JPS6279380A - Constant measurement of induction motor - Google Patents

Abstract

PURPOSE:To perform automatic measurement and setting of a constant positively and easily under the stoppage of a motor even with an unknown constant, by generating a DC current from a current control type inverter to determine the constant of an induction motor from a primary voltage thereof. CONSTITUTION:A tuning control circuit 20 has a control function to regulate an output waveform of a PWM waveform generation circuit 22 and generates a DC constant current by steps using two phases of an inverter main circuit 21 when given a measurement/setting command for a constant data. Then, a primary resistance r1 of a motor 1 is obtained by a computation using the ratio V1(infinity )/I between the final value V1(infinity ) of a primary voltage V1 of an induction motor 1 and a DC current I and a secondary inductance L2 is determined from a secondary time constant tau2 of the motor 1, a secondary resistance r2 and tau2=L2/r2 using a formula based on transient voltages V1(t1) and V1(t2) of a voltage V1 by the current I at the time t1 and t2, the final value V1(infinity ) and the current I. Then, a coefficient necessary for a coefficient generating unit 93 is automatically set.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for measuring constants of an induction motor.

In particular, the present invention relates to a method for automatically measuring the constants of an induction motor connected to a current jWII-H type inverter.

B6 Summary of the Invention The present invention provides a method for generating DC current in full steps at the output of the inverter in a friend induction motor connected to a single-current control type inverter as a drive power source.
By determining the induction machine constant from the constant value of the primary pressure of the induction motor at this time, automatic constant measurement of the induction motor can be performed reliably and easily.

C0 Conventional Technology For variable speed control of induction motors, a vector frequency control system with good responsiveness and accuracy is known. Secondary magnetic flux and secondary current vector A vector control method (for example, Japanese Patent Application Laid-open No. 165982/1982) has been implemented that achieves responsiveness equivalent to that of a hot iron machine by constantly burning the secondary magnetic flux and current vector directly.

Such vector frequency control and vector precedents are based on calculations or function generators based on the constants of the induction motor (for example, primary resistance, secondary resistance, primary inductance, secondary inductance, and excitation inductance). Necessary as a means of determining current, etc. For this reason, conventionally, necessary constants are determined from design values or measured values of the motor, and these constants are used to design and construct the control device.

D1 The point that the invention attempts to solve is that in conventional vector frequency suppression and vector control, the f
In order to realize the fflJ1lf1 device, there was a problem in that obtaining constant data for one motive required a lot of time and effort in calculations and measurements from design values, which required the entire development man-hour. In particular, in a general-purpose variable speed device, the constants of the motor to be controlled are unknown, which poses a problem that requires considerable effort and testing man-hours to obtain constant data each time depending on the model of the motor. Further, constant data obtained from design values may have a large error between the design values and the constants of the actual machine, which may require readjustment or design changes to the control device.

Tth way to solve the E6 problem The present invention has been made in view of the above problems.

A current-controlled inverter as a drive power source; in the connected induction motor, a DC current T is applied to the output of the inverter.
is generated stepwise, and the primary voltage v of the induction motor is
Final value of l V+('') and @ratio of current metal work Vt ('')
Determine the primary resistance rI of the induction motor from /I,
Transient voltage V1 (tt), Vt (tt) and final value V of the voltage VI at time t1+11 by the DC metalwork
t (-) and the secondary time constant of the rust induction machine according to the following formula % from DC electric metalwork, and the secondary resistance r, and the secondary inductance L from τt = Lt/r,.

This provides a measurement method to determine the

20 Action Induction ' By applying a DC current in all steps from the inverter to the primary input of the motor, its final value voltage V + (c DJ is equivalently obtained, and the voltage value due only to the primary resistance r1 is obtained, the primary resistance rtk is measured, and the DC current is From the transient phenomenon of voltage due to the application of current, equivalently the secondary resistance "t + secondary inductance Lt
e Quadratic time constant τ,′! i- seek.

G. Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Figure 1 shows the current control type P A circuit diagram in which the present invention is fully applied to a vector control device using R is shown. Induction motor 1 and transistor inverter main circuit 2.
All primary current is supplied from. Each transistor Tr1 to Trll of the inverter main circuit 2I is a PWM waveform generation circuit 2.
．． and gate circuit 2. Switching control is performed using a 2wM waveform, and the output '4 ME and frequency are controlled. The DC input of the inverter main circuit 2m is converted into a DC power source by a rectifier 3 and a smoothing capacitor 4, and the PWM waveform generation circuit 2. is the current command Iu.

! 5. Current transformer for current detection. ,5. The current control type inverter is controlled by feedback based on comparison with the detection signal of the current control type inverter. The PWM waveform generation circuit 22 obtains respective voltage commands Vu and Vvf from current control width amplifiers AlRu and AIR MA which perform proportional integral (PI) calculations for the U phase and M phase, and from these commands, W is obtained by an inverting adder Add. A phase voltage command Vw*f is obtained, and these command signals are compared with the triangular wave of the triangular wave (carrier wave) generating circuit TRI by comparators CPU, CPv, and CPw, respectively, to obtain three-phase PWM waveform outputs.

The speed command ωn of the induction motor 1 is calculated by proportional integral (P
I) is taken out as a secondary current (torque flow) command It to the speed control amplifier 7 of the calculation, and this command T* is A/
The D converter 8 converts it into a digital signal. The output of the A/D converter 8 is the magnetic flux current command Io, which is set as a gauge.
It is also taken into the vector calculation unit 9. The vector calculation section 9 calculates the primary ``i[flow command value! Find , *, divider 9. The ratio of the command T* and IO* found by IT*/Io* is the coefficient unit 9s.
The vector angular frequency ωai is determined by multiplying by the coefficient 17τ, and the phase angle ψ is determined by the inverse trigonometric function calculation circuit 94.
Find the subtractor 9. The difference (amount of phase change) Δψ between the phase angle ψ and the phase angle one sample before is determined by: Here, the coefficient 1/τ is the reciprocal of the secondary time constant τ1 of the induction motor 1, and the ratio L@/ of the secondary inductance L and the secondary resistance r1.
It's a goose.

The vector angular frequency ωS is determined by speed detection 15 by an adder 10.
The first-order angular frequency ω0←ωs+ωn) is obtained by adding the first-order angular frequency ω0←ωs+ωn). For this angular frequency ω0, an absolute value 1ωo1 of forward and reverse rotation is determined by an absolute value circuit 11, and a polarity determining circuit 12 determines whether the rotation is forward or reverse. The absolute value 1ωo1 is converted into a pulse of the corresponding frequency by the voltage-frequency converter 13, and this signal lNTR and polarity determination No. 18 F/R are taken into the primary current waveform unit 14 together with the above-mentioned phase change amount Δψ. The primary current signals of the U phase and V phase, that is, 5 inches (ωOt 10 Δψ) (ωOt 10 π 10 Δψ) are obtained as sample values. These A words are D
/A is converted into an analog signal by the converter 15, and during this conversion, the conversion gain is the primary current signal converter.

adjusted by.

In this manner, when performing vector control using the electric IF port 1tIII-type PWM universal inverter, the control device has a secondary time constant τ! of the coefficient unit 93. (= Lt/rt
), the secondary resistance r and secondary inductance L of the motor 1 are set. It requires constant data corresponding to .

A tuning control circuit 20 is provided as a self-tuning means for automatically measuring and setting these multiplication data. tuning? The ttlJ control circuit 20 has a control function that adjusts the output waveform of the PwM waveform generation circuit 2t! Then, when a constant data measurement/setting command is given, a DC constant current is generated in a stepwise manner using the two-phase components of the inverter main circuit 2I, and the primary voltage 1jl of the induction motor 1 at this time is
By evaluating using ll + grass value, primary resistance 'I e secondary resistance r, l secondary inductance L! Furthermore, the quadratic time constant τ! Total calculation, coefficient unit 9. Automatically set the necessary coefficients. A method for automatically measuring constant data using the tuning control circuit 20 will be described in detail below.

