JP3032681B2 - Method and apparatus for measuring secondary resistance of induction motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for measuring the secondary resistance of an induction motor, which measures the secondary resistance of the induction motor using a vector control device for the induction motor.

[0002]

2. Description of the Related Art In a vector control method for an induction motor, since the equivalent circuit of the induction motor is controlled as a control model, it is necessary to accurately set the constant of the equivalent circuit. In particular, the slip angular frequency ω _s is calculated from the secondary resistance, the magnetic flux command value, and the torque current command value according to equation (1).

[0003]

(Equation 1)

[0004] (1) ω _s : slip angular frequency r ₂ : secondary resistance φ _2d : magnetic flux command value L ₂ : secondary inductance M: mutual inductance This slip angular frequency ω _s is added to the speed command value to obtain a primary value. setting error of the secondary resistance r ₂ for controlling the frequency ω greatly affects the speed accuracy as shown in FIG.

For this reason, a method of performing a secondary resistance operation is disclosed in, for example, JP-A-62-114487 and JP-A-2-106.
No. 190 is provided.

[0006]

The former of the above prior arts has a problem that a current controller, a voltage detector and a speed detector are required. In the latter case, there is a problem that logarithmic calculation is required for the secondary resistance calculation, and the calculation content is complicated. 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 capable of easily measuring a secondary resistance without using a speed detector or a voltage detector. It is to provide a method for measuring the next resistance.

A second object of the present invention is to provide a method for measuring a secondary resistance of an induction motor in which an accurate secondary resistance can be measured without an influence of an error due to a differential term of a torque current. To provide. A third object of the present invention is to measure a secondary resistance of an induction motor in which the influence of an error can be eliminated by the differential term of the torque current, the slip angular frequency can be estimated, and the secondary resistance can be measured more accurately. In providing the device.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a vector operation device controls an induction motor by an inverter and independently controls a torque current component and an excitation current component of the induction motor. The method is characterized in that the primary frequency is changed by the torque current, the slip compensation is stopped, the primary frequency is changed in a no-load state of the induction motor, and the secondary resistance is calculated from the response waveform when the change is made. .

According to the second aspect of the present invention, the induction motor has no load.
The maximum value of the torque current when changing the primary frequency in the state is detected, and the value obtained by multiplying the magnetic flux command value and the amount of change in the primary frequency is divided by the maximum value of the response waveform of the torque current to calculate the secondary resistance. It is characterized by the following. According to the third aspect of the present invention, means for stopping the slip compensation for changing the primary frequency by the torque current, changing the primary frequency in a step-like manner, and the torque current becomes the maximum value from the maximum value of the torque current and the change in the primary frequency. Means for detecting the time until the torque current returns to zero again, and a value obtained by dividing the value obtained by multiplying the magnetic flux command value by the primary frequency change amount by the maximum value of the torque current response waveform. A secondary resistance calculation that multiplies a subtraction value obtained by subtracting a time required for the torque current to reach a maximum value from a time required for the current to return to zero, and divides the multiplied value by a time required for the torque current to return to zero. Means.

[0010]

According to the first aspect of the present invention, a vector operation device that controls an induction motor by an inverter and independently controls a torque current component and an excitation current component of the induction motor is provided.
Stop the slip compensation that changes the primary frequency by the torque current, change the primary frequency with no load on the induction motor, and calculate the secondary resistance from the response waveform when this change occurs. The secondary resistance can be easily measured without using a detector, and the speed accuracy can be improved.

According to a second aspect of the present invention, in the first aspect of the invention, the primary frequency is changed by the torque current, the maximum value of the torque current is detected, and the value obtained by multiplying the magnetic flux command value by the primary frequency change amount is obtained. Since the secondary resistance is calculated by multiplying by the maximum value of the torque current response waveform, the influence of the error due to the differential term of the torque current can be eliminated to accurately measure the secondary resistance.

According to the third aspect of the present invention, means for stopping slip compensation for changing the primary frequency by the torque current, changing the primary frequency in a step-like manner, and determining the torque current from the maximum value of the torque current and the change in the primary frequency. Means for detecting the time until the maximum value and the time until the torque current returns to zero again, and the value obtained by multiplying the magnetic flux command value and the primary frequency change amount were divided by the maximum value of the torque current response waveform. The value is multiplied by a subtraction value obtained by subtracting the time until the torque current reaches the maximum value from the time until the torque current returns to zero again, and this multiplied value is divided by the time until the torque current returns to zero. And the secondary resistance calculation means, which eliminates the influence of the error due to the differential term of the torque current and can accurately measure the secondary resistance, and can estimate the slip angular frequency. It is possible to more accurately measure the secondary resistance.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the vector control method for an induction motor, which is the basis of the present invention, will be described. The voltage equation of the induction motor is given by equation (2) in a rectangular coordinate system (hereinafter referred to as a dq coordinate system) rotating at the angular frequency (primary frequency) ω of the secondary flux linkage.

[0014]

(Equation 2)

(2) In the equation (2), r₁, R_TwoIs the primary of the induction motor respectively
And the secondary resistance value is L ₁, L_TwoAre the primary and secondary
The conductance value, M, is the mutual inductance between the primary and secondary windings.
Inductance value, σ is 1-M^Two/ L₁L_TwoBecome a leak
The coefficient is ω_sIs the slip angular frequency, and p is a fine d / dt
The minute operator, V_1d, V_1qAre the d-axis and q-axis of the primary voltage, respectively.
Component i_1d, i_1qAre the d-axis and q-axis components of the primary current, respectively.
That is, the exciting current and the torque current are represented by φ_2d, φ_2qAre the secondary chains respectively
Represents the d-axis and q-axis components of the intersecting magnetic flux.

The secondary flux linkage can be expressed as follows. φ _2d = Mi _1d + L ₂ i _2d φ _2q = Mi _1q + L ₂ i _2q (3) where i _2d and i _2q are the d-axis and q-axis components of the secondary current, respectively. Vector control means φ _2d = Mi _1d (constant), φ _2q =
This is to control the primary voltage or the primary current so as to be 0. If this condition is satisfied, the slip angular frequency ω _s is given by equation (1).

In a voltage-type inverter, in a steady state (the differential term is zero), φ _2d = Mi
_1d (constant), by substituting φ _2q = 0 and applying the voltage given by equation (4).

[0018]

(Equation 3)

(4) However, in the transient state,
An error term due to the fractional term appears, and the slip angular frequency ω _sIs (5)
It looks like an expression.

[0020]

(Equation 4)

… (5) This is transformed into equation (6) which is transformed into equation (2).

[0022]

(Equation 5)

(6) l ₁ , l ₂ = primary and secondary leakage inductance r ₂ ′ = r ₂ (M / L ₂ ) ² l ₂ ′ = l ₂ M / L ₂ Substituting equation (4) It is obtained by solving for the slip angular frequency.

Here, when the induction motor is in a no-load state, the slip angular frequency ω _s is approximately zero, and the rotational speed ω _r changes from the initial value of the primary frequency ω to the final value. Therefore,
The rotational speed, that is, the slip angular frequency ω _s can be estimated from the torque response current waveform, and the secondary resistance r ₂ can be calculated using the equation (7) obtained by modifying the equation (1).

[0025]

(Equation 6)

(7) Further, assuming that the rotational speed of the induction motor increases substantially linearly, the primary frequency change amount Δω, the time T ₁ from the primary frequency change to the torque current i _{1q reaching the} maximum value, and the torque again rotational speed of the induction motor when the current i _1q by using the time T ₂ of the up and returns to zero (8) the torque current i _1q from the equation is maximized, i.e. the slip angular frequency ω
_s can be accurately estimated, and the secondary resistance r ₂ can be calculated from equation (7).

[0027]

(Equation 7)

(8) FIG. 1 shows a configuration diagram of an embodiment of the present invention based on the above principle. In this embodiment, a vector operation unit 1, coordinate converters 2, 6, an inverter 3, an induction motor 4, a current detector 5, a delay circuit 7, a multiplier 8, an adder 9,
Integrator 10 is composed of a secondary resistance calculator 11 and the like, the vector calculation unit 11 excitation current command value i _1d ^*, the torque current i
_{Based on 1q} and the primary frequency ω, the primary voltage of the rotating coordinate system (d-axis and q-axis components of the primary voltage in the dq coordinate system)
Calculate V _1d ^* and V _1q ^* . The coordinate converter 2 converts the d-axis and q-axis components V _1d ^* and V _1q ^* of the primary voltage as voltage commands given from the vector calculation unit 1 into a fixed coordinate system in accordance with the phase angle command value θ of the secondary flux linkage vector. Voltage command value V
Conversion into u ^* , Vv ^* , Vw ^* . Inverter 3 receives voltage command values Vu ^* , Vv ^* , V
The applied voltage to the induction motor 4 is changed to, for example, PWM by w ^* .
To control the speed of the induction motor 4. Note that the symbol ^* indicates a command value, and the following notation will be performed accordingly.

The current detector 5 detects the phase current i of the induction motor 4.
u, iv, iw are detected by the coordinate converter 6
Are the phase currents iu, iv, i detected by the current detector 5.
w in accordance with the phase angle command value θ of the secondary linkage flux vector.
Converted to the coordinate system, the excitation current i _1dAnd torque current_1qAsk for
Confuse. The delay circuit 7 controls the torque output from the coordinate converter 6.
Current i_1qAnd delay torque current i_1q’
And a subtractor 7a and a controller 7b.
And the subtractor 7a outputs the torque current i_1qFrom the delay torque current
i_1q′, And outputs the subtracted value to the controller 7b.
The controller 7b controls the delay torque current so that the difference becomes zero.
i_1q′, For example, by a proportional / integrator.
Is done.

The multiplier 8 has a delay torque current i_1q’Proportional to
Multiplying by the number (K) and the slip angular frequency ω_sIn the search for
is there. The adder 9 calculates the slip angular frequency ω_sThe rotation speed command value
ω_r ^*And outputs a primary frequency ω. Integrator 10
Is the phase of the secondary linkage flux vector by integrating the primary frequency ω
The angle command value θ is output. The secondary resistance calculator 11 of the present invention
Main configuration, the torque current i_1qIs entered and all
Angle frequency ω_sControl signal 11a for turning on / off the output of
Control signal 11b for switching speed command value, rotation speed command
Value ω_r'^*And delay torque current i_1q′ To the slip angular frequency
Number ω_sIs output as a proportional constant (K).

Here, the vector operation unit 1 is φ _2d = Mi
_1d (constant), the excitation current command value i _1d such that φ _2q = 0
^* , D of primary voltage from torque current i _1q and primary frequency ω
This calculates the axis and q-axis components V _1d ^* and V _1q ^* , and is specifically given by the above equation (4). When this equation (4) is shown in a block diagram, the configuration of the vector calculation unit 1 in FIG. 1 is obtained. Note that L ₁ · i _{1d in the} equation (4) is φ in FIG.

The vector operation unit 1 calculates the excitation current command value i
The d-axis component of the primary voltage is adjusted so that _1d ^* matches the actual exciting current i _1d of the induction motor 4 . In particular,
The exciting current command value i _1d ^* and the exciting current i _1d obtained by the coordinate converter 6 are subtracted by the subtractor 12 to obtain △ i _1d , and the current controller 13 performs primary control so as to eliminate the difference △ i _1d. The d-axis component V _1d ^* of the voltage is adjusted.

Next, the operation of the secondary resistance calculator 11 will be described with reference to FIG. Secondary resistance calculator 11 outputs a control signal 11a to cut the output of the slip angular frequency omega _s,
The 'speed command ^{value *} is outputted from the secondary resistance calculating unit 11 omega _r' rotational speed command value input to the adder 9 omega _r ^*
The control signal 11b is output so that Control signal 11
a is for turning off the switch means SWa,
The control signal 11b is for switching the switch means SWb. The secondary resistance calculator 11 outputs a constant rotational speed command value ω _r ′ ^*, and after the induction motor 4 reaches a constant state (steady state), converts the rotational speed command value ω _r ′ ^* into FIG.
As shown in (a), Δω is increased stepwise. FIG. 2A shows the primary frequency ω, the approximate value of the rotational speed, the approximate value of the rotational speed, and the change in the rotational speed.

[0034] When the torque current is the maximum value i _{q (max)}
Equation (8) is obtained from the slip angular frequency of
Of the secondary resistance by substituting the slip frequency of
Find r2 _(m) .

(Equation 8) The measured value of the secondary resistance r _{2 (m)} is substituted into the equation (1).

(Equation 9) The proportionality constant (K) is determined by the slip angular frequency ω _s and the torque current i.
_Since it is a proportionality constant with _1q , the proportionality constant (K) is
From the equation (11).

(Equation 10)

[0035]

[0036]

According to the first aspect of the present invention, there is provided a vector operation device which controls an induction motor by an inverter and independently controls a torque current component and an excitation current component of the induction motor.
Stop the slip compensation that changes the primary frequency by the torque current, change the primary frequency with no load on the induction motor, and calculate the secondary resistance from the response waveform when this change occurs. There is an effect that the secondary resistance can be easily measured without using a detector, and the speed accuracy can be improved.

According to the second aspect of the present invention, in the first aspect of the present invention, the primary frequency changes while the induction motor is in a no-load state.
The secondary resistance is calculated by dividing the value obtained by multiplying the magnetic flux command value and the primary frequency change amount by the maximum value of the response waveform of the torque current. In addition, the secondary resistance can be easily measured without using a speed detector, and the accuracy of the speed can be improved.

According to the third aspect of the present invention, means for stopping the slip compensation for changing the primary frequency by the torque current, changing the primary frequency in a step-like manner, and calculating the torque current from the maximum value of the torque current and the change in the primary frequency. Means for detecting the time until the maximum value and the time until the torque current returns to zero again, and the value obtained by multiplying the magnetic flux command value and the primary frequency change amount were divided by the maximum value of the torque current response waveform. The value is multiplied by a subtraction value obtained by subtracting the time until the torque current reaches the maximum value from the time until the torque current returns to zero again, and this multiplied value is divided by the time until the torque current returns to zero. And the secondary resistance calculation means, which eliminates the influence of the error due to the differential term of the torque current and can accurately measure the secondary resistance, and can estimate the slip angular frequency. There is an effect that it is possible to more accurately measure the secondary resistance so.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory view of the above.

FIG. 3 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 Vector calculation unit 2, 6 Coordinate converter 3 Inverter 4 Induction motor 5 Current detector 7 Delay circuit 7a Subtractor 7b Controller 8 Multiplier 9 Adder 10 Integrator 11 Secondary resistance calculator 11a, 11b Control signal K proportional Constant SWa, SWb switch means

Continuation of front page (56) References JP-A-7-325132 (JP, A) JP-A-7-55899 (JP, A) JP-A-7-298688 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) H02P 5/408-5/412 H02P 7/628-7/632 G01R 27/02

Claims (3)

(57) [Claims] An induction motor is controlled by an inverter, and a vector control device for independently controlling a torque current component and an excitation current component of the induction motor is used. A method for measuring a secondary resistance of an induction motor, comprising: changing a primary frequency in a state where a motor is not loaded; and calculating a secondary resistance from a response waveform when the primary frequency is changed. 2. A maximum value of a torque current when a primary frequency is changed in a no-load state of an induction motor, and a value obtained by multiplying a magnetic flux command value by a primary frequency change amount is a maximum value of a response waveform of the torque current. 2. The method for measuring a secondary resistance of an induction motor according to claim 1, wherein the secondary resistance is calculated by dividing the secondary resistance. 3. A means for stopping slip compensation for changing the primary frequency by the torque current, and changing the primary frequency in a step-like manner to determine the maximum value of the torque current and the time from the change in the primary frequency until the torque current reaches the maximum value. Means for detecting the time and the time until the torque current returns to zero again, and a value obtained by dividing a value obtained by multiplying the magnetic flux command value by the primary frequency change amount by the maximum value of the torque current response waveform, Secondary resistance calculating means for multiplying a subtraction value obtained by subtracting a time until the torque current reaches a maximum value from a time until the torque current returns to zero, and dividing the multiplied value by a time until the torque current returns to zero; A secondary resistance measuring device for an induction motor, comprising: