US1241351A - Electric furnace. - Google Patents

Description

J. L. DIXON.

ELECTRIC FUHNACE.

APPLICATION mio rEe.23.1s\5.

1 ,24 1 ,35 1. Patented Sept 25, 1917.

4 SHEETS-SHEET 2.

A TTOHNEYS JOSEPH L. DIXON, OF SHEFFIELI), ENGLAND.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Sept. 25, 1917.

Application tiled February 23, 1915. Serial No. 9,782.

T 0 all 'whom it may concern.-

Be it known that I, Josnrn L. Dixon, a subject of the King of Great Britain, resid ing at 6 Ashgate road, in the county ot York and cityvof Sheliield, England, have' invented certain new and useful -Improvements in Electric Furnaces; and I do hereby declare the ollowing'to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it a pertains to make and use the same.

lectrie are smelting'furnaces as known heretoforecan be classified under two heads.

' 'First those wherein the current passes from one electrode to the' other, and second those in which substantially the entire current passes through the bath of metal, through the lining and back tothe generator.

Certain distinct advantages and accompanying disadvantages accompany the use of either mode of using the current alonc and, where dierent conditions are to be 'foreseen and4 provided for, a distinct imin .the furnace.-

provement will follow the devising of a suitable system wherein the two modes of using the current are made optionally available in combination or separately. Such an improvement follows from the use of my present invention.

The object of my invention is the construction of-fnrnaces in which the proportion of current passing through the bathV and lining is separately controllable, so that if desiro'll'there can -be caused to flow through t e'bath and lining much smaller proportions of with furnaces o tioned.

I carry out my invention by several methods, the method selected in any particular case beingr dependent partly on the sii/.e of the "furnaces, and partly on the nature of, the metallurgical o eration to he conducted A l-the methods are'such that the power may be taken from a stnudard poly hase supply system, n most, important euturc being that the carrying out of the invention does not necessitate any unequal loading of the supplysystcm.

In the accompanying drawings, Fiure l isa diagram lillustrativeof thc general-princilple of my il the second type above meninvention, Fig. 2 1s a diagram ustrutive of the general ease wherein three pl'msecnrrentsnre applied to furnaces having an even number of upper electrodes, Fig. 3 is a diagram showing one form of fury current than are possblenace embodying my invention, Figs. 4 and 5 are vector diagrams illustrative of the different conditions available in the system shown in Fig. 3, Fig.` 6 is a diagram illustratinv a modified' form of my invention, Figs. 8 and 9 are vector diagrams illus-l .rat-ing the modes of use of said modification, and'Fig. 10 is a diagram illustrating still another modification;

In Fig. l, Ihave shown a furnace wherein three upper electrodes AB and Care connected to asuitable source".of threev hase current from points a, b and c whose p ases are 120 degrees apart, while the lower terminal N is connected to the neutral point'n.

This arrangement is within my invention `and admits of obtaining the advantages hereinafter pointed out. l

One method of carryivri' out my invention is shown in Fi 2, in' ich F, is'the furnace, A A, B, are four electrodes (herein'nitcr termed uppcr electrodes) which arc on to the bath of metal or alloy or other material. N, is an electrode embedded in the furnace lining (hereinafter termed a lower electrode);

The furnace is fed with two-phase seco'mlary current taken from" two single phase transformers, represented in' the as a., and 7), whose primaries are fed from three-phase mains, 1, 2nnd 3.

The two secondary terminals of thetransformer, a, are connected, one to the electrode A1., and the other to the electrode AH The middle point of the secondary wind-- ing of the'transformer, a, is connected to the lower electrode N.

Similarly, the secondary terminals of the transformer, 'li are mnncctcd to the electrodes B and liz and the middle point connected to the lower electrode N, as shown in the diagram. v

It is apparent thaf u'hcn'tlle two electrodes A' and A?. urnsupplyiug to the furnace currents of equal magnitude, these currents will exactly neutralize cach other and the transformer. a, wilt supply no current to the lou'vr rlcrlrude N. The rllltrodls, A und A2 may he adjusted so that th'e currents in lhcm are not equal,l und therefore there is a current flowing along the wire connected to the middle point of the transfo. mer, "a, and through the lower electrode N. To take an extreme rase for the salio nl' illustration,

drawings the electrode A2. may he raised so that it whole of the current in the electrode A, passes through the hath and returns to the middleV point of thc transformer, a. The same adJustment may he iliade with the electrodes B1, and B2, fed by the trahsloriner, b.

Whatever adjustment is made with the four upper electrodes and whatever the amount of current flowing through the lower electrode, the electrical system will not be unequally loaded if the transformers a, and b, are supplying equal amounts of power to the furnace.

It is apparent that the invention may be carried out with the middle point of only one of the transformers connected to the lower electrode, N. l

My invention contemplates means for easily altering the connections between the transformer )rimaries and the mains l, 2 and 3 where y the phase relations in the secondaries may be so altered as to control at' will the amount of current passing through the bath to the lower electrode.

In Fig. 3 is shown an arrangement for this urpose wherein is used a number of trans ormers less than the number of upper electrodes in the furnace. In this case six upper electrodes are supplied from Afour transformers. For this purpose two electrodes A, B are connected with the terminals of one secondary a. Two others, C, D, are connected in common to one secondary terminalj of b, while E and F are connected with the outer terminals of the secondaries of qand d. 'lhe interior or contiguous secondary terminals of c and lare connected in common with the secondary of The four primaries of the four transformers are Scott-connected with the mains 1, 2 and 3, and these connections are made by means of multiple switches Irland Z.

W hen the switch 'is closed and switch l is open, the phase relations-,are indicated by the diagram inlgl, ai. When Z is closed and l: is open the phase relations are those indicated in Fig.

ln Fig. (i is shown another mode of sup,- plying six electrodes from l'our transformers l'ed from the three-phase mains l, il and,

2l. llore the multiple switches l', I, m and u cause various changes in phase relations, thus; alteringr the proportion ol current going through the bath.

l'Vitli switchesl and m closed and switches 5,5"Z and u open, thecurreuts occupy the positions shown in the fliagrani Fig. T. and the `only current flowing through the lower elec- .lrode`is' that duo to the lill'erence in the seclondary \'oltages.

FlfVhcn larger currents "through the lowel`L` electrodes are required, the switches It' and n, are open and the s\vitcln\.s','a1id m closed, and the transformer e', supplies current `in` a reversed manner, the positions of,. the` six currents heilig shown in Fig. 8. Similarly by opening the switches, Z and m, and closing' [he switches Il: and n, the transformer, c will supply current 1n a reversed manner.

When still larger currents through the lower electrode are required, the switches, I.: and m, are opened and the switches l and n, closed, and then both the transformers c' and 0, are reversed, the secondary currents occupying the positions shown in Fig. 7.

W hatercr the magnitudes and positions of the secoiulary currents, the electrical s stem will not be unequally loaded provide each of the transformers, a, and b, is supplying power equal to the total power supplied by the two transformers, o* and c.

In Fig, 6, I have shown the primary side ot' the transformers connected to the supply mains in star fashion. It is apparent that without interfering with the can-yin ont ot' the invention they can be connected in delta fashion.

In all lhe methods I have described of carrying out my invention, there is only one lower electrode embedded in the lining or sole of the furnace. At the same time, I

wish it to be understood that my invention,

ofthe t 'ausformeis a, b, c and d. The two lower electrodes are shown at N and N and are connected rcs ectively to common secondary terminals oi) a and c, and of b and d.

lVhat I claim isl. An electric furnace having suitable u said transformers, a common connection between the terminals of two of said secondaries and the lower electrode, and suitable connections between the secondaries of saidtransformers and said upper electrodes.

2. An electric furnace having suitable u per electrodes and a lower electrode, mam

leads for supplying three-phase alternating current, transformers less n1 number than `said upper electrodes and so connected with said 4main leads as to deliver two phase current from their Secundarios, switches snit-` ably connected with the primary circuits for producing alterations iu phase relations in said transformers, and suitable connections between Asaiil eleclrodes and the--secondaries of said t'ahsforiners. f

3. Pili electric furnace ,haringsix upper'A electrodes and a lower electrode two pairs connection between the remaining second- 1u of transformers, means for suppying alterar terminals and seid lower electrode. nating current to the rimaries thereof, conn testimon whereof, I aix my signature, duotors connectn t e outer terminals of in presence o two witnesses.

5 one pair of transfrmer secondaries each to two of the upper electrodes, conductors con- JOSEPH L. DIXON. nectin one secondary terminal of each of Witnesses:

the ot er transformers with one of the re- KATHARINE C. MEAD,

maining upper electrodes, and a .common GEO. A. BYRNE.

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