(1) Measurement of primary resistance r1 inverter main circuit 2. out of two phases, e.g. transistor T
A constant current i is applied between windings U and W of the motor 1 by adjusting the on/off ratio of rl and Tr6. At this time, control circuit 2
0 is set to the D/A converter 15 as a primary current signal in place of the output from 14, with the U-phase command ru*f constant and the V-phase command Iv t-zero. Through such control, the pulse current (average electric metallurgy) of the on-off ratio determined by the current command Iu is kept constant in the windings U and W by feedback control, and the primary voltage of the motor 1 at this time is changed from the Yokota value to the Calculate the resistance r1.

The T-type equivalent circuit of the induction motor 1 is shown in FIG. 2, and the following voltage equation holds between this and the step voltage 1ist-plus the primary pressure V at time t.

Here, marks 7) I] Iy from each 21 above the inverter
"L current" O actually requires rise time, but current? ! i
If the response of the 1J system is sufficiently short compared to the measured time (in fact, it is sufficiently short), the rise time can be regarded as zero.

When using Laplace transform in (1) 2 above, oc F+ (tJ = ' Ll = Am
It becomes 11gS'. From now on τx = Lx / rt s L
From Am in x. Therefore, the primary voltage Vs(i)
Hato becomes. And since A<L, Vs(t)
= I (r, 10r, e τri...(
5). This 'direct pressure V, is) ¥l! It becomes a differential waveform as shown in Figure 3.

In this equation 15), the voltage V1(
From @, the primary resistance r can be determined as j, wVtC■/I (6). Therefore, the control circuit 20 controls the current command Iu
-I as inverter main circuit 2. The final value of the primary voltage Vs(t) when a step current is supplied from The control circuit 20 may directly measure the output voltage of the inverter main circuit 2. However, there are problems such as the need for all filters for this detection.Therefore, in this embodiment, the voltage command value of the inverter is measured. Therefore, the control circuit 20 controls the U-phase voltage 1b order Vu
It is taken in as the t-detected value Vs(f).

In this case, Vl(- is obtained from the measured value twice when the current command Iu is changed so as to overwrite the detected value that compensates for the '1 voltage drop due to the dead time of the transistor 'rr, j Tr6. In other words, the voltage command Vu * and motor voltage vI have the following relationship y1=y if the control rate μ of PwM is 1 or more
, -EdB 5ense (7) ■, *=
kvu*凰...(7-a) holds true. here,
EdB is the voltage drop due to the dead time of the transistor, k is a constant, and V- is the control voltage, which is determined by the carrier frequency of the % tiger.The current Iulf in the steady state is changed and the voltage Vui at that time is measured twice, (7 -a) Calculate the next control voltage and t current Iu” from the formula, respectively t-(VlK)
, Iul'')% (Vl-IIu!*), the following relationship holds.

Therefore, EdB is obtained from both equations, and the control circuit 20 obtains Edit from equation a1, and uses this EdB i to calculate V from equations (7) and (7-1).
Vz*t" is determined from u, and the primary resistance r1 is determined from the above-mentioned equation (6).

(2) Secondary resistance r! , the secondary inductance L, and the secondary time constant τ1.
The respective transient primary voltage Vs (is1%Vx(
it)'(r is determined.

This voltage is determined by applying the voltage command Vu and the dead time EdBt-1 [described above] using appropriate time settings as shown in FIG.

These voltages Vz(it) and Vt(it) are the final value V
t (@ = rt From I and the above-mentioned equation (5), the following relationship exists.

-diV+(it) VtH=Ir鵞e ”*
・ ・ ・ ・ ・ (10-1 snow Vt(tz) VtH=Irte 't ””
IJ'A is obtained from these two formulas. Therefore, the control circuit 20 calculates the transient voltages Vs(it), Vt(it) and the final voltage Vt() according to equation 1.
= Secondary time constant τt1 from the measured value of Ir1! ! : Find this time constant τ! Using formula 69 or formula a, find the secondary resistance r, t, and further find the secondary inductance Ltt from Ma = Lt/rt.

