US2124518A - Mill department control - Google Patents

Description

Fgj.

y 19383 F. MARQUART. 2,124,518

MILL DEPARTMENT CONTROL Filed. Jan. 2, 1956 2 Sheets-Sheet l bwentafl: FewA/K Mnecguqe July 19, 1938 F. MARQUART 2,124,513

MILL bEPAiRTMENT CONTRQL Filed Jan. 2, 1936 i- 2 Sheets-Sheet 2 Patented July 19.1938 V I UNITED STATES PATENT OFFICE MILL DEPARTMENT CONTROL Frank Marquart, Cleveland, Ohio, assignor to The American Steel and Wire Company of New Jersey, a corporation oi New Jersey Application January 2, 1986, Serial No. 57,300

I 2 Claims. (01. Bil-31.1)

This invention is concerned with the operation In addition, the department includes other elecoi continuous mills 01' the type which includesa trical equipment. Each of these small mills is plurality of tandem roll-stands each provided considered a unit and is of the type initially dewith an electric driving motor, when they are scribed. That is to say, each of these units in- 5 included as a group of two or more in a mill cludes a plurality of tandem roll-stands. Fur- 5 department, thermore, these mills are operated as units, each Such a mill may be used to reduce metal strip, working on separate lengths of strip. the strip passing from one roll-stand to anotherf It follows from the above that the Wardin succession. It is obvious that each successive Leonard system is not applicable as a medium roll-stand must be run at a slightly higher speed of control for these mills, since its use would 10 to compensate for the elongation of the metal entail the provision of a motor-generator set for strip, the motors powering these stands being each of the units or mills, and this would necescommonly providedwith controlling rheostats to sitate such a large outlay of money as to be an provide the required adjustments. The strip economic impossibility. Furthermore, the other must be manually threaded through the various electrical equipment, such as coilers, slitters, coil- 15 stands before rolling operations can commence. ing machines, craneaand other devices powered This requires the Operation ofthe ar ou S a d by electrical motors, must be provided with suitat speeds that are sufilciently slow to prevent able current and this would necessitate still an accidents. When the strip has once been threadother motor-generator set over and above those ed the speeds of all the roll-stands must be required for the various mills.

accelerated to normal rolling speeds which are Because of the above described conditions preconsiderably faster than the speeds required durvailing in oldmn a d th r il departing threading. Obviously this acceleration must ments, including relatively large numbers of elecbe accomplished so that the speed ratios between trlcally powered units, a single large motor-genthe various stands do not change. There are erator set is provided thatis of sumcient capacity 25 several ways of accomplishing what has just been to electrically power the entire department. It described, follows that the output of this motor-generator In the case of strip hot-mills which are so large set cannot be varied as demanded by the Wardas to constitute a complete mill department the Leonard system because this would not only con- 39 Ward-Leonard system is commonly used. In this trol the speed of one mill but would also affect system the power for the armatures and fields of all of the other mills and electrical equipment" the motors driving the various roll-stands is proincluded by the department. vided by a motor-generator set that receives its Since all the mills in such departments are power from some outside source. This is ecopowered by the same motor-generator set, it is 85 nomically practical because the demands of such necessary to provide some means for simultaa mill are so great. This motor-generator set neously varying the speeds of the motors of each does not supply power to any electrical equipment mill from threading to full rolling speeds withother than the mill motors. The speeds of the out afiecting the motors of the other mills. Herevarious motors are controlled by the individual tofore, this has been sometimes done by prorheostats with which they are equipped to effect viding a large heavy master rheostat for each 40 the compensation required by the elongation of of the mills. In each mill one of these master the work, and the speeds of all the motors may rheostats is in series with the shunt fields of the be simultaneously varied by varying the output motors of that mill and with the rheostats which of the motor-generator set, this being possible individually control the speeds of that mills because there is no other electrical equipment to motors. This works satisfactorily when all of 45 be aifected. This system is also used in the case the roll stands in each of the mills are utilized of the huge tandem cold-mills now used to produring rolling. However, it is frequently necesduce very wide metal strip. sary to use less than all of the stands included The above system is not suited for application by one of these mills. In such instances the to continuous mills such as areused, for instance, motors of some of the stands are disconnected, 50 to cold-roll narrow metal strip. This product is and this removes their individual rheostats from commonly produced in what is called the coldtheir normal series connection with their master rolling department of a mill. These mills are rheostat. naturally rather small, and a cold-rolling depart- Now, consequently, the settings for the threadment therefore includes a number of such mills. ing and iull rolling speeds of the master rheo- 55.

- stat are "no longer" the same, and accidents are very apt to occur-in that the rollers may forget to adjust the resistance of the master rheostat to maintain the correct operating speed of the mill.

Sometimes casualties are suffered bythe rollers, and it is even possible to put an entire mill out of operation. In spite of these defects this system now being described has been in common use in departments. of the character underdiscussion. g

The primary object of the present invention is,

to provide a control that is as tool-proof and Figure 1 includes three cold-rolling mills A, B-

and C. Also, it includes a slitter D. The mill A consists of five tandem roll-stands I, which are individually driven by electric motors 2 through the usual gear boxes 3. The mill is provided at one end with a coiler 4 that handles thework leaving the last stand inthe usual manner. The operating requirements of this mill have already been generally outlined.

The mill B includes only three roll-stands 5, each individually driven by electric motors 6 through gear boxes I. This mill is also provided with a coiler 8.

The'mill C is exactly like the mill B, the rollstands being numbered 9, the motors III and the gear boxes I l.

The slitter D is conventional and need not be described in detail excepting to mention that it is powered by an electric motor I 2.

All of these mills are units in themselves, and the slitter D is also a unit. Each of these units is entirely independent of the others and must be operated and controlled independently. For reasons already described the department is provided with a single large motor-generator set E whose motor I3 is powered by a source outside of the department and whose generator H is of sumcient capacity to provide the power required by all of the mills and by the slitter. No other arrangement is economically practical.

The application of the principles of the present invention to the cold-rolling department represented by Figure l is shown "by Figure 2. The

generator I of the motor-generator set E is connected to power lines l5. These power lines power the various units in the department that are illustrated by Figure l as well as the other electrical equipment necessarily included by such a department but which is not illustrated. I

It is to be understood that practically all of the motors used in such a department are intended for D. C. current and include shunt-field windings. mill of the type under discussion are compound 'wound since this provides for smoother rolling operations. Therefore, the wiring diagram shows all of the'motors as being compound wound.

In the case of the mill A the armatures and series- field windings 2 and 2 of all of the motors 2 are directly connected to the power lines ll.

Generally the motors of a continuous The shunt-fields 2 of these motors are provided with controlling rheostats 2' so that their strength can be varied. Before the present invention these shunt-fields were energized by the lines II through a master rheostat connected in series with all of the shunt fields, the shunt fields themselves being connected in parallel relative to each other and the only way of simultaneously varying thespeeds of all of the motors together was by means of that master rheostat. The disadvantages of this procedure have already been discussed. s

In the present instance, however, the shunt-' fields 2 are connected by lines l6 to a generator II that is part of a small motor-generator set whose motor I. .is connected through lines l9 to the lines l5 so as to receive power from the motor-generator set that powers the entire department. The generator i1 is provided'with a field winding Ilethat is energized by the lines I 9 through a rheostat ll This motor-generator' set just described is of approximately no greater capacity than is required to properly energize all.

of the shunt-field windings 2 of the motors 2.

In other words, it is a very small aflair as com-.

pared to the set powering the entire department and is consequently much'less expensive. Furthermore, it is to be noted that this motor-gener ator set is entirely independent of the set powering the entire department so far as the operation of the latter is concerned. That is to say, variations in the output of the generator I! cannot possibly afiect the output '0! the generator it.

If this were not so all of the other'electrical' equipment in the department would'be affected.

In the case of the mill B the armature and series-field windings 6 and 6 of the motor 6 are all directly energized by the generator I4 through the lines l5. This unit is likewise provided with a small motor-generator set whose generator 20 energizes the shunt-field windings 6 of the motor 6 through lines 2|, the shuntfield rheostats 6 of these motors 6 serving as controls. The motor 22 of this little motor generator-set is powered by the lines l5 through lines 23 and thefleld 20 of the generator of this set is energized by these lines 23 through a rheostat 20 The operation of these two mills will now. be described, it being kept in mind that they are two diil'erent units entirely independent of one another.

To'efiect threading of the mill A the rheostat I'l is adjusted so as to increase the strength of the field ll of the generator IT. This causes-the motors 2 to operate at sufiiciently slow speeds to permit manual threading of the various ro lstands of this mill. When this is completed the rheostats- 2 are, adjusted toobtain the proper speed ratios between the various motors powering the various stands so as to compensate for the elongation of the work. As soon as this is done the "rheostat ll is operated to decrease the field strength of the generator ll, whereupon the B are each provided with a suitable electrical control which permits these mills to be operatively independent of one another and which at the same time does not involve the great expense of the Ward-Leonard system. The motor-generator. sets consisting of the motors l8 and 22 and the generators l1 and 20 are sufilciently small to render the control economically practical. Upkeep is inexpensive and no electrical complications are involved.

Now in the case of the mill the armatures I0 and series-fields Iii of the various roll-stand motors in, are all directly connected to the power lines IS. The shunt-fields 1 and individual rheostats Iii of the various motors in, are connected to the power lines l5 through a master rheostat 24.

To operate the mill C it is necessary to adjust the rheostat 24 to obtain the slow speeds that permit threading, the rheostats Hi being adjusted to compensate for the elongation oi the work and the rheostat 25 then set to accelerate the mill. This provides for reasonably good operation so long as all three of the roll stands of the mill C are used. However, it is often desirable to use less than all of these roll stands, and it is then necessary to eliminate one of the motors Hi. This removes the rheostat ill of that motor and the motor itself from the circuit, and the settings of the rheostat 24 are then no longer an indication of the speed of the mill.

It is to be understood that the controller elements of these rheostats are marked to indicate threading and full rolling speeds, and are relied upon by the rollers during the operation of the mill. Therefore, unless a suitable additional resistance is put into the circuit by means of the master rheostat to take the place of the omitted equipment, the rollers cannot properly operate the mill. As previously mentioned, it frequently happens that carelessness in this respect leads to serious accidents. 7

The armature I2 series-field l2 and shuntfield ii of the slitters motor l2 are shown as being connected to the power lines i 5 in the usual manner. trate the fact that the'cold-rolling department not only includes anumber of mills but also other-electrical equipment.

The mill C is included partly to emphasize the fact that the department includes a number of unit mills and partly to illustrate the deficiencies of the old arrangement. The outputs of the little motor-generator sets that are used to energize the shunt-windings of their motors are relatively constant regardless of the number of shunt-fields energized so long as the outputs of these sets are sufiicient to properly energize all of the shunt fields of the motors in each instance.

Although the various units have been described as being connected directly to the power lines IE, it is to be appreciated that the branches of these power lines leading to these units do not necessarily have the carrying capacity of the power This motor is included simply to illus-' lines themselves, since the latter must carry power to all of the electrical equipment of th entire department.

In spite of the advanced state of the electrical control art there is no instance known to the pres ent inventor .where a plurality of motors which must be speeded or slowed in unison have been controlled by means of a small motor-generator set which energizes the shunt-fields of these motors and which is entirely independent of the main power source which powers the armature circuits of the motors. So far asis known, the Ward-Leonard system is the only fool-proof control, while the rheostat control illustrated in the case of the mill 0 is the only control sufficiently inexpensive to be used in a cold-rolling or similar department. As a matter of fact, the average control used in conjunction with a small mill unit having tandem roll-stands consists simply of the rheostats which control the shunt-fields of these motors, no master rheostat being used because of the dangers involved. Hence a length of strip is .frequently almost completely rolled before the shunt-field rheostats can be juggled to positions which provide for full rolling speeds and at the same time compensate for the elongation of the work. A

There are, of course, variations of the Ward- Leonard system which include a motor-generator set that powers the armature circuits of a series of mills and which is provided with a field exciting motor-generator set which is relatively small and which in some instances energizes the shuntfields of the motors. This cannot be used in a cold-rolling department for the reason that any variation in the output of the exciting motor-gen erator set not only varies the shunt-fields of the motors but varies the field of the generator of the motor-generator set that is powering the entire mill. This obviously varies the output of the motor-generator set, and if this set were used to power an entire cold-rolling department, which is the only economically possible arrangement, all of the other electrical equipment of the department would be afiected and the entire department thrown into confusion.

I claim:

1. In a mill department, a continuous mill including a plurality of tandem roll-stands each provided with an electric driving motor having a shunt-field winding, other electrical equipment operatively independent of. said mill and said motors, a motor-generatorsetofsufhcientcapacity to electrically power said motors and said other equipment, power lines arranged to carry the output of said motor-generator set to the armature windings of said motors and to said other electrical equipment that is operatively independent of said motors, whereby variations in the output of said motor-generator set will affect said motors and said other electrical equipment as well, a motor-generator set of approximately no greater capacity than is required to properly energize the said shunt-fleldwindings. of said motors, means for electrically connecting the motor of the second named motor-generator set to said power lines, said second named motor-generator set being otherwise entirely independent of the first named motor-generator set, electric lines arranged to carry the output of said second named motor-generator set to said shunt-field windings o1. said'motors, variable resistances arranged in said lines so as to individually control the energizingcurrent supplied each of said shunt-field windings of said motors, and means ior varying the output of said second named motor-generator set,.whereby the speeds of said motors may be simultaneously varied without substantially aiiecting their respective speed ratios and without materially aflecting said other electrical equipment or said first named motorgenerator set.

2. A method of controlling the speeds of a plurality oi. tandem roll-stands driven by electric motors having shunt-field windings and powered by a source that also powers other electrical equipment whereby its output cannot be varied without afl'ecting the latter. said shunt-field windings being each provided with variable reangers sistances, said method including powering the armaturea oi said motor directly by said source. energizing said shunt-field windings through said resistances by means 01 a second source whose output maybe varied without materially aflecting the output of the first named source, varying said resistances to obtain the speed ratios between said motors required for the proper operation ofv said roll-stands and varying the output 01' said secondsource as required to cause said motors to drive said roll-stands at slow or threading speeds and to subsequently accelerate so as to drive said roll-stands at fast or rolling speeds.-

' MARQUART.

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