US3382311A - Low frequency induction melt plant - Google Patents

Low frequency induction melt plant Download PDF

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Publication number
US3382311A
US3382311A US462019A US46201965A US3382311A US 3382311 A US3382311 A US 3382311A US 462019 A US462019 A US 462019A US 46201965 A US46201965 A US 46201965A US 3382311 A US3382311 A US 3382311A
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US
United States
Prior art keywords
phase
furnace
melt
low frequency
stirring
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US462019A
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English (en)
Inventor
Rydinger Mats
Sundberg Yngve
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ABB Norden Holding AB
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ASEA AB
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Filing date
Publication date
Application filed by ASEA AB filed Critical ASEA AB
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Publication of US3382311A publication Critical patent/US3382311A/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/02—Induction heating
    • H05B6/06—Control, e.g. of temperature, of power
    • H05B6/067—Control, e.g. of temperature, of power for melting furnaces
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
    • H05B2213/02—Stirring of melted material in melting furnaces

Definitions

  • a low frequency induction furnace has an induction coil formed of three parts with a symmetrizing device and a change-over switch for alternatively connecting the coil over the symmetrizing device to single phase or multiphase to the same multiphase network.
  • the multiphase connection results in motoric stirring.
  • the present invention relates to a device for network frequency induction melt furnace plants, preferably for those operating under vacuum.
  • furnace coil In melting and/or heat retaining of metal melts, such as steel metls, it is usual to connect the furnace coil with single-phase across a symmetrizing device, which in its turn is connected to the secondary windings of a threephase furnace transformer, suitably provided with tap changers for input regulation.
  • a symmetrizing device which in its turn is connected to the secondary windings of a threephase furnace transformer, suitably provided with tap changers for input regulation.
  • tap changers for input regulation.
  • the single-phase connection of the furnace coil gives a so-called repulsive stirring of the melt.
  • This is mainly symmetrical around the horizontal centre plane of the furnace coil, which means that the melt which is below the centre plane circulates within its part in the same way as the melt above said plane circulates within its part. There is no appreciable exchange of melt between the two halves.
  • a certain axial and upwardly directed stirring is thus carried out usually in connection with vacuum on account of upward rising gas bubbles, for example in connection with the formation of CO, which effect is thus limited to the upper part of the melt, while however the bottom of the melt remains uninfluence-d.
  • the latter case is particularly common with large furnace where the depth of the melt is relatively great.
  • the present invention effects a simple and space-saving plan-t, which substantially consists of the components which are used in a conventional network frequency melt furnace plant.
  • the invention is characterised by the furnace being connected alternately singleaphase across a symmetrizing device known per se to a multi-phase, preferably three-phase network, or multiphase/three- 3,382,131 1 Patented May 7, 1968 ice phase to the same network.
  • the single-phase connection is used when heating is desired and the three-phase connection for motoric stirring.
  • FIG. 1 shows a connection of a low frequency crucible furnace plant with inductive heating with single-phase operation for heating and three-phase operation, Y-connection for stirring.
  • FIG. 2 shows a corresponding plant with three-phase operation, A-conn'e'ction, for stirring.
  • FIG. 3 shows a connection diagram and shows diagrams for a symmetrizing device of known type.
  • FIG. 1 at 11 the secondary side of a furnace transformer, Y-connected is shown.
  • the transformer is connected to a three part induction coil 12, 13, 14 for an induction furnace or inductive heat retention plant. Parallel with the coils 12- 14 are connected one ('16) or two (17) parallel capacitors for phase compensation.
  • a change-over switch 15 Between the transformer and the furnace is arranged a change-over switch 15 for alternate heating-single-phase, and stirringthree-phase. In the case of heating, the change-over switch 15 is placed in the lower position (A). Between phase R and S a capacitor C is connected in this position and between phase S and T a reactance L.
  • the reactance L and the capacitor C are included in the symmetrizing device known per se for single phase connection of a load to a multi-ph-ase, here three-phase, network and for symmetrical loading of this. Many such symmetry devices are known and this is only one example.
  • Phase R of the transformer is connected to the upper side and phase T to the lower side of the three coils 12-14.
  • the symmetry device operates according to FIG. 3.
  • the load (the furnace) r+jx is connected between phase R and T in delta connection. With the letters according to FIG. 3 the following is obtained:
  • FIG. 2 shows the same plant as FIG. 1, but with the furnace coils 12-14 connected in A-connection.
  • the change-over switch 18 connects in position A the furnace coils 12-14 in single-phase connection across the syn!- metrizin g device L-C and in position B the furnace coils in three-phase connection for motoric stirring of the melt. As seen, the coils are A-cOnnected. Tap changing on the transformer is carried out during heating as well as during stirring. The Winding connection is not shown.
  • the device according to the invention can be varied in many ways within the scope of the "following claims.
  • said symmetrizing device being three-phase coupled to said secondary windrngs.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Furnace Details (AREA)
  • General Induction Heating (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Crucibles And Fluidized-Bed Furnaces (AREA)
US462019A 1964-06-18 1965-06-07 Low frequency induction melt plant Expired - Lifetime US3382311A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE7495/64A SE311201B (enrdf_load_stackoverflow) 1964-06-18 1964-06-18

Publications (1)

Publication Number Publication Date
US3382311A true US3382311A (en) 1968-05-07

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Family Applications (1)

Application Number Title Priority Date Filing Date
US462019A Expired - Lifetime US3382311A (en) 1964-06-18 1965-06-07 Low frequency induction melt plant

Country Status (3)

Country Link
US (1) US3382311A (enrdf_load_stackoverflow)
GB (1) GB1103026A (enrdf_load_stackoverflow)
SE (1) SE311201B (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3472941A (en) * 1966-02-15 1969-10-14 Leybold Heraeus Gmbh & Co Kg Coreless induction furnace and method of melting and stirring metals in this furnace
US3536983A (en) * 1967-12-12 1970-10-27 Inductotherm Corp Frequency multiplier and stirring circuit for an induction furnace
US3906181A (en) * 1972-08-18 1975-09-16 Mitsubishi Electric Corp Induction heating apparatus for minimizing vibration and noise
US3980858A (en) * 1973-08-22 1976-09-14 Mitsubishi Denki Kabushiki Kaisha Exciter for induction heating apparatus
US5889812A (en) * 1994-02-11 1999-03-30 Otto Junker Gmbh Process for the operation of coreless induction melting furnaces or holding furnances and an electrical switching unit suitable for the same

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1822539A (en) * 1929-03-09 1931-09-08 Ajax Electrothermic Corp Induction electric furnace
US3012083A (en) * 1959-02-26 1961-12-05 Asea Ab Electric stirring windings

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1822539A (en) * 1929-03-09 1931-09-08 Ajax Electrothermic Corp Induction electric furnace
US3012083A (en) * 1959-02-26 1961-12-05 Asea Ab Electric stirring windings

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3472941A (en) * 1966-02-15 1969-10-14 Leybold Heraeus Gmbh & Co Kg Coreless induction furnace and method of melting and stirring metals in this furnace
US3536983A (en) * 1967-12-12 1970-10-27 Inductotherm Corp Frequency multiplier and stirring circuit for an induction furnace
US3906181A (en) * 1972-08-18 1975-09-16 Mitsubishi Electric Corp Induction heating apparatus for minimizing vibration and noise
US3980858A (en) * 1973-08-22 1976-09-14 Mitsubishi Denki Kabushiki Kaisha Exciter for induction heating apparatus
US5889812A (en) * 1994-02-11 1999-03-30 Otto Junker Gmbh Process for the operation of coreless induction melting furnaces or holding furnances and an electrical switching unit suitable for the same

Also Published As

Publication number Publication date
GB1103026A (en) 1968-02-14
SE311201B (enrdf_load_stackoverflow) 1969-06-02

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