US3657623A - System for tracking mill stand motor currents for optimizing the duty cycle - Google Patents

System for tracking mill stand motor currents for optimizing the duty cycle Download PDF

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Publication number
US3657623A
US3657623A US64450A US3657623DA US3657623A US 3657623 A US3657623 A US 3657623A US 64450 A US64450 A US 64450A US 3657623D A US3657623D A US 3657623DA US 3657623 A US3657623 A US 3657623A
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Prior art keywords
motor
mill
signal
instantaneous
current
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Expired - Lifetime
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US64450A
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English (en)
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Jan M Fludzinski
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CBS Corp
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Westinghouse Electric Corp
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P7/00—Arrangements for regulating or controlling the speed or torque of electric DC motors
    • H02P7/06—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current
    • H02P7/18—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power
    • H02P7/24—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices
    • H02P7/28—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices
    • H02P7/285—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature supply only
    • H02P7/2855—Arrangements for regulating or controlling the speed or torque of electric DC motors for regulating or controlling an individual dc dynamo-electric motor by varying field or armature current by master control with auxiliary power using discharge tubes or semiconductor devices using semiconductor devices controlling armature supply only whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/46—Roll speed or drive motor control

Definitions

  • This invention relates to a system for tracking mill stand motor currents for the purpose of optimizing loadings on a mill stand motor, consistent with the known duty cycle prescribed by the manufacturer.
  • Mill stand motors are rated for overload conditions by the manufacturer. For example, a motor may be rated at 125 percent overload for 2 hours, and 175 percent maximum overload for frequently repeated momentary loads. Where the mill has not been used to 100 percent capacity, the result is that the operator may without any danger of overheating, overload the mill stand motor to increase work output.
  • a system for tracking currents in a mill motor operating in the weakened field range between base and maximum speeds, for the purpose of optimizing the duty cycle under constant inertial conditions Means coupled to the mill motor, provide a first signal which is a function of the preselected acceleration ramp current for the mill motor. Means also provide a plurality of signals which are respectively, a function of the instantaneous magnitude of the total mill motor current. Algebraic summation means, operatively connected to the first signal means and the plurality signal means, provide a succession of summed output signals, each discrete summed output signal being a function of the'instantaneous motor load current.
  • means provide a'selectable predetermined percentage of the instantaneous motor load current. Further, means are adapted to receive the discrete summed output signal and the predetermined percentage of instantaneous motor load current for the purpose of comparison and for delivering an inhibit signal when the compared magnitudes are equal. Finally, means receive the inhibit signal and terminate the preselected acceleration ramp current at a steady state magnitude for application as a speed reference to the mill motor.
  • FIG. 1 is a schematic diagram showing the mill stand motor current tracking system in accordance with the invention
  • FIG. 2 is a diagram depicting the relationship between flux and speed in the region between base speed and maximum speed.
  • FIG. 3 is a diagram of the percentage load torque versus rpm showing various acceleration rates in relation to stand load current for a given load.
  • the instant invention is intended to be practiced in the environment of a cold rolling mill indicated generally at 10, comprises an upper roller member 12, and a lower roller member 14 operative to longitudinally displace a strip of material 16.
  • the material 16 is to be reduced in the rolling mill, the thickness between the rollers 12 and 14 being regulated by means of a screwdown motor 18. Since the actuation of the screwdown motor 18 fonns no part of this invention, the remaining details concerning its actuation are omitted.
  • a mill motor 20 is mechanically coupled to the roller members 12 and 14 or to 12A and 14A to control displacement of the strip of material 16 through the mill.
  • the mill motor 20 is physically large than the screwdown motor 18, and to it falls the burden of reducing the material.
  • the speed of the mill motor 20 is selected in logic circuitry 22 which sends a mill speed command to a ramp function generator 24 which generates a speed reference to for application to a speed regulator indicated generally at 26.
  • the output signal of the speed regulator 26 is applied to a power supply for the motor indicated generally at 28.
  • the power supply 28 may be a thyristor power supply or a generator power supply.
  • a tachometer generator 30 is coupled to the shaft of the mill motor 20 to generate a feedback signal or which is fed back to the speed regulator 26.
  • the circuitry for deriving the accelerating current signal is indicated generally at 32.
  • the circuitry may utilize the motor operated potentiometer to be described or it may be a static multiplier/divider.
  • the speed reference signal on is fed to a driver amplifier 34 which is connected to motor operated potentiometer having a motor identified at 36 and a number of ganged parallel plate potentiometers two of which are identified at 38 and 40 respectively.
