US1449887A - Furnace-regulator system - Google Patents

Description

Mar. 27, V1923.

. C. A. BODDIE.

FUHNACE REGULATOR SYSTEM.

FILED NOV. 13, 1919.

`vlvlwuisslis: Q. Q. @Mu

Patented Mar. 27, 1923.

UNITED STATES PATENT OFFICE.

CLARENCE A. BODDIE, F PITTSBURGH, IPENNSYLVANIA, ASSIGNOR T0 WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION 0F PENN- SYLVANIA,

. FURNACE-REGULATOR SYSTEM.

Application led November 13, 1919. Serial No. 337,687. i

To all whom it may concern.'

Be 'it known that I, CLARENCE A. Bonnin, a citizen of the United States, and a resident of Pittsburgh, inthe county of Alle- 5 gheny and State of Pennsylvania, have invented a new and useful Improvement in Furnace-Regulator Systems, of which the following is a specification.

My invention relates to regulator systems and particularly to regulator systems for governing the operation of the movable electrodes in electric furnaces.

One object of my invention is to providel a furnace-regulator system that shall govern each movable electrode, not only in ac'- cordance with the current ,flowing through it but also in accordance with the potential difference obtaining between the neutral point of thev supply circuit and the bath of material being treated to maintain equal heating effects by the various electrodes, and that shall be so operated as to prevent hunting action.

In operating electric furnaces of the movable-electrode type, and, particularly, if the furnace is connected to a three-phase supply circuit, considerable trouble is generally` experienced in obtaining equal heating effects by the various electrodes or in obtaining a fixed ratio of heating effects by the various electrodes. Such uneven heating effects are liable toy be experienced if a charge having an uneven resistance throughout its structure is being treated in the furnace. In case the electrodes of the furnace produce unequal heating effects, the lining of the furnace is not subjected to an even temperature and, consequently, the length of time which the furnace may be operated without repairs is greatly reduced. Thus, the producing of'unequal heating effects by the various .electrodes is liable to impair the value of the material being treated in the furnace and, moreover, to` `cause a more` rapid deterioration of the furnace than would be effected if the ratio of the work performed. by the various electrodes were v maintained substantially constant.

In an electric furnace constructed in acelectrode is provided with means for soadjusting it that the ratio of work ,performed by the various electrodes shall. vbe maintained substantially constant, irrespective cordance with my invention, each movabley of the operating conditions of the furnace, and,moreover, means is provided for in suring the system against hunting action.

' More specifically, my invention relates to an electric furnace having three movable r electrodes which are connected to a threephase supply circuit. Each of the electrodes is provided with a motor for raising and lowering it and each motor is provided with a regulator for operating it to maintain the ratio of the heating 'effect produced by the associated electrodes to the heating effects produced by the remaining electrodes substantially constant. Each of the regulators embodies an electromagnet having two windings which operate two rent passing through the second winding of each electromagnet will have lsuch phase relation to the current passing through the first windingv as to add to, or subtract from, the energizing effect of the firstwinding, according to whether the associated electrode is being operated to produce a greater or a less than normal portion of the heating effect of the furnace. Moreover, means is provided which is operated by the two switches for varying the energization of the current winding in each regulator to prevent hunting action.

This invention is an improvement on the furnace-regulator system disclosed in the patent application Serial No. 288,832. filed April 9, 1919, by Robert D. Evans and assigned to the Westinghouse Electric & Manufacturing Company, and reference may be had to the above application for au vanalysis of the phase relation of the currents owing through the current and potential windings of 'the main magnet-.of the regulator.

'ulator system constructed in accordance with my invention. a

Referring to the drawing, an electric furnace 1, comprising a receptacle containing a bath of material` 3, is provided with three movable electrodes 4, 5 and 6 which are-directly connected to a three-phase supply circuit comprisin conductors 7, 8 and 9. Each of the movab e electrodes 4, 5 and 6 is provided with a motor for raising and lowering it and a regulator for so governing the electrode motor as to maintain the ratio of heating effects by the various electrodes substantially constant: Inasmuch as the electrode motors and the associated regulators are similar in construction and operation, it is deemed suflicient to illustrate and describe but one motor and one regulator, namely, the motor and regulator which are associated with the movable electrode 6.

A motor 10, comprising an armature 11 and a field winding 12, is provided for raising and. lowering the electrode 6 to maintain a substantially constant heating effect by the electrode. The field winding l2 is directly connected to an auxiliary supply circuit comprising conductors 13 and 14, and the armature 11 -is selectively connected to the supply conductors 13 and 14 by means of two switches 15 and 16. The motor 10 is mechanically connected-to the electrode 6 inany suitable manner, as by means of a winding reel 17 and a fiexible connector 18 which passes over a pulley 19.

A regulator 20, comprising a main control electromagnet 21 and thel two switches 15 and 16, is provided for governing the operation of the motor 10, not only in accordance with the current fiowing through the electrode 6 but Aalso in accordance with the potential obtaining between an artificial neutral point of the supply circuit and the' bath of material 3 being treated in the furnace. The main control elect-romagnets for the regula-tors which govern the operation of the electrodes 4 and 5 are designated by the reference characters 23 and 22.

The main control electromagnet 21 em.- bodies a current winding 24 having taps 25,

26 and`27 extending from it, a potential winding 28 and a co're armature 29. The

core armature 29 is provided with a dash pot 30 for adjusting the speed of its operation and is pivotally connected to a contact arm 31. The current winding 24v is connected to the three-phase supply conductor 9 by means of a transformer 32 in order to be energized in accordance with the current flowing through the electrode 6. The potential winding 28 is connected across two conductors 33 and 34 which are respectively connected to the bath-of material 3 being treated and an artificial neutral point of the 'When two windings are so connected, the neutral point of the three-phase circuit 1s obtained 'by a tap from the winding 36 which divides the winding 36 in the ratio of 2 to 1. In brief, the neutral point of the supply circuit is represented by the potential'existing in the winding 36 at a point one-third of 'its length from the point of connection to the winding 35. The tap 37 from the winding 36 is directly connected to the conductor 34. Inasmuch as the above described means for obtaining an artificial neutral point in a supply circuit is well-known, it is deemed unnecessary to make a complete analysis of the potentials obtaining in .the two windings when so connected. i

The main control magnet 22 is provided with a current winding 38, which is connected to the three-phase supply conductor 8 bymeans of a current transformer 39, and with a potential winding 40 which is connected across the conductors 33 and 34. The.

main magnet 23, which is associated with the electrode 4, is provided with a'current winding 41 which is connected to the threephase supply conductor 7 by means -of a current transformer 42, and a potential winding 43 which is connected across the conductors 33 and 34. l

The contact arm 31 is fulcrumed at 44 and carries a main contact member 45 which engages contact members 46 and 47, according to the operative position of the main magnet 21. members 45 and 46,v a circuit is completed from the supply conductors 13 and 14 for operating the switch 16 and, upon engagement between' the contact members 45 and Upon engagement between the contact,

47, a circuit is completedl for operating the switch 15.

The switch 15 comprises a winding 48 and a core armature 49 which is controlled by it.

The core armature 49 is directly connected to two switch members 50 and 51 and two interlock switch members 52 andv 53. The two switch members 50 and 51 serve to-connect the armature llacross the supply con? `ductors 13 and 14 for effecting counter-clockwise rotation of the motor 10. The counterclockwise rotation of the motor 10 raises the electrode 6 to decrease the current flow` main magnet to prevent any hunting action when the electrode is being raised from the bath of material.

The switch 16 comprises a winding 54 and an armature 55 which is controlled by it. The armature 55 is directly connected to two switch members 56 and 57 and two interlock switch members 58 and 59. The two switch members 56 and 57 serve to connect the armature 11 across. the supply conductors 13 and 14 for operating the motor 10 in a clockwise direction to lower the electrode 6 in the furnace. The interlock switch member 59, upon operation of the switch 16, serves to open a short-circuit which normally obtains across that portion of the winding 24 which is included between the taps 26 and 27. Such operation of the interlock switch member 59 serves tol prevent any hunting action when the electrode 6 is being lowered in the furnace.

.'When the two switches 15 and 16 are deenergized, the two interlock switch members 52 and 58 complete an energizing circuit from the supply conductors 13 and 14 for a brake relay 60. `The brake relay 6() completes a dynamic-braking circuit for the armature 11 through a resistor 61.

Assuming that the electrode 6 is performing more than its normal portion of the work of the furnace 1, there is either an increased current flow through thel electrode 6 or an unbalancing of the phase relation of the current flow through the electrodes 4, and 6, the amount of which will be indicated by the potential obtaining between the neutral point of the supply circuit and the potential of the bath of material 3 being treated in the furnace. If an increased current flows throuoh the electrode 6, the energization of the winding 24 willbe increased to operate the contact arm 31 and effect engagement between the contact members 45 and 47 and, if an unbalanced phase relation obtains, the winding 28, which is energized in accordance with the potential existing between the neutral point of the supply circuit and the bath of material 3, will be energized to assist the winding 24 in moving the contact arm 31 to effect engagement-between the lcontact members 45 and 47. Upon engagement between the contact members 45 and 47, a circuit .is completed from the supply conductor 13, through the contact arm 31, contact members 45 and 47 and the winding 48 of the switch 15, to the supply conductor 14. Thereupon, the switch is operated to complete a circuit through the armature 11 for operating the motor 10 in a counterclocki wise direction. The circuit through the armature 11 is traced from the supply conductor 13, through the switch member 51, armature 11 and the switch member 50 to the supply conductor 14.

In case no means were provided for pre- Venting any hunting action, the main control magnet 21 would be controlled solely by the circuit conditions of the electrode 6 and, consequently, the main magnet would not be operated to separate the contact members and 47 and stop the motor until normal conditions obtained in the electrode circuit. Consequently, the inertia4 of the various movingparts of the regulator and the inertia of the armature would cause overtravel and, accordingly, would raise the electrode 6 above the desired point to obtain normal operating conditions. In order to prevent such overtravel, and the consequent hunting action, the interlock switch member 53 is operated simultaneously with the operation of the motor 10 for short-circuiting a portion of the winding 24 to decrease the energization of the main magnet 21 and, consequently, to effect a separation of the contact members 45 and 47 just prior to the obtaining of normal conditions in the electrode circuit.

In case the electrode 6 is performing less than its normal portion of the work of the furnace, the energization of the winding 24 is decreased or the winding 28 is energized by a smaller current or by current having such power factor as to oppose the action of -the current flowing through the winding 24 and thus permit the operation of the contact arm 31 to effect engagement between the contact members 45 and 46. Upon engagement between the contact members 45 and 46, a circuit is completed which extends from the supply conductor 13 through the Contact arm 31, contact members 45 and 46 and the winding 54 to the supply conductor 14. Thereupon, the swltch 16 is operated for connecting the armature 11 across the supply conductors 13 and 14 to operate the motor 10 in a clockwise direction. The clockwise rotation of the motor 10 lowers the electrode 6 to obtain normal operating conditions.

In order to prevent any hunting action when the electrode is being lowered in the -furnace, the interlock switch member 59 is operated, simultaneously with the operation of the motor 10, to open the short-circuit which normally obtains across that portion of the winding 24 which is included between the taps 26 and 27. Thus, the energization ofth'e main magnet 21 is increased and its setting is so changed` as to, effect separation of contact members 45 and 46 just prior to `the obtaining of normal conditions in the circuit of the electrode 6.

yAlthough the operation of but one electrode has been described in detail, itshould be noted thatthe main control magnets 21, 22 and 23 are operated to simultaneously adjust the three electrodes 4, 5 and 6 to maintain the ratio of work performed -by them substantially constant. The current esv -flowing through the potential windings 28,

g 40 and 43 will have phase relations relative to the currents flowing through the wind- v ings 24, 38 and 4l to assist or to oppose the action of the windings 24, 38 and 4l, according to the heating effects of the associated electrodes. For a complete analysis of the yrelations of the currents flowing through the potential and the currentwindings, reference may be had to the application Serial No. 288,832, above referred to.

Modifications in the system and arrangement and location of parts may be made Within the spirit and scope of my invention,

and such modifications are intended to be y covered by the appended claims.

I claim as my invention:

1. In a furnace regulator system, the combination comprising a polyphase supply circuit, a plurality of movable electrodes connected thereto, means for automatically contro-lling each of said electrodes to equalize the heating effect of the various electrodes, and automatic means for preventing hunting action.

2. In a furnace-regulator system, the combination comprising a polyphase supply circuit, a plurality of movable electrodes conlnected thereto, a motor for raising and lowering each of said electrodes, means for operating each motor to equalize the heating effects produced by the various electrodes, and automatic means associated with each electrodev for preventing hunting action.

3. In a furnace-regulator system, the combination comprising a three-phase supply circuit, three movable elec-trodes connected thereto, a motor for raising and lowering each of-said electrodes, means for selectively operating said motors in accordance with the characteristics of the current supplied to the electrodes to equalize the heating effectsA produced by the various electrodes, and automatic means for preventing hunting action.

4. In a furnace-regulator system, the com- I bination comprising a supply circuit, three movable electrodesconnected to the supp-ly circuit, means for adjusting said electrodes in accordance with the difference in potential between` the bath of material being treated and the neutral point of the supply circuit, and means for insuring the system against hunting action.

5. In a furnace-regulator system, the combination comprising a supply circuit, three movab-le electrodes connected-to the supply circuit, means for adjusting said electrodes in accordance with the difference in potential between the bath of material being treated and theneutral point of said supply circuit and in accordance with the current supplied tothe electrodes, and means for preventing hunting action. 6. In a furnace-regulator system, the combination comprising a three-phase supply circuit, three movable electrodes connected to the supply circuit, means controlled by the potential existing between the neutral point of the transformer and the bath of material being treated for maintaining the ratio of work performed by the various electrodes substantially constant, and'means for insuring the system against hunting action. i 7. In a furnace-regulator system, the combination of a polyphase supply circuit, a

ciated electrode with respect to the other electrodes, and means for varying the energization of each current winding to prevent hunting action.

8. In a furnace-regulator system, the combination with a three-phase supply circuit, three movable electrodes connected to said circuit, and a motor for operating each of said electrodes, of means comprising a main magnet having a potential winding for neutralizing the potential between the electrodes and the bath of material being treated, said potential winding being energized in accordance with the difference in potential between the neutral point of the supply circuit and the bath of material being treated, and means for controlling said electromagnet to prevent hunting action.

9. In a furnace-regulator system, the combin'ation with a three-phase supply circuit, three movable electrodes connected to. said supply circuit, and a motor for raising and lowering each electrode, of means comprising a main magnet having a current and a potential winding for controlling each electrode to maintain'the ratio of work performed bythe various electrodes substantially constant, each of said current windings being energized in accordance with the cur-` between the neutral point of said supplyl circuit and the bath of material being treated, and means for varying the energizatioln of said. current windings to prevent hunting action'. A

10. In a furnace-regulator system, the combination with a polyphase supply circuit, a movable electrode connected to said supply circuit, and a motor for raising and lowering said electrode, of means comprising a main magnet having a current and a potential Winding for operating the electrode to maintain a substantially constant heating effect by the electrode arc, said potential windingbeing energized in accordance with the potential obtaining between the neutral point of the supply circuit and the bath of material being treated, and means for varying the energization of the current winding to prevent hunting action.

11.1n a furnace-regulator syst-em, the combination comprising a plurality-of movable electrodes, means for maintaining al constant current flow through the electrodes and for equalizing the potentials across the various electrode arcs, and automatic means for preventing hunting action.

1Q. In a furnace-regulator system, the combination comprising a plurality of movable electrodes, means comprising a pluralcoil electromagnet operatively associated with each electrode for maintaining a predetermined ratio of heating el'ects by the various electrodes and means for preventing hunting action.

In testimony whereof7 I have hereunto subscribed my name this 27th day of Oct.,

CLARENCE A. BODDIE.

Images