US1089783A - Electric-motor drive. - Google Patents

Description

K. A. PAULY.

ELECTRIC MOTOR DRIVE.

APPLICATION FILED 11110.29, 191s.

1,089,783. Patnted Mar.10,1914.

WTTNESSES JNYENTUH .KZHHL .131 Pa ULII;

' H25 Arranzvzx TfivIirEI) STATES PATENT OFFICE.

KARL A. PAULY, OF

SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC-MOTOR DRIVE.

Specification of Letters Yatent.

To all whom it may concern Be it known that I, KARL A. PAULY, a citizen of. the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Electric-Motor Drives, of which the following is a specification.

My invention relates to electric motor drives and is particularly applicableto such drives for machines, driven by a plurality of motors which must be reversed, as for instance, universal reversing rolling mills.

A universal rolling mill is one in which a piece of steel can be rolled simultaneously on all four sides, the mill being equipped with both horizontal and vertical rolls. The speeds of the rolls of such, a mill depend upon the reductions produced in the piece of steel in the two sets of rolls and the direction in which it is passing, that is, whether it is passing through the horizontal rolls first-and then through the vertical rolls, or vice versa. If the reductions, and therefore, the speeds of the horizontal and vertical rolls could be adjusted for a ass and these maintained continuously, eac of the rolls might be driven by a motor the speed of each of which being adjusted once "and for all. Since, however, a mill of this kind is required for a great variety of products, the

relative s eeds of the rolls are required to vary, an furthermore, the speeds of the rolls must be controlled so that the pieces of sttiel will not buckle or stretch between the ro ls. i

To this end, my invention has for its object'a novel electric motor drive for such a mill, or for any machine driven by a plurality of motors, which' must be reversed.

In accordance with my invention, I provide the machine with a lurality of motors, the speed of one of w ich is arranged to depend upon the load thereon, and cause the motors to have different relative speeds when their direction of rotation is reversed.

Other features of novelty which characterize my invention are pointed out withv particularity in the claims annexed to and forming a partof this-specification.

For a better understanding of my invention reference may be had to the following description taken .in'connection with the accompan ing drawing in which the single figures ows diagrammatically a universal rolling mill provided with an electric motor drive in accordance with my invention.

In the drawing, l are horizontal rolls dr ven'by a motor 9, and 8 are vertical rolls driven by a motor 4. The armatures of these motors are supplied with urrent from any suitable source, as for example, a fly-Wheel motor generator set 5 as shown. The field windings of these motors may be supplied from the same source as are the armatures, or any other suitable source. I have shown a motor generator set 6 supplying these field windings.

- If a piece of steel 7 enters the horizontal rolls 1 first, then the speed of the vertical rolls 3 must be higher than that of the horizontal rolls while if the steel enters the vertical rolls first then .the speed of the vertical rolls must be lower than that of the hori-' zontal rolls. Since the maximum reduction usually takes place in the horizontal rolls, the difl'erence in speeds of the horizontal and vertical rolls is usually comparatively slight in the first case, but is usually considerable in the second case. If the steel enters the horizontal rolls first, the motors 2 and 4 revolve in one direction, while if the steel enters the vertical rolls first the motors 2 and 4 revolve in the opposite direction. This reversal of the motors is taken care of by suitable means, as by a reversing or control switch 8 having stationary and movable. contacts. In order that the rolls will have the relative speeds referred to above, I cause the motors to have different relative speeds when their direction of rotation is reversed, preferably by changing the field strength of one of the motors, as by cutting Patented Mar. 10, 1914.

aresistance intothe circuit of itsfield winding. I also provide one of the motors with means for causin its speed to depend upon its load, 'preferab y causing it to slow down as the load thereon increases. I may accomplish this by means of a field winding sup- 'plied with current proportional to the armature current and connected accumulatively with respect to the main field winding on the motor. With the motor driving the vertical rolls rovided. with such means, its speed will rop to the normal value assuming that the vertical rolls are taking a draft which calls for full load torque. If the draft is less than that which would call for full load on this motor, the tendency of this motor will beto run at a speed greater than that required and will assist the motor driv ing the horizontal rolls, the speed of the vertical rolls adjusting itself to that corresponding to full load torque. If the draft of the vertical rolls is such as to require a torque in excess of full load torque on the motor 4 driving the vertical rolls, it will slow down beyond normal and the motor driving the horizontal rolls will assist the motor driving the vertical rolls in forcing the steel between them. This transfer of the load from one motor to the other and consequent change of speed of the .motor driving the vertical rolls will tend toprevent any buckling or stretching of the steel between the rolls.

If, under certain conditions which might arise in certain universal rolling mills, there is danger of the vertical rolling mill motor having such an excessive torque as to stretch or buckle the material, this tendency can be reduced to harmless proportions by providing the n1otor'2 driving the horizontal rolls with means for causing its speed to depend upon the load on motor 4 driving the vertical rolls, that is, causing the motor 2 to speed up when the load on motor 4 increases. I prefer to accomplish this by meansof a field windin on the horizontal rolls motor supplied with current proportional to the armaturecurrent of the motor driving the vertical rolls and connected difierentially with respect to the main field winding of the motor driving the horizontal rolls.

Referring to the drawing more in detail,

the fly-wheel motor generator set consists ofa separately excited generator 9, a fly-wheel 10 and induction motor 11. The induction motor is supplied with alternating currentfrom mains 12. An automatic rheostat or slip regulator 13 is arranged to cut resistance into or out of the rotor circuit of the motor 11, and consists of a slip regulating or torque motor 14 connected in series with the motor 11 and of a water rheostat 15, the plates of which are separated or brought together by the slight motion of the motor 14.

The exciter motor generator set 6 comprises an induction motor 16 driving a shunt wound exciter 17 and a series exciter 18. The shunt wound exciter 17 supplies current to the mains 19 to which are connected the field windings 20 and 21 of motors 2 and 4, through adjusting rheostats 22 and 23. The field winding of enerator 9 is also connected to the mains 19 through the reversing switch 8 and an adjusting rheostat 24.

The armaturesof motors 2 and 4 are connected in parallel with the armature of generator 9. The field winding of exciter 18 is connected in series with the armature of motor 4 so that the voltage generated by this exciter is directly proportional to the current flowing through the armature of motor 4, and consequently the load thereon. A field winding 25, which is cumulatively connected with respect to field winding 21, is connected to the armature of exciter 18 through the reversing switch 8 and an adjusting rheostat 26. Under certain conditions as explained above it may be deemed desirable to supply motor 2 with a field winding 27 connected differentially with respect to field winding 20. This winding 27 and an adjusting rheostat 28 are shown as connected in parallel with winding 25 and rheostat 26.

Since the voltage of exciter 18 is proportional to the load on motor 4, and since wind ing 25 on this motor is connected to the brushes of this exeiter so as to be cumulative with respect to winding. 21, motor 4 slows down upon an increase in the load on this motor. Since, winding 27 of motor 2 is also connected to the brushes of exciter 18 and so as to be difi'erential with respect to winding 20, the speed of motor 2 also depends upon the load on motor 4, but in such a way'as to increase with the load on motor 4 instead of decreasing.

I have shown the control switch 8 with four positions forward and fourreverse. WVhen the control switch is in any of the forward positions 1, 2', 3 or 4, connections are made so that motors 2 and 4 turn the rolls 1 and 3 in such a direction that steel, in order to be rolled, must enter the horizontal rolls first, When the control switch is in any of the reverse positions 1 2 3 or 4 the motors turn the rolls 1 and 3 in the opposite direction so that in order to roll the steel, it must enter the vertical rolls first. The system of control employed is that known as the Ward Leonard system. The exciter 17 supplies excitation to the generator 9, the armature of which supplies current to the motors 2 and 4. In order to control the speed of these motors resistance sections 29 are inserted by the switch 8 in series with the field windin of generator 9, and in order to reverse tiese motors the potential of generator 9 is reversed by reversing the connections of its field winding with the exciter 17 by the control switch 8.

As explained above, the field windings 20 and 21 of motors 2 and 4, respectively, are connected in parallel across the mains 19 supplied with current by exciter 17, and since motor 4 must drive the rolls 8 at a higher relative speed than the rolls 1 are driven when steel enters the horizontal rolls 1 first, a resistance 30, which is preferably adjustable, is arranged to be cut into the circuit of field winding 21. This resistance weakens the field of motor 4 when the switch 8 is in any of the forward positions, and thereby causes the motor 4 to revolve at a higher speed than motor 2. By making the rheostat 30 adjustable, the speed of motor 4 may be changed when the motors are running forward if desirable because (of a difference in the size, section or characteristic ofthe steel to be rolled. But when the steel enters the verticalrolls first, motor 4 must run slower than motor 2, and I therefore provide the switch 8 with a pair of contacts 31 for short-circuiting the resistance 30 during all of the reverse positions.

Since the field of exciter 18 is in series with the armature of motor 4, and since the motors are reversed by reversing the direction of the current in their armatures, it is necessary to reverse the connections between the armature of exciter 18 and the fieldwindings 25 and 27 whenthe motors 2 and 4 are reversed, in order that field winding 25 is always connected cumulatively with respect to field winding 21, whereby motor 4 slows down when the load thereon increases, and field winding 27 is always connected differentially with respect to field vindingQO, whereby motor 2 speeds up when the-loadlon motor 4 increases. The

connections between the armature of exciter 18 and field windings 25 and 27 are reversed through the lower four contacts of reversing switch 8 in the well known manner. Although I have described my invention in connection with a particular system of rolling mill drive, I desire it to be understood that it is not limited thereto, and may be used in-any system of reversing motor drive, and I aim in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

lVhat I claim as new and desire to secure by Letters Patent of the United States, is

1. In combination, a plurality of motors, means for causing the speed of one of said motors to depend upon the load thereon, means for reversing said motors, and means for causing said motors to .have different relative speeds when their direction of rotation is reversed.

2."In combination, a lurality of motors, means for causing one of said motors to slow down as the load thereon increases, means for reversing said motors, and means for causing said motors to have difl'erent relative speeds when-their direction of rotation is reversed.

In combination, a plurality of motors, means for causing the speed of one of said motors to depend upon the load thereon,

means for reversing said motors, and means for changing the field strength of one of said motors when its direction of rotation is reversed.

4. In combination, a plurality of motors, means for causing one of said motors to slow down as the load thereon increases, means for reversing said motors, and 'means for changing the field strength of one of said motors when its direction of rotation is re versed.

5. In combination, a plurality of motors, means for causing the speed of one of said motors to depend upon the load thereon,

.means for reversing said motors, aresistance, and means for cutting said resistance into the field circuit of one of said motors when its direction of rotation is reversed.

6. In combination, a plurality of motors, means for causing one of said motors to slow down as the load thereon increases, means for reversing said motors, a resistance, and

means for cutting said resistance into the field circuit'of one of said motorswhen its direction of rotation is reversed.

7. In combination, a plurality of motors, a. separately excited generator supplying the armatures thereof, means for energizing the field windings of said motors and generator, means for varying the field strength of said generator so as to vary the speeds of-said motors, means for causing the speed of one of said motors to depend upon the load thereon, means for reversing said motors, and means for causing said motors to have different relative speeds when their direction of rotation is reversed.

8. In combination, a plurality of motors,

a separately excited generator supplying the armatures thereof, means for energizing the field windings of said motors and generator, means for varying the field strength of said generator so as to vary the speeds of said motors, means for causing one of said motors to slow down as the load thereon increases, means for reversing said motors, and means for causing said motors to have different relative speeds when their dlrection of rotation is reversed.

9. In combination, a plurality of motors, a separately excited generator supplying the arn'iatures thereof, means for energizing the field windings of said motors and generator, means for varying the field strength of said generator so as to vary the speeds of said motors, means for causing the speed of one of said motors to depend upon the load thereon, means for reversing said motors, and means for changing the field strength of one of said motors when its direction of rotation is reversed.

10. In combination, a plurality of motors, a se iarately excited generator supplying the armatures thereof, means for energizing the field windings of said-motors and generator, means for varying the field strength of said generator so as to vary the speeds of said motors, means for causing one of said motors to slow down as the load thereon increases, means for reversing said motors, and means for changing the field strength of one of said motors when its direction of rotation is reversed.

11. In combination, a plurality of motors, a separately excited generator supplying the armatures thereof, means for energizing the field windings of said motors and generator,

means for varying the field strength of said generator so as to vary the speeds of said motors, means for causing one of said motors to slow down as the load thereon increases, means for reversing said motors, a resistance, and means for cutting said resistance into the field circuit of one of said motors when its direction of rotation is reversed.

13. In combination, two motors, means for causing the speed of one of said motors'to depend upon the load thereon, means for causing the speed of the other of said motors to depend upon the load on said first mentioned. motor, means for reversing said motors, and means for causing said motors to have different relative-speeds when their direct on of rotation is reversed.

14. In combination, two motors, means for causing oneof said motors to slow down as the load thereon increases, means for causing the other of sald motors to speed up as the load on said first mentioned motor increases,

means for reversing said motors, and means for causmg said motors to have dlfierent relative speeds when their direction of rotation is reversed.

15. In combination, two motors, means for causing the speed of one of said motors to depend upon the load thereon, means for causing the speed of the other of said motors to depend upon the load on said first mentioned motor, means for reversing said motors, and means for changing the field strength of one of said motors when its direction of rotation is reversed.

16. In combination, two motors, means for causing the speed of one of said motors, to

depend upon the load thereon, means ;for,

causing the speed of the other of saidmotors to depend upon the load on said first mentioned motor, means for reversing said motors, a resistance, and means for cutting said resistance into the field circuit of one 0t said 'motors when its direction of rotation is reversed.

17 In combination, two motors, means for causingioneof said motors to slow down as the load thereon increases, means forcau'sing the other of said motors to speed up 'as the load on said first mentioned mot-or 1ncreases, means for reversing said motors, and means for changin the field strength of one of said motors w on its direction of rotation is reversed.

18. In combination, two motors, means for causing one of said motors to slow down as the load thereon increases, means for causing the-other of said motors to. speed up as the load on said first mentioned motor increases, means for reversing said motors, a resistance, and means for cutting said resistance into the field circuit of one of said motors when its direction of rotation is re versed.

19. In combination, two motors, a separately excited enerator supplying ,the armatures thereo ,,means for energizing the field windings of said motors and generator I means for varying the field strength of said generator so as to vary the speeds ofsaid motors, means for causing one of said motors to slow down as the load thereon increases, means for causing the other of said motors to speed up as the load onsaid first mentioned motor increases, means for reversing said motors, and means for causing said motors to have different relative speeds when their direction of rotation is reversed.

20. In combination, two 'inotors, a separately excited enerator supplying the armatures thereo means 'for energizing the field windings of said motors algd generator, means for varying the field str ngth of said generator so as to vary the speeds of said motors, means for causing one of said motors to slow down as the load thereon increases, means for causing the other of said motors-to speed up as the load on said first mentioned motor increases, means for reversing said motors, and means for changing the field strength of one of said motors when its direction of rotation is reversed.

21. In combination, two motors, a separately excited generator supplying the armatures thereof, means for energlzlng the field windings of said motors and generator means forv varying thefield strength of sal generator so as to vary the speeds of said motors,' means for causing one of said motors to slow down as the load thereon in-, creases, means for causing the other of said motors to speed up as the load on said first mentloned motor increases, means for reversing said motors, a resistance, and means for cutting said resistance into the field circuit of one of said motors whenits direction of rotatlon is reversed.

22. In combination, two motors, aseparately excited generator supplying the armatures thereof, means for energizing the field windings of said motors and generator, means for varying the field strength of said gen rator so as to vary the speeds of said mo ors, means. for causing one of said mo tors to slow down as the load thereon increases, means for causing the other of said motors to speed up as the load on said first mentioned motor increases, means for reversing said motors, an adjustable resistance, and means for cutting said resistance into the field circuit of one of said motors when its direction of rotation is reversed.

23. In combination, a plurality of motors, means for causing the speed of one of said motors to depend upon the load thereon, means for reversing said motors, an adjustable resistance, and means for cutting said resistance into the field circuit of one of said motors when its direction of rotation is reversed.

24. In combination, a plurality of motors, means for'causing one of said motors to slow down as the load thereon increases, means for reversing said motors, an adjustable resistance, and means for cutting said resistance'into the field circuit of one of said motors whenv its direction of rotation is reversed.

25. In combination, a plurality of motors, a separately excited generator supplying the armatures thereof, means for energizing the field windings of said motors and generator, means for varying the field strength of said generator so as to vary the speeds of said motors, means for causing one of said motors to slow down as the load thereon increases, means'for reversing said motors, an'

adjustable resistance, and means for cutting said resistance into the field circuit of one of said motors when its direction of rotation is reversed.

26. In combination, two motors, means for causingone of said motors to slow down as the load thereon increases, means for causing the other of said motors to speed up as the load on said first mentioned motor increases, means for reversing said motors, an adjustable resistance, and means for cutting said resistance into the field circuit of one of said motors when its direction of rotation is reversed. v

27. In combination, a plurality of motors having main field windings, one of said motors having a second field winding connected accumulatively with respect to said main field winding and supplied with current proportional to the armature current thereof, means for reversing said motors, a resistance, and means for cutting said resistance into the main field circuit of one of said motors when its direction of rotation is re field winding and supplied with current proportional to the armature current thereof,

means for reversing said motors, an adjustable resistance, and means for cutting said resistance into the main field circuit of one of said motors when its direction of rotation is reversed.

29. In combination, a plurality of motors having main field windings, one of said motors having a second field winding connected accumulatively with respect to said main field winding and supplied with current proportional to the armature current thereof, a resistance, a control switch for reversing said motors and for cutting said resistance into the main field circuit of one of said motors when its direction of rotation is reversed.

30. In combination, a plurality of motors having main field windings, one of said motors having a second fieldwindin'g connected accumulatively with respect to said main field winding and supplied with current pro portional to the armature current thereof, an adjustable resistance, a control switch for resistance into the main field circuit of one of said motors when its direction of rotation is reversed.

31. In combination, two motors having main field windings, one of said motors having a second field winding connected-accumulatively with respect to its main field winding and supplied with current proportional to the armature current thereof, the other of said motors having a second field winding connected differentially with respect to its main field winding and supplied with current proportional to the armature current of said first mentioned motor, means for reversing said motors, a resistance, and means for cutting said resistance into the main field circuit of one of said motors when its direction of rotation is reversed.

32. In combination, two motors having main field windings, one of said motors having a second field winding connected accumulatively with respect to its main field winding and supplied with current proportional to the armature current thereof, the other of said motors having. a second field winding connected difierentially with respect to its main field winding and supplied with current proportional to the armature current of said first mentioned motor, means for reversing said motors, an adjustable resistance, and means for cutting said resist ance into the main field circuit of one of said motors when its direction of rotation is reversed. c

33. In combination, two motors having main field windings, one of said motors having a second field winding connected accumulatively with respect to its main field winding and supplied with current proportional to the armature current thereof, the

reversing said motors and for cutting said I other of said motors having a second field winding connected differentially with respect to its main field winding and supplied with current proportional to the armature current of said first mentioned motor, a resistance, and a control switch for reversing said motors and for cutting said resistance into the main field circuit of one of said motors when its directionof rotation is reversed.

34. In combination, two motors, having main field windings, one of said motors having a second field winding connected accumulatively with respect to its main field winding and supplied with current proportionalto the armature current thereof, the

other of said motors having a second field winding connected differentially with respect to its main field winding and supplied with current proportional to the armature current of said first mentioned motor, an adjustable resistance, and a control switch for reversing said motors and for cutting said resistance into the main field circuit of one of said motors when its direction of rotation is reversed. j In witness whereof, I- have hereunto set my hand this 28th day of August 1913.

KARL A. PAULY. Witnesses:

BENJAMIN B. HULL, MARGARET E. WOOLLEY.

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