JP3349610B2 - Load change measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In equipment and devices that use induction motors, microscopic load changes are measured by analyzing the frequency components of the power consumed by the induction motors, and control and abnormalities of various devices are measured. A method for making a diagnosis.

[0002]

2. Description of the Related Art Conventionally, the load of an induction motor has been measured by electric power and shaft torque of the motor, and is used for various controls and abnormality diagnosis. This is a method of measuring the moment of static force received from a load.

[0003] The above measurement is a method of measuring the moment of a static force received from a load.

However, the conventional measuring method has the following problems. That is, since this method measures the moment of the static force received from the load, the measurement element for control or abnormality diagnosis is not the moment of the static force but a short-term change in load (for example, acceleration / deceleration torque). ) Or the operating state of the induction motor (for example, load stability).

[0005]

Therefore, the present inventors have measured the static moment of the force received from the load in the prior art. However, the present inventors have newly developed an apparatus using an induction motor. A method of measuring a microscopic load change, specifically, a method of measuring the short-time working force received by a load from an induction motor.A method of measuring the operation state of an induction motor, and thereby controlling and abnormally controlling various devices. A method for making a diagnosis is obtained.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and has been described with reference to FIG.
The method of measuring a load is provided by the configuration of (1). In FIG. 1, the device used in the present invention includes a detection unit (power meter) 2, an analysis unit (FFT analyzer) 3, and a control / abnormality determination unit (personal computer) 4.

The wattmeter 2 is a device for converting the load of the induction motor into a power signal, and it is desirable that the measurement circuit does not perform internal calculations such as averaging and integration of the power signal. Also,
It is desirable to be able to adjust the zero point and the measurement width.

[0008] The FFT analyzer is a device for frequency-decomposing a power signal by Fourier transform to quantify frequency components. The control / abnormality determination performed by the following personal computer may be performed here.

A personal computer is a device that displays and records data quantified by an FFT analyzer, controls various facilities and devices, and outputs an abnormality diagnosis signal.

The measuring method according to the present invention measures microscopic load changes characterized by frequency analysis of the power of an induction motor in a facility or an apparatus using an induction motor, and based on this, measures various types of equipment. It performs control and abnormality diagnosis of devices and devices, and its principle is as follows. In the exchange
When the power supply frequency is ω [rad / sec] and a certain time t [se
c] is the phase difference between the voltage v [V] and the current i [A].
[Rad], assuming that the instantaneous value is v = √2Vsinωti = √2Isin (ωt−φ), the instantaneous power p [VA] is given by p = vi = VIcosφ−VIcos (2ωt−φ) (1) Can be When the induction motor is operating in an equilibrium state, its power is obtained as a value obtained by integrating the equation (1) in one cycle, that is, as an active power P [W] P = VIcos φ (2). In addition, the induction motor has a characteristic of rotating at an equilibrium speed Np [rpm] at a stable operation point where the output torque and the load torque of the induction motor are balanced during a steady operation, that is, a so-called constant speed characteristic. Therefore, when the load torque of the electric motor changes significantly, the induction motor changes the current consumed by itself and responds to the change in the load torque. When the acceleration / deceleration torque is added to the load torque of the motor, the induction motor changes the phase difference φ between the voltage and the current to respond to the change in the acceleration / deceleration torque.

The present invention pays attention to the characteristics of these induction motors and the equation (1). First, when the acceleration / deceleration torque is received from the load and the induction motor is not operating in a balanced state, the instantaneous power is in two states. I found a change. Specifically, acceleration / deceleration torque is applied to the induction motor from the load, and t2 [s] after Δt [sec] at time t1 [sec]
ec], the phase difference is changed from φ1 [rad] to φ2 [rad].
(1), the following power difference Δp1 [V
A] and Δp2 [VA]. Δp1 = VI (cosφ2-cosφ1) (3) Δp2 = VI (cos (2ωt2-φ2) −cos (2ωt1-φ1)) (4) (However, Δt = t2-t1 ≒ 0, VI = constant) These fluctuations Although both factors are phase differences, it can be said that Δp1 is a power difference based on a change in the phase difference, and Δp2 is a power difference proportional to the difference in the phase difference. In other words, the magnitude of the short-time working force that the induction motor receives from the load can be measured from Δp1. From Δp2, it is possible to measure the operating state of the induction motor based on a change in the load state, and determine the equilibrium state (Δp2 = 0 when in the equilibrium state).

