JP2015061492A - Constant measurement apparatus and constant measurement method of induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant measurement apparatus and a constant measurement method which allow for operation of the motor constants, that have been measured in no-load test, based on the directly measurable measurement results.SOLUTION: A constant measurement apparatus of induction motor includes a tuning voltage command value calculation unit 17 for applying a voltage from an inverter circuit 13 to an induction motor 1 by outputting three-phase voltage command signals Vu*, Vv*, Vw* to a PWM gate signal generator 16, a U phase current detector 14 for detecting a current flowing through the induction motor 1, and a motor constant calculation unit 20a for calculating the motor constants (primary resistance, secondary resistance and leakage inductance) by using the voltage Vu and the current value iu. The motor constant calculation unit 20a calculates one constant of the motor, i.e., an exciting current I, by using the motor constants (primary resistance, secondary resistance and leakage inductance) that can be calculated using the voltage Vu and the current value iu, and the motor information accepted.

Description

  The present invention relates to an induction motor constant measuring apparatus and a constant measuring method for measuring a motor constant of an induction motor in a restraint test.

  When controlling an induction motor with high performance, vector control for controlling magnetic flux and torque individually is used. Recently, market needs for sensorless vector control, in which control is performed without detecting the speed of an induction motor using a speed (PG) sensor or the like, are increasing. When performing sensorless vector control with high accuracy, it is necessary to grasp a plurality of motor constants of an induction motor to be controlled. Therefore, in general-purpose inverters that do not specify the induction motor to be used, auto-tuning that automatically measures the motor constant of the induction motor so that highly accurate vector control can always be performed even when various induction motors are used. It has a function.

  For example, in Patent Document 1, an AC motor is operated in a steady state, and a motor current vector effective power component and a reactive power component are calculated from a phase obtained by integrating the primary angular frequency command at this time and a current detection value of the AC motor. It is shown that the current is calculated and the primary self-inductance of the motor is calculated based on the primary angular frequency command value and the primary voltage command value, and the active power component current and the reactive power component current.

  Auto-tuning (automatic measurement) of the motor constant of the induction motor is shown in JEC-37 (Electrical Society Electrical Standards Committee Standards Standard), and is realized by performing processing based on a restraint test and a no-load test. In restraint tests, primary resistance can be measured by applying a DC voltage, secondary resistance and leakage inductance can be measured by applying a single-phase AC voltage, and excitation current, self-inductance, and mutual inductance can be measured in a no-load test. It is known that can be measured.

  Here, the no-load test must basically be performed in a state where no load is connected. However, it is difficult to separate the induction motor alone in an apparatus where the induction motor is actually used. In many cases, the motor constant must be measured without rotating the motor. Therefore, in the conventional constant measuring apparatus 10 that measures the motor constant of the induction motor 1, as shown in FIG. 7, the excitation current, the self-inductance, and the mutual inductance, which are motor constants that cannot be directly measured unless the induction motor 1 is rotated, A motor data table 19 stored in advance for each capacity of the induction motor 1 is provided, and only motor constants that can be directly measured are updated.

  Referring to FIG. 7, the conventional constant measuring apparatus 10 includes a rectifier circuit 11, a smoothing circuit 12, an inverter circuit 13, a U-phase current detector 14, a W-phase current detector 15, and a PWM gate signal generator. 16, a tuning voltage command value calculator 17, a current effective value calculator 18, a motor data table 19, and a motor constant calculator 20. The rectifier circuit 11 is realized by a diode, the smoothing circuit 12 is realized by a capacitor, and the inverter circuit 13 is realized by a power switching element. The PWM gate signal generator 16, the tuning voltage command value calculator 17, the current effective value calculator 18 and the motor constant calculator 20 are a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory). ) Etc., and a program stored in a ROM, a RAM, or the like. Furthermore, the motor data table 19 is a storage means such as a flash memory.

  The AC voltage supplied from the commercial three-phase AC power supply 2 is converted into a DC voltage by the rectifier circuit 11, and the converted DC voltage is smoothed by the smoothing circuit 12. The DC voltage smoothed by the smoothing circuit 12 is supplied to the inverter circuit 13, and the induction motor 1 is DC excited or AC excited by the inverter circuit 13.

  The tuning voltage command value calculator 17 outputs the three-phase voltage command signals Vu *, Vv * and Vw * to the PWM gate signal generator 16 when auto-tuning is instructed in the restraint test. A DC voltage and a single-phase AC voltage are sequentially applied from the inverter circuit 13 between terminals in which the U phase, the V phase, and the W phase are collected. The motor constant calculator 20 includes three-phase voltage command signals Vu *, Vv *, Vw *, a U-phase current Iu detected by the U-phase current detector 14, and a W-phase detected by the W-phase current detector 15. Based on the current Iw, the primary resistance is calculated when a DC voltage is applied, and the secondary resistance and the leakage inductance are calculated when a single-phase AC voltage is applied. The motor constant calculator 20 receives the input of the capacity of the induction motor 1 by an input means (not shown) for the excitation current, the self-inductance, and the mutual inductance, and is stored in advance in the motor data table 19 based on the received capacity. The motor constant is specified.

JP2011-199024

  However, the prior art cannot directly measure the excitation current, the self-inductance, and the mutual inductance, so that there is a large error, and there is a problem that a torque error is increased in sensorless vector control. In the prior art, a motor data table 19 in which similar motor constants corresponding to the induction motor 1 to be driven must be stored in advance, and the induction motor 1 is a special motor or the like and is similar to the motor data table 19. When the motor constant is not stored, the motor constant of the induction motor 1 to be driven cannot be specified, and there is a problem that the sensorless vector control cannot be performed.

  In view of the above problems, the object of the present invention is to solve the problems of the prior art and calculate the motor constant measured in the no-load test based on the measurement result that can be directly measured in the restraint test. An object of the present invention is to provide a constant measuring apparatus and a constant measuring method for an electric motor.

An induction motor constant measuring apparatus according to the present invention is an induction motor constant measuring apparatus that measures a plurality of motor constants used for sensorless vector control of an induction motor driven by a three-phase AC power source by a restraint test without rotating a shaft. A voltage application means for applying a voltage to the induction motor; a current detection means for detecting a current flowing through the induction motor; a voltage value applied to the induction motor by the voltage application means; and a current detected by the current detection means Motor constant calculation means for calculating the motor constant using a value, and the motor constant calculation means includes the motor constant that can be directly calculated using the voltage value and the current value, and the received motor. The excitation current which is one of the motor constants is calculated using the information.
Further, in the constant measuring apparatus for an induction motor according to the present invention, the motor constant calculating means calculates a power factor from the effective power and apparent power of the induction motor, and calculates the excitation current from the power factor. good.
Furthermore, in the constant measuring apparatus for an induction motor according to the present invention, the motor constant calculating means may perform a limit process for keeping the calculated power factor in a range between a preset upper limit and lower limit.
Furthermore, in the constant measuring apparatus for an induction motor according to the present invention, the motor constant calculating means may receive a rated voltage, a rated current and a capacity of the induction motor as the motor information.
In addition, the induction motor constant measuring method of the present invention is an induction motor constant measuring method for measuring a plurality of motor constants used for sensorless vector control of an induction motor driven by a three-phase AC power source by a restraint test without rotating the shaft. The voltage application means applies a DC voltage to the induction motor, the current detection means detects the current flowing through the induction motor, and the motor constant calculation means applies the voltage value applied to the induction motor and the induction motor. A primary resistance calculation processing step of calculating a primary resistance using a current value flowing through the current, and an AC voltage is applied to the induction motor by the voltage application means, and a current flowing to the induction motor is detected by the current detection means. The active constant, the current value flowing through the induction motor, and the primary resistance are calculated by the motor constant calculation means. A secondary resistance calculation processing step of calculating a secondary resistance from the above, applying an AC voltage to the induction motor by the voltage application means, detecting a current flowing through the induction motor by the current detection means, and detecting the motor constant As a motor information, a leakage inductance calculation processing step of calculating a leakage inductance from a current value flowing through the induction motor and a frequency of the applied AC voltage by collectively applying an AC voltage to each input of the motor by a calculation means. The power factor from the effective power and apparent power of the induction motor that can receive the rated voltage, rated current, and capacity of the induction motor and that can be calculated from the motor information, the primary resistance, and the secondary resistance by the motor constant calculation means. Excitation current calculation processing step of calculating the excitation current from the power factor, and the motor information Receiving a rated frequency of the induction motor, a primary inductance calculation processing step of calculating a primary inductance from the excitation current, the motor information, and the primary resistance by the motor constant calculation means, and the motor constant calculation means, And a mutual inductance calculation processing step of calculating a mutual inductance from the primary inductance and the leakage inductance.