  • the wiper 42 of the potentiometer 38 is connected to provide a position feedback signal to the drive amplifier 34.
  • the signal 0) is also applied to a difierentiation-multiplier circuit 44, the output of which provides a signal K0) which is connected across the potentiometer 40.
  • the output of the potentiometer 40 is connected to a summation amplifier indicated generally at 46.
  • Another input to the summation amplifier 46 is the total current I, which is derived from the shunt resistor 48 in the motor armature circuit of the mill moor 20.
  • the output of the summation amplifier I is connected to a load percentage selection network indicated generally at 48; this circuitry comprises an amplifier proper at 50, with a feedback loop having a plurality of resistors 52, 54, 56 and so forth, serially connected with open contacts identified at 58, 60, 62 respectively. As indicated by the dotted lines the selective closure of the contacts 58, 60, 62 is made through the logic circuitry 22.
  • a contact relay 64 is connected in the output of the amplifier 50, with the cooperating contacts being within the logic circuitry 22.
  • the DC motor 20 is runup to base speed w
  • the counter EMF CEMF
  • Kdxo Kdxo
  • I that is the load current
  • I that is the load current
  • w the maximum speed
  • the counter EMF is kept constant and the field is weakened in order to increase the speed (FIG. 2). More current is now needed to obtain the same torque.
  • the load current 11 is a function only of the speed-it does not depend upon the acceleration rate. The higher the speed the more load current I i is required for the same load and for the same reduction. The important parameter then as far as the mill operator is concerned is the load current 1,; however, his instrumentation is such that only I the total current is displayed. Therefore, if he observes only the total current, he hasno way of knowing where to stop, and most probably he will stop short of the overload condition which he has selected. The important parameter then is 11 the load current.
  • the expression for motor load current may be derived as follows:
  • K a constant (I) motor field flux -I, armature current a 1 a 5) where K a constant a acceleration current Solving Equation (5) for I a a/ 14) T; I, +1 7 where I, armature current I IV load current 1,, acceleration current Solving for 1' II t la Substituting Equation (6) for Equation (8) 1! I: 11 Km Substituting for T..
  • a complete run down of the operation of the system will serve to provide an overall and comprehensive understanding of the system.
  • the mill may have been running at perhaps percent load, and a job now comes through the mill, and the operator decides to run at perhaps say percent load.
  • the logic circuitry in response to a manual or a computer command selects the mill speed, and a mill speed command signal is sent to the ramp function generator 24, which generates a ramp appropriate of slope which is fed to the speed regulator 26.
  • the actual speed of the motor 20 is monitored by the tachometer 30 which feeds back a signal to the speed regulator 26. When the inputs to the speed regulator 26 are equal, the motor will then be running at the correct selected speed. If the operator decides that he now desires to run at 1 10 percent overload, (see FIG.
  • the logic circuitry then closes the appropriate contacts in the load selection network 48.
  • the accelerating current will be determined by the circuitry 32 which supplies an accelerating current 1,, to the summation amplifier 46.
  • the total motor current I is derived from the shunt sensor 48 which is applied as I, to the have a choice of a number of acceleration rates as indicated by the captions Rate 1, Rate 2, and Rate .3..
  • Rate 1 had been selected.
  • the load percentage selection network 48 would deenergize the contact relay 64 when I had reached point b; I, would be at point a. If Rate 2 or Rate 3 had been selected, I, would reach points 0 or d respectively,
  • means for algebraic summation operatively connected to said first signal means and said plurality signals means, to provide a succession of summed output signals, each discrete summed output signal being a function of the instantaneous motor load current;
  • said means coupled to said mill motor comprises logic circuit means and ramp function generator means, said logic circuit means being coupled to said ramp function generator means for providing a selection command for said preselected acceleration ramp current, and adapted to receive said inhibit signal to further command said ramp function generator means to deliver said means adapted to receive said discrete summed output steady-state magnitude speed reference for said mill motor.
  • said means adapted to receive said discrete summed output sig'nalsand said predetermined percentage of instantaneous motor load current comprises feedback amplifier means having an input to receive said discrete summed output and a feedback path which feeds back said predetermined percentage in opposite polarity for algebraic addition with said discrete summed output signals.
  • a system for tracking currents in a mill motor operating in the weakened field range between base and maximum speeds, for optimizing the duty cycle under constant inertial conditions comprising:
  • means for algebraic summation operatively connected to said first signal means and said plurality signal means, to provide a succession of summed output signals, each discrete summed output signal being a function of the instantaneous motor load current;

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Electric Motors In General (AREA)
  • Control Of Multiple Motors (AREA)
US64450A 1970-08-17 1970-08-17 System for tracking mill stand motor currents for optimizing the duty cycle Expired - Lifetime US3657623A (en)

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US6445070A 1970-08-17 1970-08-17

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US (1) US3657623A (fr)
JP (1) JPS521383B1 (fr)
FR (1) FR2104434A5 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3809452A (en) * 1971-05-19 1974-05-07 R Heinz System for controlling number of revolutions of the tape drive in a tape recording and replaying apparatus
US4383208A (en) * 1979-12-31 1983-05-10 International Business Machines Corporation Dynamic determination of friction in a closed loop control system
US4460852A (en) * 1981-02-06 1984-07-17 Sumitomo Kinzoku Kogyo Kabushiki Gaisha Method of controlling mill motors speeds in a cold tandem mill
US4549122A (en) * 1983-09-14 1985-10-22 Allen-Bradley Company Method and circuit for DC motor field regulation with speed feedback
US4565952A (en) * 1983-11-04 1986-01-21 Mitsubishi Denki Kabushiki Kaisha Speed controlling device for rolling mills
US4645992A (en) * 1984-12-24 1987-02-24 Sperry Corporation Electronically controlled servomotor limit stop
US4659976A (en) * 1985-04-24 1987-04-21 Dresser Industries, Inc. Method and apparatus for maximizing utilization of an electric motor under load
US5617000A (en) * 1995-04-13 1997-04-01 Alps Electric Co., Ltd. Apparatus for detecting and controlling the rotational position of a motor shaft
EP1622253A3 (fr) * 2004-07-30 2008-01-16 Hitachi, Ltd. Procédé de régulation et dispositif de régulation d'un moteur à induction, et acier ou non-ferreux, véhicule ferroviaire, enrouleuse, véhicule marin, implement de machine, système de machines de papier et système de transport employants la procédé de régulation et le dispositif de régulation

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5075013U (fr) * 1973-11-15 1975-07-01
JPS5084728U (fr) * 1973-12-07 1975-07-19

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3317086A (en) * 1965-02-02 1967-05-02 Interconsul Ab Storage apparatus for granular or pulverulent material
US3413534A (en) * 1966-03-14 1968-11-26 Westinghouse Electric Corp Non-regenerating dc motor regulating circuit having improved stability
US3416058A (en) * 1964-04-30 1968-12-10 Westinghouse Electric Corp Apparatus for controlling a variable of moving elongate material
US3452853A (en) * 1966-10-10 1969-07-01 Data Products Corp Paper drive system

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2847632A (en) * 1957-04-25 1958-08-12 Raytheon Mfg Co Electric motor controls
GB1076624A (en) * 1963-11-15 1967-07-19 Materiel Electrique S W Le Acceleration-control systems for direct-current motors
FR1478088A (fr) * 1965-06-04 1967-04-21 Centre Nat Rech Metall Procédé de commande automatique des cylindres de laminoirs

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3416058A (en) * 1964-04-30 1968-12-10 Westinghouse Electric Corp Apparatus for controlling a variable of moving elongate material
US3317086A (en) * 1965-02-02 1967-05-02 Interconsul Ab Storage apparatus for granular or pulverulent material
US3413534A (en) * 1966-03-14 1968-11-26 Westinghouse Electric Corp Non-regenerating dc motor regulating circuit having improved stability
US3452853A (en) * 1966-10-10 1969-07-01 Data Products Corp Paper drive system

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3809452A (en) * 1971-05-19 1974-05-07 R Heinz System for controlling number of revolutions of the tape drive in a tape recording and replaying apparatus
US4383208A (en) * 1979-12-31 1983-05-10 International Business Machines Corporation Dynamic determination of friction in a closed loop control system
US4460852A (en) * 1981-02-06 1984-07-17 Sumitomo Kinzoku Kogyo Kabushiki Gaisha Method of controlling mill motors speeds in a cold tandem mill
US4506197A (en) * 1981-02-06 1985-03-19 Sumitomo Kinzoku Kogyo Kabushiki Kaisha Method of controlling mill motors speeds in a cold tandem mill
US4549122A (en) * 1983-09-14 1985-10-22 Allen-Bradley Company Method and circuit for DC motor field regulation with speed feedback
US4565952A (en) * 1983-11-04 1986-01-21 Mitsubishi Denki Kabushiki Kaisha Speed controlling device for rolling mills
US4645992A (en) * 1984-12-24 1987-02-24 Sperry Corporation Electronically controlled servomotor limit stop
US4659976A (en) * 1985-04-24 1987-04-21 Dresser Industries, Inc. Method and apparatus for maximizing utilization of an electric motor under load
US5617000A (en) * 1995-04-13 1997-04-01 Alps Electric Co., Ltd. Apparatus for detecting and controlling the rotational position of a motor shaft
EP1622253A3 (fr) * 2004-07-30 2008-01-16 Hitachi, Ltd. Procédé de régulation et dispositif de régulation d'un moteur à induction, et acier ou non-ferreux, véhicule ferroviaire, enrouleuse, véhicule marin, implement de machine, système de machines de papier et système de transport employants la procédé de régulation et le dispositif de régulation

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Publication number Publication date
JPS521383B1 (fr) 1977-01-13
JPS474858A (fr) 1972-03-10
FR2104434A5 (fr) 1972-04-14

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