US2399351A - Control system - Google Patents

Description

p i 30, 19 6. J. P. HOUCK Em 2,399,351

CONTROL SYSTEM Filed April 21, 1945 3 Sheets-Sheet 1 WITNESSES: INVENTORS April 30, 1946.

J. P, HoucK ETAL CONTROL SYSTEM 3 Sheets-Sheet 2' Filed April 21, 1945 WITNESSES: 54% J E Z 5 m WWW M T6. ZN mL/ V .0 m ma m .2 WW JP April 30, 1946. J H U K ET AL 2,399,351

CONTROL SYSTEM Filed April 21, 1945 3 Sheets-Sheet 3 5'0 fec fire Der/ c6 Loz L l L96 390 INVENTO R5 ,famaPf/oucx and Fer/,6? 566/36/0700,

Patented Apr. 30, 1946 James P. Bond: and Ralph A. Geiselman, Pltts-' burgh,'Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 21, 1945, Serial No. 589,664

13 Claims.

This invention relates to control systems and in particular to control systems utilized in conjunction with are furnace regulators.

Heretofore, it has been common practice to supply are furnaces through a power transformer disposed to be connected through a cir cult breaker to a source of powersupply. The

operators of the arc furnaces are not always skilled in the operation of the switching equipment and numerous breaker failures have been encountered because of the improper operation of the breaker. For example, when a short. circuit isencountered as by reason of one or more of the electrodes being in contact withthe furnace charge, the operator often tries to reclose the circuit breaker before the short circuited electrode is raised to a position to clear the charge. If the breaker is repeatedly closed against the fault, fiashover within the breaker housing is encountered and the breaker is damaged.

An object of this invention is to provide in a control system for arc furnaces for regulating the feeding of an electrode and to control the operation of a circuit breaker to prevent its re closing for the duration of a fault.

Another object of this invention is to provide for controlling the operation of a circuit breaker in the supply circuit to an arc furnace to prevent the reclosing of the circuit breaker unless the furnace is free of short circuit faults.

A more specific object of this invention is to provide a system and apparatus for preventing the operation of a circuit breaker in the-supply circuit to an arc furnace to prevent the reclosing of the circuit breaker unless the furnace is free of short circuit faults and to insure the raising of the electrode in the furnace to clear the fault.

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

Figures 1A and 13 form a composite drawing illustrating diagrammatically the circuits and apparatus utilized in an embodiment of this invention;

Fig. 2 is a diagrammatic illustration of limit switches employed in conjunction with the circuits of Figs. 1A and 1B, and

Fig. 3 is a diagrammatic illustration of the circuits and apparatus embodying the teachings of this invention as applied to an arc furnace having a diiferent regulating system than the embodiment of Figs. 1A and 13.

Referring to Figs. 1A and 1B of the drawings,

' negative symbols.

an electric furnace I0 is illustrated, the furnace comprising a receptacle l2 containing a charge I4 and three movable electrodes l6, l8 and 29. The electrodes l6, I8 and 20 are connected by conductors 22, 24 and 26, respectively, to the sec ondary windings ofa power transformer 28, the primary windings of which are disposed to be connected through the'contact members 30, 32 and 34 of a circuit breaker 36 to a source of power supply (not shown). As illustrated flexible cables 38, 40 and connected to electrodes [6, l8 and 20, respectively, are disposed to be wound on winding drums 44, 46 and 48, respectively, which are disposed to be operated by motors 50, 52 and 54, respectively.

The motors 5|], 52 and 54 comprise armature members 56, 58 and 60, respectively, and field windings 62, 64 and 66, respectively, the field winding of each motor being connected to an energizing source represented by the positive and In order to supply energy to the armature windings 56, 58 and 60, the armature windings are connected across the armature windings 68, 10 and 12, respectively, of main generators l4, l6 and 18, respectively. The main generators l4, l6 and 18 are provided withfield windings 80, 82 and 84, respectively, which are connected to be supplied with energy from armature windings 86, 88 and 90, respectively, of exciter generators 92, 94 and 96, respectively. Each of the main generators and its associated exciter generator is disposed to be driven by a motor in accordance with well known practice, the motors not being shown for simplicityof the drawings.

In the embodiment illustrated, each of the exciter generators 92, 94 and 96 is illustrated as having four field windings although other forms of the exciter generators or combination of main generator and exciter generator may be utilized as long as the exciter is provided with two opposed control field windings as will be described. The exciter generator 92 is provided with two opposed control field windings 98 and Hill, a self- ,excited field winding I02 connected in shunt relation to the armature winding 86 and a differential field winding I04 connected to be energized in accordance with the output voltage of the main generator 14.

Likewise, the exciter generator 94 is provided with two opposed control field windings 'IOBand I08, a self-excited field winding H0 and a differential field winding H2 and the exciter generator 96 is provided with two opposed control field windings H4 and H5, a self-excited winding H8 and a differential field winding I20.

The control field windings 93, I26 and H4 are shown connected across rectifiers I22, I24 and I26, respectively, to b supplied therefrom with a unidirectional cur .znt that is a measure of the alternating current flowing through phase conductors 22, 24 and 2 5, respectively, in a manner hereinafter described, Whereas the control field windings I39, I98 and IIS are connected across rectifiers I23, I30 and I32, respectively, which are disposed to be connected to supply energy that is a measure of the drop in voltage across the arc of electrodes I5, I 8 and 20, respectively.

