CA1135364A - Method and apparatus for measuring the degree of fullness of a mill driven by an electric motor - Google Patents
Method and apparatus for measuring the degree of fullness of a mill driven by an electric motorInfo
- Publication number
- CA1135364A CA1135364A CA000335012A CA335012A CA1135364A CA 1135364 A CA1135364 A CA 1135364A CA 000335012 A CA000335012 A CA 000335012A CA 335012 A CA335012 A CA 335012A CA 1135364 A CA1135364 A CA 1135364A
- Authority
- CA
- Canada
- Prior art keywords
- mill
- fullness
- degree
- variation
- signal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C25/00—Control arrangements specially adapted for crushing or disintegrating
Landscapes
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Control Of Electric Motors In General (AREA)
- Crushing And Grinding (AREA)
- Control Of Direct Current Motors (AREA)
- Basic Packing Technique (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The degree of fullness of a mill driven by an electric motor is measured by, firstly, measuring the variation of the power input of the mill and, secondly, determining the degree of fullness on the basis of the degree of variation of said power input, whereby use is made of test or calibration measurements performed, previously with different degrees of fullness. Perferably a current or voltage signal descriptive of the power input is created and then a signal representing the degree of full-ness is generated as proportional to the amplitude of said voltage or current signal.
The degree of fullness of a mill driven by an electric motor is measured by, firstly, measuring the variation of the power input of the mill and, secondly, determining the degree of fullness on the basis of the degree of variation of said power input, whereby use is made of test or calibration measurements performed, previously with different degrees of fullness. Perferably a current or voltage signal descriptive of the power input is created and then a signal representing the degree of full-ness is generated as proportional to the amplitude of said voltage or current signal.
Description
~13S36~
The present invention relates to a method and apparatus for measuring the degree of fullness of a mill driven by an electric motor.
It is kncwn that, for example, the sound of an autogenic mill varies according to its load and thereby also according to its degree of fullness.
Also, feed control devioe s have been constructed which are based on this phenomenon, in order to maintain the degree of fullness of a mill at a desired value. One such arrangement is described in Canadian Patent Application S.N.
243,757.
In ccnnection with the present invention it has been observed that the pcwer intake of a mill varies within a relatively low frequency and that the amplitude of this variation is dependent on the degree of fullness of the mill in the manner described belcw. The present invention relates to this phenomenon.
According to the present invention, there is provided a method for measuring the degree of fullness of a mill driven by an electric motor, which comprises measuring the variation in pcwer intake of the mill and determining the degree of fullness of the mill on the basis of amplitude of power variation in comparison with calibration measurements established previously at different degrees of fullness.
In another aspect, the present invention provides an apparatus for measuring the degree of fullness of a mill driven by an electric m~tor compris-ing a p~wer transmitter connected to the motor of the mill in order to convert power intake of the mill to a voltage or current signal, and circuit means for forming an output signal representing amplitude of variation of the said signal.
In studies performed it was observed that in an unfiltered pawer curve there may also be oscillation within the frequency of the rotational velocity, owing to the asymmetricity of the mill or similar factors. But in addition to this, in an autogenic mill, for example, a low-frequency oscilla-~ ~S~ .
: `, ~, `
1~35364 tion in the order of a few Hertz can be observed in the power curve, theamplitude of the oscillation depending on the degree of fullness of the mill.
When a signal representing the degree of fullness is formed, it is advantage-ous, by means of high pass and low pass filters, to define a suitable fre-quency band within which the measurement of such signal is to be made. In order to enable the determination of the degree of fullness on the basis of the signal, it is, of course, necessary first to perform calibration mea-surements using different degrees of fullness.
Other characteristics and details of the invention and of preferred embodiments are described in more detail below. Reference is made to the accompanying drawingsJ in which Figure 1 is a diagrammatic representation of the variation in amplitude of the power intake of an autogenic mill as a function of the degree of fullness of the mill, Figure 2 is a block diagram of the apparatus according to the invent-ion, and Figure 3 is one possible circuit diagram.