Next, as a measuring method, it has been found that frequency analysis in which power is frequency-decomposed by Fourier transform and quantified for each frequency component is effective. Specifically, the change in the phase difference is caused by the acceleration / deceleration torque that the induction motor receives from the load. That is, the phase difference is a frequency component around the rotational speed of the load. Δp1 is a change in cos φ, and its frequency component is similar to the phase difference. Therefore, Δ
p1 can be measured from the magnitude of the frequency component around the load rotation speed. Further, since Δp2 is a subtraction of a sine wave that changes in a cycle twice the power supply frequency, it can be measured from the magnitude of the frequency component twice the power supply frequency. In addition, the signal obtained here can be used for control and abnormality diagnosis of various facilities and devices. That is, the two microscopic load change measuring methods in the present invention are performed by frequency-decomposing the power consumed by the induction motor and quantifying it for each frequency component.

Therefore, a specific measuring method will be described below.
First, the power of the induction motor is measured by a wattmeter, and the output is input to an FFT analyzer. After removing the DC component, the frequency is resolved by Fourier transform. Next, the following analysis is performed by the FFT analyzer to obtain two values.

Since Δp1 can be measured from the magnitude of the frequency components before and after the rotational speed of the load, a specific region (for example, 0 to 0)
Quantification is performed based on the overall power spectrum (10 Hz section). The reason is as follows.

That is, from equation (3), the variation factor of Δp1 is cos φ, and in a trigonometric function such as cosine, a variation similar to the variation of φ occurs at cos φ, and Δp1 is cos φ
As a result, the variation of Δp1 is similar to the variation of the phase difference φ. Therefore, Δp1 can be measured from the magnitude of the frequency component in the frequency range around the rotation speed. The magnitude of this frequency component can be measured from the power spectrum obtained by Fourier-transforming the power signal. In addition, since the rotation speed varies with a certain width, accurate measurement cannot be performed by focusing only on a specific frequency component. Therefore, quantification is performed using an overall function that integrates all the magnitudes of the frequency components within a certain range.

Since Δp2 is a frequency component twice as large as the power supply frequency, if the power supply frequency is 60 Hz, for example, 12
Quantify with a 0 Hz power spectrum. The reason is as follows.

That is, from equation 4, it can be seen that the variation factors of Δp2 are the phase difference φ and the power supply frequency ω. Furthermore, in Equation 4, since there is a factor of power supply frequency × 2 (2ω), it can be said that Δp2 occurs only in a component twice as large as the power supply frequency. Therefore, Δp2 can be measured from a frequency component that is twice the power supply frequency, and the value measured there depends on the fluctuation of the phase difference φ. The power spectrum is effective for quantifying such frequency components as in the case of Δp1.

However, this quantitative value is not instantaneous power,
This is a power signal from the sampling time S1 [sec] to S2 [sec] of the FFT analyzer. Therefore, as shown in Expressions (5) and (6), Δp1 is POA [W],
Δp2 is measured as Pf [W]. These are collected by a personal computer and the measurement results are displayed. At this time, setting values based on past experience values and the like are set in the personal computer, and control and abnormality diagnosis of various facilities and devices can be performed by outputting control and abnormality diagnosis signals from the personal computer. It becomes possible.

[0019]

According to the present invention, it is possible to measure the short-time working force received by the induction motor from the load and the operating state of the induction motor. Different accurate and quick control and abnormality diagnosis become possible.