In the system of Figs. 1A and 1B the connections to the rectifiers I22, I24 and I231: and to rectifiers I23, I36 and I32 are ccntrolledin a predetermined manner by the operation of one or more switching apparatus such as the electromagnetic switching device I34, the master controller I36, the independent phase manual controllers. I38, I43 and I42 and the circuit break er 36.

As illustrated, the master controller I33 may be employed for so controlling the excitation of exciter generators S2, 94 and 93 as to effect-a simultaneous change in the operation or the electrode motor as to simultaneously raise or lower the electrodes 56, I8 and 29, respectively, depending upon the direction in which thecontroller I36 is manually actuated. The master controller I36 is provided with segments MIL-I46, HIE-459 and I52-I54 disposed in the off position for connecting the control field windings of exciter generators 92, 94 and 96 respectively, to sources of energy, and segments I56--I5B- -I69, I62- I64I66, and I38--IIIl-II2 disposed in the raise position associated with generators 92, 94 and 96-, respectively, and segments II4--IIG I18, I8D-I82I84 and IS6I88I9Il-, respectively, disposed in the lower position. In addition to these segments, a segment I92 is also provided in the off position, the purpose of which will become apparent hereinafter.

The controllers I38, I40 and I42 are similar in construction. The controller. I42 comprises a drum I94 disposed for predetermined rotational and slidable movement whereby segments I96- I98 or segments 239-292-2Il4 areselectively moved to raise or lower or to 0ff" or automatic positions. In the'position shown, the controller I42 is in the automatic positionwith the segments of the drum out of alignment withthe pairs of. contact fingers. which they will bridge in the raise or lower positions. In the automatic position, three contact members 296, 238 and 2H engage contact fingers whereby control of the energization of the control field windings H4 and H6 lies in the operation of the electromagnetic switching device I34, the circuit breaker 36'and the master controller I36.

With the handle 2I2 of the controller I42 in the automatic position, a finger 2I4 carried by the shaft 2I6 is positively held by opposed springs on one side of an arcuate stop plate 2I8 to maintain a spring member 220 compressed between the drum I94 and a stop 222. The arcuate stop plate ZIB is provided with a notch 224 50 positioned that When the handle 2I2 is manually moved to the off position, the finger 2I4 is movedto a position where it is in alignment with the notch 224 and passes therethrough to the other side of the arcuate stop member 2 I8 and the force of the spring 220 eiTects a sliding movement of the drum 94 and segments thereon to a position where the segments can bridge associated pairs of contact fingers when the handle 2I2 is rotated to the "raise or lower positions. The segments 225, 228, 233, 232 and 234 of controller I40 and segments 236, 238, 243, 242 and 244 of controller I38 correspond to segments I96, I98, 293, 232 and 234, respectively, of controller I42, controller I46 also being provided with contact members 243, 243 and 253 and controller I38 with contact members 252, 254 andI256 corresponding to contact members 2B6, 20B and 2H3, respectively, of controller I42.

In order to control the operation of the circuit breaker 36, a relay system comprising the relays 253, 263 and 232 and the electromagnetic switching device I34 is utilized. The relay 253 issprovided with awindin 234 grounded at one end as at340' and connected across the secondary windin ofatransformer 236 the primary winding of which is disposed to be connected through a switch 238 to a source of supply. When energized the contact member 279 oi. the relay 258 is disposed to connect the energizing winding 212 of the switching device I34 across a source of supply represented by the positive and. negative symbols. The electromagnetic switching device I34 is provided with a contact member 2'54 disposed when a manually operated switch 213 is in a circuit closing position and the winding 272 is energized to establish a circuit extending from the positive terminal of a source of supply. (not shown) through the switch 213, contact member 214 of the device I34, contact member 278 of relay 233 and the energizing winding 28?! of relay 262 to the negative terminal of the source of electrical energy to actuate the contact member 282 of relay 232 to a circuit closing position. The contact member 282 thus establishes a circuit through the winding 284 of a circuit breaker to effect the operation of the circuit breaker to cause the ings of the different exciter generators.

contactim'embers 3'9, 32 and 34 of the breaker 36 to connect the power transformer 28 to the source of power supply.

The electromagnetic switching device 534 is provided with a number of corresponding contact members for controlling the circuits to the rectifiers supplying the opposed control field wind- Thus contact' membersZSB, 233 and 23D aredisposed to be in open circuit position when the winding 2'12 is deenergized to interrupt the circuit to rectifiers I28, I30 and I32, respectively. Contact members 292-294, 295-233, and 333-392 associated with rectifiers I22, I 24 and 25, respectively, are also disposed to be in the open circuit position when the electromagnetic switching device I3'4 is deenergized whereas contact members 304-433, 3il83|0 and 3I23I4, respectively, are in circuit closing position with respect to their associated rectifiers I22, I24 and I26, respectively.

Again referring to the circuit breaker 33, the breaker is provided with contact members 313, 3 I8, 320, 322 and 324 disposed in a circuit opening position and a contact member 325 disposed in a circuit closing position when the main contact members 39, 32 and 34 of the breaker 39 are in a circuit opening position.

The contact member 3I6 functions when the circuit breaker 36 is in a circuit closing position to connect one end of the energizin winding 329 of an electro-magnetic trip device 339 to a terminal of a source of electrical energy, the other end of winding 328 being disposed to be connected through a trip switch 332 to the other terminal of the source of electrical energy.

As illustrated, the circuit breaker 36 carries a lug 334 disposed to move upwardly as the circuit breaker closes to slide beyond a latch 336 carried by the trip device 338 whereby the latch 336 engages the lug 334 to hold the breaker in a circuit closing position untilithe winding 328 is energized to release the latch and consequently the circuit breaker.