According to the present invention, the excitation current I ₀ , which is a motor constant measured in the no-load test, can be calculated based on the measurement result that can be directly measured in the constraint test without relying on the motor data table. Therefore, it is possible to measure the constants of the induction motor with high accuracy, and to perform sensorless vector control with high accuracy.

It is a circuit block diagram which shows the structure of embodiment of the constant measuring apparatus of the induction motor which concerns on this invention. It is a flowchart which shows the calculation operation | movement of the motor constant calculator shown in FIG. FIG. 2 is an equivalent circuit diagram when a DC voltage is applied to the induction motor shown in FIG. 1. FIG. 2 is an equivalent circuit diagram when a single-phase AC voltage is applied to the induction motor shown in FIG. 1. FIG. 2 is a current vector diagram at the rated load of the induction motor shown in FIG. 1. It is an equivalent circuit diagram at the time of no-load operation of the induction motor shown in FIG. It is a circuit block diagram which shows the structure of embodiment of the conventional constant measuring apparatus.

  Next, embodiments of the present invention will be specifically described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and a part of the description is omitted.

  Referring to FIG. 1, the constant measurement device 10a of the present embodiment is not provided with the motor data table 19, and the motor constant calculator 20a is conventionally provided with a motor constant (excitation current) measured in a no-load test. And self-inductance and mutual inductance) are calculated based on measurement results that can be directly measured by a constraint test.

Hereinafter, the auto-tuning operation in the constant measuring apparatus 10a of the present embodiment will be described in detail with reference to FIGS.
The tuning voltage command value calculator 17 outputs the three-phase voltage command signals Vu *, Vv * and Vw * to the PWM gate signal generator 16 when auto-tuning is instructed in the restraint test. A DC voltage application process for applying a DC voltage from the inverter circuit 13 is performed between terminals in which the U phase, the V phase, and the W phase are combined, and the motor constant calculator 20 is applied to the induction motor 1. A voltage / current average value calculation process for calculating the average value of the voltage Vu and the current iu flowing through the induction motor 1 is executed (step 101). In step 101, the tuning voltage command value calculator 17 is fed back with the effective current value I calculated by the effective current value calculator 18 so that the current flowing through the induction motor 1 is not too large. The magnitude of the command signals Vu *, Vv *, Vw *) is adjusted.

Figure 3 is an equivalent circuit of the induction motor 1 at the time of DC voltage application in step 101, the motor constant calculator 20 uses the voltage Vum and current ium computed average in step 101, a primary resistance R ₁ The primary resistance calculation process calculated by the following equation [Equation 1] is executed (step 102). Note that the voltage Vum and current ium used for the operation of the primary resistance R _1, by using the average value in a certain period in the steady state, to enhance the detection accuracy.

  Next, the tuning voltage command value calculator 17 outputs the three-phase voltage command signals Vu *, Vv * and Vw * to the PWM gate signal generator 16, so that the U phase, V phase and W of the induction motor 1 are output. A single-phase AC voltage application process for applying a single-phase AC voltage from the inverter circuit 13 is performed between the terminals whose phases are integrated, and the motor constant calculator 20 calculates the active power Pm and the reactive power Qm. The active power / reactive power calculation process is executed (step 103). In step 103 as well, when the DC voltage is applied, the current effective value I calculated by the current effective value calculator 18 is fed back to the tuning voltage command value calculator 17, and the current flowing through the induction motor 1 is too large. The magnitude of the applied voltage (three-phase voltage command signals Vu *, Vv *, Vw *) is adjusted so as not to be present.

  FIG. 4 is an equivalent circuit of the induction motor 1 when the single-phase AC voltage is applied in step 103. The motor constant calculator 20 multiplies the voltage command value Vu * (effective value) at the time of applying a single-phase AC by √2, multiplies it by sin θ by the phase θ, and then multiplies it by the instantaneous current. The active power Pm is calculated by integration processing according to the equation [Equation 2]. Further, the motor constant calculator 20 multiplies the voltage command value Vu * (effective value) at the time of applying the single-phase alternating current by √2, multiplies cos θ by the phase θ to obtain an instantaneous voltage value, and then multiplies the instantaneous current. Then, the reactive power Qm is calculated by integration processing according to the following equation [Equation 2].

Next, the motor constant calculator 20 performs a secondary resistance-leakage inductance calculation process for calculating the inductance l ₁ leakage and secondary resistance R ₂ (step 104). The motor constant calculator 20 uses the primary resistance R ₁ obtained by the above equation [Equation 1], the U-phase average current ium, and the active power Pm obtained by the above equation [Equation 2], and by 3] computing a secondary resistance R _2.

In addition, the motor constant calculator 20 uses the frequency f when the single-phase alternating current is applied, the U-phase average current ium, the reactive power Qm in the above equation [Equation 2], and the leakage inductance by the equation [Equation 4]. l ₁ is calculated.

Next, the motor constant calculator 20 executes excitation current calculation processing for calculating the excitation current _I0 (step 105). The excitation current I ₀ cannot be directly derived from the measurement result that can be measured in the constraint test. Therefore, the motor constant calculator 20 receives input of known motor information (numerical values that can be easily grasped by the user) described on the rating nameplate of the induction motor 1 from an input means (not shown), and uses the received constants. performing the calculation of the excitation current I ₀ Te.

FIG. 5 shows a current vector diagram of the induction motor 1 at the rated load. During vector control, because it is always supplying a constant excitation current I _0, the current vector I _n at the rated output is related corner (90 ° -θm) formed by the excitation current I _0. Here, θm is the power factor angle of the induction motor 1 at the rated load. The magnitude of the current vector I _n are usually relatively easily grasped because it is the rated current of the induction motor 1 can be power factor angle θm is calculates the excitation current I ₀ Knowing. Here, the power factor angle θm can be calculated by the following equation [Equation 5] using the effective power P and the apparent power W at the rated output of the induction motor 1 as the power factor cos θm. The apparent power W can be calculated by the following equation [Equation 5] using the rated voltage Vn and the rated current In.

  Further, the active power P can be calculated by the capacity Pmot of the induction motor 1, the efficiency η of the induction motor 1, and the following equation [Equation 6].

  Here, the rated voltage Vn, the rated current In, and the capacity Pmot of the induction motor 1 are known motor information (numerical values that can be easily grasped by the user) described on the rating nameplate of the induction motor 1, and are not illustrated. Although it can be accepted by the input means, the efficiency η is a value that is difficult to grasp.

  The efficiency η is expressed by the following equation [Equation 7] when the loss of the induction motor 1 is divided into an electric loss Weloss and a mechanical loss Wmloss.

Here, the electrical loss Weloss is expressed by the following equation [Equation 8] by the primary resistance R ₁ obtained by the above equation [Equation 1], the secondary resistance R ₂ obtained by the equation [Equation 3], and the rated current In. ] Can be calculated.

  The mechanical loss Wmloss is difficult to measure directly, but is set as a ratio to the capacity Pmot. By grasping the mechanical loss Wmloss of the representative induction motor 1 for each capacity Pmot, the mechanical loss Wmloss is set by the received capacity Pmot.

Therefore, the motor constant calculator 20 shows the rated voltage Vn, the rated current In, and the capacity Pmot of the induction motor 1 as known constants (constants that can be easily grasped) described on the rating nameplate of the induction motor 1 and the like. The rated voltage Vn, the rated current In and the capacity Pmot of the induction motor 1 received and received by the input means, the primary resistance R ₁ obtained by the above equation [Equation 1], and the secondary obtained by the above equation [Equation 3]. The power factor cos θm is calculated by the above equation [Formula 5] using the resistor R ₂ .

  Then, the motor constant calculator 20 performs limit processing at the upper limit and the lower limit on the power factor cos θm calculated by the above equation [Equation 5]. As the upper limit of the power factor cos θm cannot be a value close to “1”, 0.95 is set as the upper limit. The lower limit of the power factor cos θm is set to “0.65” with reference to a motor having a relatively poor power factor. In addition, arbitrary values can be set as the upper limit value and the lower limit value of the power factor.

Further, the motor constant calculator 20 calculates the excitation current I ₀ by the following equation [Equation 9] using the power factor cos θm after the limit processing and the rated current In.

Next, the motor constant calculator 20 executes an inductance (self / mutual) calculation process for calculating the self-inductance L1 and the mutual inductance Lm (step 106). The motor constant calculator 20 has an excitation current I ₀ , a rated voltage Vn, a rated frequency fn, and an upper value obtained from the equivalent circuit of the induction motor 1 during no-load operation shown in FIG. The primary inductance L ₁ is calculated by the following equation [Equation 10] using the primary resistance R ₁ obtained by the equation [Equation 1]. The rated frequency fn is received by an input means (not shown) as a known constant (a constant that can be easily grasped) described on the rating nameplate of the induction motor 1. The secondary inductance L ₂ from the almost unchanged the primary inductance L _1, can be used as the value of the primary inductance L ₁ determined by the following equation [Equation 10].

The motor constant calculator 20 uses the primary inductance L ₁ obtained by the above equation [Equation 10] and the leakage inductance l ₁ obtained by the above equation [Equation 4] to obtain a mutual equation by the following equation [Equation 11]. The inductance Lm is calculated and the auto-tuning process is terminated.

As described above, the present embodiment is a constant measuring device for induction motor 1 that measures a plurality of motor constants used for sensorless vector control of induction motor 1 driven by a three-phase AC power source by a restraint test that does not rotate the shaft. The tuning voltage command value calculator 17 applies a voltage from the inverter circuit 13 to the induction motor 1 by outputting the three-phase voltage command signals Vu *, Vv *, Vw * to the PWM gate signal generator 16. A U-phase current detector 14 for detecting the current flowing through the induction motor 1 and a motor constant calculator 20 for calculating motor constants (primary resistance, secondary resistance and leakage inductance) using the voltage Vu and the current value iu. The motor constant calculator 20 is a motor constant (primary resistance, secondary resistance and leakage inductor) that can be directly calculated using the voltage Vu and the current value iu. Scan) and is configured to calculate the excitation current I ₀ which is one of the motor constant by using the motor information received.
Since this arrangement, the excitation current I ₀ is a motor constant was measured at no-load test, without resorting to motor data table can be calculated based on the direct measurable measurement results restraint test, precision The constant measurement of a high induction motor can be performed, and sensorless vector control can be performed with high accuracy.

Further, according to the present embodiment, the motor constant calculator 20 is configured to calculate the power factor cos θm from the effective power P and the apparent power W of the induction motor 1 and to calculate the excitation current I ₀ from the power factor cos θm. Has been.
With this configuration, the excitation current I ₀ can be calculated based on a measurement result that can be directly measured by a constraint test.

Furthermore, according to the present embodiment, the motor constant calculator 20 is configured to perform a limit process that keeps the calculated power factor cos θm within a preset upper and lower limits.
With this configuration, the power factor cos θm can be within an appropriate range. Note that any value can be set for the upper limit and the lower limit.