[0020]

EXAMPLES The present invention will be described with reference to examples. FIG. 2 shows an embodiment in which the present invention is applied to an agitation granulator in the process of producing Drug A. The equipment used is as follows. Electric motor: Cage-type three-phase induction motor with a continuously variable transmission (rated power: 37 kW, number of poles: 8P) Power supply: Power supply frequency: 60 Hz, rated voltage: 440 W Stirring blade: Standard blade for stirring granulation with fins (lower stage), flat with fins Blade (upper, middle) Apparatus shape: Henschel type (large cylindrical) Apparatus capacity: 780 L Rotation speed: 180 rpm The powder raw material and the binding liquid are as follows. Prescription of powder raw material-Corn starch: 120, 0 kg-Avicel: 30, 0 kg-Talc: 7, 5 kg Formulation of binding solution-Drug A: 30, 0 kg-Water: 24, 5 kg-Ethanol: 6, 5 kg Well, container 5 When the powder inside is stirred horizontally by a stirring blade 6 having a certain shape, the powder is given a centrifugal force and a rising propulsive force from the stirring blade 6, and swirls on the inner wall of the container. The agitation granulation method uses the rolling / consolidating action on the powder due to this swirling motion, the adhesion of particles to the powder surface by adding a binding liquid (mainly moisture), and the capillary force inside the powder. It is a granulation method. As a feature of the present granulation method, a spherical and heavy granule 7 is obtained. Conventionally, the measurement of the state of granulation and the end detection have been performed with current or power, but a more accurate measurement method is desired for quality improvement (uniform particle size distribution of granulated material). .

FIG. 3 shows a flow of the measurement in the present measurement method. First, the power consumption signal of the induction motor of the agitation granulator 1 is measured, and then input to the FFT analyzer to obtain POA and Pf. These are displayed and collected by a personal computer. The measurement frequencies of POA and Pf were 0 to 10 Hz and 120 Hz, respectively.

FIG. 6 shows the measurement results of POA and Pf. These changes in the acceleration / deceleration torque applied to the stirring blades due to the change in the fluidity of the granulated material as the granulation progresses, and the POA
And a change in Pf.

FIG. 6 shows that POA changes with time and that S2
The maximum value was shown between 200 and 200 sec, and the minimum value was shown after S4. In the change over time in the powder properties, the average particle size of the granulated product increased most rapidly between S2 and 200 sec, and the moisture content of the granulated product decreased with time until the late granulation stage. From these, it can be seen that the working force of granulation is changed by the moisture, and that the POA captures the change.

As shown in FIG. 6, Pf showed almost zero at S3b, and S2 before and after S3a and stable values different after S4. In the change of powder properties with time, S
Prior to 3b, the granules grew and spheroidized, and in S3b the particle surface was the smoothest. After S4,
As compared to the point S3b, slight irregularities began to be noticeable on the particle surface. From these, it can be said that the fluidity of the granulated material became the best at the point S3b, and the resistance that the stirring blade 6 receives from the granulated material became the smallest. That is, it can be said that granulation occurs before the point S3b, and after that, resistance due to granulation and crushing occurs, and it is understood that Pf captures the change.

The experiment was performed twice, the first experiment being RUN1 and the second experiment being RUN2, as shown in FIGS. FIG. 6 summarizes the RUN1 data of FIGS. 4 and 5. Taking the powder properties into consideration, it can be determined by the present measurement method that the stirring granulation has four regions from I to IV shown in FIG. 6, and the change in the granulation state is better than the conventional measurement of current or the like. It can be said that it can be measured. Further, S3b to S4
In the case where the end point of the granulation is set as the end time, a granulated material having good fluidity can be stably obtained.