The contact member 3 I8 carried by the breaker 36 is disposed to close an energizing circuit throughthe energizing winding of relay 268 when the switch 216 is in a circuit closing position and the circuit breaker 36 is actuated to its circuit closing position wherebycontact member 218 is disposed in a circuit closing position when the breaker 36 is in an open circuit position to establish a circuit extending from one end of the winding 264 of relay 258 to conductor 24 whereby the winding 264 is effectively deenergized when a short circuit of any one of the electrodes I6, I8 and 28 in the furnace is encountered. This is apparent for if one end of winding 264 is'grounded as at 338, the other end will be grounded through contact member 326, conductor 24, through the secondarywindings of the transformer 28, con- 1 ductor 22 or 26, electrode [6 or I8 and the grounded furnace or directly through conductor 24 and electrode l8 to the grounded furnace depending upon which of the electrodes is short circuited. 01' course, if a short circuit condition does i not exist in the furnace, the winding 264 will not be deenergized when the contact member 326 is in a circuit closing position unless the switch 268 is moved to a circuit opening position to deenergize the transformer 266.

In addition to the trip switch 332, the electromagnetic trip device 338 is disposed to be energized and operated by an overload condition in the furnace I8. For this purpose, an overload protective device 348 is provided, being connected through current transformers 342, 344 and 346 associated with conductors 22, 24 and 26, respectively, and having a contact member 348 disposed upon the occurrence of a predetermined overload condition such as the flow of a predetermined current in any one of the conductors 22, 24 and 26, to be actuated to a circuit closing position to establish an energizing circuit for the winding 328 to trip the circuit breaker 36.

With the circuit breaker 36, the electromagnetic switching device I34, the master controller I36 and the individual controllers I38, I48 and I42 as described, therectifiers I22, I24 and I26 are disposed to be connected to be supplied from the current transformers 358, 352 and 354, respectively, associated with conductors 2 2, 24 and 26, respeci tively, whereas the rectifiers I28, I38 and I32 are source of electrical energy to cause the operation of the electrode motors to raise the electrodes.

' In order to provide for limiting the amount of movement of the electrodes in the raise and lower directions, suitable limit switches may be disposed to be operated by the movement of the electrodes to interrupt the circuits to the rectifiers associated with the opposed control fields of the respective exciter generators or to interrupt the field circuit itself. As an example of the use of limit switches, reference may be had to Fig. 2 of the drawings whereinlimit- switches 356 and 358 are disposed to be operated by a projection 368 carried by electrode 28 to interrupt the circuits to fieldwindings H4 and H6, respectively, depending upon the direction of movement of the electrode 28. Similar limit switches (not shown) are provided for electrodes I6 and I8, it being understood that such limit switches are employed in conjunction withthe circuitof Figs. 1A and 1B but are not shown thereon in order to simplify the drawings. V

In operation, with the circuits and apparatus asshown, the switch 268 is moved to a circuit closing position to supply power to transformer 266, whereby the winding 264 of the relay 258 is energized to actuate the contact member 218to a circuit closing position. The contact member 218 establishes an energizing circuit for the winding .232 'of electromagnetic switching device I34 whereby contact members 214, 286, 282, 284, 288, 296, 298, 298, 388 and 382 of the switching device I34 are actuated to circuit closing positions and the contact members 384, 386, 388, 3I8, 3I2 and 3I4 of the switching device I34 are actuated to circuit opening positions.

The movement of the contact member 214 of the switching device I34 sets up an energizing circuit for the winding 288 of relay 262 which may be established by the manual operation of the switch 216 to a circuit closing position. With the winding 280 of relay 262 thus energized, the contact member 282 of relay 262 is actuated to a circuit closing position to establish the energizing circuit for the winding 284 of circuit breaker 36, whereby the contact members 38, 32, 34, 3I6, M8, 328, 322 and 324 of the circuit breaker are actuated to circuit closing positions and the contact member 326 is actuated to a circuit opening position.

As the circuit breaker 36 moves to the circuit closing position for the contact members 38, 32 and 34', the lug 334 carried by the circuit breaker slides over the latch 336 of the trip device 338 and is engaged thereby to hold the circuit breaker 36 in circuit closing position until the winding 328 of th trip device 338 is energized to effect the tripping of the breaker.

The electrodes I6, I8 and 28 are lowered toward the charge l4 in the furnace I8 by moving the master controller I36 to the lower position where segments I14, I16, I18, I88, I82, I84, I86,

.I88 and I98 are in engaging relation with cooperating contact fingers whereby circuits are established from separate sources of electrical energ represented by the positive and negative symbols associated with each set of segments through rectifiers I28, I38 and I32 to effect the energization of the control field windings I 88, I88 and I I6, respectively. With control field windings I88, I88 and H6 energized in this manner the exciter generators 92, 94 and 86, respectively, are so excited as to control the excitation of the main generators 14, 16 and 18, respectively, to effect the operation ofthe electrode motors 58, 52 and 54,

respectively, tothe lower ofthe electrodes I6, I8 and-28 respectively. These circuits may be. traced from the positive symbol shown below each of the controllers I38, I48 andv I42 through segments I18, I84 and- I98-of the master controller I36 to a terminal of the rectifiers I28, I38 and I 32,.respectively, from the opposite terminal of the rectifiers through contact members 286, 288 and 298, respectively, or the electromagnetic switching device I34, segments I15, I82and I88, respectively, of the master controller I36 to the negative terminals of the. separate sources of supply.

The motors 58, 52 and 54 are thus operated to lower the electrodes. I8, I8 and 28, respectively, until an arc is established, at which time the master controller I36 is returned to its oil posi tion and the. opposed control field windings of the exciter generators 92, 94 and. 96, respectively, assume the automatic regulation of the positioning of the electrodes I6, I8 and 28.

Under the conditions of automatic operation, the field windings I88, I88 and II 6 are supplied by the rectifiers I28, I38 and I32, respectively, these rectificrs being connected by circuits which extend from conductors 22, 24 and 26, respectively, through contact members 324, 322 and 328, respectively, of the breaker 35, contact members 252, 246 and 286, respectively, of the controllers I38, I48 and I42, respectively, segments I44, I 48 and I52, respectively, of the master controller I35, contact members 286, 288 and 298, respectively, of the electromagnetic device I34 through the rectifiers I28, I38 and I32, respectively, contact members 254, 248'and 288, respectively, of the individual controllers to the common segment I92 of master controller I and from thence t ground.

At the same time, the control field windings 88, I88 and H4 of the exciter generators 92, 84 and 86. respectively, are supplied from rectifiers I22, I24 and I26, respectively, which are connected in circuits extending from the current transformers 358, 352 and 354 through contact members 256, 258 and 2I8, respectively, of the controllers I38, I48 and I42, respectively, segments I46, I58 and I54, respectively, of the master controller I38, contactmembers 284, 298 and 382, respectively, of the electromagnetic switching device I34, through the rectifiers I22,.I24 and I26, respectively, contact members 292, 286 and 388, respectively, of the switching device I34, contact members 254, 248 and 288, respectively, of the controllers I 38, I48 and'l42, respectively, to the common segment I82 of the master controller I35 and from thence to ground, whereby the field windings 98, I88 and II4 are energized in accordance with a measure of the current flowing in the conductors 22, 24 and 28, respectively.

With the electrodes I5, I8 and 28 properly positioned in the furnace I8, the are potential and arc currents are properly balanced so that the opposed. control field windings 98--I88, I86-I88 and I I4I l8 ar in balance and the motors 58, 52 and 54, respectively, are not operated. An tendency toward unbalanced relation between the arc current and are potential immediately causes a change in the excitation of the exciter generators to effect immediate operation of the electrode motors to position the electrodes associated therewith so as to maintain an are having a predetermined are potential and are current.

If, during the operation of the arc furnace, one or more of the electrodes should become short circuitedas by reason of a cave-in of the charge I4 against oneormore of the electrodes, the increase in current flowing through the conductor 22, 24 or 26 supplying the electrode thus short circuited effects operation of the protective device 348150 actuate the contact member 348 to a circuit closing position to effect the energization of the winding 328 of the trip device 338 torelease the circuit breaker 38 and'interrupt the supply of power to the power transformer 38. The movement of the circuit breaker 36 to the open circuit position for interrupting the power supply causes the contact member 328 to move to a circuit closing position to close a circuit from the ungrounded end of winding 264 of the relay 258 through the contact member 326 to conductor 24 and from thence to ground through the short circuited electrode and the grounded receptacle I2.

The closing of the ground circuit by the contact member 326 effectively shunts the winding 264 of relay 258 whereby the winding is deenergized and the contact member 2'78 moves to a circuit opening position to effect the deenergization of the winding 272 of the electromagnetic switching device I34. With the switchingdevioe I34 ius deenergized, contact members 214', 285, 292, 28 i, 288, 86, 288, 288, 388 and 882 move to a circuit opening position and contact members 384, 388, 388, 3I8, 3I2 and 3I4 of the switchin device 34 move to a circuit closing position whereby the rectifiers I22, I24 and I26 are supplied from a separate source of electrical energy. The circuits supplying the rectifier-s I22, I24 and 428 under such conditions may be traced from the positive terminals of the separate sources of supply indicated adjacent the individual controllers through contact members 386, 3I8 and 3I4, respectively, of the switching device I34, rectifiers I22, I24 and I28, respectively, contact members 384, 388 and 3I2, respectively, of the switch ing, device I34 to the negative terminals of the separate source of supply. With the rectifiers supplied in this manner, the control field windings 98', I86 and H4 of the exciter generators 92, 84 and 86, respectively, are so energized that the output of the exciter generators effects the excitation of the main generators 74, I8 and I8, respectively, to cause an operation of the motors 58, 52 and 54, respectively, to raise the electrodes I6, I8 and 28, respectively.

As shown in Fig. 2 of the drawings, unless some other condition changes the operation of the motors 58, 52 and 54 the limit switches are operated before the movement of the electrodes'causes damage to the furnace and system. For example the lug 368 carried by the electrode 28 engages the trip switch 356 to interrupt the circuit to the field winding II4 to prevent operation of the motor 54 so as to prevent the raising of the electrode 28 beyond a predetermined limit. Although not shown, similar limit switches are provided to control the positioning of the electrodes I6 and I8.

It is to be noted that as the contact members 324, 322 and 328 of the circuit breaker 36 and contact members 288, 288 and 288, respectively, of the switching device I34 are in open circuit position they prevent energization of the field windings I88, I88 and H6, respectively, when a short circuit condition for the electrodes I6, I8 and 28, respectively, is encountered.

As soon as the short circuit condition clears, even though the circuit breaker is in its-circuit opening position where the contact member 328 connects the ungrounded end of the winding 284 of relay 258 to conductor 24, the winding 264 is again energized to cause the contact member 210 to establish the energizing circuit for the winding 212 of the electromagnet switching device I34. Under such conditions, the'contact members 324, 322 and 320 of the circuit breaker- 36 being in an open circuit position prevents the energization of the field windings I00, I B'and II6 byany-fiow of current from the transformer the individual electrodes I6, I8 and 20, the same may be accomplished by'o'perating the associated individual controller I38, I and I42, respectively. For example, if it is desired to raise electrode 20, while maintaining automatic operation or control of thepositioning of the electrodes I6 or I8, the handle 2 I2 of individual controller I42 is moved from, the automatic position to the off position where the finger 2 I 4 passes through the notch 224 in the arcuate stop member 2I8 and the drum I94 slides under the influence of the spring 220 to a position where the segments carried by the drum I94 are in alignment with the cooperating contact fingers, The handle 2I2 is then turned to the raise position where the segments 200, 202 and 204 engage cooperating contact fingers. In this position the segment 200 establishes a circuit from the current transformer 354 through the segment 200 directly to ground, thereby preventing an open circuit from the normal supply for the rectifier I26. time the segments 202 and 204 cooperateto establish a circuit extending from the positive terminal of the separate source of supply through segment 204 of controller I42, contact member 302 of the switching device I34, rectifier I26, contact member 300 of the switching device I34, segment 202 of the controller I42 to the negative terminal of the separate'source of supply.

If instead of raising the electrode it is desired to lower the electrode 20, the handle 2I2 is turned to the lower position where the segments I96 and I98 engage cooperating pairs of contact fingers to establish a circuit extending from the positive terminal of the separate source of supply At the same i through the segment I98, rectifier I32, contact 1 tor 64 is a. reversible motor having an armature winding and a separately excited'fleld winding 66, In order to control thedirection of operation' of the motor 54, a pair of contactors 362 and 364jare employed for. so changing the fiow'of current'in themotor armature. as to'cause it to operate in the raise and lower directions respectively; The contactors 362 and 364 are provided with contact members 366 and 368, respectively, disposed'for movement to predetermined circuit making positions depending upon the energizationof the { contactor windings 310 and 312, respectively. a

As illustrated, one end of the contactor winding 310 is disposed to be connected through a limit switch 356 to a terminal represented by the negative symbol ofa separate source of supply and one end of'the contactor winding 364 is disposed tobeconnected through a limit switch 358 to the same terminal, the other ends of windings 31.0 and 312 being disposed to be selectively connected through contact member 314 of a balanced beam regulator 316 to the other terminal, represented bythe'positive symbol, of the separate source of supply when the controllers I 36 and I 42 are in the position shown. j The regulator 316'is of a type well known having two energizing windings 318 and 380 connected to be responsive to the are potential and the current flowing through the electrode 20, respectively, so that when the windings are energized and the magnetic pulls are balanced the contact member 314isin an intermediate position as shown. Each of the motors and regulators therefore represented by the blocks 382 and 384' for electrodes I6 and l8,'respectively, are the same as the apparatus enclosedin the block 386 for the electrodes 20 and therefore need not be further described.

' The controllers I38, I40 and I42 are similar having segments 388, 390iand 392 in the lower, off and raise positions, respectively, whereas the master controller I36 has three sets of corresponding segments composed of segments 394, 396 and398 in the lower,, "01? and raise positio'ns,'respectively, each set being associated with the regulating apparatus for one of the electrodes. In ,this embodiment; the electromagnetic switching device I34 is similar to that in the embodimentshown and described with respect to ,Figs. ,1A. and 1B in that it has contact member 214 disposed for setting up the energizing circuit for the relay 262 and consequently for the circuit eration of the motor I54 to effect the lowering of the electrode 20. The operation of the controller I42 can be duplicated for either controller I38 or I40 where it is desired to effect independent positioning of the electrodes I6 and I8, respecvice I34, master controller I36 and individual con trollers I38, I40 and I42 being modified somewhat in accordance with the changes in the regulator and circuits required therefor.

g In the embodiment of Fig. 3. the electrode'rnog breaker 36. However, in this embodiment, the

electromagnetic switching. device has three sets of pairs of contact members 400 and 402 for cooperating in establishing predetermined circuits in conjunction with the master controller I36 and the independent controllers I38, I 40 and I42.

Since'theregulators employed for controlling the operation of the electrode motors in this embodiment are different from those illustrated in Figs.

1A and 1B, the circuit breaker 36 utilized in this embodiment isdevoid of the contact members 320,

322 and 324 utilized in the previous embodiment.

The operation of the embodiment of the inven- 'tion illustrated in Fig.3 is somewhat similar to that ofthe. embodiment of the invention shown lin..Fig s., 1A and 1B in that the closing of the switch 266 establishes the energizing circuit for the relay 258, the contact member 210 of which establishes the energizing circuit for the winding 212 of the electromagnetic switching device I34. When thus energized, contact members 214 and 400 of the switching device I34 are actuated to circuit closingpositions and the contact memhers 462 of the switching device I34 are actuated to circuit opening positions. The movement of the contact member 214 .sets up the circuit which may be closed by manual operation of the switch 216 and extends through the contact member 216 of relay 266 and the energizing winding 286 of relay 262 whereby the contact member 282 closes the energizing circuit for the winding 284 of the circuit breaker 36. When thus energized, the circuit breaker 36 moves to a circuit closing position where its contact members 36, 32, 34 and 318 are in the circuit closing position and the contact member 328 is in a circuit opening position. As in the previous embodiment, when the circuit breaker 36 is thus actuated to close the circuit for supplying power to the power transformer 28, the latch 336 of the latching device 336 engages the lug 334 to maintain the circuit breaker in its circuit closing position until the winding 328 of the latching device'is energized in a predetermined manner.

