US1631667A - Electric-furnace system - Google Patents

Description

June 7 1927.

1,631,667 J. BECKMANN ELECTRIC FURNACE SYSTEM Filed March 3. 1927 Inventon Johannes Beckmann His Attorney Patented June 7, 1927.

UNITED STATES PATENT OFFICE.

J'OHANNES IBEOKMANN, OF CHARLQ'I'TENBUBG, GERMANY, ASSIGNOB 'IO GDTEBAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC-FURNACE SYS'IEI.

Application filed larch 8, 1927, Serial No. 172,446, and in Germany August 19, 1998.

My invention relates to electric furnace s stems, more particularly to high frequency elhctric furnace systems, and has for its object the provision of a simple and reliable 6 system of this character.

It is known, both with a view to improving the power factor as well as to obtain resonance, to place condensers in A. C. networks or circuits in parallel or in series with inductive resistances. This method is of particular importance when the load on the generator is mainly or exclusively an inductive one, such for example, as in high fre- 'quency furnaces. Such known connections or high frequency furnaces, however, present various drawbacks. Where the condenser is connected in parallel, the generator only acts upon the condenser if the inductive resistance suddenly drops out, such as in the event of an open circuit in the furnace coil, which entails inadmissibly highjvoltages owing to excitation of the generator by the leading current taken by the condenser notwithstanding any voltage regulators that may have been provided.

According to my invention'these overvolt ages are avoided by subdividing the furnace coil and by connecting condensers in parallel with each part of the'coil. Should any part of the coil now be interrupted by an open circuit, there still remains the other coil section or sections whose inductive reactance limits the leading current in the generator armature to values which can be handled by the voltage regulator.

The accompanying drawing is a diagrammatic representation of a system of connections embodying my invention.

Referring to the drawing, the furnace coil 1 surrounding the crucible 2 is connected in the circuit 3, connected with any suitable source of A. C. 4. In the form shown, the coil 1 is subdivided into two approximately or exactly equal parts 5 and 6; Condensers 7 and 8 are connected in parallel with the sections 5 and 6 of the 0011 respectively, a conductor 9 connecting the point of division 10 between the coil sections with a point 11 between the condensers. .If desired an connected in wattless current. If the condensers are.cor-

rectly proportioned, an approximate resonance of the oscillating circuit may be brought about. An interruption of a coil 7 or 8 entails no excess voltage, owing to the inductive reactance of the other coil 8 or 7 remaining effective. In such case the generator may also be disconnected by means of overload cutouts, because the current in the non-disconnected half coil rises.

It will be-understood that the furnace coil may be divided into more than two sections, if desired, and that these sections may or ma not be equal.

at I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The combination with a high frequency electric furnace, of a high frequency 0011 therefor divided into sect1ons, and condensers connected across said sections.

2. The combination with a high frequenc electric furnace, of a. high frequency coil therefor, an intermediate connection dividing said coil into sections, anda condenser parallel with eachof said sections. 4

3. The combination with an electric furnace provided with a high frequency coil, of an electrical connection leading to an intermediate oint of said coil, and condensers connecte across the portions of said coil on opposite sides of said intermediate point.

4, The combination with an electric furnace provided with a high frequency heating coil, of an earth connection leading to an intermediate point of said coil, and a con de iser connected across each portion of said co1 ln witness whereof, I have hereunto set my hand this 14th day of Febi-uary 192.7.

JOHANNES BECKMANN.

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