JPH02106190A - Vector controller for induction motor - Google Patents

Abstract

PURPOSE:To measure a secondary time constant in a short time and to perform vector control with temperature correction by obtaining the time constant from 3 sampled values of the primary voltage or current change of a motor and eliminating waiting time until the primary voltage or current becomes constant. CONSTITUTION:A primary voltage detector 15 detects a primary voltage v1(t1) at a time t1, the voltage v1(t2) at a time t2 (=t1+ t), and the voltage v1(t3) at a time t3 (= t2+ t) at a predetermined time interval t. A secondary time constant calculator 14 obtains a secondary time constant tau2 from the detected voltages v1(t1), v2(t2), v3(t3) according to an equation. Accordingly, the constant tau2 is obtained from the detected values of the voltages v1(t1)-v3(t3) in a short time from the application of a constant current to the time t3, and the measurement of a voltage to become a normal value i1r1 required for a relatively long period of time is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a vector control device for an induction motor, and more particularly to a secondary time constant measuring device.

B1 Summary of the Invention The present invention detects three samples of primary voltage or current every time Δt when a constant current or constant voltage is applied to a motor, and performs vector control by determining a secondary time constant τ. time constant τ
By determining , the temperature-corrected secondary time constant can be measured in a short time.

C1 Conventional technology Vector control of an induction motor divides the motor's primary current into an excitation current and a secondary current and controls the magnetic flux and secondary current (torque current) vectors so that they are always orthogonal to each other. Try to obtain variable speed performance.

FIG. 5 shows a vector control device. Speed ω determined by the speed calculation unit 3 from the speed command N and the speed detector 2 of the induction motor 1
n, and the torque calculation unit 4 calculates the torque current command 11 by proportional integral (PI) calculation. This torque current and excitation current setting value! . The primary current value 11 is obtained from the primary current calculation section 5.

On the other hand, the phase calculation unit 6 calculates the phase angle φ between the torque current ■ and the excitation current r, and the slip frequency calculation unit 7 calculates the phase angle φ between the torque current ■ and the excitation current I. and motor secondary time constant τ2τt = L −
/Rt L,: Find the secondary self-inductance R2, the secondary resistance, and the sliding frequency ωS.

t ω S − 1Oτ! This slip frequency ωS is determined by the adder 8 as the speed detection value ω
The primary angular frequency ω is obtained by adding with n. seek.

The primary current calculation unit 9 calculates the primary current phase, phase angle φ, and angular frequency ω. The primary currents 1a, Ib, and Ic of the motor l are obtained from the equations 1 and 2, and the inverter lO supplies the primary current to the motor l by using these currents as a current command for the inverter 10. The calculation of the calculation unit 9 is performed according to the following formula.

r a=J 2 1r, l s+n (θ+φ) In such a vector control device, 2 is a quadratic time constant for determining the slip frequency ωS, and 2 is the constant R7, L of the motor 1.
However, fluctuations in the secondary resistance R7 due to the temperature of the motor result in fluctuations in the secondary time constant τ2 and, in turn, a shift in the primary current phase.

Therefore, temperature correction of the quadratic time constant τ has traditionally been performed,
As a method for this correction, there is a method of calculating from the primary voltage when a constant current is applied to the motor.

Figure 6 shows the primary voltage τ when a constant '1-[current 11 is applied.
2 v+(t)=i+(r++rte). Therefore, the next set pressure V+(j+
), V+(j*) to obtain the quadratic time constant τ,
is obtained from the following equation, and this second-order time constant τ is used in the slip frequency calculation to remove the influence of temperature.

D1 Problems to be Solved by the Invention The conventional secondary time constant correction method requires steady values i, r of the primary assembly pressure v+(t), and this measurement requires the primary current phase (
t) requires a long time to reach a steady value. For this reason, it takes a long time to prepare the motor for operation, and the vector control device has a slow start-up.
There was a problem with the primary assembly pressure v+(t).

SUMMARY OF THE INVENTION An object of the present invention is to provide a vector control device that can perform temperature-corrected vector control by shortening the measurement of a secondary time constant.

81 Means and Effects for Solving the Problems The present invention achieves the above object by applying a constant current or constant voltage to the motor in determining the secondary time constant τ of the induction motor and vector-controlling the motor. Primary voltage change (t+), v, (t,), v + for each time ΔL when
(t 3) or primary current ++ (1+).

A primary voltage or primary current detection circuit that detects r + (t 2) and i + (L 3), and a secondary time constant calculation that calculates a secondary time constant τ from the -blow mold pressure or primary current according to the following formula. The second-order time constant τ is obtained from three sample values of the primary voltage change or the primary current change of the motor, thereby eliminating the need to wait for the time until the blowing mold pressure or the primary current becomes constant.

F. Embodiment FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention. In the same figure, the control circuit 11 is a multi-connected calculation unit 4 to 5 in FIG.
9, and the inverter main body 12 and rectifier 2313 are shown corresponding to the inverter 10.

Here, the control circuit 11 is given the second-order time constant τ2 as the calculation result of the second-order time constant calculation circuit 14.

This arithmetic circuit I4 detects the primary voltage V(tl), v, from the primary voltage detection circuit 15 which detects the primary voltage of the induction motor l
(, t2), v, (t3) and measurement interval Δ1 (=1°t
+ t 3t 2) is given, find the quadratic time constant.

The control circuit 11 controls the on/off ratio of the switch transistors of the inverter main body 12 using the detected value of the current detector 16 as feedback in order to apply a constant current to the motor 1 during secondary time constant calculation. When this constant current is applied, the blow mold pressure detection circuit 15 detects the primary voltage v at time t at a constant time interval Δt, as shown in FIG.
(t , ), -blow mold pressure v1 ([2) at time t v (-t ++ Δt), and time 3 (-t 2 + Δt
) -Blow mold pressure V(t3) is detected.

This detection voltage v, (to, v2(t,), Va(j3)
From this, the second-order time constant calculation circuit 14 calculates the second-order time constant τ according to the following equation.

Therefore, to calculate the secondary time constant τ, the primary voltage v 1 (t +) to V within a short time from constant current application to time t3 is calculated.
This eliminates the need for voltage measurements to reach steady-state values i, r, which are determined from the detected values at 3 (t 3) and take a relatively long time.

The above-mentioned primary voltage detection circuit 15 and secondary time constant calculation circuit 1
4 can be realized, for example, by using the circuit configuration shown in FIG. 3 or by performing most of the calculations on a computer.

In Figure 3, the electric motor! Primary voltage change wave filter 1
The sampling voltage is sampled three times every time Δt by the sample and hold circuit 17 through 6, and this sampling voltage is converted into a dinotal value every time Δ[ by the A-D converter 8,
Sequentially transfer to Renostar 19°20. By this (1) formation, the first sample data v +
(t+) is stored, sample data v+(t2) of No. 2 1] is stored in the reno star 19, and the A/D converter 1
The output data of 8 is the third sample data v, (t3
) is obtained as The subtractors 21 and 22 subtract data v + (
t+), v, (t,), vl(t3),
i "V + (L +) V 1 (j 2
) V + (t 2) V I (L : l) is determined.

And the divider 23 is the subtracter 2! , 22, and this result is subjected to a logarithmic operation by a number calculator 24, and a quadratic time constant r is obtained by dividing by a time Δt by a divider 25.

In the example, a constant voltage was applied to the motor to obtain the second-order time constant τ, and the one-blow type flow r was calculated as shown in FIG.
+(t +) ~ ++(t3) is determined at time ΔL intervals,
It can also be calculated using the formula below.

G1 Effects of the Invention As described above, according to the present invention, three samples of -blow mold pressure change or -blow mold flow change are detected and a temperature-corrected quadratic time constant is determined, so that -blow mold pressure or - This eliminates the need to measure the steady-state value of the blow mold flow, allowing short-time measurements and speeding up the start-up of vector control. Further, when a stop time is included during the variable speed control of the electric motor, even if the stop period is short, the secondary time constant can be measured again during the period and readjusted.

[Brief explanation of the drawing]

Fig. 1 is a device configuration diagram showing one embodiment of the present invention, Fig. 2 is a voltage measurement mode diagram of an actual example, Fig. 3 is a quadratic time constant calculation circuit diagram in Fig. 1, and Fig. 4 is Other examples of current measurement @ diagrams,
FIG. 5 is a block diagram of a hector control device, and FIG. 6 is a diagram of a conventional voltage measurement mode. 11... Control circuit, 12 Inverter main body, 14 Secondary time constant calculation circuit, 15...-Blow mold worker detection circuit, 192
0--Renostar, 24. Logarithm operator. Fig. 2 Fig. 3 Second-order time constant calculation circuit of the embodiment 2 people not shown Fig. 4 Voltage measurement mode diagram of the embodiment Vector control device configuration diagram Fig. 6 Conventional voltage measurement mode diagram □ Time (L)

Claims (1)

[Claims] (1) In determining the quadratic time constant τ_2 of the induction motor and vector-controlling the motor, a temporary voltage v_1(
t_), v_1(t_2), v_1(t_3) or primary current i_1(t_1), i_1(t_2), i_1(t
_3) A primary voltage or primary current detection circuit that detects 1. A vector control device for an induction motor, comprising a second-order time constant calculating circuit.