With power supplied to the power transformer 23 in the manner described, the electrodes l6, I8 and 26 may be lowered to engage the charge I4 in the furnace I6 and to establish an are by a movement or the master controller I36 to the lower position where segment 394 engages cooperating contact fingersand a circuit for each of the regulators, described hereinafter with respect to only regulator 316, is closed extending from the positive terminal of a separate source of supply through contact member 1460 of the switching device I34, segment 394 of the. master controller I36, winding 312 of the contactor 364, limit switch 358 to the negative terminal of the constant source of supply. By establishing this circuit the winding 312 is so energized that the contact member 368 of the contactor 364 is actuated upwardly to a circuit closing position. The circuit thus established extends'from the positive terminal of a separate source of supply through the contact member 368, armature member 66 of the motor 54 and contact member'366 of the contactor 362 to the negative terminal of the separate source of supply, whereby the motor 54 is operated to eifect a lowering of the electrode 26. Simultaneous positioning of the electrodes I6 and I8 is obtained by the operation of the motors and regulators in the blocks 382 and 384 through the circuits established bythe associated seg-- ments 394 of the mastercontrollerI36. As soon as the arc is established, the master controller 436 is returned to its neutral position, whereby automatic operation of the electrode motor associated with each electrode is obtained in response to variations in the arc potential and are current.

For example, if the arc current should increase, the current flowing through the current transformer 356 so energizes the winding 386 of the regulator 316 as to overcome the balance or pull of the winding 318 and cause the contact memher 314 to move to a circuit closing position. The movement of contact member 314 establishes a circuit extending from the positive terminal of a separate source of electrical energy through the segment 396 of master controller I36, segment 396 of controller I42, contact member 314, winding 316 Of contactor 362, and limit switch 356 to the negative terminal of the separate source of supply whereby the winding 316 is so energized as to effect a movement of the contact member 365 upwardly to a circuit closing position. By establishing-the circuit which exends from the positive terminal of the separate source of supply through the contact member 386, armature member 68 of the motor '54 and contact member 368 to the negative terminal of the source of supply, the motor 54 is operated to raise the electrode 26.

If the flow of current in the conductor'26 is large as, for example, where a short circuit is encountered, the current transformer 346 is so energized as to efiect an operation of the protective device 346 to actuate its contact member '348 to a circuit closing positionto effectthe energization of the winding 328 of the trip device 336. When this occurs the circuit breaker 36 is tripped and the contact member 326 or the breaker establishes a circuit from the ungrounded end of winding 264 of relay 258 to the conductor 24. If the short circuit still exists, the winding '264 is shunted to effect the deenergization thereof, whereby its contact member 216 .moves to an open circuit position to deenergize the winding 212 of the switching device I34 and cause the contact members 214 and 466 to move to an open circuit position and the contact members 462 to move to a. circuit closing position. The movement of the contact members 462 establishes circuits to effect the operation of the electrode motors to cause them to raise the electrodes. The circuits are similar for each of the regulators and may be understood by reference to the circuit extending from the positive terminal of a separate source of supply, through contact member 462 Of the switching device I34, winding 316 of contactor 362, limit switch 356 to the negative terminal of the separate source of supply. The

, establishment of these circuits effects the operation of the electrode motors to raise the respective electrodes.

As long as the short circuit condition on any one of the electrodes is maintained, the contact member 326 of breaker 36 functions to effect the shunting of the winding .264 of relay 258. However, as soon as the short circuit condition is cleared, the winding 264 of relay 258 again be comesenergized whereby the operation of relay 258 effects the energization of the switching device I34 to again establish the circuits referred to hereinbefore.

With the switching 'device'l34 and'the breaker 36 in their circuit closing positions, if it is desired to independently effect the positioning of any one of the electrodes I6, I8 and 26, theindi-vidual controllers I38, I46 and I42, respectively,,ca-n be movedtothe raise or lower position depending upon the changein position of the electrodes desired. If, for example, it is desired tolower the electrode .26 independently of the electrodes I6 and I8, only the controller I42 is'moved to the lower position where thesegment 388 closes a circuit extending from the positive terminal of the source of supply through contact member 466 of switching device I34, segment 368 of controller I42, winding-312 of contactor 364 and the .limit switch 358 to the negative terminal of the separate source of supply. The closing of this circuit effects the energization of the contactor 364 whereby its contact member 368 moves upwardly to establish the circuit to cause the mo- ,tor 54 to operate in the direction to effect the lowering of the electrode 26.

,If itis desired to raise the electrode. 28 ind pendently of the electrodes I6 and 18, then the controller I42 is moved to the raise" position to establish the circuit extending-from thepositive terminal of theseparate source-of supply through the segment, 392, winding 316 of contactor 362 and the limit switch 356 to the negative terminal of the separate source of supply. The contactor 362 is thus energized to actuate its contact member 366 upwardly to establish a circuit to cause a flow of current through the armature 60 in such a direction as to efiect the operation of the motor 54 in a direction to raise the electrode 20.

The limit switches 356 and 358 are efiective for opening the circuits to the winding 310 and 312, respectively, of the contactors 362- and 364, respectively, to prevent operation of the motor 54 to-move the electrode in-either the raise or lower direction beyond predetermined limits. Similar operation of the electrode motors may be had for controlling the position of the electrodes l6 and Hi.

'In both of the embodiments described hereinbefore, it is, of course, apparent that the circuit breakers 36 may be moved to a circuit opening positionat the will of the operator as the movement of the contact member3l8 carried by the circuit breaker 36 to the circuit closing position effects the energizationof the winding of relay 260 whereby the contact member 218 is moved to a'circuit opening position to effect the deenergization of the relay 262' and consequently the deenergization of thewinding 284 of the circuit breaker. The operation of the relay 260 is substantially instantaneous with the closing of the contact member 3! so that the energizing winding 284 is deenergized even though the switch 216 is held in a circuit closing position. Under such conditions, the manual operation of the switch 332 to a circuit closing position closes the circuit from the separate source of supply through the winding 328 of the trip device 336 to release the circuit breaker 36 at any time that the operator desires to interrupt the circuit which supplies the power to the power transformer 38.

By employing the circuits and apparatus of this invention, it is impossible to reclose the circuit breaker against a short circuit fault, adequate provision having been made for effecting the clearing of the fault before a circuit breaker can be closed. The circuits and apparatus of this invention consequently prevent fiashover in the breaker, together with possible damage to the power transformer and regulating equipment.

Theinvention utilizes standard apparatus and.

can be readily duplicated in the numerous types of regulating systems now available.

We claim as our invention: 1. In a system for controlling the feeding of an electrode and the production of an electric,

are supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed;

I circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means responsive to the arc potential to erect -"the operation of the motor to "lower the electrode, means responsive to the arccurrent to effect theoperation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to "connect the winding of the circuit breaker to be energized, another'relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means operable under short circuit conditions of the electrode when the circuit breaker is in the circuit opening position to effect the deenergization of the relay means, and means responsive to the deenergization of the relay mean to connect the means responsive to the arc current to be energized to eflfect the raising of the electrode.

2. In a'system for controlling the feeding of an electrode and the production of an electric arc supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in circuit closing position, means operable under short circuit conditions of the electrode to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means responsive to the are potential to effect the operation or the motor to lower the electrode, means responsive to the arc current to effect the operation of the motor to raise the electrode, relay means disposed to be-energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means carried by the circuit breaker operable under short circuit conditions of the electrode to effect the deenergization of the relay means when the circuit breaker is in the circuit opening position, and means responsive to the deenergization of the relay means to connect the means responsive to the arc current to be energized to effect the raising of the electrode. i

3.In a system for controlling the feeding of an electrode and the production of an electric arc supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in circuit closing position, means operable under predetermined conditions to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means responsive to the are potential to effect theoperation of the motor to lower the electrode, means responsive to the arc current to effect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position toeffect the deenergization of the winding of the circuit breaker, means operable under short circuit conditions of the electrode whenzthe circuit breaker is in the circuit opening position to effect the deenergization of the relay means, and means carried by the relay means disposedwhen the relay means is deenergirtedv tov connect the means responsive to the are current to :be independently energized to effect the raising of the electrode.

4. In a system forcontrolling the feeding of an electrode and theproduction of an electric are supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in circuit closing position, means operable under short circuit conditions of the electrode to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means responsive to the are potential to effect the operation of the motor to lower the electrode, means responsive to the arc current to effect the operation of the motor to raise the electrode,relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means carried by the circuit breaker operable under short circuit conditions-of the electrode to effect the deenergization of-the relaymeans when the circuit breaker is in the circuit opening position, and means carried by the relay means disposed when the relay means is deenergized to connect the means responsive to the are current to be independently energized to effect the raising of the electrode.

5. In a system for controlling the feeding of an electrode and the production of an electric are supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breakerdisposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in a circuit closing position, means operable under short circuit conditions of the electrode to release the holding means whereby the circuit breaker moves to a circuit Op position, means manually operable for also releasing the holding means, a motor disposed for raising and lowering the electrode, means responsive to the arc potential to'efiect the operation of the motor to lower the electrode, means responsive to the arc current to effect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means actuated by movement of the circuit breaker to the circuit opening position to be operable under short circuit conditions only of the electrode to effect the deenergization of the relay means, and means responsive to the deenergization of the relay means toconnect the means responsive to the arc current to beenergized to effect the raising of the electrode.

6. In a system for controlling the feeding of an electrode and the production of an electric are supplied from a source of power supply, in combination, a power transformer connected .to the electrode, a circuit breaker disposed coconnect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in circuit closing position, means operable under short circuit conditions of the electrode to release the holding means whereby the circuit breaker moves to a circuit opening position, means manually operable for also releasing the holding means, a motor disposed for raising and lowering the electrode, means responsiveto the are potential to effect the operation of the motor to lower the electrode, means responsivetothe arc current to effect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be'energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means-actuated by movement of the circuit breaker to the circuit opening position to be operable under short circuit conditions only of the electrode to effect the deenergization of the relay means, and means carried by the relay means disposed when the relay means is deenergized to connect the means responsive to the arc current to be independently energized to effect the raising of the electrode.

7. In a system for controlling the feeding of an electrode and the production of an electric are supplied froma source of power supply, in

combination, a power transformer connected to the electrode, a'circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to .be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuitbreaker in circuit closing position, means operable under predetermined conditions to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means responsiveto thearc potential to effect the operation of the motor to lower the electrode, means responsive to the are current to effect the operation of the-motor to raise the electrode, relay-means disposed to be energized under predetermined conditions toconnect the winding of the circuit breaker tobe energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, the holding means maintaining the circuit breaker in circuit closing position until the releasing mean is operated, means operable under short circuit conditions only of the electrode when the circuit breaker is in a circuit opening position to effect the deenergization of'the relay means, and means carried by the relay means disposed when the relay means is deenergized to connect the means responsive to the arc current to be independently energized to effect the raising of the electrode.

8. In a system for controlling the feedingof an electrode and the production of an electric are supplied from a source of power supply, in combination, a power transformer connected to the electrode, a'circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in circuit closing position,

a circuit closing position,

means operable under predetermined conditions to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means connected to be responsive to the are potential to effect the operation of the motor to lower the electrode, means connected to be responsive to the arc current to efiect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means operable under short circuit conditions only of the electrode when the circuit breaker is in the circuit opening position to effect the deenergization of the relay means, means operable when the circuit breaker is in the circuit opening position to disconnect the means responsive to the arc potential whereby the motor will not operate to lower the electrode, and means responsive to the deenergization of the relay means to connect the means responsive to the arc current to be energized to effect the raising of the electrode.

9. In a system for controlling the feeding of an electrode and the production of an electric are supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in circuit closing position, means operable under predetermined conditions to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means connected to be responsive to the are potential to effect the operation of the motor to lower the electrode, means connected to be responsive to the arc current to effect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to efiect the deenergization of the winding of the circuit breaker, means carried by the circuit breaker operable under short circuit conditions only of the electrode to effect the deenergization of the relay means when the circuit breaker is in the circuit opening position, means operable when the circuit breaker is in the circuit opening position to disconnect the means responsive to the are potential whereby the motor will not operate to lower the electrode, and means responsive to the deenergization of the relay means to connect the means responsive to the arc current to be energized to effect the raising of the electrode.

10. In a system for controlling the feeding of an electrode and the production of an electric are supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to means for normally holding the circuit breaker in circuit closing position,

9 means operable under predetermined conditions to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means connected to be responsive to the arc potential to effect the operation of the motor to lower the electrode, means connected to be responsive to the arc current to effect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposedlto be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means operable under short circuit conditions only of the electrode when the circuit breaker is in the circuit opening position to efiect the deenergization of the relay means, means operable when the circuit breaker is in the circuit opening position to disconnect the means responsive to the are potential whereby the motor will not operate to lower the electrode, and means carried by the relay means disposed when the relay means is deenergized to connect the means responsive to the arc current to be independently energized to effect the raising of the electrode.

11. In a system for controlling the feeding of an electrode and the production of an electric are supplied from a source of power supply, in combination, a, power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in circuit closing position, means operable under predetermined conditions to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means responsive to the arc potential to effect the operation of the motor to lower the electrode, means responsive to the arc current to effect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means operable under short circuit conditions only of the electrode when the circuit breaker is in the circuit opening position to effect the deenergization of the relay means, means responsive to the deenergization of the relay means to connect the means responsive to the arc current to be independently energized to effect the raising of the electrode, and means disposed to be manually operated to selectively connect the means responsive to the are potential and the means responsive to the arc current to be independently energized when the relay means is energized to selectively lower or raise the electrode.

12. In a system for controlling the feeding of an electrode and the production of an electric are supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to a circuit closing position, means for normally holding the circuit breaker in circuit closing position,

means operable under predetermined conditions to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means connected to be responsive to the are potential to efiect the operation of the motor to lower the electrode, means connected to be responsive to the arc current to effect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means operable under short circuit conditions only of the electrode when the circuit breaker is in the circuit opening position to effect the deenergization of the relay means, means operable when the circuit breaker is in the circuit opening position to disconnect the means responsive to the are potential whereby the motor will not operate in response to the are potential, means responsive to the deenergization of the relay means to connect the means responsive to the arc current to be independently energized to effect the raising of the electrode, and means disposed to be manually operated to selectively connect the means responsive to the arc potential and the means responsive to the arc current to be independently energized when the relay means is energized to selectively lower or raise the electrode.

13. In a system for controlling the feeding of an electrode and the production of an electric are supplied from a source of power supply, in combination, a power transformer connected to the electrode, a circuit breaker disposed to connect the power transformer to the source of power, a winding for the circuit breaker disposed to be energized to actuate the circuit breaker to acircuit closing position, means for normally holding the circuit breaker in circuit closing position, means operable under predetermined conditions to release the holding means whereby the circuit breaker moves to a circuit opening position, a motor disposed for raising and lowering the electrode, means connected to be responsive to the are potential to effect the operation of the motor to lower the electrode, means connected to be responsive to the arc current to effect the operation of the motor to raise the electrode, relay means disposed to be energized under predetermined conditions to connect the winding of the circuit breaker to be energized, another relay means disposed to be energized when the circuit breaker is in a circuit closing position to effect the deenergization of the winding of the circuit breaker, means actuated by movement of the circuit breaker to the circuit opening position to be operable under short circuit conditions only of the electrode to effect the deenergization oi the relay means, means operable when the circuit breaker is in the circuit opening position to disconnect the means responsive to the arc potential whereby the motor will not operate in response to the arc potential, means carried by the relay means disposed when the relay means is deenergized to connect the means responsive to the arc current to be independently energized to effect the raising of the electrode, and means disposed to be manually operated to selectively connect the means responsive to the are potential and the means responsive to the arc current to be independently energized when the relay means is energized to selectively lower or raise the electrode.

JAMES P. HOUCK. RALPH A. GEISELMAN.

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