US2518580A - Arc furnace control - Google Patents

Description

image 9 195% L. A. TROFIMOV ,580 ARC FURNACE CONTROL Filed March 24, 1948 5 Sheets-Sheet l INVENTOR. Lav. A. Thoma/10v AT OPNEY Aug. 15, 1950 L. A. TROFIMQV 5 ARC FURNACE CONTROL Filed March 24, 1948 3 Sheets-Sheet 2 INVENTOR. LEV .TROF'dMOV ATTGPJVEY ARC FURNACE CONTROL.

Filed March 24, l$48- 3 Sheez'bs -Sheet S INVENTOR.

. A Y L 3 LEV ATRoFaMov ATTORNEY latented Aug. 15, 1950 UNITED STATES PATENT OFFICE ARC FURNACE CONTROL Lev A. Trofimov, Willoughby, Ohio Application March 2 1, 1948, Serial No. 16,719

11 Claims. 1

This invention relates to apparatus for automatically controlling the arc standing between consumable electrodes, to maintain thereat predetermined quantitative electrical conditions.

The invention is applicable to the control of arcs as utilized in various arts such as lighting, welding, etc., but one of its most important uses is to control the arc of an electric arc furnace; and for the illustrative embodiment of the invention required by law upon application for a patent, I have chosen to illustrate and describe it herein as applied to that use.

In prior controls of this general class, one of the electrodes supporting the arc is mounted for movement toward and from the other electrode whereby the arc may be shortened or lengthened, to control it; and this general principle is utilized in the present invention; but otherwise the present invention departs from all prior practice so far as I am aware in at least the following elements of apparatus and mode of operation thereof.

A continuously running motor supplies power through a mechanical power transmission, to move the movable electrode with step-less movement, or to hold it at rest. The transmission supplies powerirom a rotary take-off, which in the preferred form of the invention responds to the joint effects of a pair of electromagnetic windings; and remains at rest when the effects of the windings balance or neutralize each other, and rotates in one direction or the other when the effect of one winding predominates over that of the other. The respective windings are encrgized commensurably with certain quantitative electrical conditions at the arc and their eifects are balanced as aforesaid when predetermined conditions obtain at the are; and upon deviation from said predetermined conditions become unbalanced and actuate the transmission to move the movable electrode to restore the predeter mined conditions at the arc and to restore the balance at the transmission.

Among the advantages of the control over prior controls are that: the movement of the electrode to restore the predetermined conditions at the arc is initiated immediately upon deviation therefrom, because the power supplying motor is continuously running and no delay is introduced by the time required to start the motor; or stop and reverse the motor; and the rate of restoring the deviated condition is directly commensurable with the extent of the deviation; whereby the control or regulation is rendered exceedingly sensitive but at the same time hunting is ob- 2 viated. And this is true even in cases in which the electrode to be moved is of great mass and inertia and correspondingly large motor power is required to move it.

Furthermore, upon accidental interruption of ie arc due to any cause, the transmission responds automatically to the resulting change of conditions at the arc, to immediately re-strike the arc and resume automatic control of it as before.

Upon failure of supply voltage to the control, the transmission responds to withdraw the mov able electrode to a safety position and prevents it from dropping into the furnace or furnace charge as is true of some prior controls.

The invention may be practiced in various forms whereby the transmission may be made to respond to current in the are, or to potential across the arc, or to both current and potential concurrently and thereiore to watts in the arc; and by means of manual adjustments, the effectiveness of the response in either case may be adjusted to adapt a given control to a particular installation, and to adjustably vary, as desired, the voltage at the arc, the length of the arc, the power factor of the electrode circuit, etc.

The objects of the invention are to provide an arc control having among others, the features referred to above.

The invention is fully disclosed in the followin description of an embodiment thereof taken in connection with the accompanying drawing in which:

Fig. 1 is a diagrammatic view of an embodiment of the invention in a preferred form, illustrating an arc furnace and an electric system and apparatus for controlling the arc of the furnace, having the features of operation above referred to;

Figs. 2 and 3 are views similar to Fig. 1 but showing in simplified embodiments or modifications, some of the features of Fig. 1 and which in some installations may be sufiicicnt for complete operation;

Fig. 4 is a view similar to Fig. 1 but simplified, illustrating certain elements energized with alternating current, which in Fig. 1 are energized with direct current.

Referring to the drawing, there is shown diagrammatically at I an arc furnace having a wallenclosed furnace chamber 2. A stationary electric terminal 3 projects upwardly sealedly through the bottom chamber wall 4. An electrode 5 projects downwardly through an opening 6 in 3 the top chamber wall I, being reciprocable in the opening.

Within the chamber 2 is shown in broken lines at 88 a quantity of metal pieces (or other charge) to be melted; and in solid line at 9 a quantity of molten metal; either of which in contact with the terminal 3 in the operation of the apparatus to be described, constitutes an electrode, between which and the electrode 5, an arc is drawn and maintained. Without any charge, an arc will be drawn and maintained between the electrode and the terminal 3 as the other electrode for any chamber heating purpose.

A transformer Hi having a primary H connected to supply mains l2 by a switch 13, has a secondary l4 connected at one end by a main is to the terminal 3; and at its other end connected to the electrode 5 by a main i6 having a flexible portion I! to allow for free reciprocatory movement of the electrode 5.

The weight of the electrode 5 may be artificially increased by a metal block I8, attached to it outside of and above the chamber 2.

A cable I9 is connected at one end to the electrode 5, preferably by attaching it to the block I8, extends upwardly therefrom, and passes over horizontally spaced pulleys -26, and thence downwardly to a drum 2! on which it is wound. Rotation of the drum in one direction winds up the cable and raises the electrode 5; and rotation in the other direction pays off cable and allows the weight of the electrode 5 and of the block I8 to lower the electrode by gravity.

A power transmission 22 for rotating the drum M will now be described. It comprises two differential gearings 23 and 24 preferably alike. The gearing 23 comprises a spider 25 rotatably supporting pinions 2626 meshed with differential gears 27 and 28.

' The gearing 24 comprises a spider 2Q rotatably supporting pinions 30-30 meshed with differential gears 3i and 32.

The spiders 25 and 29 have toothed peripheries preferably of equal diameter, meshed together. A pinion 33, meshed with the spider 29, and driven by a continuously rumiing motor 36 connected to supply mains by a switch 36 continuously runs and drives the meshed spiders 25 and 29 in opposite directions.

The differential gears 2! and 3! are respectively connected to gears 31 and 38, preferably alike, both of which mesh with an intermediate gear 39 connected to the drum 2!.

The differential gears 28 and 32 are respectively connected to shafts 40 and 4! to which are connected the rotors 42 and 43 of direct current dynamo-electric machines 44 and 635; having fields represented by field windings 46 and 5'6 respectively. The two machines 44 and 415 are preferably alike.

A local electric load circuit is provided comprising a wire 48 connecting adjacent brushes t9 and 50 of the machines 44 and 45; and a wire 5i connecting the opposite brushes 52-53.

The fields 46 and 41 are energized in a manner to be described later.

With this arrangement, and with like polarities for the fields 46 and 41 and assuming equal energization of the fields, the machines 44 and 45 will be driven as generators in opposite directions; their potentials will be equal and opposite; no current will flow in the local load circuit 485i; and the rotors 42 and 43 will be driven at equal speeds and what torques are developed to drive the rotors will be equal and opposite.

4 This will cause the torques on differential gears 28 and 32 to be equal and opposite in direction, and cause the gears 21 and 3| to impress equal and opposite torques on the pinion 39 and its conmachine at, through the return wire 5|; and the machine 36 will be driven thereby as a motor, in the same direction as before.

The electric load torque on the machine 35 now predominates and slows down its speed; the torques on differential gears 28 and 32 are in the same direction as before, but the gear 32 slows down and gear 3! which was at rest, starts to rotate, and through gears 38 and 39 applies torque to the gear-connected drum in the winding-up direction.

The machine 35 driven as a motor, rotates at an increased speed; the differential gear 28 increases in speed, and the differential gear 2?] which was at rest starts to rotate in the reverse direction, and through the gears 31 and 35 applies torque to the gear connected drum again in the winding-up direction.

Thus the braking energy at the generator 415 is returned to the gearing system as motor power energy, by the motor i l.

If the field it were made stronger than the field 4i? (instead of vice versa as above), then exactly the reverse action would take place and torque would be applied to the drum Ed in the paying off direction.

Whenever equality of the fields 36 and ll is restored the torques applied to the drum again become equal and opposite.

As described, if the two units Ad and 45 are alike and have fields it and iii alike and if the homologous parts of the gearings 28 and 26, etc, are alike, the torques applied to the drum 2i will be alike and in opposite directions when the fields it and ill are equally energized. If under these conditions, there were no load torque on the drum 2i, it would remain at rest; and if then the winding fill were energized more strongly than the winding :15, the drum 25 would rotate in the winding up direction.

It will be apparent that there is always load torque on the drum 2i in the unwinding direction due to the weight of the electrode 5 and mass 58. To hold the drum 2| at rest therefore, torque must be applied to it in the winding-up direction to balance the load torque and this is done by energizing the field 47 more strongly than the field at by a suitable amount. A balanced condition of the transmission and so-called balanced energization of the windings i6 and 51 is attained by providing this difference of energization of these windings.

There are several modes of field energization and control, manual and automatic, which will now be described.

At 54 is a double throw manual change-over switch, comprising four pivoted blades 55, 56, 5?, and 58; and four upper contacts, 59, til, 69, and 62, and two lower contacts 63 and 6d therefor.

When the blades 55 to 58 are in the lower position, the field 46 takes current from the outside brush 52 of its corresponding rotor 42, through the field 46, by wire 65 to blade 51, to contact 56, by wire 66 through part 61 of the resistor 6&3 of

a potentiometer rheostat it, through a manually movable contact "I of the potentiometer, to wire H, by way of wire I! to the other brush 49.

correspondingly, the field H takes current from brush 53 through the field 41, by wire 12 to blade 56 to contact 53 by wire 13 through the other part 14 of the potentiometer resistor 68, by contact to wire II, and by wire 4! to the other brush 50.

By adjusting the potentiometer contact 10, the fields 46 and H can be balanced as aforesaid or one made to predominate over the other.

Optionally, either field can be energized full strength, regardless of the potentiometer-set strength for the other field, by a double throw manual switch having a pivoted blade i5 connected to the wire ll and two contacts l6'l'i connected respectively to the wires 65 and i3. Throw or the switch blade 15 to the right short circuits the part it of the potentiometer resistor t3 and to the left short circuits the other part 61.

When these manual field strength controls are used, the fields are self-energized from their corresponding rotors as described; and by adjusting their relative strengths, the drum 2! can be caused g to rotate in one direction or the other to raise or lower the electrode 5.

The automatic field control referred to comes into effect as follows, when the change-over switch Ed is thrown to the upper position.

The manual controls are rendered ineffective by being opened at the contacts 63--E4.

The field Alt is connected by wires and 18 to blades iii-58 and thence to contacts ilk-62, and by wires iii-fill to the output points of a rectifier loop ill. The input wires 82-83 of this loop are connected through a double throw switch 184 to points t5 and 86 on the mains l6 and i5, that is, to the electrode 5 and the terminal 3. The field it during operation is thus subjected to potential commensurable with that across the are formed between the electrodes. A manual rheostat 87 is placed in the line of wire 82 for adjustment to be referred to.

The field ll is connected by wires I2 and 88 to the blades 55 and 56 and thence to contacts 59-60, and by wires B9-9 to the output points of a rectifier 100p ill. The input wires 8293 of this loop are connected through a double throw switch M to the secondary 95 of a current transformer 96 in the line of one of the mains, for example the main l6 as shown.

The field 41 during operation is thus subjected to potential commensurable with the current in the main l5 flowing in the are. A manual rheostat 91 is placed in the line of the wire 92 for adjustment to be referred to.

Meters are preferably used in the operation of the apparatus. An ammeter 98 is placed in the line of one of the mains, for example the main 15 as shown to indicate arc current.

A volt meter .99 is connected across the points 85 and 86 by wires IOU-! to indicate potential across the arc.

A watt meter N12 has its volt terminals connected by wires l03l04 to the volt meter wires i00-l 0 l and has its current terminals connected by wires lll5l06 to the secondary ll" of 9. current transformer I08 in the line of one of the mains for example the main l5 as shown.

To start up the apparatus and set it in automatic operation, it will be assumed that the electrode 5 is above the lower electrode, namely the charge in the furnace chamber or the terminal 3 as the case may be.

The line switch I3 is closed, putting potential on the electrodes.

The change-over switch 54 is put in the lower position for manual operation.

The switch 36 is closed starting up the trans mission motor 34.

The contact H! of potentiometer N is now turned in the direction to equalize the fields and 41 or to strengthen field 4G and weaken field 41. As described above, this will allow the drum 2| to be turned in the cable unwinding direction by gravity or will cause it to so turn and the electrode 5 will descend by gravity and engage the other electrode. Main current then flows in the engaged electrodes. Then the contact II is turned in the other direction to strengthen field ll and weaken field l6 and the drum 2| reverses and winds up cable and withdraws the electrode 5 drawing an are between the electrodes.

The potentiometer contact 10 is then adjusted until the winding up torque on the drum just balances the weight of the weighted electrode 5, and it is held stationary, or at least rises very slowly, maintaining the arc.

When a torque balance position is once determined in this manner for the potentiometer 83, the electrode '5 can be lowered and raised to strike an arc and then left in the balanced raised position, by first throwing the manual switch blade 15 to the left to give full strength to field ii to lower the electrode; and then to the right to give full strength to the field 47 to raise the electrode; and then to the middle position to restore the fields to the potentiometer efiectcd torque balance condition.

The are having now been drawn and standing, with the electrode 5 substantially stationary, the change-over switch 5% is thrown to the upper position for automatic operation, which as described cuts oif the manual controls, and energizes the held 46 from across-the-arc-potential, and energizes the field 47 from are current derived potential. The rheostats 91 and ll are now manually manipulated to adjust the fields 4i and 4'! to establish a balance of torques on the drum 2| and desired conditions at the arc.

It is known that for a given are furnace, at given kind and size of electrode, a given charge, etc, there is an optimum wattage in the are, for stability of the arc and allowable power factor.

By means of the ammeter 98, volt meter '1, and wattmeter N2, the wattage in the arc, and the power factor can be observed and determined; and these optimum conditions can be brought about by adjusting the rheostats l1 and H.

In the system as above described, the strength of the field 46 for any given voltage across the arc can be adjusted by the rheostat l1; and the strength of the field 41 for any given current in the arc can be adjusted by the rheostat 91.

The two fields can thus be given values such that by their joint action the electrode 5 is held stationary at a given length of are.

If a longer are is wanted, for example, the rheostat 9'! can be operated to artificially strengthen the field 41. This will cause the electrode 5 to be raised, and the arc to be lengthened, until the consequent increasing potential across the arc and the decreasing current in the arc. bring the fields into torque balance again at a. longer arc.

If a change of wattage is wanted, for example, the rheostats 81 and 91 can be jointly or severally manipulated while observing the wattmeter to adjust the arc to establish the desired wattage.

.. conditions.

amaaao -.-si ve field 41 would become de-energized upon ces- Qsation of current fiow, but the across-the-arcpotential-responsive field 56 would still be energized. This would cause the drum 26 to be 1 rotated to lower the electrode until it engaged the other electrode. would -fiow and field 41 would become strongly Thereupon heavy current energizedybut due to the absence of arc, the field be resumed and regulate the arc to the present Upon failure of supply voltage, or, upon shut- ,'.ting, down the furnace, it is desirable to have Ythe electrode pulled out of the furnace. or, at

Q least retracted far from the charge.

, Provision is made in the instant apparatus for this result. On the shaft ll of the transmission is mounted a brake drum E09. A brake shoe Md is normally held out of contact with it by a wind- ,ing iii energized from the line 35, when the switch 36 is closed. Upon failure of potential .in the line 35 or upon opening the switch 36, the

fwinding l l i will be de-energized and brake shoe energized strongly, as described, and finally stopsv .i It) will engage the drum Hi9. This slows down.

the shaft M, the same as when the field fill is the. shaft 45; and this causes the drum to Lrotate to elevate the electrode 5, and this goes .on throughout the time that the motor which ,has no braking action on it, continues to rotate Iby inertia.

torque at the drum 2i in the winding up direction.

When homologous parts of the transmission are,

,identical or approximately so, the field ll will 1 at such times be stronger than the field (l5; and

this will result from unequal currents in the respective windings 41 and 46. Thereafter a relative strengthening of field 41 will raise the elecwinding 46 at constant strength the double throw switch 84 is thrown from its lower illustrated position to an upper position, thereby disconnecting the wires 82-83 from the mains l6 -l5, and connecting them by wires il3|ll 'to a transformer secondary H5, energized from a transformer primary H9 connected to the mains 35.

As illustrative of the operation of this modification, the strengths of the fields t6 and H are adjusted as described, for the desired conditions at the arc and with a balance of the torques on the drum 28. As the electrode 5 is consumed and the current in the arc decreases. the resulting weakening of energization of field ill and the constant energization of held causes the field $1 to .be relatively weaker, and this as described causes the drum Zi to rotate to lower the electrodet and restore the are conditions.

To optionally energize the winding ll at constant strength, the double throw switch 86 is re'- turned to its illustrated position to energize the winding teat variable strength, and the double throw switch St is thrown from its illustrated lower positionto an upper position thereby disconnecting" the wires 92-413 from the current transformer Q5 and connecting them by wires llfi--lllto a transformer secondary lit.

. As illustrative of the operation of this modification, the field strengths are again adjusted for balanced torques at the drum M for desired are conditions. As the electrode 5 is consumed the potential across the arc rises, the resulting strengthening of the field it andthe constant strength of field i'l, unbalances the torques on the drum 2i and lowers the electrode 5 to restore the are conditions.

In the modification of Fig. 2, a, single difieren= tial gearing i29 is utilized, instead of the double differential 23-2l of Fig. 1, with corresponding simplification. A briefer description for this form will suffice, in view of the more complete detrode .5, and a relative strengthening of the field 4s will lower it.

The constant wattage to which the apparatus regulates the arc, may be changed by means of taps H2 on the primary winding i l of the trans-v I former l0.

While I prefer as described, to energize the fields 46 and 4'l respectively by variable potential commensurable with that across the arc, and by variable current commensurable with that in the arc, because of the constancy, sensitivity and non-hunting character of the regulation result- L ing therefrom; the scope of my inventionv comprehends modifications in which one or the other of the fields is energized with substantially constant current.

of more drawings. To optionally energize the scription of Fig. 1..

A continuously running motor l2l drives the spider i22 which in turn drives the gears M3 and H26 which are connected respectively to the cable drum 2! and to a generator 825. The generator 25 has a local energy dissipating electric load circuit H25 containing adjustable resistance 926A; and has a field winding Hi. When a double throw switch 628 is in the down position, the field li'l is connected to wires lZt-ltd; and thence may be directly connected across the brushes of the generator G25 through a manual knife switch l3i; or, through an adjustable resistor i32 when the switch lei is open. When the switch Hit is in the upper position the field i2? is energized through a rectifierloop H33 from the secondary i3 5 of a current transformer in series with the electrode main it, and adjusted by a manual rheostat I35;

The movable electrode 5 is suspended by a cable is wound on the drum 2i, as in Fig. 1.

The electrode circuit i5-i6 is energized by a transformer ill and its electrical quantities are indicated on instruments 98, 99, and 802 as in Fig. l.

In this form, the weight of the electrode 5 and its overhauling weight is put torque on the drum 26 in the unwinding direction. Load on the gen= erator, varied by variation of the strength of the field i271, applies variable torque on the drum in the winding up direction. The field lZl may be weakened or strengthened by the rheostat I35 to cause the drum 'to unwind or wind up cable I, to lower or raise the electrode 5. The desired current in the arc may be established by making the field I21 more or less effective by adjusting the rheostat I35, until the torques balance.

Thereafter changes in arc current will automatically unbalance the torques, and the electrode will be moved, and this will restore the current and the torque balance. For example, when the arc currentdecreases due to burning away of the electrode 5, the field I21 weakens, the torque applied to the drum 2I by generator I25 weakens, the electrode descends, the current in the arc increases, the generator torque rises and a, balance is again reached.

The electrode can be lowered and raised manually, with the switch I28 in the lower position, by operating the switch I3I to strikean arc; or can be moved gradually by operating the rheostat I32, when the switch I3I is open.

For an intermediate field strength, in a suitable adjusting range thereof, the electrode 5 and its weight I8 may be torque-balanced by adjusting the generator produced torque at the resistance MBA; and similarly, the length of the arc gap can be adjusted for any given field current adjustment by adjusting the resistance I26A.

In the event of accidental arc interruption, the field I21 becomes de-energized, the generator i 25 rotates freely and little torque develops thereat, and correspondingly little torque is applied to the drum 2! in the winding up direction. The weight of the electrode, 5I8, overpowers the winding up torque, and the electrode descends. When it contacts the charge 8 or 9, current flows, field I2? is again energized, and the drum winds up cable and strikes an arc and the above described regulation ls resumed.

If voltage on the motor mains 55 should fail, or if the switch 36 should be opened, the brake IIIl- -III (described for Fig. 1) sets and stops the rotation of gear I22, and so long as inertia of the motor rotor keeps it rotating, the drum M will be rotated in the winding up direction and withdraw the electrode 5. To keep the weight of the electrode 5-!8 from overhauling the drum 2i and causing the electrode 5 to descend again, the driving connection between the spider I22 and motor driven pinion 33A may be a non-reversible worm and worm gear connection.

In the modification of Fig. 2 (as above described) an arc-current-responsive field winding I21, causes torque to be applied at the drum 2I in the winding up direction, to balance the weight of the electrode, 5-I8.

In the modification of Fig. 3 (now to be described), torque at the drum 2| in the winding up direction overbalances the weight of the electrode 5I8, and an arc-voltage-responsive field winding causes torque to be applied to the drum 2I in the unwinding direction to balance the overbalancing torque.

In Fig. 3, as in Fig. 2, a single differential gearing I36 has its spider I31 continuously driven by a motor I38, and drives gears I39-I4II connected respectively to a generator I and the drum 2|. The cable I9 wound on the drum is connected at one end to the electrode 5 and at its other end to a weight I42. The weight I42 is suificient to overbalance the weight of the electrode 5I8 and apply torque to the drum 2I in the winding up direction.

The field I43 for the generator I is controlled manually by the switches I28 and III and potentiometer I32 when energized from the generator I as described for Fig. 2; and in automatic operation with the switch I28 in its upper position, is energized by way of wires I44-I4I connected across the mains I5-I6 and therefore across the arc, an adjusting rheostat I45, a rectiiler loop I41, wires I48-I49 and I5II-I5I.

The generator I has a local load circuit resistance I52.

The arrangement will be seen to be substantially the same as that of Fig. 2 (and needs no further description); but here a balance is reached when the field I43 is energized sufliciently to cause the torque at the generator I to rise to the value at which the corresponding torque at the drum 2I tending to unwind cable I 9 and lower the electrode is balanced by the weight I42.

11' the potential across the arc increases due to consumption of the electrode 5, and lengthening of the arc, and energizes the field I 43 more strongly, the drum M will wind up cable supporting the weight I42 and raise the weight, and unwind cable supporting the electrode 5--I8 and allow the electrode 5 to move downwardly and restore the potential and the balance.

Upon failure of the arc, the potential across the electrodes will rise and strengthen the field I43 and cause the electrode 5 to be lowered into engagement with the charge 8 or 9; and current will at once fiow, causing a reduction in potential which will weaken the field I43 and allow the weight I42 to raise the electrode 5 and draw an arc.

Upon failure of power in the motor mains 35 or upon cutting off the motor at the switch 38, the brake IIOIII, as described hereinbeiore, will set and stop the gear I39, and gear I40 and drum 2i will be driven in the unwinding direction and lower the electrode 5 so long as inertia in the rotor of the motor I38 persists; but as soon as the inertia is dissipated, the weight I42 will turn the drum 2| in the winding up direction and withdraw the electrode 5 as referred to.

In the foregoing embodiments of the invention, the drum is balanced or caused to turn in one direction or the other by the changing load developed in a direct current generator caused by a change of generator field energization sup ply, rectified from alternating current mains feeding the arc.

Themodification of Fig. 4 is introduced to show that the generators may be of alternating current type and have alternating current fields.

Fig. 4 corresponds otherwise to Fig. 1, already described and therefore some of the manual controls have been omitted for simplification, but in view of their description for Fig. 1, those skilled in the art will know how to apply manual controls to Fig. 4.

Supply mains I2, transformer ID with primary II and secondary I4, electrode mains I5-I6, electrodes 53, winding drum 2!, cable I9, and furnace 8 (indicated in broken line) are all reproduced from Fig. 1.

Two differential gearings 23 and 24 like those of Fig. 1 are connected to the drum 2| as in Fig. 1. Shafts 40-4I drive gears I53I54, and speed step up pinions'|55|56 connected to the rotbrs I5'I-I55 of generators I59I50.

These generators have the construction of three phase squirrel cage induction motors. The stator windings I5II52--I53, which, when used as motor field windings, are connected each across one of the three supply phases, are here all connected in series, and across single phase 11 mains I6l--Il9 for the generator I09, and I60- I61 for the generator I60.

The mains I64-I65 are connected to the secondary I66 of a transformer I69, the primary I10 of which is connected across the arc mains Iii-I6, the secondary I60 having taps and a movable arm I'll for adjusting the output potential.

The mains I66-I61 are connected across the secondary I12 (adjustable by taps and a movable arm I19) of a current transformer I14 in the line of the main I6. I

With the arrangement shown in Fig. 4 and as here described, when alternating current in, say, the mains I6l-I65 energize the field or stator of the generator I59, and the rotor I51 is driven at speeds above the synchronous speed corresponding to the frequency of the mains (insured by the speed step up at the gear and "pinion I59I55), alternating current will be generated in the mains I6lI65 and supplied back through them to the transformer M9 and thence to the electrode mains I5-I6 and through the transformer I to the supply mains I2; this current constituting an electrical load on the generator I59; the mains I6lI65 constituting mains for the exciting current of the stator of the generator and also load circuit mains therefrom; it being understood that there is a difference of phase between them caused by inherent conditions of the circuits. (Reference may be had if desired to a similar arrangement in my .Patent 2,365,982, December 26, 1944.)

By changing the energization of the stator windings I 6II62I63 the output load on the generator I59 and the torque to drive its rotor I51 will correspondingly be changed.

The generators I59 and I60 may be alike and the above description applies to both.

Load on the generator I60 tends to exert torque on the drum 2| to rotate it in the winding up direction and raise the electrode and this occurs responsive to current in the arc and corresponding secondary voltage at the transformer I14, and fleld energization of the generator I60 and its current load, and the torque necessary to drive it.

Similarly, load on the generator I59, resulting from potential across the arc and on the secondary I68 of transformer I69, tends to exert torque on the drum 2I to rotate in the unwinding direction and allow the electrode 5 to descend.

The two torques are brought to a balance, the drum 2I remaining at rest and the potential and current of the arc at desired preselected values, by adjustment of the transformer output potentials at the movable contacts I1I-l10.

Thereafter predominance of load on one generator or the other by change of field strength occasioned by a change of said preselected values at the arc, will cause the drum 2| to rotateand reposition the electrode 3 to restore the balance and the preselected values.

From the foregoing description, it, will be apparent to those skilled in the art that the invention is not limited to details of construction; but admits of a variety of embodiments, and modifications thereof and changes therein; and my invention is comprehensive of all such ,changes and modifications that come within the scope of the appended claims.

I claim:

1. In an apparatus for adjustably moving a consumable arc-supporting electrode to maintain at a predetermined value an electrical quantity at the arc that tends to vary; a differential power transmission comprising a rotary power output element and an electric generator having an electric load'circuit, anda field winding; the transmission constructed to receive power from a continuously running motor and apply equal torques differentially to the output element and to the generator; and to respond to variations of energization of the field winding to vary the torque of the generator to correspondingly vary the torque of the output element; means biasing the electrode to move it in one direction; means communicating torque of the output element to the electrode in opposition to its bias; circuit means energizing the field winding proportionally to an electrical quantity at the arc, to cause the output element to effect movement of the electrode to restore the electrical quantity to a predetermined value upon deviation of the quantity from said value.

2. In an apparatus for adjustably w. consumable arc-supporting electrode to maintain the current in the are at a predetermined value as it tends to vary; a differential power transmission comprising' a rotary power output element and an electric generator having an electric load circuit, and a field winding; the transmission constructed to receive power from a continuously running motor and apply equal torques differentially to the output element and to the generator; and to respond to variations of energization of the field winding to correspondingly vary the torque of the generator and of the output element; means biasing the electrode to move in one direction to tend to change the current; means communicating torque of the output element to the electrode in opposition to its bias; circuit means energizing the field winding proportionally to the current in the arc to cause the output element to effect movement of the electrode to restore the current to a predetermined value upon deviation of the current from said value.

3. In an apparatus for adjustably moving a consumable arc-supporting electrode to maintain the voltage across the are at a predetermined value as it tends to vary; a differential power transmission comprising a rotary power output element and an electric generator having an electric load circuit, and a field winding; the transmission constructed to receive power from a continuously running motor and apply equal torques differentially to the output element and to the generator; and to respond to variations of energization of the field winding to correspondingly vary the torque of the generator and of the output element; means biasing the electrode to move in one direction to tend to change the voltage; means communicating torque of the output element to the electrode in opposition to its bias; circuit means energizing the field winding proportionally to the voltage across the arc, to cause the output element to effect movement of the electrode to restore the voltage to a predetermined value upon deviation of the voltage from said value.

4. In an apparatus for adjustably moving a consumable arc-supporting electrode to maintain the current in the arc and the voltage across it at predetermined values as they tend to vary; a power transmission comprising a pair of rotary torque developing means and a rotary output element and differential gearing constructed to be driven by the torque of a continuously running motor and differentially connected to the output element and to the two torque developing means respectively; a pair of electric controlling windings for the respective torque developing means relative energization of which varies relatively the torques developed by the two torque developing means and in consequence the direction and amount of resultant torque at the output element; means including means to apply torque oi the output element to the electrode to eilect movement of it; circuit means energizing the respective windings proportionally to current in the arc and voltage across it, respectively, to cause the torque on the output element to effect movement of the electrode to restore the current and voltage to predetermined values, upon deviation thereof from said values.

5. In an apparatus for adjustably moving a consumable arc-supporting electrode to maintain the current in the arc and the voltage across it at predetermined values as they tend to vary; a power transmission comprising a pair of rotary torque developing'means and a rotary output element and differential gearing constructed to be driven by the torque of a continuously running motor and differentially connected to the output element and to the two torque developing means; a pair of electric controlling windings for the respective torque developing means relative energization of which varies relatively the torques developed by the two torque developing means and in consequence the direction and amount of resultant torque at the output element; means including means to apply torque of the output element to the electrode to efl'ect movement of it; circuit means energizing one winding at values proportional to current in the arc and the other winding at a constant value, to cause the effects of the windings to be balanced at a predetermined value of current and to cause the effects to be unbalanced and the electrode to be moved to restore the current to said value upon deviation therefrom.

6. In an apparatus for adjustably moving a consumable arc-supporting electrode to maintain the current in the arc and the voltage across it at predetermined values as they tend to vary; a power transmission comprising a pair of rotary torque developing means and a rotary output element and differential gearing constructed to be driven by the torque of a continuously running motor and differentially connected to the output element and to the two torque developing means; a pair of electric controlling windings for the respective torque developing means relative energization of which varies relatively the torques developed by the two torque developing means and in consequence the direction and amount of resultant torque at the output element; means including means to apply torque of the output element to the electrode to eifect movement of it; circuit means energizing one winding at values proportional to voltage across the arc and the other winding at a constant value, to cause the effects of the windings to be balanced at a predetermined value of voltage and to cause the effects to be unbalanced and the electrode to be moved to restore the voltage to said value upon deviation therefrom.

7. In an apparatus for adjustably moving a consumable are supporting electrode to maintain the current in the arc and the voltage across it at predetermined values, as they tend to vary; a power transmission comprising a pair of load developing electric generators and a rotary output element, and differential gearing constructed to be driven by the torque of a continuously running motor and to differentially apply torque to the output element and to the two generators; a pair of controlling windings relative energization of which varies relatively the developed load torque of the generators and in consequence the direction and amount of resultant torque at the output element; means including means to apply torque of the output element to the electrode to eflect movement of it; circuit means energizing the respective windings proportionally to current in the arc and voltage across it, respectively, to cause the torque on the output element to effect movement of the electrode to restore the current and voltage to predetermined values, upon deviation thereof from said values.

8. In an apparatus for adjustably moving a consumable arc supporting electrode to maintain the current in the arc and the voltage across it at predetermined values as they tend to vary; a power transmission comprising a pair of electric generators and a rotary output element and differential gearing constructed to be driven by the torque'of a continuously running motor and to differentially apply torque to the output element and to the two generators; a common load circuit for the generators, a pair of field windings for the respective generators, relative unbalanced energization of which, rendering one winding more effective than the other, causes one or the other of the generators to generate load current in the common load circuit and drive the other generator as a motor and develop braking torque, and as a consequence to determine the direction of torque at the output element; means including means to apply torque of the output element to the electrode to efiect movement of it: circuit means for energizing the respective field windings proportionally to current in the arc and voltage across it, respectively and for balancing their energizations when the current and voltage are at said predetermined values, and when their energizations are unbalanced, to cause the torque at the output element to effect movement of the electrode in the direction to restore the current and voltage to said predetermined values, upon deviation thereof from said values.

9. In an apparatus for adjustably moving a consumable are supporting electrode to maintain the current in the are at a predetermined value as it tends to vary; a power transmission comprising a pair of electric generators and a rotary output element and differential gearing constructed to be driven by the torque of a continuously running motor and to differentially apply torque to the output element and to the two generators; a common load circuit for the generators, a pair of field windings for the respective generators, relative unbalanced energization of which, rendering one winding more effective than the other, causes one or the other of the generators to generate load current in the common load circuit and drive the other generator as a motor and develop braking torque, and as a consequence to determine the direction of torque at the output element; means including means to apply torque of the output element to the electrode to effect movement of it; circuit means for energizing one field winding proportionally to current in the arc and the other at constant energization; and for balancing their energizations when the current is at said predetermined value; and, when their energizations are unbalanced, to cause the torque at the output element to efiect movement of the electrode in the direction to restore the current to said predetermined value upon deviation thereof from" said value.

l0. In'an apparatus lor adjustablymoving a consumable ar supporting electrode to maintain the voltage aeross the arc at'a predetermined value as it; tends to vary; a power transmission comprising" a pair of electric generators and a rotary output element and differential gearing constructed. to be. driven by the torque of a continuously running motor and to diflerentially apply torque to the output element and'to the 'twogenerators; a common load circuit for the generators, a pair of field windings for the respective generators, relative unbalanced energlaation oi which, rendering one winding more elfective than the other, causes one or the other 01' the generators to generate load current in the common load circuit and drive the other generator as a motor and develop braking torque, and asf'a consequence to determine the direction 01' torque at the output element; means including means to apply torque of the output element to the electrode to ei'lect movement or it; circuit at a predetermined value an electrical quantity 3 at the arc that tends to vary; a difl'erential power transmission comprising a rotary output ele-;

ment, and a rotary torque developer comprising a winding; the transmission constructed to re-- ceive torque from a continuously running motor and apply equal torques differentially to the output element and to'the torque developer independently of speed of the motor; and constructed to respond to variations of energization of the.

winding to vary the torque developed by the:

torque developer, to correspondingly vary the torque of the output element; means biasing theelectrode to move it in one direction; means communicating torque of the output element to the electrode'in opposition to its bias circuit 'means energiz t e winding proportionally to an electrical quantity at the are, to cause the output element to eil'ect movement of the electrode to restore the electrical quantity to a predetermined value upon deviation 0! the quantity from said value.

LEV A. TROOV;

REFERENCES CITED The following references are of record in the me of this patent:

Number Name Date 1,374,404 Soons et a1; Apr. 12, 1921 1,514,591 Smyser Nov. 4,1924 1,514,592 Smyser Nov. 4,, 1924 2,079,956 Burgett May 11, 193'?v 2,132,479 Holslag Oct. 11,1938, 2,183,473 Burgett Dec. 12, 1939 2,393,662

Skuhrovec Jan. 29, 1946

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