JPH10164891A - Induction motor constant measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a high-quality control of an induction machine available by outputting secondary magnetic flux with the inputs of induction machine voltage and current, a primary resistance, a primary and a secondary self- inductance, and a mutual inductance and outputting a secondary time constant with the inputs of the secondary magnetic flux, the induction machine current, and the mutual inductance. SOLUTION: A magnetic flux calculator 9 outputs secondary magnetic flux Ψ2 with the inputs of the induction machine voltage (v) and current (i) and a preliminarily given primary resistance R1, primary self-inductance L1, secondary self-inductance L2, and mutual inductance M. A time constant calculator 10 outputs a secondary time constant T2 with the inputs of the secondary magnetic flux Ψ2, the induction machine current (i), and the mutual inductance M. Since DC current is caused to flow in a secondary circuit, measured values of the secondary time constant T2 and secondary resistance R2 are the ones which are close to those at the normal operation of the induction machine. And, a voltage detector 3 detects or estimates the voltage V when the induction machine 4 is rotating at nearly a rated rotating speed, and therefore there is only a little error by the voltage detector 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring an electric constant of an induction motor (hereinafter abbreviated as an induction machine), and more particularly to a device for measuring a secondary time constant.

[0002]

2. Description of the Related Art Generally, when controlling the speed, torque, etc. of an induction machine, it is necessary to know the electric constant of the induction machine. Therefore, an induction machine constant measuring device for measuring the electric constant of the induction machine is required. FIG. 5 is a block diagram showing a conventional example. 5, 1 is a single-phase test means, 2 is a current detector, 3 is a voltage detector, 4 is an induction machine, 5 is a resistance calculator,
6 is a memory. Hereinafter, the operation will be described with reference to FIG.

The single-phase test means 1 inputs a single-phase test frequency command value f1 * and supplies power to the induction machine 4. The current detector 2 detects a current flowing through the induction machine 4 and outputs an induction machine current i. Voltage detector 3 detects the voltage of induction machine 4 and outputs an induction machine voltage v. The resistance calculator 5 includes the current detector 2
And the output v of the voltage detector 3 are input, and the sum (R1 + R2) of the primary resistance R1 and the secondary resistance R2 is obtained from the phase difference between the current i and the voltage v and their magnitudes, and stored in the memory 6 in advance. The secondary resistance value R is obtained by subtracting the set primary resistance value R1.
Get 2. The secondary resistance value R2 thus obtained is stored and set in the memory 6. As described above, the secondary resistance value, which is one of the electric constants of the induction machine, can be obtained and can be stored and set in the memory. In addition, it can be used for controlling the speed, torque, etc. of the induction machine in combination with the induction machine electrical constants other than the secondary resistance stored and set in advance.

[0004]

The secondary resistance measurement by the above-described single-phase test is based on an induction machine that is not affected by the skin effect.
This is effective because the secondary resistance does not change with the single-phase test frequency. However, a problem arises when the secondary resistance value greatly changes depending on the single-phase test frequency due to the effect of the skin effect as in a double-cage induction machine. less than,
The problems caused by the skin effect are listed.

[0005] 1. During operation of the induction machine, the frequency of the current flowing through the secondary resistor is equivalent to the slip frequency, and is generally several Hz.
It is. However, if the frequency of the single-phase test is reduced, the induction machine may rotate, and the single-phase test frequency cannot be so reduced. Therefore, the measured value of the secondary resistance in the single-phase test is different from the secondary resistance value during operation, and various improvements are required. 2. In addition, when the single-phase test is performed at a frequency of several Hz, the voltage of the induction machine decreases, and the detection accuracy of the voltage detector deteriorates. Due to the problems described above, there is a possibility that accurate measurement of the electrical constant of the induction machine may not be performed. The present invention has been made in view of the above points, and an object of the present invention is to provide an induction motor constant measuring device which solves these drawbacks.

[0006]

Means for achieving the object are a current command calculator for outputting a current command, and a current for inputting the current command and performing current control to supply power to the induction motor. Control means, a voltage detector for detecting or estimating the voltage of the induction motor and outputting an induction motor voltage v, and a current detector for detecting a current of the induction motor and outputting an induction motor current i. Further, the induction motor voltage v
And the induction machine current i and a previously given primary resistance R
1, the primary self-inductance L1, the secondary self-inductance L2, and the mutual inductance M are input and the secondary magnetic flux Ψ
2 and a time constant calculator for inputting the secondary magnetic flux Ψ2, the induction machine current i and the mutual inductance M and outputting a secondary time constant T2.

The current command output from the current command calculator is changed from time t0, and the time constant calculator obtains a secondary time constant T2 after time t0 by equation (1).

[0008]

(Equation 3)

[0009] The secondary magnetic flux Ψ2 is obtained by the secondary magnetic flux calculation equation of the equation (2).

[0010]

(Equation 4)

Further, the integral of the secondary magnetic flux calculation formula can be substituted by a first-order delay. The output of the time constant calculator is a secondary time constant at an arbitrary time after time t0 or an average value of secondary time constants at a plurality of times after time t0. The output value of the time constant calculator thus obtained is the value of the secondary time constant corresponding to the slip frequency. Further, when the induction machine is operated at a rotation speed of the rated rotation speed, the induction machine voltage v detected or estimated by the voltage detector becomes a value close to the rated voltage, and the voltage detection error is reduced. Further, if the current command is changed after time t0 to, for example, about 10% corresponding to the time before time t0, the induction machine current is not 0 when the time constant calculator is performing the calculation. The influence of the dead time of the induction machine voltage detected or estimated by the inductor is reduced. Further, even if the rotation speed of the induction machine fluctuates, a calculation error hardly occurs.

If a secondary resistance is required for controlling the induction machine, a secondary resistance calculator for inputting the output of the time constant calculator and the secondary self-inductance and outputting a secondary resistance is added.
A memory is provided for the above means, and at least one of the output of the time constant calculator and the secondary resistance is stored and set in the memory so that it can be used for induction machine control. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, 7 is a current command calculator,
8 is a current control means, 2 is a current detector, 3 is a voltage detector,
Reference numeral 4 denotes a three-phase induction motor (hereinafter abbreviated as induction machine), 9 denotes a magnetic flux calculator, and 10 denotes a time constant calculator. FIG. 2 is a waveform diagram showing an example of the operation of the current command calculator 7 of the present invention. An embodiment of the present invention will be described below with reference to FIGS.

The current command calculator 7 outputs a three-phase current command (hereinafter abbreviated as a current command) i * shown in FIG. That is, the current command i * after time t0 is changed to 1 before time t0.
Stepwise change to a 3-phase AC command of about 0%. The current control unit 8 receives the current command i *, performs current control, and supplies power to the induction machine 4 so that a current corresponding to the current command i * flows to the induction machine 4. Note that the induction machine 4 is rotated around the rated rotation speed before time t0. Current detector 2 detects induction machine current i. The voltage detector 3 detects the induction machine voltage v
Is detected or estimated. The magnetic flux calculator 9 calculates the induction machine current i
, The induction machine voltage v, and the primary resistance R1, the primary self-inductance L1, the secondary self-inductance L2, and the mutual inductance M, which are part of the induction machine electrical constant, are input. The magnetic flux Ψ2 is calculated.

[0015]

(Equation 5)

Here, the primary resistance R1, the primary self-inductance L1, the secondary self-inductance L2, and the mutual inductance M are measured or set in advance. here,
The integral of the equation (3) may be replaced with a first-order delay. The time constant calculator 10 inputs the secondary magnetic flux Ψ2, the motor current i, and the mutual inductance M after the time t0, and the following (4)
The secondary time constant T2 is calculated according to the equation.

[0017]

(Equation 6)

The time constant T2 obtained by the equation (4) is
Output. If the secondary magnetic flux Ψ2 after the time t0 is in a transient state, the secondary time constant T2 at an arbitrary time can be obtained by using the equation (4). Here, the respective secondary time constants T21, T22,..., T2n at arbitrary plural (for example, n) times t1, t2,.
The calculation may be performed using the equation, and the average value obtained by the following equation (5) may be used as the output of the time constant calculator 10 as T2.

[0019]

(Equation 7)

Further, a secondary time constant is calculated for each current control cycle by using the equation (3), and a value obtained by filtering the calculation result is set to an average value equivalent to the equation (4) to obtain a value of the time constant calculator 10. It may be output. FIG. 2 shows an example of how to give the current command i *. If the secondary magnetic flux Ψ2 is in a transient state after the time t0, the secondary time constant T2 at an arbitrary time point can be obtained using the equation (3). Therefore, if the denominator of the equation (3) does not become 0, it is not necessary to change the current command i * in steps as shown in FIG.

The effects of the embodiment of FIGS. 1 and 2 will be described below. 1. After time t0, a DC current flows on the secondary side until the secondary magnetic flux Ψ2 reaches a steady state, so that the output of the time constant calculator 10 is a secondary time constant T2 corresponding to the slip frequency. 2. Since the induction machine 4 is rotating near the rated rotation speed, the voltage applied to the induction machine becomes close to the rated voltage and the voltage detector 3
The error of the induction machine voltage v detected or estimated by the above is small. 3. Since the induction machine current i at the time of calculating the secondary time constant T2 is not 0, the influence of the dead time of the induction machine voltage v detected or estimated by the voltage detector 3 is small. 4. Even if the rotation speed of the induction machine 4 fluctuates, the calculation error of the secondary time constant T2 hardly occurs, so that the induction machine 4 may be loaded.

FIG. 3 is a block diagram showing an embodiment for obtaining the secondary resistance R2 from the secondary time constant T2 obtained as described above. 130 is an induction machine constant measuring device (hereinafter, referred to as a first constant measuring device) shown in FIGS. 1 and 2, and 11 is a secondary resistance calculator. The secondary resistance calculator 11 calculates the secondary resistance R2 from the secondary time constant T2 and the secondary self-inductance L2, which are the outputs of the first constant measuring device 130, according to equation (6), and outputs the secondary resistance R2. .

[0023]

(Equation 8)

FIG. 4 shows an application example of the present invention. Reference numeral 131 denotes a first constant measuring device or an induction machine constant measuring device shown in FIG. 3 (hereinafter, referred to as a second constant measuring device). 6 is a memory, 12 is an induction machine control means, 14 is a selector, and 4 is an induction machine. Hereinafter, an application example of the present invention will be described with reference to FIG.

The second constant measuring device 131 has a secondary time constant T2
Alternatively, it outputs the secondary resistor R2. Further, electric current can be supplied to the induction machine 4 by the current control means 8 in the second constant measuring device 131 to control the current of the induction machine 4. The memory 6 has a second
A constant required for the calculation by the constant measuring device 131 is given to the second constant measuring device 131, and a secondary time constant T2 or a secondary resistance R2 output from the second constant measuring device 131 is stored and set.
Further, the memory 6 provides the induction machine control means 12 with constants necessary for the calculation in the induction machine control means 12. Induction machine control means 1
2 can perform an operation for controlling the induction machine 4 and supply power to the induction machine 4 to control the induction machine 4. The selector 14 selects whether to connect the second constant measuring device 131 to the induction machine 4 or to connect the induction machine control means 12.

First, the selector 14 selects the second constant measuring device 131, measures the secondary time constant T2 and the secondary resistance R2, and determines the measured secondary time constant T2 and secondary resistance R2. The setting is stored in the memory 6. Next, the selector 14 selects the induction machine control means 12, performs induction machine 4 control calculation using the induction machine 4 electric constants stored and set in the memory 6, and controls the induction machine 4. According to these procedures, high-performance operation of the induction machine 4 becomes possible.

[0027]

As described above, according to the present invention, since a DC current flows through the secondary circuit, it is possible to measure the secondary time constant and the value of the secondary resistance which are close to those in the normal operation of the induction machine. Further, since the voltage when the induction machine is rotating near the rated speed is detected or estimated, errors due to the voltage detector are small. Further, by not setting the current command after time t0 to zero, it is possible to perform calculations with less influence of dead time. In addition, since a calculation error due to a change in the rotation speed of the induction machine hardly occurs, the load state of the induction machine may be either no load or loaded. Further, since the electrical constant of the induction machine can be accurately measured, the induction machine can be controlled with high performance.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a waveform diagram showing one calculation example of a current command calculator of the present invention.

FIG. 3 is a block diagram showing one embodiment of the present invention.

FIG. 4 is a block diagram showing one application example of the device of the present invention.

FIG. 5 is a block diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single-phase test means 2 Current detector 3 Voltage detector 4 Induction motor 5 Resistance calculator 6 Memory 7 Current command calculator 8 Current control means 9 Magnetic flux calculator 10 Time constant calculator 11 Secondary resistance calculator 12 Induction machine control Means 130 First constant measuring device 131 Second constant measuring device 14 Selector f1 * Single-phase test frequency command i * Current command v Induction machine voltage i Induction machine current Ψ2 Secondary magnetic flux T2 Output value of time constant calculator t0 Current command R1 Primary resistance R2 Secondary resistance M Mutual inductance L1 Primary self inductance L2 Secondary self inductance

Claims (8)

[Claims] 1. An induction motor constant measuring apparatus for measuring a motor constant required for performing a high-performance operation of an induction motor, wherein the current command calculator outputs a current command, and the current command calculator outputs the current command. A current control means for inputting a current command and performing current control to supply power to the induction motor, a voltage detector for detecting or estimating a voltage of the induction motor and outputting an induction motor voltage v, and detecting a current of the induction motor. A current detector that outputs an induction machine current i, inputs the induction machine voltage v, the induction machine current i, and a given primary resistance R1, primary self inductance L1, secondary self inductance L2, and mutual inductance M. A magnetic flux calculator that outputs a secondary magnetic flux Ψ2, inputs the secondary magnetic flux Ψ2, the induction machine current i, and the mutual inductance M, and outputs a secondary time constant T2. The induction motor constant measuring apparatus characterized by being composed of constant calculator time that. 2. The current command calculator calculates an arbitrary time t0.
The time constant calculator calculates a secondary time constant T2 after time t0 by the following equation: The induction motor constant measuring apparatus according to claim 1, wherein the calculation is performed by: 3. The magnetic flux calculator calculates the secondary magnetic flux Ψ2 after time t0 by the following equation: The induction motor constant measuring apparatus according to claim 1, wherein the calculation is performed by: 4. An induction motor constant measuring apparatus according to claim 3, wherein the integral of said secondary magnetic flux calculation expression is substituted by a first-order delay. 5. The time constant computing unit computes secondary time constants at a plurality of time points after time t0, and uses an average value of the values as an output T2 of the time constant computing unit. Induction motor constant measuring device. 6. The induction motor constant measuring apparatus according to claim 1, further comprising a memory, wherein the output T2 of the time constant calculator is stored and set in the memory. 7. The induction motor constant measuring apparatus according to claim 1, further comprising a secondary resistance calculator for inputting the output T2 of the time constant calculator and the secondary self inductance L2 and outputting a secondary resistance. 8. The induction motor constant measuring apparatus according to claim 7, wherein a memory is added, and the secondary resistance is stored and set in the memory.