In one experiment it was observed that the amplitude of the power oscillation in an autogenic mill is dependent on the degree of fullness of the mill in the manner shown in Figure 1. Thus, at first the amplitude increases along with the degree of fullness, whereas after a certain maximum amplitude the amplitude decreases as fullness is approached. In order to enable the correct use of this dependency it is necessary to know the range within which this phenomenon takes place. Since the aim is usually to main-tain a constant degree of fullness, it must also be known whether the depend-ency at a given point is positive or negative.
It should also be mentioned that the frequency of the oscillation is dependent on the rotational velocity of the mill and on the number of ~ll353~i4 lifting beams on its periphery. The creep caused by the wear of the lifting beams is a very slow phenomenon and can be taken into consideration on an experimenta~ basis.
Figure 2 shows diagrammatically one measuring apparatus according to the invention. The mill, which can be, for example, an autogenic mill and which is not shown in the figure, is rotated by a 3-phase electric motor ~onq~
3L~ M. A power transmitter, type ~*~x Mu 3 Wdu, is connected to the feed wires of the motor in a manner known per se; the transmitter measures the voltages of the phases and the currents of two phases.
The unfiltered signal given by the power transmitter 1 is fed to the band pass filter composed of an high pass filter 2 and a low pass filter 3, and the signal thus obtained is full-wave rectified in block 4, whereby a direct-voltage signal representing the variation in the amplitude of the current is obtained. This signal is amplified by the amplifier 5, if necessary.
A mini computer can for example be used for controlling the feed into the mill; the signals representing the current itself, as well as those representing its variation, are fed into the mini computer in the manner shown diagrammatically in Figure 2.
Figure 3 depicts the circuit diagram of blocks 2-5 in Figure 2.
The first operational amplifier OAl serves as an active high pass filter and amplifier. Its amplification is approx. 10 Hz and with a limit frequency of 2 Hz. Separation from the direct-current circuit is also obtained in a simple manner by coupling by means of the first capacitor Cl of the filter.
The second operational amplifier OA2 serves as a low pass filter and its limit frequency is 25 Hz.
The signal, which is within the frequency range 2-25 Hz, is then fed into the full-wave rectifier, which consists of operational amplifiers OA3 , . . .
1~3536~
and 0~4. Next, there is an RC CRange~ f~lter ClOOd~, 1000 u~) having a rather high time constant in order to level out sudden changes. A current signal prcportional to the ~oltage signal is produced with the aid of the last operational amplifier OA5 and the pair of transistors connected next in Cce5~
~L~ ~*e~R~5~0~; th~s current signal is within the range 4-20 mA and ls fed to a load of 0-300d~.
The voltage source of the circuits is shown at the top left of Flgure 3. Connected to it there can Be, for example, a control circuit, into whi~ch is ~ed the ~ormed signal, representing the degree of fullness, as the 0 actual value and signal corresponding to the desired degree o~ fullness as n q C a reerence value. The later signal, for its part, controls the-fil~J
of the mill by some method known per se, with the aid of some mechanical actuator.
The present invention relates to a method and apparatus for measuring the degree of fullness of a mill driven by an electric motor.
It is kncwn that, for example, the sound of an autogenic mill varies according to its load and thereby also according to its degree of fullness.
Also, feed control devioe s have been constructed which are based on this phenomenon, in order to maintain the degree of fullness of a mill at a desired value. One such arrangement is described in Canadian Patent Application S.N.
243,757.
In ccnnection with the present invention it has been observed that the pcwer intake of a mill varies within a relatively low frequency and that the amplitude of this variation is dependent on the degree of fullness of the mill in the manner described belcw. The present invention relates to this phenomenon.
According to the present invention, there is provided a method for measuring the degree of fullness of a mill driven by an electric motor, which comprises measuring the variation in pcwer intake of the mill and determining the degree of fullness of the mill on the basis of amplitude of power variation in comparison with calibration measurements established previously at different degrees of fullness.
In another aspect, the present invention provides an apparatus for measuring the degree of fullness of a mill driven by an electric m~tor compris-ing a p~wer transmitter connected to the motor of the mill in order to convert power intake of the mill to a voltage or current signal, and circuit means for forming an output signal representing amplitude of variation of the said signal.
In studies performed it was observed that in an unfiltered pawer curve there may also be oscillation within the frequency of the rotational velocity, owing to the asymmetricity of the mill or similar factors. But in addition to this, in an autogenic mill, for example, a low-frequency oscilla-~ ~S~ .
: `, ~, `
1~35364 tion in the order of a few Hertz can be observed in the power curve, theamplitude of the oscillation depending on the degree of fullness of the mill.
When a signal representing the degree of fullness is formed, it is advantage-ous, by means of high pass and low pass filters, to define a suitable fre-quency band within which the measurement of such signal is to be made. In order to enable the determination of the degree of fullness on the basis of the signal, it is, of course, necessary first to perform calibration mea-surements using different degrees of fullness.
Other characteristics and details of the invention and of preferred embodiments are described in more detail below. Reference is made to the accompanying drawingsJ in which Figure 1 is a diagrammatic representation of the variation in amplitude of the power intake of an autogenic mill as a function of the degree of fullness of the mill, Figure 2 is a block diagram of the apparatus according to the invent-ion, and Figure 3 is one possible circuit diagram.
In one experiment it was observed that the amplitude of the power oscillation in an autogenic mill is dependent on the degree of fullness of the mill in the manner shown in Figure 1. Thus, at first the amplitude increases along with the degree of fullness, whereas after a certain maximum amplitude the amplitude decreases as fullness is approached. In order to enable the correct use of this dependency it is necessary to know the range within which this phenomenon takes place. Since the aim is usually to main-tain a constant degree of fullness, it must also be known whether the depend-ency at a given point is positive or negative.
It should also be mentioned that the frequency of the oscillation is dependent on the rotational velocity of the mill and on the number of ~ll353~i4 lifting beams on its periphery. The creep caused by the wear of the lifting beams is a very slow phenomenon and can be taken into consideration on an experimenta~ basis.
Figure 2 shows diagrammatically one measuring apparatus according to the invention. The mill, which can be, for example, an autogenic mill and which is not shown in the figure, is rotated by a 3-phase electric motor ~onq~
3L~ M. A power transmitter, type ~*~x Mu 3 Wdu, is connected to the feed wires of the motor in a manner known per se; the transmitter measures the voltages of the phases and the currents of two phases.
The unfiltered signal given by the power transmitter 1 is fed to the band pass filter composed of an high pass filter 2 and a low pass filter 3, and the signal thus obtained is full-wave rectified in block 4, whereby a direct-voltage signal representing the variation in the amplitude of the current is obtained. This signal is amplified by the amplifier 5, if necessary.
A mini computer can for example be used for controlling the feed into the mill; the signals representing the current itself, as well as those representing its variation, are fed into the mini computer in the manner shown diagrammatically in Figure 2.
Figure 3 depicts the circuit diagram of blocks 2-5 in Figure 2.
The first operational amplifier OAl serves as an active high pass filter and amplifier. Its amplification is approx. 10 Hz and with a limit frequency of 2 Hz. Separation from the direct-current circuit is also obtained in a simple manner by coupling by means of the first capacitor Cl of the filter.
The second operational amplifier OA2 serves as a low pass filter and its limit frequency is 25 Hz.
The signal, which is within the frequency range 2-25 Hz, is then fed into the full-wave rectifier, which consists of operational amplifiers OA3 , . . .
1~3536~
and 0~4. Next, there is an RC CRange~ f~lter ClOOd~, 1000 u~) having a rather high time constant in order to level out sudden changes. A current signal prcportional to the ~oltage signal is produced with the aid of the last operational amplifier OA5 and the pair of transistors connected next in Cce5~
~L~ ~*e~R~5~0~; th~s current signal is within the range 4-20 mA and ls fed to a load of 0-300d~.
The voltage source of the circuits is shown at the top left of Flgure 3. Connected to it there can Be, for example, a control circuit, into whi~ch is ~ed the ~ormed signal, representing the degree of fullness, as the 0 actual value and signal corresponding to the desired degree o~ fullness as n q C a reerence value. The later signal, for its part, controls the-fil~J
of the mill by some method known per se, with the aid of some mechanical actuator.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for controlling the feed of material to a mill driven by an electric motor to achieve a desired degree of fullness in the mill which comprises establishing reference values representing variations in amplitude of the power intake of the mill at various degrees of fullness of the mill, measuring the variation of the power intake of the mill in operation, comparing the measured variation with said reference values, and controlling the filling of the mill in accordance with differences between the measured variation and the reference values.
2. The method according to claim 1, wherein the frequency range is from about 2 to about 25 Hz.
3. An apparatus for controlling the feed of material to a mill driven by an electric motor in response to measurements of variations in the power intake of the mill to achieve a desired degree of fullness in the mill, comprising a power transmitter connected to the motor of the mill in order to convert the power intake of the mill to a voltage signal, and circuit means for forming an output signal representing the amplitude of the vari-ation of said signal, means for comparing such variation with reference values representing different degrees of fullness of the mill, and control means responsive to said means for comparing for controlling the filling of the mill.
4. An apparatus for controlling the feed of material to a mill driven by an electric motor in response to measurements of variations in the power intake of the mill to achieve a desired degree of fullness in the mill, comprising a power transmitter connected to the motor of the mill in order to convert the power intake of the mill to a current signal, and circuit means for forming an output signal representing the amplitude of the variation of the current signal, means for comparing such variations with reference values representing different degrees of fullness of the mill, and control means responsive to said means for comparing for controlling the filling of the mill.
5. An apparatus according to claim 4, wherein in succession to the power transmitter there are connected filters for defining a frequency range of about 2 to about 25 Hz within which the signal is to be measured.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI782732A FI57026C (en) | 1978-09-06 | 1978-09-06 | SAFETY RELEASE FOR THE MAINTENANCE OF THE FULLNINGSGRADEN HOS EN ELMOTORDRIVEN KVARN |
| FI782732 | 1978-09-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1135364A true CA1135364A (en) | 1982-11-09 |
Family
ID=8511983
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000335012A Expired CA1135364A (en) | 1978-09-06 | 1979-09-05 | Method and apparatus for measuring the degree of fullness of a mill driven by an electric motor |
Country Status (8)
| Country | Link |
|---|---|
| AU (1) | AU529658B2 (en) |
| CA (1) | CA1135364A (en) |
| ES (1) | ES483814A1 (en) |
| FI (1) | FI57026C (en) |
| MX (1) | MX147018A (en) |
| NO (1) | NO155715C (en) |
| SE (1) | SE432205B (en) |
| ZA (1) | ZA794715B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5325027A (en) * | 1991-01-15 | 1994-06-28 | Outokumpu Mintec Oy | Method and apparatus for measuring the degree of fullness of a mill with lifting beams by monitoring variation in power consumption |
-
1978
- 1978-09-06 FI FI782732A patent/FI57026C/en not_active IP Right Cessation
-
1979
- 1979-08-24 MX MX179052A patent/MX147018A/en unknown
- 1979-08-31 ES ES483814A patent/ES483814A1/en not_active Expired
- 1979-09-05 SE SE7907397A patent/SE432205B/en not_active IP Right Cessation
- 1979-09-05 NO NO792879A patent/NO155715C/en unknown
- 1979-09-05 AU AU50591/79A patent/AU529658B2/en not_active Ceased
- 1979-09-05 CA CA000335012A patent/CA1135364A/en not_active Expired
- 1979-09-06 ZA ZA00794715A patent/ZA794715B/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5325027A (en) * | 1991-01-15 | 1994-06-28 | Outokumpu Mintec Oy | Method and apparatus for measuring the degree of fullness of a mill with lifting beams by monitoring variation in power consumption |
Also Published As
| Publication number | Publication date |
|---|---|
| NO155715C (en) | 1987-05-13 |
| SE7907397L (en) | 1980-03-07 |
| AU529658B2 (en) | 1983-06-16 |
| NO792879L (en) | 1980-03-07 |
| SE432205B (en) | 1984-03-26 |
| ZA794715B (en) | 1981-04-29 |
| MX147018A (en) | 1982-09-22 |
| AU5059179A (en) | 1980-03-13 |
| FI57026C (en) | 1980-05-12 |
| FI57026B (en) | 1980-01-31 |
| NO155715B (en) | 1987-02-02 |
| ES483814A1 (en) | 1980-04-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |