JP2629309B2 - Vector controller for induction motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vector control device for an induction motor, and more particularly to a secondary time constant measuring device.

B. The present invention, in which vector control seeking secondary time constant tau _2, and 3 sample detected a primary voltage or current per time Δt when applying a constant current or constant voltage to the motor by two by obtaining the following time constant tau _2, it is obtained by allowing measurements in a short time the temperature corrected secondary time constant.

C. Conventional technology Vector control of an induction motor controls the primary current of the motor by dividing it into an excitation current and a secondary current, and always makes the magnetic flux and the secondary current (torque current) vector orthogonal to each other to make it equal to or higher than that of a DC motor. Of variable speed performance.

FIG. 5 shows a vector control device. The combined impact the speed ωn from the speed detector 2 of the induction motor 1 and the speed command N is speed calculation unit 3 obtains obtain a torque current command I _T in proportional integral (PI) calculation on the torque calculation unit 4. From the torque current and the exciting current set value I ₀ , a primary current value I ₁ is obtained in the primary current calculator 5. On the other hand, the phase calculating unit 6 and the torque current I _t excitation current
Phase angle φ with I ₀ Look, also slip frequency calculating unit 7, the torque current I _t and the excitation current I ₀ and a motor secondary time constant _{τ 2 τ 2 = L 2 /} R 2 L 2: secondary self inductance R _2: from the secondary resistance The slip frequency ωs is obtained.

The slip frequency ωs is determined primary angular frequency omega ₀ by the addition of the speed detection value ωn by the adder 8.

Primary current arithmetic unit 9 the primary current I ₁ and the primary current Ia of the motor 1 from the phase angle φ and the angular frequency ω _0, Ib, seeking Ic, the inverter 10 the electric current as a current command for the inverter 10 to the motor 1 Provides primary current. The calculation of the calculation unit 9 is performed according to the following equation.

θ = ∫ω ₀ dt In such a vector control device, the secondary time constant τ ₂ for obtaining the slip frequency ωs is a constant of the electric motor 1.
Although determined by R ₂ and L ₂ , a change in the secondary resistance R 2 due to the temperature of the motor results in a change in the secondary time constant τ ₂ and a shift in the primary current phase.

Therefore, temperature correction of the secondary time constant τ _{2 has been} conventionally performed, and as a correction method, there is a method of obtaining the temperature from the primary voltage when a constant current is applied to the electric motor.

FIG. 6 shows a primary voltage v ₁ (t) when a constant current i ₁ is applied.
And the primary voltage v ₁ (t) is Is approximated by Therefore, the primary voltage v _{1 at} times t ₁ and t ₂
By measuring (t ₁ ) and v ₁ (t ₂ ), the secondary time constant τ ₂
Is , And using the secondary time constant τ ₂ in the slip frequency calculation to eliminate the influence of temperature.

D. INVENTION An object conventional secondary time constant correction method to be solved requires the steady value i ₁ r ₁ of the primary voltage v ₁ (t), the primary voltage v ₁ (t) is constant for this measurement It takes a long time to reach a value. For this reason,
There is a problem that it takes a long time to prepare the operation of the electric motor, and the vector control device has a poor start-up.

An object of the present invention is to provide a vector control device capable of performing temperature-corrected vector control in a short time by measuring a secondary time constant.

E. Means and Action for Solving the Problems In order to achieve the above object, the present invention obtains a secondary time constant τ ₂ of an induction motor and performs vector control on the motor, in which a constant current or a constant voltage is applied to the motor. Temporary voltage v ₁ (t ₁ ), v ₁ (t ₂ ), v ₁ (t ₃ ) or primary current i ₁ (t ₁ ), i ₁ (t ₂ ), i ₁ ( t ₃ ) primary voltage or primary current detection circuit for detecting And a secondary time constant calculating circuit for obtaining a secondary time constant tau ₂ according obtains the secondary time constant tau ₂ of 3 sample values of primary voltage change or primary voltage change of the motor, the primary voltage or primary current is constant Eliminates the need to wait until it becomes

F. Embodiment FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention.
In the figure, the control circuit 11 is provided with the arithmetic units 4 to 4 in FIG.
9 and the inverter body 12 and the rectifier 13
Shown corresponding to 10.

Here, the control circuit 11 receives the secondary time constant τ ₂ as an operation result of the secondary time constant operation circuit 14. This arithmetic circuit 14
Is a primary voltage detection circuit for detecting the primary voltage of the induction motor 1
Given the primary voltages v ₁ (t ₁ ), v ₁ (t ₂ ), v ₁ (t ₃ ) and the measurement interval Δt (= t ₂ −t ₁ , t ₃ −t ₂ ) from ₁₅ , the secondary time Find a constant.

The control circuit 11 controls the on / off ratio of the switch transistor of the inverter body 12 using the detection value of the current detector 16 as feedback in order to apply a constant current to the electric motor 1 at the time of calculating the secondary time constant. In this constant current application, as shown in FIG. 2, the primary voltage detection circuit 15 outputs the primary voltage v ₁ (t ₁ ) at time t ₁ at a fixed time interval Δt and the primary voltage v ₁ (t ₁ ) at time t ₂ (= t ₁ + Δt). Primary voltage v ₁ (t ₂ ) and time
The primary voltage v ₁ (t ₃ ) at t ₃ (= t ₂ + Δt) is detected.

From the detection voltages v ₁ (t ₁ ), v ₁ (t ₂ ), and v ₁ (t ₃ ), the secondary time constant calculation circuit 14 obtains a secondary time constant τ ₂ according to the following equation.

Accordingly, the calculation of the secondary time constant τ ₂ is obtained from the detection values of the primary voltages v ₁ (t ₁ ) to v ₁ (t ₃ ) within a short time from the application of the constant current to the time t ₃ , and is relatively long. Time-consuming steady value i ₁
eliminating the need for voltage measurement to be r _1.

The above-described primary voltage detection circuit 15 and secondary time constant calculation circuit 14
Is realized, for example, by using the circuit configuration shown in FIG. In FIG. 3, three samples are taken at every time Δt by a sample-and-hold circuit 17 through a primary voltage low frequency filter 16 of the electric motor 1, and this sampling voltage is converted into a digital value at every time Δt by an A / D converter 18 and sequentially. To the registers 19 and 20. With this configuration, the register 20 stores the first sample data v ₁ (t ₁ ), the register 19 stores the second sample data v ₁ (t ₂ ), and the A / D converter 18 Is obtained as the _third sample data v ₁ (t ₃ ). The subtracters 21 and 22 output the data v ₁ (t ₁ ), v ₁ (t ₂ ), v
₁ (t ₃ ) is subtracted, and v ₁ (t ₁ ) −v ₁ (t ₂ ) v ₁ (t ₂ ) −v ₁ (t ₃ ) in the above equation is obtained. Then, the divider 23 divides the operation result of the subtracters 21 and 22, and the result is , And a second order time constant τ ₂ is obtained by division by the divider 25 with the time Δt.

In the embodiment, a constant voltage was applied to the electric motor to obtain the secondary time constant τ _2, and the primary current was changed as shown in FIG.
i ₁ (t ₁ ) to i ₁ (t ₃ ) are obtained at intervals of time Δt, and Can also be obtained from

G. Effects of the Invention As described above, according to the present invention, the primary voltage change or the primary current change is detected in three samples and the temperature-corrected secondary time constant is obtained, so that the steady-state value of the primary voltage or the primary current is calculated. The measurement can be performed in a short time without the need for the measurement, and the vector control and the rise can be made faster. Further, when the stop time is included in the middle of the variable speed control of the motor, even if the stop period is short, the secondary time constant can be measured again during the stop period and readjusted.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus configuration showing an embodiment of the present invention, FIG. 2 is a diagram showing a voltage measurement mode of the embodiment, FIG. 3 is a circuit diagram of a secondary time constant calculation circuit in FIG. 1, and FIG. Current measurement mode diagram of the embodiment of
FIG. 5 is a block diagram of a vector control device, and FIG. 6 is a diagram of a conventional voltage measurement mode. 11: Control circuit, 12: Inverter body, 14: Secondary time constant operation circuit, 15: Primary voltage detection circuit, 19, 20: Register, 24: Logarithmic operation unit.

Claims (1)

(57) [Claims] 1. In a vector control of an induction motor in which a secondary time constant τ ₂ of an induction motor is obtained, a temporary voltage v for each time Δt when a constant current or a constant voltage is applied to the motor.
₁ (t ₁ ), v ₁ (t ₂ ), v ₁ (t ₃ ) or primary current i ₁ (t ₁ ), i
₁ (t ₂ ), primary voltage or primary current detection circuit for detecting i ₁ (t ₃ ), and the following equation from the primary voltage or primary current: And a secondary time constant calculating circuit for obtaining a secondary time constant τ ₂ according to the following equation: