US1739174A - Motor-control system - Google Patents

Description

Dec.- 10, 1929. P. McSHANE 1,739,174

MOTOR CONTROL SYSTEM Filed Sept. 23, 1927 Z Sheets-Sheet 1 INVENTOR Phe [an Nc Shane I 6/ BY ATTORNEY Dec. 10, 1929. P. M SHANE 1,739,174

MOTOR :CONTROL SYSTEM Filed Sept. 23,v L927 2 Sheets-Sheet 2 56c 58 .629 56 INVENTOR Ph elan Me 572 ane BY W ATTORNEY Patented Dec. 10, 1929 Lauren sures PATENT; orrice PHEL AN MCSHANE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC 82; MANUFAGTURING GOMEANY, A CORPORATION OF PENNSYLVANIA MOTOR-CONTROL SYSTEM Application filed September 23, 1927. Serial No. 221,414.

employedin connection with mill tables for steel rolling mills.

The object of the invention, generally stated, is the provision of a simple and reliable system of control whereby the period of operation of the apparatus controlled is reduced to a minimum.

A more specific object of the invention is to provide for dynamically bralring'the motors coupled to one table of a rolling mill, after the metal being worked has been delivered by that table to the mill and the motor coupled to the oppositetable has been energized to return the metalto the mill.

It is also an object of the invention to provide, in a control system of'the nature set forth, for operating one motor at a time independently of the other, or for operating both motors simultaneously in the same direction. v

Another object of the invention is to provide a control system for mill table motors the manipulation and handlingofthe metal. It is, therefore, evident that any increase 1n mill output will be accomplished by improv' ing the means and methods of manipulating the mills and it is toward this endthat this invention is directed.

lVhile the invention may be applied to many differentcontrol systems similar in nature to the control systems for mill tables,

in the particular embodiment of the invention illustrated, it is applied to control the operation of the front and back roll tables of a rolling mill.

The general practice in mill operation is to energize the motor coupled to the rolltable on one side of the mill to convey the metal on that table into the main rolls of the mill, and allow the motor coupled to the roll table on the other side of the mill .to'reinain idle.

When the metal has once passed through the mill and out onto the idle table, the operation is reversed, the motor coupled to the idle table is set in motion to convey the metal back into the mill at the same time the motor driving the front table is permitted to stop. There are times when the tables run so freely that the rolls'will continue rotating toward the mill after the metal being Worked is received and returned by the mill, and because of this continued rotation of the rolls, the netal will be carried back into the mill be fore the manipulation of the metal to re-enter the mill is completed. When metal is prematurely returned to the mill, a great deal of time is lost in readjusting the metal and also there is a possibility of injuring the apparatus. To overcome the drifting of the roll tables, the motors driving them may bestopped in several ways,-as for example, by mechanicalbrakes, plugging the motors or dynamically braking them.

In this invention, provision is made for dynamically braking the motors coupled to the tables, therefore, after one of the tables has conveyed the metal to the mill, and the motor driving the other table has been energized to reconvey the metal to the mill a sec- 0nd time, the first motor will have a dynamic braking circuit established to stop the table.

By means of this system, a considerable saving of power is effected, inasmuch as it is notnecessary to plug the'motors to stop the rolls when they are drifting toward the mill.

I The period of time over which the braking takes place being relatively long, the braking currentis comparatively small, and the shock of the l'iraking. operation on the motor is negligible. The invention, accordingly, is disclosed in the embodiment thereof shown in the accompanying drawing, and more fully explained with reference to the drawing, in which;

Figure 1 illustrates a well known form of rolling mill with afront and back roll table driven by electric motors.

Figs. Q and 3 illustrate the operating; cir- Cir cuits and the controlling circuits, respectivey, for operating the motors.

Referring more particularly to Fig. 1, I have shown a rolling mill having a set of main rolls 1, a front roll table 2 and a back roll table 3, for carrying stock to and from the main rolls 1. In order to operate the front and back tables of the mill, a pair of motors 5 and 6 are provided which are coupled through suitable gear trains to the table rolls 4.

Figures 2 and 3, as has been stated hereinbefore, illustrate the operating circuits and the control circuits, respectively, for the motors, and in connection with these, for the purpose of clearness, the same numbers will be used to indicate the same circuits and parts in both figures.

In order to operate the system, it is necessary to connect the same to a source of supply, which in this instance is the line conductors 7 and 8. This is accomplished by means of the double pole switches 9, 10 and 11. Before current will flow in any of the control circuits, it is necessary to close the multiple pole low voltage relay 12, and to do this, it is necessary to place the operating handles and 16 of the two master controllers 13 and 14, respectively, in their oil-positions, as illustrated in the drawing.

When the handles are in the indicated. oilpositions, an actuating circuit for the low voltage relay 12 may be traced from the negaive side of the double pole line switch 11, through conductor 17, contact member 18 on the master controller 13, the master controller bridging member 15a, contact member 19, conductors 20, 21 and 22, the interlock on relay 23, conductor 24, contact member 25, on the master controller 14, the bridging member 16a of contact member 26, conductor 27, conductor 28, actuating coil of the low voltage relay 12, conductor 29, the overload relays and 31 and conductor 32 to the positive side of the double pole line switch 11.

After the low voltage relay 12 has been actuated, in order that the master switches 13 and 14 may be manipulated without caus ing the relay to open, a holding circuit is established which extends from line conductor 17, through conductor 33, interlock 12?), the coil 12a of the relay 12, conductors 29 and 32 to the positive side of the switch 11.

When it is desired to rotate the front roll table in a direction to carry the metal into the main mill 1, the handle 15 of the master controller 13 may be thrown to the forward position, as indicated by the dotted lines in Fig. 3. In such manner, an energizing circuit, for the control apparatus, may be established which extends from the negative line conductor 8 through one blade of the double pole switch 11, conductors 17 and 33, interlock 12?), conductors 28 and 34, interlock 120 on the low voltage relay 12, conductors 35 and 20, contact member 19 on the master controller 13, the bridging member 13a, contact member 36, conductor 37, the actuating coil of the reversing contactor 38, the actuating coil of contactor 39, conductor 40, the operating coil of line contactor 41, the normally closed interlocks 422') and 435 of the dynamic braking cont- actors 42 and 43, respectively, to the positive line conductor 32 and thence to the double pole switch 11.

lVhen the actuating coils are energized, the reversing contactors 38 and 39 of the front table motor 5 and the line switch or contactor 41 are closed. The double pole switch 9, having been closed, a circuit for operating the motor 5 disposed to operate the front table in its forward direction, will be established and it extends from the negative line conductor 8, through conductor 44,

-one blade of the double pole s 'itch 9, the

actuating coil 30a of the overload relay 30, line contactor 41, the two sections of resistors 45 and 46, conductor 47a, the series iield 48, conductors 47 and 49, interlock 50 on the reversing contactor 39, conductors 51 and 52, the armature 5a, conductor 53, interlock 38?) of reversing contactor 38, conductors 54 and 55, he positive side of the double pole switch 9, to the positive side of the power source or the conductor 7. It will be readily seen that upon the completion of this circuit, the motor will start to operate in the desired direction.

In order to accelerate the motor, the two resistor sections 45 and 46 may be shunted by a pair of accelerating contactors 56 and 57. Upon the closure of the reversing contactor 38, a control circuit for actuating the contactors 56 and 57 which extends from ctntact member 19 on the master controller 13, through conductors 20, 21, 58, 59, interlock 390 on reversing contactor 39, conductor 60, conductor 61, the actuating coil 56a of accelerating contactor 56, and conductor 62 to the positive side of the line 32, thereby closing the accelerating contactor 56 to short circuit rosistor 45. Vhen accelerating contactor 56 closes, a circuit for contactor 57 is established, extending from contact member 19 on the master controller 13, through conductors 20, 21, 58, interlock 560 on accelerating contactor 56, conductor 63, the actuating coil 57a of the accelerating contactor 57, and conductor 62 to the positive side of the line 32, and when energized, accelerating contactor 57 closes to short circuit resistor section 46, )ermitting the front table motor 0 to be brought up to full speed.

For the purpose of setting up a dynamic braking circuit for the motor coupled to the table which is being stopped when the reversing contactor 38 closes, a circuit is established which extends from the negative side of the source or conductor 8, through the double pole switch 11, conductors 17 and 33, interlock 126 on the low voltage relay 12, conductors 28 and 27, contact member 26 on the master controller 14, bridging member 16a, contact member 25, conductors 24 and 64, interlock 380 on the reversing contactor 38, conductor 65, the actuating coils 67a and 68a of the dynamic braking contactors 67 and 68, conductor 32 through the double pole switch 11 to the positive line conductor 7. The energizing or actuation of the dynamic braking contactors 67 and 68 causes the interlocks 67b and 68b to open and the bridging members 67 c and 680, respectively, to close.

The closure of contactors 67 and 68 causes a dynamic braking circuit to be established for the back table motor 6, which extends from the armature 6a through conductor 70, bridging member 670 of the dynamic braking contactor 67, conductors 71, 72, 73, the series field Winding 74, conductors 75, resistors 76 and 77, conductors 78 and 79, bridging member 680 of the dynamic braking contactor 68, conductors 80 and 81 to the other side of the armature 6a.

When the motor 5a has caused the front table to rotate sufliciently to feed the metal being worked through the main mill 1, and it has been deposited on the back roll table 2, the front mill table may be denergized and the back table energized to pass the metal back into the mill by simply throwing the master controller 13 from the forward to the reverse position.

In order to deenergize the front table motor 5, when the handle 15 of the master controller 13 is thrown to the reverse position, the bridging member 1542 Will interrupt the circuit to the actuating coils of the reversing contactors 38 traced hereinbefore, and 39 and the line contactor 41, causing these contactors to interrupt the power circuit of motor 5. When the bridging member 15a is placed in the indicated reverse position, a dynamic braking circuit for motor 5 and a power circuit for motor 6 will be established by the operation of the apparatus connected in the circuit extending from the negative line conductor 8 through the double switch 11, conductors 17 and 33, interlock 12b onthe low voltage relay 12, conductors 28 and 34, interlock 120, conductors 35 and 20, contact member 19 of the master controller 13, bridging member 15a, contact member 82, conductor 83, the actuating coil 84a of the reversing contactor 84, actuating coil 85a of the revers ing contactor 85; conductor 86, the actuating coil 87 a of the line contactor 87, conductor 88, interlock 67 b of the dynamic braking contactor 67, interlock 68?) on the dynamic contactor 68 to the positive line conductor 7, by way of conductor 32 and double pole switch 11.

This circuit, as will be readily seen, cannot be established until the actuating coils 67 a and 68a have been deenergized to permit the dynamic braking contactors 67 and 68 to fall to their normally closed position, and inasmuch as they are energized" by a circuit which may be traced through interlocks 380 011 the reversing contactor 38, the circuit of the front table motor 5 must be interrupted before the back table motor actuatingcircuit can be established. However, when the circuit through the reversingcontactors 84 and 85 and the line contactor 87 is completed, the back table motor 6 will start to rotate in a direction to carry the metal being worked into the mill 1.

The power circuit for the back table motor extends from the negative line conductor 8 through conductor 89, double pole switch 10, the actuating coil 90a of the protective overload relay 90, conductor 91, the interlock on the line contactor 87, conductor 92, through resistors 77 and 76, conductor 75, the series field coil 74, conductors 7 3and 94, interlock 846 on the reversing contactor 84, conductors 95, and 81, the armature 6a, conductors 96 and 97, interlock 856 on the reversing contactor 85, conductors 98 and 99 and the double pole switch 10 to the positive line conductor 7. In order to accelerate the motor 6, a plurality of circuits similar to those described hereinbcfore, in connection with the front table motor 5, are provided for shunting out resistors 77 and 76. One of these circuits may be traced from the contact member 19 on the master controller 13 through conductors 20.

100, interlock 850 on the reversing contactor 85, conductors 101 and 102, the actuating coil 103a of the accelerating contactor 103 and by conductor 104 to the positive line conductor 7 by way of conductor 32 and double pole switch 11.

When the circuit is completed, the accelerating contact-or 103 will close and cut out the resistor section 77. Upon the closure of accelerating contactor 103, a circuit is established extending from contact point 19 through conductors 20, 105, interlock 1030 on the accelerating contactor 103, conductor 106, the actuating coil 107a of the accelerating conductor 107 to the positive side of the line 7 by way of conductor 32 and the double pole switch 11. The completion of the circuit just traced causes the accelerating contactor 107 to close, cutting out the resistor section 76, permitting the motor 6 to be brought up to full speed in the direction for which it is set to operate.

In order to stop the front table motor from drifting towards the mill after it has been operating, a dynamic braking circuit for it is established when the back table motor is I started. A circuit for actuating the apparatus which establishes the dynamic braking circuit for the back table motor extends from and 27, contact member 26, bridging member 16a of the master controller 14, contact member 25, conductors 24 and 109, interlock 840 on the reversing contactor 84, conductor 110, the actuating coils 42a and 43a of the dynamic braking circuit contactors 42 and 43, respectively, to the positive line conductor 7, by way of conductor 32 and double pole switch 11.

