US1242971A - Stabilizing and power-factor correcting means for electrical circuits. - Google Patents

Description

v -1 F.-.P Tns,, STABIEIZNG AND POWER FACTOR COREKECTlNG MEANS FOR ELECTRICAL CIRCUITS.

f I I Anucmon FI LED mm. a}. ms. E 1 3242,9171, Patented Oct 16,1917.

WITNESSES I INVENTOR Jag/7 f'Re/em Y 7 ATTORNEY 4 UNITE STATES rlrrnnr FFICE.

JOHN F. PETERS, OF EDGEWOOD PARK, PENNSYLVANIA, ASSIG NQR 1'0 WESTING= HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPQRATION OE IENN SYLVANIL Specification of Letters Patent.

PatentedOct. 1c, 1918?.

Application filed March 4, 1916,. Serial No. 82,079.

To all whom it may concern:

Be it known that I JOHN F. Pn'rnns, a citizen of the United tates, and a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvania, have in vented a new and useful Improvement inpacity.

In furnaces of the electric-arc type which are utilized for steel manufacturing purposes or for nitrogen fixation processes, the electric arcs employed are very unstable and tend to become disrupted when any slight disturbance afiects their stability. The electrodes of such a furnace, on being consumed, must be properl regulated in order to maintain the arcsw ich tend more and more to extinguish themselves as their lengths are increased. At the same time, the electrical system supplying power to an electric-arc furnace operates at a relatively low power-factor. At best, however, the power-factor obtaining in the power system is totally inadequate to insure good operating eificiency. This defect is more serious when several furnaces are supplied from the same power mains and required to be simultaneously operated therefrom.

Since the electric currents employed in electric-arc furnaces are usually of extremely high values, the heating efiects obtaining in portions of the circuit where such effects are extremely undesirable, may be very serious, at times, by reason of the extremely high valued wattless currents flowing in the system. Because of the instability of the electric arcs employed in these furnaces and the low power-factor obtaining in the system, the control systems heretofore employed in connection with such furnaces to overcome the aforementioned defects have been, of necessity, very complicated and intricate requiring a great deal of attention on the part of operators.

My present invention is adapted to improve the power-factor 'of power systems supplying energy to electric-arc furnaces, and, at the same time, to stabilize the result ant arcs in order to insure their continuance during the operation of the furnaces. Both of the aforementioned results may be jointly obtained when a plurality of electric-arc furnaces operatin from a common supply circuit are availab e, since stabilizing means having diflerent electrical qualities are associated with the arc-producing elements of the separate furnaces to procure the aforementioned joint results, as will be hereinafter described.

While the present description and draw ing are limited to electric-arc furnaces utilized for melting metal billets, it will be understood that my invention may be employed in any electrical power system furnishing power to power-consuming devices depending upon the production of electric arcs for their operation. Among such devices may be mentioned those employed for the fixation of nitrogen, refining furnaces and a variety of other uses.

To more fully understand my invention,

scription and the accompanying drawing,

the single diagrammatic figure of which, for illustrative purposes only, shows my invention employed in connection with a power system that furnishes current to electric-arc furnaces.

A three-phase alternator 1 is connected to a primary winding 2 of a step-down transformer 3, a secondary winding 4- of which is employed to transform the energy furnished by the alternator 1 into low-voltage and high-current energy. An electric-arc furnace 5 comprising three electrodes or areproducing elements 6, and another similar furnace 7 having three similar electrodes 8 are connected to three mains 9 extending from the secondary winding 4: of the trans former. A. charge 10, contained in the cruci= bio of the furnace 5, is shown as metal billets which are to be melted by the electric en= ergy supplied to the furnace. The melting of the billets is effected by the arcs that extend from the electrodes 6, each of which is connected to a main 9 of the three-phase supply circuit. In this particular instance, the arcs are formed by reason of the current flow periodically extending between the three electrodes-6, as is characteristic of electric furnaces of this general ty e. The furnaces 5 and 7 being represente as identical,

which will oppose rapid changes or variations in the amount of electric current traversing, or the power introduced into, the arc. For instance, it will be apparent that a choke coil or inductive reactance device will perform the aforementioned function,.namely, that of opposing abrupt changes in the amount of electrical power obtaining in the circuit supplying current to the arc. To this end, I have introduced in each of the leads 11, connecting the electrodes 6 to the power supply mains 9, a reactance coil 12 which, byreason of the inductive reactance afiorded thereby, will stabilize the arc extending from each of the electrodes 6. In some types of furnaces, especially those of large capacity, the inherent impedance orinductive reactance of the leads 11 may be suflicient to stabilize the arcs.

Of course, the reactance devices 12 will further decrease the power-factor obtaining in the i'powercircuit, and means should be provided forovercoming the inductive reactance imparted by the reactors '12 which will improve the power factor of the circuit and insure economical and efficient operation of the system. To this end, I introduce in each lead '13 which extends to the electrodes 8 of the furnace 7, condensive reactance elements 14. The condensers 14 are preferably not connected directly in circuit, but are associated with series transformers 15 having their primary and secondary turns so proportioned that the condensive reactance afforded by the condensers 14 may be made adequate while-condensers of small capacity only are utilized. The condensers 14, which are usually adapted for high-voltage operation, perform a double function, one of which is to stabilize the arcs extending from the electrodes 8, and the other of which is to neutralize the inductive effects introduced in the power system by reason of the insertion of the inductive reactance elements 12. As a result, the inherent low power factor resulting from the arc furnaces alone is improved. The capacity of the condensers 14 need not necessarily be so high as to establish unity power factor in the system when the furnaces 5 and 7 are simultaneously opera-ted, but their capacity should be such as to insure an economical operation of the power system whereby the power-factor obtaining therein may compare favorably with other power systems furnishing power to consumin devices.

From t e foregoing description, it will be noted that I have provided means for stabi lizing the arcs produced in electric arc-furnaces and, at the same time, have selected the stabilizing devices so that by their separate actions upon the system, the resultant power-factor of the system may be increased to a sufficiently high value to insure economical operation of the system.

While my description has been limited to one application only, namely, that of electric arc furnaces, it will be understood that my invention may be employed in connection with a variety of electric arc utilizing devices which impart, by reason of their inherent qualities, undesirable electrical characteristics to the system that should be improved to insureeconomical operation thereof, and I desire, therefore, that only such limitations shall be imposed upon my invention as are indicated in the appended claims. 7

I claim as my invention:

1. The combination with an alternatingcurrent power-supply system and a plurality of electric arc utilizing devices connected thereto, of means severally possessing diverse electrical characteristics and severally associated with said devices for both stabilizing the attendant electric arcs produced and improving the power-factor obtaininlg in the supply system.

2. he combination with an alternatingcurrent power-supply system and a plurality of electric arc-utilizing devices connected thereto, of stabilizers severally possessing diverse electrical characteristics and associated with the arc-producing elements, said stabilizers being so selected that, in combination; the value of the power-factor obtaining in the supply system may be controlled.

3. The combination with an alternatingcurrent power-supply system and a plurality of electric arc-utilizing devices con nected thereto, of inductive reactors only in serted in circuit with some of the electric arcing elements, and condensive reactors only inserted in circuit with others of the electric arcing elements, said condensive and inductive reactors stabilizing their attendant electric arcs and, in combination, regulating the power-factor of the supply system.

4. The combination with an alternatingcurrent power-supply system and a lurality of electric arc furnaces having t eir electrodes connected thereto, of stabilizers possessing inductive characteristics only connected in series circuit with some of the electrodes, and stabilizers possessing condensive characteristics only connected in series circuit with others of the electrodes in order to stabilize the attendant electric arcs, said stabilizers, in combination, being so selected that the power-factor obtaining in the power-supply system may be improved over that normally obtainin therein.

5; Analternating-current 'stributing stem comprising power-supply mains, a p urality of electric arc-utilizlng devices connested thereto which inherently establish a low power factor in the system, and means severally possessing diverse electrical characteristics and severally associated with the electric arcing elements which both stabilize the attendant electric arcs and increase the value of the power-factor normally obtaining in the system.

6. An alternating-current distributing system comprising power-supply mains, a plurality of electric arc-utilizing devices connected thereto which, of themselves, inherently establish a low power factor in the system, and stabilizers possessing inductive reactance only associated with some of the electric arcing elements, and stabilizers possessing condensive reactance only associated with others of the electric arcing elements, said reactors stabilizing the attendant electric arcs and, in combination, providing means for increasing the value of the power factor normally obtainin in the system.

In testimony whereo I have hereunto subscribed my name this 29th day of Feb.,

' JOHN F. PETERS.

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