US1198625A - Electric furnace. - Google Patents

Description

J. L. mxow. ELECTRIC FURNACE.

APPLICATION FIL ED AFR-10. 1916.

Patented Sept. 19,1916.

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To all whom it may concern;

Be it known that l, Josnrni L. BIXUN? a subject of the King of Great Britain, residing in the city of Detroit and State of Michigan, have invented certain new and useful Improvements in Electric liurnaces and do hereby declare the following to be of electric smelting furnaces wherein the current may be made to pass either from one electrode to another over the bath or from one or more of these either wholly or in part through the bath and furnace lining.

The object of my invention is to supply an improved construction for electric smelt ing furnaces of this kind whereby threephase currents fed from specially arranged transformers are made controllable to their phase relations by suitable-switches, so as to cause different proportions of the total current to flow through the bath and lining It is a further object of the, invention to so accomplish this that a maximum of flexibility in such current changes may be attained, and to 0 this without unbalancing the load on the feeding mains.

A preferred embodiment of the invention is illustrated diagrammatically in the ac-' companying drawings wherein- Figure 1 shows a furnace having two groups of three upper electrodes supplied with three-phase alternating current and Figs. 2 and 3 are vector diagrams illustrating different phase conditions produced by certain changes in the electric connections shown in Fig.

In Fig. 1, the usual'hearth, crucible or container is shown at 10, the molten bath within it is shown at 11 while the six upper electrodes 12, 13.14, 15, lfiand ll project downward toward the bath through the in sulating cover 18. The current which passes downward through the bath, when so desired returns through the lower electrode 19. The working current is derived from the threephase alternating current mains, 20, 21 and 22 through two groups of three transformers shown respectively at 23; 2 1 and 25 and at 26, 27 and 28. The three primaries of the transformers 23, 24- and25 are connect 1. Elle. 55,1 32. iserial 8 3,652,

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gular connection with the leads or mains 39,391 and 22; while the remaining three transformers 26, 27 and 28 are coniected in star fashion. A common. conducor leads "to the lower electrode 19, and to this one is connected one terminal of each of the secondaries of all the transformers. The remaining secondary terminal of each transformer connected to its appropriate upper terminal, as shown.

While I have shown one three-transformer group fed by triangularly connected conductors and one such group combined therewith as described and fed by star-connected conductors, it is to be understood that my invention is notlimited to the use of a single group of each kind but covers combinations of triple groupsof these two kinds whether one or more of each of such 1 groups is used.

system; and other modes of changing con nections may be used for altering the phase relations without departing from my invention.

.When the switches 31 are closed and switches 30 are open the phase relations shown in Fig. 3 are obtained. in this case, assuming the currents to be equal in all of the upper electrodes, the value of vthe current through the bath will be zero. When, on the other hand, switch 31 is open and switch 30 is closed, the phase relations will be as indicated in 3. In this case, assuming currents of equal unit magnitudes in the upper electrodes, the value of the current through the bath will be 1.0%. Uther possible arrangements willvbe obvioils, and by increasing the number of shade aveilanla lay choice at it as:

which various proportions of current fiow may be made to reach the lower electrode through the bath,

By using two groups of transformers, one connected to the supply mains in triangular and the other in star fashion the proportion of current which may be caused to flow through the bath to the electrode can .be much more extensively varied than would be possible if the electrodes were fed from groups of transformers delivering threephase star-connected currents in the ordinary manner. In such ordinary cases, the only changes available are those brought about by the reversal of one phase, which,

in the case of a furnace with six upper electrodes causes the current in the lower electrode to be four times as great as that in each of the upper electrodes.

This application is a division of my earlier application for improvement in electric furnaces, filed February 23, 1915, Serial No. 9782.

-What I claim is:

1. An electric furnace having a lower electrode and two or more groups of three upper electrodes, main leads for supplying threephase alternating current, transformers in groups of three corresponding in number with said upper electrodes, and having their secondary coils suitably connected with said upper and lower electrodes, conductors con- Gopies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

ductors connecting the primaries of one or more of said three-transforiner groups to triangular fashion, one or more similar.

groups connected with said main leads in star-fashion, and suitable switches arranged to reverse the terminal connections of one primary in each triangularly connected group with relation to two of said main leads.

4. In a heating equipment for electric'furnaces, main leads for supplying three-phase alternating current, one or more. groups of three transformers having their priniary coils connected to said leads in triangular fashion, one or more similar groups connected with said main leads in star fashion, and suitable switches arranged to reverse the terminal connections of one primary in each star connected group with respect to the interior or common connection of the star.

4. In a heating equipment for electric furnaces, main leads for supplying three-phase alternating current, one or more groups of three transformers having their primary coils connected to said leads in triangular fashion, one or more similar groups connected with said main leads in star fashion, and two 0 more sets of multiple switches arranged to reverse the terminal connections of one primary in each triangularly connected group with relation to two of said main leads, while also reversing the terminal connections of one primary in each star connected group with respect to the interior or common connection of the star.

In testimony whereof, I have affixed my signature.

JOSEPH LAWTON DIXON.

Washington, D. G.

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