As a result of the above measurements, the control circuit 20 has determined that the primary resistance r8
．． Secondary resistance r3. The secondary inductance L and the primary time constant τ are determined, and in this embodiment, the necessary constant τ is set to the full coefficient multiplier 9s to enable subsequent vector control.

In the embodiment, when the vector control device is constituted by a microcomputer or the like, it goes without saying that the control circuit 20 can be incorporated into the control device as a constant measurement program.

Further, although the embodiment is applied to a vector control device using a current-controlled PWM type inverter and the following case is shown, the present invention is not limited to this, and can be applied to a current-controlled vector control device, and the present invention is not limited to this. By setting the frequency to zero and changing the direct current command in steps, the constant can be determined from the detected value of the primary voltage.

Effects of the Invention As described above, according to the present invention, direct current is generated from a current control type inverter that serves as a drive power source for an induction motor,
In order to find the constant of an induction motor at 11°C from the primary voltage of the induction motor, it is applied to a control device that controls the entire inverter using this constant or the secondary constant based on this constant, so that even if the constant is unknown, the constant is determined in the stopped state. To ensure and facilitate automatic measurement of a constant, and further facilitate self-tuning in which the constant is automatically set. In addition, the constant measurement requires nine measurements including the motor wiring, which has the effect of improving practical measurement, setting, and control accuracy.

Brief explanation of page 41 Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is an equivalent circuit diagram of an induction motor, and Fig. 3 is a primary circuit diagram of a stepped DC current induction motor at 9. It is a pressure waveform diagram.

■...Induction motor, 21...Inverter main circuit, 2
．． ... PWM waveform generation circuit, 6 ... Speed detector, 7
... Speed limiter, 8... A/D converter, 9...
・Vector calculation unit, 9... Coefficient unit, 11... Absolute value circuit, 12... Polarity discrimination circuit, 13... r i pressure -
Frequency converter, 14...Primary current waveform output section, 15.
...D/A converter, 20...Tuning control times P!
.

Diagram 2: 9 reasons for the 11 temptations and misunderstandings
-Figure 3

Claims (3)

[Claims] (1) In an induction motor to which a current-controlled inverter is connected as a drive power source, a DC current I is generated in steps at the output of the inverter, and the final value V_1 (∽) of the primary voltage V_1 of the induction motor and the DC current Ratio of I V_1
The primary resistance r_1 of the induction motor is determined from (∽)/I, and the time t_1 of the voltage V_1 due to the DC current I,
Transient voltage V_1(t_1) at t_2, V_1(t_2)
From the final value V_1 (∽) and DC current I, the following formula τ_2
=(t_2-t_1)/loge{[(V_1(t_1
)-V_1(∽)]/[V_1(t_2)-V_1(∽
)]}V_1(t_1)-V_1(∽)=Ir_2e^
- According to ^(t_1)^/^(τ_2), the secondary time constant τ_2 of the induction motor and the secondary resistance r_2 and τ_2=L
A method for measuring constants of an induction motor, characterized by determining secondary inductance L_2 from _2/r_2. (2) The primary voltage V_1, V_1(t_1), V_1
2. The method for measuring constants of an induction motor according to claim 1, wherein (t_2) is obtained by measuring the voltage command Vu^* of the inverter. (3) The output of the inverter is a control voltage V_1_1^* for two currents I_1 and I_2 with different DC currents I.
, V_1_2^*, the following formula EdB=(I_1V_1_1^*−I_2V_1_2^
*)/(I_1-I_2), calculate the voltage drop E_d_B due to the dead time of the switching elements of the inverter, and calculate the primary voltage V_1 using the following formula: V_1=V_1^*-E_d_B V_1^*=kVu^*(Ed/2 ) The method for measuring constants of an induction motor according to claim 2, wherein k is a constant determined by the control rate, and Ed is determined according to the DC voltage of the inverter.