Furthermore, according to the present embodiment, the motor constant calculator 20 is configured to receive the rated voltage Vn, the rated current In, and the capacity Pmot of the induction motor 1 as motor information.
With this configuration, the excitation current can be obtained only by receiving the rated voltage Vn, the rated current In, and the capacity Pmot of the induction motor 1, which are known constants (constants that can be easily grasped) described on the rating nameplate of the induction motor 1. I ₀ can be calculated based on a measurement result that can be directly measured by a constraint test.

  Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a number, position, shape, and the like that are suitable for implementing the present invention. In each figure, the same numerals are given to the same component.

DESCRIPTION OF SYMBOLS 1 Induction motor 2 Commercial three-phase alternating current power supply 10, 10a Constant measuring device 11 Rectifier circuit 12 Smoothing circuit 13 Inverter circuit 14 U-phase current detector 15 W-phase current detector 16 PWM gate signal generator 17 Tuning voltage command value calculator 18 Current effective value calculator 19 Motor data table 20, 20a Motor constant calculator

Claims (5)

An induction motor constant measuring device that measures a plurality of motor constants used for sensorless vector control of an induction motor driven by a three-phase AC power source by a constraint test that does not rotate the shaft,
Voltage applying means for applying a voltage to the induction motor;
Current detecting means for detecting a current flowing through the induction motor;
Motor constant calculation means for calculating the motor constant using the voltage value applied to the induction motor by the voltage application means and the current value detected by the current detection means,
The motor constant calculating means calculates an excitation current that is one of the motor constants using the motor constant that can be directly calculated using the voltage value and the current value, and the received motor information. A characteristic constant measuring device for induction motors.   The induction motor constant measuring apparatus according to claim 1, wherein the motor constant calculation means calculates a power factor from the effective power and apparent power of the induction motor and calculates the excitation current from the power factor.   The induction motor constant measuring apparatus according to claim 1, wherein the motor constant calculating means performs a limit process for keeping the calculated power factor in a range between a preset upper limit and a lower limit.   4. The induction motor constant measuring apparatus according to claim 1, wherein the motor constant calculating means receives a rated voltage, a rated current and a capacity of the induction motor as the motor information. An induction motor constant measuring method for measuring a plurality of motor constants used for sensorless vector control of an induction motor driven by a three-phase AC power source by a constraint test without rotating a shaft,
A DC voltage is applied to the induction motor by the voltage application means, a current flowing through the induction motor is detected by the current detection means, and a voltage value applied to the induction motor and a current flowing through the induction motor are detected by the motor constant calculation means. A primary resistance calculation processing step of calculating a primary resistance using a value;
An AC voltage is applied to the induction motor by the voltage application unit, a current flowing through the induction motor is detected by the current detection unit, and an active power and a current value flowing through the induction motor are detected by the motor constant calculation unit. A secondary resistance calculation processing step of calculating a secondary resistance from the primary resistance;
An AC voltage is applied to the induction motor by the voltage application means, a current flowing through the induction motor is detected by the current detection means, and an AC voltage is collectively applied to each input of the motor by the motor constant calculation means. A leakage inductance calculation processing step of calculating a leakage inductance from the value of a current flowing through the induction motor and the frequency of the applied AC voltage;
The rated voltage, rated current, and capacity of the induction motor are received as motor information, and the effective power and apparent power of the induction motor that can be calculated from the motor information, the primary resistance, and the secondary resistance by the motor constant calculation means. An excitation current calculation processing step of calculating a power factor from the power factor and calculating an excitation current from the power factor;
A primary inductance calculation processing step of receiving a rated frequency of the induction motor as the motor information, and calculating a primary inductance from the excitation current, the motor information, and the primary resistance by the motor constant calculation means;
An induction motor constant measuring method comprising: a mutual inductance calculation processing step of calculating a mutual inductance from the primary inductance and the leakage inductance by the motor constant calculation means.

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