JP2849645B2 - Inverter with constant measurement setting function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for driving an induction motor by an inverter, and more particularly to a device for simply and accurately adjusting an induction motor.

[0002]

2. Description of the Related Art In order to control an induction motor with high accuracy, the winding resistance of primary and secondary windings, which are the electrical constants of the induction motor,
Primary and secondary leakage inductance and mutual inductance values may be required. FIG. 2 shows a conventional means for measuring these electric constants and setting them in the inverter. The conventional technique will be described below with reference to FIG.

The inverter 1 receives a switching signal output from the selector 10 and operates the inverter according to the switching signal. The output of the inverter 1 is connected to the motor 2 via the current detector 3 and the voltage detector 4, and the inverter 1 can apply a voltage to the motor 2.

First, the motor 2 is set to no load, and the selector 10 is turned off.
Selects the switching signal output from the no-load test means 6 and outputs it to the inverter 1. The motor 2 rotates at a high speed, and the no-load test means 6 inputs the input current and the input voltage of the motor 2 from the current detector 3 and the voltage detector 4 to obtain the magnitude and phase of the fundamental wave. Motor 2 from the relationship
The primary self-inductance L ₁ is obtained and output to the constant calculating means 9.

[0005] Next, the selector 10 selects the switching signal output from the DC test means 7 and outputs it to the inverter 1. When the motor 2 is stopped, two of the three-phase input terminals
DC voltage is applied between the two terminals. The DC test means 7 receives the current and the voltage detected by the current detector 3 and the voltage detector 4, obtains a primary winding resistance R _{1 based} on a ratio therebetween, and outputs it to the constant calculation means 9.

[0006] Finally, the selector 10 selects the switching signal output from the single-phase test means 8 and outputs it to the inverter 1. When the motor 2 is stopped, two of the three-phase input terminals
A single-phase AC voltage is applied between the two terminals. The single-phase test means 8 inputs the current and the voltage detected by the current detector 3 and the voltage detector 4, obtains the magnitude and phase of the fundamental wave, and obtains the primary and secondary leakage from the relationship. An approximate value l ′ of the sum of the inductances and an approximate value R ′ of the sum of the primary and secondary winding resistances are obtained and output to the constant calculating means 9.

In the constant calculation means 9, the no-load test means 6,
The outputs of the DC test means 7 and the single-phase test means 8 are input,
Assuming that the primary leakage inductance is equal to the secondary leakage inductance, the leakage inductance 1 is obtained at l = 0.5l ′, the mutual inductance M is obtained at M = L ₁ −l, and the R ₂ = R′−R ₁ is obtained. seeking secondary winding resistance R _2, and outputs the setting storage unit 11 with the primary winding resistance R _1.

The setting storage means 11 sets and stores the input electric constants in a memory of the inverter. The magnetic flux torque controller 5 selects a switching signal for controlling the magnetic flux and torque of the electric motor 2 based on the constants stored and set in the selector 1.
0 to the inverter 1.

[0009]

In the single-phase test means 8, the exciting current I ₀ (here, I ₂ and I ₀₎ is compared with the secondary current I ₂ in the equivalent circuit of the motor shown in FIG.
Since both are very small phasors), as shown in FIG. 4, assuming an equivalent circuit ignoring the excitation circuit, an approximate value of the sum of the primary and secondary leakage inductances and the primary and secondary The approximate value of the sum of the winding resistance is determined. However, the constant calculating means 9 calculates the electric constant not as an approximate value but as the sum of the primary and secondary leakage inductances or the sum of the primary and secondary winding resistances. And the secondary winding resistance R ₂ includes an error ignoring the excitation circuit.

For the above reasons, the measurement accuracy of the constants deteriorates, and the control performance in normal operation using them deteriorates.
The present invention has been made to solve the problem of deterioration of control performance.

[0011]

In order to solve the above-mentioned problems, an inverter with a constant measurement and setting function according to the present invention is characterized in that, when the constant calculation means obtains a secondary winding resistance and a leakage inductance, a mutual inductance is set. And an excitation circuit correction calculating means for correcting the current flowing in the excitation circuit by using.

[0012]

In the excitation circuit correction calculating means in the constant calculating means according to the present invention, the approximate leakage inductance is set to l _d , and the approximate secondary winding resistance is set to R _2d , first, as in the prior art.

L _d = 0.5 l ′ (1) R _2d = R′−R ₁ (2) is obtained, and an approximate mutual inductance M _d is obtained.

[Equation 2] M _d = L ₁ −l _d (3)

Next, from an equivalent circuit in which l on the primary side of FIG. 3 is set to l _d , the excitation voltage E (phasor) is

Equation 3] E = Since _{V- (R 1 + jωl d)} I 1 (4), the excitation current I ₀ (phasor) is

I ₀ = E / (jωM _d ) (5) Where V is the primary voltage (phasor), ω is the angular frequency of the single-phase test, j is the square root of −1, and I ₁ is the primary current (phasor).

The primary voltage V is

V = (R ′ + jωl ′) I ₁ (6), and the secondary current I ₂ (phasor) is

I ₂ = I ₁ −I ₀ (7) The input power P in the single-phase test is

Equation 7] ^{_{P = | I 1 | 2 R}} 1 + | I 2 | 2 R 2 (8) or

(8) Since P = R ′ | I ₁ | ² (9), the equations (1) to (7) and (9) are substituted into the equation (8).

Equation 9] _{R 2 = R 2d / {(} 1-l d / M d) 2 + (R 2d / ωM d) 2} (10) , and the secondary windings to correct the current I ₀ flowing through the exciting circuit resistance R ₂ can be obtained.

Next, the reactive power Q is

[Number 10] _{Q = ωl '| I 1 |} 2 = ωl (| I 1 | 2 + | I 2 | 2) + ωM d | I 0 | 2 (11) , so, as well

Equation 11] _{l = [2l d -M d {} (l d / M d) 2 + (R 2d / ωM d) 2}] / {1+ (1-l d / M d) 2 + (R 2d / ωM _d ) ² ｝ (12), and the leakage inductance 1 obtained by correcting the exciting current I ₀ flowing in the exciting circuit is obtained.

The mutual inductance M is

M = L ₁ −l (13)

If l _{d in} equation (4) is not l, the secondary winding resistance R ₂ and the leakage inductance l in which the exciting current I ₀ is completely corrected cannot be obtained, but the error due to this is very small. So there is no problem. Also, when trying to eliminate this error, there remains a problem that equations (10) and (12) become very complicated.

[0018]

FIG. 1 shows an embodiment of an inverter having a constant measurement setting function according to the present invention. The description of the same parts as in FIG. 2 of the conventional system is omitted, and the different part is a single-phase test means 8 '
The constant calculation means 9 'and the internal excitation circuit correction calculation means 91 will be described.

The single-phase test means 8 ', like the conventional single-phase test means 8, has an approximate value l' of the sum of the primary and secondary leakage inductances and the sum of the primary and secondary winding resistances. Approximate value R '
And outputs it to the constant calculation means 9 '.
Is also output to the constant calculating means 9 '.

The constant calculation means 9 'receives the outputs of the no-load test means 6, the DC test means 7 and the single-phase test means 8', and obtains l _d , R from the equations (1), (2) and (3). _2d, seeking M _d, more thereof with the angular frequency omega, in the excitation circuit correction calculation unit 91 (10), (12) seeking and the secondary winding resistance R ₂ leakage inductance l from equation (13 ) set together with the mutual inductance M and the primary winding resistance R ₁ obtained in the equation storing means 11
Output to

[0021] Since the magnetic saturation of the iron core of the motor in the single phase test is considered that there is no primary self-inductance L ₁ used for calculation of the M _d are those core of the motor is measured in a state where no magnetic saturation Desirably.

[0022]

According to the present invention, the leakage inductance and the secondary winding resistance in which the current flowing in the excitation circuit is corrected can be measured and set in the inverter, so that the accuracy of the constant is improved, and the normal operation using them is performed. Speed and torque control performance are improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an inverter with a constant measurement setting function according to the present invention.

FIG. 2 is a block diagram illustrating an example of a conventional inverter with a constant measurement setting function.

FIG. 3 is an equivalent circuit diagram of the induction motor.

FIG. 4 is an equivalent circuit diagram of an approximated induction motor during a single-phase test.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Inverter 2 Motor 3 Current detector 4 Voltage detector 5 Magnetic flux torque controller 6 No-load test means 7 DC test means 8, 8 'single-phase test means 9, 9' constant calculation means 10 Selector 11 Setting storage means 91 Excitation Circuit correction calculating means E Excitation voltage (phasor) I ₁ Primary current (phasor) I ₂ Secondary current (phasor) I ₀ Excitation current (phasor) L ₁ Primary self-inductance l 'Sum of leakage inductance between primary and secondary Approximate value l Leakage inductance l _d Approximate leak inductance M Mutual inductance _Md approximate mutual inductance R 'Approximate value of the sum of primary and secondary winding resistances R ₁ Primary winding resistance R ₂ Secondary winding resistance R _2d approximate secondary winding resistance V primary voltage (phasor) ω angular frequency

Claims (3)

(57) [Claims] 1. A three-phase inverter for supplying power to a three-phase induction motor, comprising: a no-load test means for measuring a primary self-inductance of the motor; and a DC test means for measuring a primary winding resistance of the motor. A single-phase test means for measuring an approximate value of the sum of the primary and secondary leakage inductances and an approximate value of the sum of the primary and secondary winding resistances; and With a constant measurement setting function comprising constant calculation means for calculating the leakage inductance, mutual inductance, primary winding resistance, and secondary winding resistance of the motor, and setting means for storing the output of the calculation means in the memory of the inverter. In the inverter, when the constant calculation means obtains the secondary winding resistance and the leakage inductance, the excitation for correcting the current component flowing through the excitation circuit using the mutual inductance. Constant measurement setting function inverter which is characterized in that additional circuitry correction calculation means. 2. The constant according to claim 1, wherein a mutual inductance in a state without magnetic saturation is used when the secondary winding resistance and the leakage inductance are obtained by correcting a current flowing in the excitation circuit. Inverter with measurement setting function. 3. The method according to claim 1, wherein the mutual inductance obtained from the primary self-inductance obtained by said no-load test means is used when calculating the secondary winding resistance and the leakage inductance by correcting the current flowing in the excitation circuit. The inverter with a constant measurement setting function according to claim 1.