The circuit is completed when the handle 15 of the master controller 13 is thrown to the indicated reverse position and the reversing contactor 84 and the dynamic braking circuit contactors 42 and 43 are closed. The closure of the dynamic braking circuit contactors establishes the braking circuit extending from one side of the armature 5a of the front table motor 5, through conductors 53, 111, interlock 420 on the dynamic braking circuit contactor 42, conductors 112, 113 and 47, the series field winding 48, conductor 47a, resistors 46 and 45, conductors 115 and 116, interlock 430 on dynamic braking circuit contactor 43, conductors 117 and 52, to the other side of the armature 5a.

When the dynamic circuit has been c0mpleted, it will be obvious that the front roll table and motor 5 will be brought to rest, when the back table motor is started with the master controller 14 in its .off position. Further, it will be readily seen that as the metal is passed back and forth through the mill through the operation of the master controller 13, that first one motor will be energized to carry the metal toward the mill and then the other motor, and at the same time, the opposite motors will be brought to rest by means of dynamic braking.

Assuming that the metal has been completely worked and it is desired to deliver it from the mill, then the rolls of one of the tables may be caused to rotate in a direction to carry the metal away from the mill.

The master controller 14 is arranged to control both motors so that either can be operated to carry the metal away from the mills. Then the operating lever 16 of the master controller 14- is placed in the indicated forward position, it will cause the back table motor 6 to rotate table 3 to deliver the metal to a run out table.

The control circuit for establishing the required powe circuits for operating the motors to deliver the metal, may be traced from the negative line conductor 8, through the double pole switch 11, conductors 17 and 33, interlock 12b on the low voltage relay 12, conductors 28 and 27 contact'point 26, and bridging member 16a of the master controller 14, contact member 118, conductor 119, the actuating coils 120a and 121a of reversing contactors 120 and 121, conductors 122 and 86, the actuating coil 87a of the line contactor 87, conductor 88, interlocks 67 0 and 686 on the dynamic braking eontactors 67 and 68 to positive line conductor 7, by way of conductor 32 and double pole switch 11.

The reversing contactors 120 and 121, as well as the line contactor 87, will close in response to controller 14 when actuated in the above manner, establishing an actuating circuit through the back table motor 6, ex tending from line conductor through conductor 89, switch 10, coil 90a, conductor 91, contaetor 87, conductor 92, resistors 77 and 76, conductors 75, series lield winding 74, conductors 73 and 72 interlock 1216 conductor 96, armature 6a, conductors 81 and 95, contactor 120, conductor 99, through switch 10 to line conductor 7, thereby causing the motor to rotate in a direction opposite to that previously described, or to rotate the table rolls to carry the metal away from the mill.

If the back table motor 6 is rotating to carry the metal into the mill and it is desired to actuate the front table motor to carry the metal away from the mill, the operating handle 16 of the reversing controller 14 may be actuated to the reverse position, in which position a circuit is established which extends from the contact member 26 on reversing controller 14 through the bridgin'g member 1664, contact member 122, conductor 123, actuating coils 124a and 12560 of the reversing contactors 124 and 125; conductors 126 and 40, the actuating coil 41a, of the line cont-actor 41 in the front table motor circuit, conductor 40a, the interlocking members 42b and 436 on the dynamic braking circuit contactors 42 and 43 to the positive line c0nductor7, by way of conductor 32 and double pole switch 11.

Therefore, the actuating circuit of the front table motor hereinbefore traced is established and the rolls are operated, to carry the metal away from the mill, similar in manner to that ust described with respect to the back table motor.

It will be noted that when the controller handle 16 of the master controller 14 is in either of the forward or reverse positions, that no dynamic braking circuit for either of the motors can be established, inasmuch as the circuit to the actuating coils of the dynamic braking circuit contactors is established only when the control handle 16 of the master controller 14 is in the of position. Therefore, upon the operation of the master controller 14, no dynamic braking circuit can be established for either of the motors.

If, for any reason, the low voltage relay should fall open, it is essential before it can again be reset, that the master controllers 13 and 14 be placed in their 01f positions. This protection means that neither motor can start up of its own accord, after a failure or interruption of power to the system. This feature becomes necessary where two separate master switches are utilized in order to have the necessary protection for safe operation. I

In this application, I have chosen to use series motors. However, if compound motors were used, a similar dynamic braking circuit could be established by making slightly different connections.

While the illustrated assembly constitutes a preferred embodiment of my invention, I do not limit myself strictly to the details herein presented, since manifestly the same may be considerably varied without departing from the spirit of the invention as defined in the appended claims.

