electric motor, and the constant is used to design and manufacture the control device.

D. Problems to be solved by the invention In conventional slip frequency control and vector control, it takes time to calculate and measure from the design value to obtain the constant data of the electric motor to realize the control device, and the development man-hour increases. I got it. In particular, in a general-purpose variable speed device, the constant of the controlled electric motor is unknown, and there is a problem in that the time and effort required to obtain the constant data each time and the number of test steps increase depending on the model of the electric motor.
Further, in the constant data obtained from the design value, the error between the design value and the constant of the actual machine may become large, and it is necessary to readjust the control device or change the design.

E. Means for Solving the Problems The present invention has been made in view of the above problems. In an induction motor using an inverter as a driving power source, the output of the inverter has a duty ratio of 50%, a half cycle T _H , and an amplitude. _Ed
Pulse voltage is generated to detect the output peak current I _O of the inverter, However, r provides a measuring method for obtaining the equivalent leakage inductance L _σ according to the sum of the primary resistance r ₁ and the secondary resistance r ₂ of the induction motor.

F. Action By applying a pulse voltage from the inverter to the primary input of the induction motor, the time constant T can be obtained from the current change of the peak current I _O.
Equivalent leakage inductance L _σ is obtained by obtaining _σ (= L _σ = r) and separately obtaining r.

G. Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a circuit diagram when the present invention is applied to a voltage type non-interference vector control device using a PWM type inverter. Induction motor 1 with transistor inverter main circuit 2
₁ for supplying the primary voltage from. Each transistor T _r1 through T _r6 of the inverter main circuit _{2 1} switching-control is made by Yotsute PWM waveform to the PWM waveform generation circuit _{2 2} and the gate circuit _{2 3,} the output voltage and frequency is controlled. Primary voltage supplied from the inverter main circuit 2 ₁ to the electric motor 1 is controlled so that the magnetic flux and the secondary current are orthogonal to each other in the electric motor 1. For this control, the direction of the magnetic flux is the α-axis, the direction of the secondary current is the β-axis orthogonal to the α-axis, and the α-phase primary current i _{1 α} ^* and β-phase primary current _{1 β} ^* as the command values are In order to obtain the two-phase voltage signals of the α-phase primary voltage e _{1 α} and the β-phase primary voltage e _{1 β} , respectively, the correction arithmetic circuit 3 causes the β-phase primary current i _{1 β} of the electric motor 1 to interfere with the magnetic flux and α. Interference with the secondary current due to the phase primary current i _{1 α} is eliminated. The correction arithmetic circuit 3 multiplies the β-phase primary current i _{1 β} ^* by the power supply angular frequency ω _o by the multiplier 3 ₂ with respect to the value of the primary resistance r ₁ that has passed through the coefficient unit 3 _1, and the multiplication result is The value passed through the coefficient unit 3 ₃ having the equivalent leakage inductance Lσ as a coefficient is subtracted. The coefficient with respect to through the coefficient multiplier 3 ₄ value, the power supply angular frequency omega _o is multiplied by the multiplier ₃₅ to the alpha-phase primary current i _{1 alpha} ^*, the primary inductance L ₁ as a coefficient to the multiplication result adds the value through the vessel 3 _6.

The β-phase primary current command i _{1 β} ^* is taken out as the output of the speed controller 5 by matching the speed setting value V _s ^* and the detection value ω _r of the speed detector 4 of the electric motor, and the power source angular frequency ω _o is the angular frequency. It is obtained from the calculated value of the slip angular frequency ω _s and the detected speed value ω _{r by the} calculation circuit 6. The angular frequency calculation circuit 6 sets the set value i _{1 α}
^* And a divider ₆₁ that performs i _{1 beta} ^* division, and a coefficient unit 6 ₂ for multiplying a coefficient 1 / tau ₂ in the divider ₆₁ of the division result i _{1 beta} ^* / i _{1 alpha} ^* Then, the slip angular frequency ω _s is calculated. Here, τ ₂ is the secondary time constant of the electric motor 1, and the secondary resistance r ₂
And the secondary inductance L ₂ .

The phase voltage calculation circuit 7 is adapted to obtain the three-phase voltage command signals e _a ^* , e _b ^* , e _c ^* of the inverter from the three-phase voltage signals e _{1 α} , e _{1 β,} and the sine wave signals required for this conversion. sinω _o t, cosine wave signal
Cos ω _o t is obtained from the trigonometric function generating circuit 8 using the power supply angular frequency ω _o . Further, PWM waveform generation circuit 2 ₂ three-phase voltage command signal oe _a ^*, e _b ^*, is to obtain a Yotsute pulse width modulated waveform to a level comparison between e _c ^* and the triangular wave signal (carrier), and thus The triangular wave signal T _{ri of} is the power source angular frequency ω from the circuit 6.
It is obtained from the triangular wave generating circuit 9 which uses _o to synchronize with the frequency. 10 supplies DC power to the inverter main circuit 2 _1.

As described above, in the vector control of the primary voltage of the electric motor by the PWM inverter, the control device requires constant data corresponding to the primary resistance r ₁ of the electric motor 1 for the coefficient setting of the coefficient units 3 ₁ and 3 _2. The coefficient units 3 ₃ and 3 ₅ have an equivalent leakage inductance L _σ and a primary inductance L ₁
However, the coefficient unit 6 ₂ requires constant data corresponding to the secondary resistance r ₂ and the secondary inductance L ₂ of the electric motor 1 to set the secondary time constant τ ₂ (= L ₂ / r ₂ ).

As a self-Chi Yu training means to measure and set these constant data automatically, Chiyuningu control circuit 11 and the inverter main circuit 2 ₁ of the output voltage, the voltage detector 12 for current respectively detecting comprises a current detector 13. Chiyuningu control circuit 11 has a control function for adjusting the PWM waveform generation circuit 2 ₂ of the output waveform, the inverter main circuit 2 ₁ of the use connexion pulse voltage two phases by being given a measurement and setting instruction constant data The primary resistance r ₁ , the secondary resistance r ₂ , the secondary inductance L ₁ , the secondary inductance L ₂ , the secondary resistance L ₂ The next time constant r ₂ and the equivalent leakage inductance L _σ are calculated, and the coefficients of the coefficient units 3 ₁ , 3 ₃ , 3 ₄ , 3 ₆ , and 6 ₂ are automatically set. Below, the tuning control circuit 1
Equivalent leakage inductance L which is the gist of the present invention according to 1.
_The method for automatically measuring _σ will be described in detail.

The control circuit 11 includes two phases of the inverter main circuit 2 _1, for example, a transistor T _r1, T _r6 and T _r3, T _r4 on and off controlled by the control constant zero alternately winding U of the motor 1, W inter Pulse voltage is applied to. At this time, the control circuit 11 is PWM waveform generating circuit 2 to the _second voltage command e _a ^*, e _b ^*, in place of the e _c ^* Set the constant voltage V, the PWM waveform output also transistor T _r1, T _r6
Control is performed to allow only the outputs of T _r3 and T _r4 , and the output frequency of the triangular wave generation circuit 9 is set as high as possible.

Such control windings U, W half period T _H of the triangular wave _output, duty ratio of 50% of the pulse voltage is applied with the amplitude of the DC voltage E _d of the inverter main circuit 2 _1, this voltage, the current The detected value is taken into the control circuit 11 from the detectors 12 and 13, and the equivalent leakage inductance L _σ is calculated by the control circuit 11.

The T-type equivalent circuit diagram of the induction motor 1 is as shown in FIG. 2, and when a high-frequency pulse voltage is applied to it, the exciting inductance l _m is sufficiently larger than the equivalent secondary inductance l _{2 and the} like. , R ₁ + r ₂ = r (1) l ₁ + l ₂ ≈L _σ (2), the current i is given by the following equation.

However, I _(o) is an initial value T _σ = L _σ / r where the control rate is zero (duty ratio 50%), the input voltage and current waveforms are the initial values of the current i as shown in FIG. The sign of the value and the closing price are opposite and the absolute value is the same.

The initial value and the final value of this current i are peak values,
Substituting t = T _H into the equation (3) to obtain Io Becomes Therefore, the control circuit 11 controls the voltage E _d and the period 2 × T.
_A control is performed to obtain a pulse voltage of _{H 2} and a duty ratio of 50% as the output of the inverter main circuit 2 ₁ , and the peak current I _{o at} this time and the voltage E _d as necessary are detected to detect the primary resistance r.
₁ , by measuring the secondary resistance r ₂ in advance, the leak time constant T _{σ, and} thus the equivalent leak inductance L _σ , can be calculated by the above equation (5) or its modified equation. Can be obtained from Thus equivalent leakage inductance L _sigma determined to permit subsequent vector control by setting the coefficient unit 3 _3.

The effect of the current i by Detsudotaimu between the transistors of the inverter main circuit 2 _1, by connexion eliminated for the following reasons. The waveform of each part is shown in Fig. 4, and the duty ratio is 5
In order to obtain a PWM waveform of 0%, this method uses T _r1 and T _r6 , T
Turn on and off _r3 and T _r4 at the same time. With transistor T _r1
A dead time is secured between the base signals of T _r4 , T _r3 and T _r6 . However, for example, the direction of the current i is always positive at the ignition timing of the transistor T _r4.
Even if there is a delay (dead time) in turning on T _r4 , T _r1 stays at O
At the time of FF, the diode D ₄ is turned on to form a current path, so that the influence of the dead time on the current i disappears.

In the embodiment, the control circuit 11 can, of course, be incorporated in the control device as a constant measurement program when the vector control device is composed of a microcomputer or the like.

H. Effect of the Invention As described above, according to the present invention, a pulse voltage is generated from an inverter that serves as a drive power source for an induction motor, and the equivalent leakage inductance of the induction motor is obtained by peak detection of the output current of the inverter. Therefore, the present invention is applied to a voltage type non-interference vector control device to ensure and facilitate automatic measurement even in a motor in which the constant is unknown, and facilitate self-tuning in which the constant is automatically set. In addition, the constant measurement includes measurement of the electric motor wiring, which has the effect of improving the practical measurement, setting, and control accuracy.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a voltage type non-interference vector control device showing an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of an induction motor,
FIG. 3 is a current waveform diagram when a pulse voltage is applied to the electric motor, and FIG. 4 is a waveform diagram of each part showing the relationship between the dead time and the current waveform of the inverter main circuit in FIG. 1 ...... induction motor, _{2 1} ...... inverter main circuit, _{2 2} ...
... PWM waveform generation circuit, 3 ... correction circuit, 3 ₁ , 3 ₄ ,
3 ₃ , 3 ₆ , 6 ₂ ... Coefficient multiplier, 6 ... Angular frequency calculation circuit, 7 ... Phase voltage calculation circuit, 9 ... Triangle wave generation circuit, 1
1 ... Tuning control circuit, 12 ... Voltage detector, 1
3 ... Current detector.

Claims (2)

[Claims] 1. An induction motor using an inverter as a drive power supply, wherein a pulse voltage having a half cycle T _H and an amplitude E _d is generated at the output of the inverter at a duty ratio of 50% to detect an output peak current I _O of the inverter. And the following formula However, r is the constant measuring method of the induction motor, characterized in that the equivalent leakage inductance L _σ is obtained according to the sum of the primary resistance r ₁ and the secondary resistance r ₂ of the induction motor. 2. The constant measuring method for an induction motor according to claim 1, wherein the inverter simultaneously turns on and off each of the upper and lower arms for two phases to generate a pulse voltage.