Since the change in POA and Pf adds to the power consumption, granulation can be measured by the following analysis method. 1) Standard deviation of probability density function of power waveform 2) Distortion of power waveform (skewness) 3) Sharpness of power waveform (Kurtosis) 4) Positive / negative area of power waveform 5) Positive / negative maximum value of power waveform 6) Autocorrelation coefficient twice the power supply frequency

(Other Embodiments) In the following example, when an abnormality or change occurs, the value of POA or Pf increases. In a normal state, the values of POA and Pf show stable values.

Example of Crystallizer POA values tend to increase above a certain crystal concentration. Crystallization is an operation for precipitating crystals, and as crystallization progresses,
The crystal concentration increases. From this, when the POA value exceeds a certain POA set value, a crystal end signal is output,
Used to determine the end of the crystal operation.

Example of a rotating machine When an abnormality such as bending of a rotating shaft, damage to a bearing, or distortion of a sliding portion (a portion to be rubbed) occurs, P
The value of OA or Pf increases rapidly. For this reason, when the measured value exceeds a certain set value, a failure signal of the device is issued.

Examples of Transport Machines If bottles, cans, and the like fall during transport, they may cause poor transport or clogging in the transport machine, preventing smooth transport. At the time of these falls, the measured value increases in the same manner as described above, and when the measured value exceeds a certain set value, an abnormal signal of the device or the like is output.

Example of Cutting Machine When cutting with a drill using a lathe or the like, deterioration of the drill blade causes an increase in cutting time, a decrease in mechanical accuracy of the cutting portion, and breakage of the drill. When the deterioration of the drill occurs, the measured value increases in the same manner as in the case of the above. When the measured value exceeds a certain set value, an abnormal signal of the device is output.

[0032]

As described above, according to the present invention, a method of detecting a microscopic load change by analyzing a frequency component of electric power of an electric motor is applied to agitation granulation, whereby a conventional granulation by an electric current is performed. Compared with the end detection, the measurement of the stirring granulation process can be performed with high accuracy, and the granulated material having good fluidity can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a load measuring method according to the configuration of the present invention.

FIG. 2 is an agitation granulator in the process of producing Drug A to which the present invention is applied.

FIG. 3 is a diagram showing a flow of measurement in the present measurement device.

FIG. 4 is a diagram showing measurement results of POA.

FIG. 5 is a view showing a measurement result of Pf.

FIG. 6 is a diagram summarizing RUN1 data of FIGS. 4 and 5;

[Brief description of reference numerals]

 1, electric motor 2, detection unit (power meter) 3, analysis unit (FFT analyzer =) 4, control / abnormality judgment unit (personal computer) 5, container 6, stirring blade 7, granulated material

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI G01R 31/34 G01R 31/34 A H02P 7/36 302 H02P 7/36 302S (56) References JP-A-2-51386 (JP) JP-A-1-321890 (JP, A) JP-A-61-82127 (JP, A) JP-A-55-60830 (JP, A) JP-A-61-167884 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01L 5/00 G01R 31/34

Claims (6)

(57) [Claims] An electric power consumed by a motor is measured and a frequency component of the electric power is analyzed to obtain a certain calculated value (POA).
Alternatively, a microscopic load change measuring method in which a change in the value of Pf is used as a load change. 2. The control method according to claim 1, wherein the method is applied to control of various devices. 3. The abnormality diagnosis method according to claim 1, wherein the method is applied to abnormality diagnosis of various devices. 4. The method according to claim 1, wherein the measuring method uses two frequency components. 5. The method according to claim 4, wherein one frequency component is a frequency component around the rotation speed of the load, and the other frequency component is a frequency component twice as high as the power supply frequency. 6. A stirring granulation apparatus of a type in which a stirring blade is rotated by an electric motor, wherein the stirring granulation apparatus has a control device for controlling the electric motor, and the control device controls the electric power consumed by the electric motor. And analyzing the frequency component of the electric power to control the granulation by grasping that the fluidity of the granulated material changes with the progress of granulation as a change in acceleration / deceleration torque applied to the stirring blade. A stirring granulation apparatus characterized by the above-mentioned.