JPH0336984A - Detection of primary voltage of induction motor - Google Patents

Abstract

PURPOSE:To improve resolution of a detected waveform by setting in advance primary and secondary side resistance values to a controller, operating a predetermined bias amount and a gain ratio based on them, and automatically correcting a primary voltage. CONSTITUTION:Control means 14 stores in advance primary and secondary side resistance values r1, r2, operates the steady component i1Xr1 of a primary voltage from the value r1, determines a bias amount based on the result, further calculates a gain ratio corresponding to the unsteady component of the voltage from the reciprocal of the value r2, and outputs to a D/A converter in a converter group 15. The bias amount from the converter 15 is reduced from a detection voltage form a differential amplifier 12, a noise, etc., is simultaneously suppressed by a filter 13 having a capacitor C, a resistor R and a comparator, a gain ratio from the converter 15 is multiplied by a multiplier 16, and a voltage V1' is output to the converter 15.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a primary voltage detection method used for measuring a secondary time constant during vector control of an induction motor that drives an elevator, and particularly relates to a primary voltage detection method used for measuring a secondary time constant. The present invention relates to a detection method that corrects each of the stationary portion and the unsteady portion.

B. Summary of the Invention The present invention provides a primary voltage detection method used for measuring a secondary time constant during vector control of an induction motor that drives an elevator. The steady part of the voltage is corrected, and the unsteady part of the primary voltage is corrected with a gain factor based on the reciprocal of the preset secondary resistance value, and the gain can be adjusted to improve the resolution of the detected waveform. This paper discloses a technology that can be applied to various types of electric motors.

C9 Prior Art Generally, elevators are driven by induction motors.

Vector control of an induction motor is an attempt to obtain variable speed performance equal to or better than that of a DC motor by dividing the blow-type flow into an excitation current and a torque current, and by orthogonalizing the vector of the torque current and the magnetic flux. There is.

FIG. 3 is a block diagram showing an example of a vector control device, in which 1 is an induction motor and 2 is its speed detector. A speed calculation unit 3 is connected to the speed detector 2, and the speed ωn calculated by the speed calculation unit 3 from the detected value is compared with the speed command N to input the torque calculation 141, and the proportional integral (
A torque current command it is determined by the PI) calculation, and a primary current value 11 is determined by the primary current calculation section 5 from this torque current It and the excitation current setting value 1o. On the other hand, the phase calculation section 6 calculates the phase angle φ between the torque current It and the excitation current ro as φ-jan-'(It/Io), and the frequency calculation section 7 calculates the phase angle φ between the torque current It and the excitation current No. The shear frequency ωS is calculated from the second-order time constant r2 of the motor as follows. Note that the time constant τ2 is τ2 with respect to the secondary self-inductance L2 and the secondary resistance R2.
=L2/R2.

ω5=It/(Io·τ2) This slip frequency ωS is added to the detected speed value ωn by an adder 8 to obtain the -included angular frequency ω0.

The above single blow type flow value 111 phase angle φ and angular frequency ω0 are input to the three-phase current calculation section 9, and the primary current 1a of the motor 1,
Ib and Ic are calculated. Using this current as a current command for the inverter lO, the inverter lO supplies a primary current to the electric motor l. The calculation by the three-phase current calculation section 9 is performed using the following equation.

θ−S ωodt Ia=J2 l 11 l s in(θ+φ) Ib=
72 l r I l s in (θ+2/3π+φ)
Ic=J21111sin(θ-2/3π+φ) In such a vector control device, the secondary time constant τ2 for determining the slip frequency ωS is the motor constant L2. It is determined by R2, and the fluctuation of the secondary resistance R2 due to the temperature of the motor becomes the difference in the secondary time constant τ2 and the -blow mold flow phase. Therefore, temperature correction of the secondary time constant τ2 has been conventionally performed, and there is a method of calculating from the primary voltage when a constant current is passed through the motor. FIG. 4 is a characteristic diagram showing the change in primary voltage vl(t) when a constant current if is applied.
(t) is v I (t) = i I (r l+r2e−””2
′). Therefore, at time t1. By measuring the primary voltages vl (tl) and vl (t2) at t2, the secondary time constant τ2 can be found from the following formula.
2 is used in the slip frequency calculation to remove the influence of temperature.

D3 Problems to be Solved by the Invention The conventional secondary time constant correction method described above applies a constant current or constant voltage to an induction motor, measures the generated transient current or voltage at fixed time intervals, and calculates changes in its waveform. When applying a constant current or constant voltage to an induction motor, a voltage detection circuit having a configuration as shown in Fig. 5 is generally used. It is used.

That is, a differential amplifier 1 is connected to the output terminal of the inverter IO shown in FIG. 3 via an attenuator 11.
2 is connected to detect the output voltage of the inverter IO, and after suppressing noise etc. with a filter 13 consisting of a capacitor C1 resistor R and a comparator, the voltage vl is detected.

FIG. 6 is a waveform diagram showing the detected voltage.

In the figure, the current is a constant current if, but the voltage consists of a portion rlXil due to the primary side resistance value l and a portion r2Xil due to the secondary side resistance r2.

- The part due to the next-side resistance rl is the steady value of vl, but conventionally, detection was performed with this steady value level as the lower limit, so it was not possible to increase the gain for transient states.
Resolution was sacrificed.