I claim as my invention:

1. In a control system, in combination, a plurality of propelling motors, means for effecting the operation of the motors independently, and means effecting dynamic braking of the motors disposed to function automatically to brake one motor upon the starting of another motor;

2. In a control system, in combination, a plurality of driving motors, means for controlling the operation of the motors, and means for effecting the dynamic braking of the motors, said means being responsive to the starting of one motor to automatically effect the dynamic braking of another motor.

3. In a control system comprising a plurality of motors for driving the front and back tables of a rolling mill, control means for operating either the front or back table motors alternately in either direction, and means for automatically effecting dynamic braking of the motor running one table when the motor driving the other table is caused to run in the opposite direction.

l. In a control system, in combination, a plurality of electric motors, means for operating the said motors alternately in opposite directions, and means for automatically effecting dynamic braking of one motor when the other motor is operated.

5. In a control system, in combination, a plurality of electric motors, means for operating the motors alternately in opposite directions, means for operating the motors simultaneously in the same direction, and means for dynamically braking the motors, said dynamic braking means being disposed to function when the motors are operated alternately in opposite directions, so that the starting of one motor automatically effects the dynamic braking of another motor.

6. In a control system, in combination, reducing rolls, two roll-tables for feeding stock to the reducing rolls, said roll tables being on opposite sides of the rolls, an independent driving motor for each roll-table, two controllers for the motors, each controller being connected to both motors, said controllers being operable to eifectoperation of the mo tors and roll-tables in opposite directions alternately to pass the stock back and forth through the rolls and in the same direction continuously to deliver the stock from the rolls.

7. In a control system, in combination, a"

rolling mill having front and back roll-tables, a motor for operating each table, two controllers for the motors, one of said controllers being operable to, effect the operation of the motors to rotate the table rollers toward the mill, the other controller being operable to effect the operation of the motors to rotate the table rollers away from the mill,

said controllers being so disposed that either operation of each motor and roll table toward,

the reducing rolls to feed the stock, and the other of said controllers being disposed to effect the operation of each motor and rolltable away from the rolls to convey the finished stock therefrom,thereb v to provide for operating the motors and roll-tables continuously in either direction to feed and carr 1 the stock away from the rolls simultaneously.

9. In a control system. in combination, a.

rolling mill provided with front and back roll-tables for feeding stock to the mill, an

independent driving motor for each roll table. two master controllersfor the motors, each controller being connected to both motors, one controller being operable to effect operation of themotors to rotate the roll tables toward the mill alternatelv for passing the stock back and forth throuqh he m ll, the other controller being operable to effect operation of the motors to rotate the rolltables away from the mill alterna ely to carry stock from either side of the mill, and means responsive to the operation of the controller, which operates the motors and roll tables toward the mill alternately, for effecting the dynamic braking of one motor when the other is energized.

10. In a control system for rolling mills provi ded with front and back roll-tables, in combination, an independent driving motor for each roll-table, two controllers for the motors, each controller being connected to both motors, one of said controllers being disposed to effect the operation of the motors and roll-tables toward the mill alternately, the other controller being disposed to effect the operation of the motors and roll tables away from the mill alternately, and means operable in response to the operation of the first controller for effecting dynamic braking of one motor when the other is energized and means responsive to the operation of the second controller for rendering the means for effecting dynamic braking of the motors inoperative.

11. In a control system, in combination, a rolling mill having a front and back table for carrying material to and away from the mill, motor for operating each table, two controllers, one for controlling the operation of the driving motor connected to each table causing said tables to run toward the mill, the other controller being disposed to control the operation of the driving motors coupled to the table to carry the material away from the mills, the controllers also permitting either of the driving motors to be operated independently of the other, also simultaneously operating both at the same time, and means for automatically dynamically braking one of the driving motors when running in one direction when the other motor is caused to run in the other direction.

12. In a control system, in combination, a rolling mill having a front and back table for carrying material to and away from the mill, separate motors coupled to each table, two controllers, electro-reeponsive means controlled by said controller for running either motor alternately toward or away from the mill or one table toward and the other away from the mill, and means for dynamically braking the motors running one table in one direction when the other motor is caused to operate the other table in the opposite direction, and further means for preventing the motors from starting after a failure of power to the system until the two controllers have been returned to the offposition.

In testimony whereof, I have hereunto subscribed my name this 12th day of September,

PHELAN MGSHANE.

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