In addition, if the specifications of the induction motor are different, the ratio between rl and r2 will also be different, so if you do not add an adjustment element to this detection circuit, it is possible to detect the secondary time constant with high accuracy. could not.

The present invention was created in view of these problems, and therefore,
The purpose of this invention is to provide a primary voltage detection method that allows gain adjustment, improves the resolution of detected waveforms, and is applicable to various types of electric motors.

89 Means for Solving the Problems In the present invention, the means for solving the above problems are based on the first-order time constant used to measure the second-order time constant when performing vector control of the induction motor based on the second-order time constant. In the voltage detection method, the steady portion of the primary voltage is corrected with a bias amount based on a preset primary resistance value, and the blow mold pressure is corrected with a gain factor based on the reciprocal of a preset secondary resistance value. The primary voltage detection method for the induction motor corrects the unsteady portion.

F9 action In the present invention, the negative side resistance value and the secondary side resistance value are set in advance in the control device, the required bias amount and gain rate are calculated based on them, and the primary voltage is automatically corrected. It is something.

A microcomputer is used in a speed control device that performs vector control on an induction motor for an elevator, and design values of a primary resistance and a secondary resistance of the motor are stored in its memory. The control means of the present invention includes:
Perform calculations using those values, - correct the bias amount corresponding to the steady part of the blow mold pressure, and
Improve the detection resolution of the unsteady portion by correcting the gain so that the /D conversion region can be used effectively.

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

FIG. 1 is a configuration diagram of an embodiment of the present invention.

In the figure, +1 is an attenuator, 12 is a differential amplifier, 13 is a filter, 14 is a control means, ! 5 is a converter group;
16 is a multiplier, and a differential amplifier 12 is connected to the output terminal of the inverter described in n1ffi via an attenuator (attenuation 5) 11, and a filter 13 consisting of a capacitor WkC, a resistor R, and a comparator is further connected. .

The control means (CPU) 14 stores the negative side resistance value rl and the secondary side resistance value r2 in advance, calculates the steady portion 11Xrl of the primary voltage from the negative side resistance value rl, and calculates the steady portion 11Xrl of the primary voltage based on the result. Determine the bias amount, further calculate the gain rate corresponding to the unsteady part of the voltage from the reciprocal of the secondary side resistance value r2,
Each is output to the D/A converter in the converter group 15.

The detected voltage from the differential amplifier 12 is applied to the D/A converter 1.
The bias amount is subtracted from 5, and at the same time the capacitance C1 resistance R
After suppressing noise and the like by a filter I3 consisting of a filter I3 and a comparison 2X, a multiplier 16 multiplies the gain factor from the D/A converter 15 and outputs the voltage vl' to the A/D converter 15.

In this way, it becomes possible to accurately measure the secondary time constant τ2 while effectively utilizing the conversion area of the A/D converter and automating the adjustment for each motor.

FIG. 2 is an explanatory diagram showing the correction effect of this embodiment. In the upper part of the figure, v l (t) - i 1Xr [ is shown, and in the lower part, V de (t) - ifxrl - Bfas is shown. It is shown. Suppose that the A/D conversion resolution on the CPU detection side is 1000.
(0 to 999), if vl(1) has a waveform as shown in the upper part of the figure, then due to the lower limit of vl11Xrl,
Even if the gain can be adjusted, the resolution is limited.

However, as shown at the bottom of the figure, the bias was adjusted to ±300. If the gain is set by 2 and Mt is corrected, Vd(1) will be optimized and the resolution will be improved.

The embodiments of the present invention have the following effects.

(1) - Since the lower limit of the blow mold pressure vl is not limited to the steady value and gain adjustment is possible, the resolution of the detected waveform, that is, the resolution of temperature detection is improved.

(2) Resistances rl and r2 differ depending on the specifications of the induction motor, and their ratio (rl/r2) also differs, so when applying to various types of motors, an adjustment element is required in the circuit, but in this method, Since the correction is performed automatically, there is no need for adjustment.

(1) Effects of the Invention As described above, according to the present invention, it is possible to provide a primary voltage detection method that allows gain adjustment, improves the resolution of the detected waveform, and is applicable to various types of electric motors.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the correction effect of the embodiment, Fig. 3 is a block diagram of a vector control device, and Fig. 4 is a characteristic diagram of the primary voltage. FIG. 5 is a configuration diagram of a voltage detection circuit, and FIG. 6 is a waveform diagram of a conventional example. ! ... Induction motor, 2 ... Speed detector, 3 ... Speed calculation section, 4 ... Torque calculation section, 5 ... -th order IX flow calculation section, 6 ... Phase calculation section, 7 ...Frequency calculation section,
8... Adder, 9... Three-phase current calculation section, IO...
Inverter, It...attenuator, 12...differential amplifier, 13...filter,! 4...control means, 1
5... 4 conversion groups, 16... Multiplier. Figure 3: Elliptical diagram of vector III control equipment

Claims (1)

[Claims] (1) In the primary voltage detection method used to measure the secondary time constant when vector controlling an induction motor based on the secondary time constant, the primary voltage is A method for detecting a primary voltage of an induction motor, comprising: correcting a steady portion of the primary voltage; and correcting an unsteady portion of the primary voltage with a gain factor based on a preset reciprocal of a secondary resistance value.