Furnace with bottom induction coil

• US 6,693,950 B2
• Filed: 05/21/2002
• Issued: 02/17/2004
• Est. Priority Date: 05/22/2001
• Status: Active Grant

• Current Assignee: Inductotherm Corp
• Original Assignee: Inductotherm Corp
• Inventors: Peysakhovich, Vitaly A., Fishman, Oleg S.
• Primary Examiner(s): Hoang, Tu Ba
• Application Number:
  US10/153,049
• Publication Number:
  US 20030002559A1
• Time in Patent Office: 637 Days
• Field of Search: 373/138, 373/146, 373/147, 373/151, 373/153, 373/155, 373/156, 373/7, 373/59, 373/158, 219/647, 219/648, 219/649, 219/650, 219/628, 266/234, 266/349, 266/216, 266/197, 266/900, 366/349, 366/147, 366/274, 75/101.4
• US Class Current: 373/146
• CPC Class Codes: H05B 2213/02 Stirring of melted material in melting furnaces
• CPC Class Codes: H05B 6/24 Crucible furnaces H05B6/30 takes precedence
• CPC Class Codes: H05B 6/44 having more than one coil or coil segment

Abstract

An induction furnace is provided with a bottom induction coil to melt, heat and/or stir an electrically conductive material placed in the furnace. The furnace is particularly useful for electrically conductive materials having a relatively low value of thermal conductivity, such as aluminum or an aluminum alloy.

Claims

1. An induction furnace for heating an electrically conductive material, comprising:

a crucible to contain the electrically conductive material;

a bottom support structure to support the bottom of the crucible, the bottom support structure having passages therein for the transmission of an electromagnetic field;

a magnetic flux concentrator disposed below the bottom support structure; and

an at least one induction coil disposed between the bottom support structure and the magnetic flux concentrator, the at least one induction coil formed from an at least one active coil section and an at least one passive coil section whereby a magnetic field generated by a flow of current through the at least one induction coil penetrates the electrically conductive material to induce an eddy current in the electrically conductive material that heats the electrically conductive material.

2. The induction furnace of claim 1 wherein the crucible forms a substantially cylindrical volume for containing the electrically conductive material, the substantially cylindrical volume having a diameter to height ratio in the range of approximately 3:

1 to 6;

1.

10. The induction furnace of claim 1 further comprising a plenum formed between the magnetic flux concentrator and the bottom support structure for the flow of a cooling medium to cool the at least one induction coil.

3. A method of heating an electrically conductive material comprising the steps of:

supporting a crucible on a bottom support structure having passages therein for the transmission of an electromagnetic field;

placing the electrically conductive material in the crucible;

generating a primary magnetic field from the flow of a current from an ac power source through at least one active coil section of at least one induction coil disposed below the bottom support structure;

placing a magnetic flux concentrator below the at least one induction coil;

directing the primary and secondary magnetic fields towards the bottom of the crucible at least partially through the passages in the bottom support structure; and

inducing a secondary current in at least one passive coil section of the at least one induction coil by magnetically coupling the at least one passive coil section to the primary magnetic field generated by the at least one active coil section, the secondary current generating a secondary magnetic field exterior to the at least one passive coil section;

magnetically coupling primary and secondary magnetic fields with the electrically conductive material in the crucible to inductively heat the electrically conductive material.

4. The method of claim 3 wherein the frequency of the current is adjusted to electromagnetically stir the electrically conductive material.

5. An induction furnace for heating an electrically conductive material, comprising:

a crucible to contain the electrically conductive material;

a bottom support structure to support the bottom of the crucible;

a magnetic flux concentrator disposed below the bottom support structure, the magnetic flux concentrator comprising a plurality of discrete ferromagnetic elements disposed in a non-electrically conductive material; and

an at least one induction coil disposed between the bottom support structure and the magnetic flux concentrator, whereby a magnetic field generated by a flow of an ac current through the at least one induction coil penetrates the electrically conductive material to induce an eddy current in the electrically conductive material that heats the electrically conductive material.

6. An induction furnace for heating an electrically conductive material, comprising:

a crucible to contain the electrically conductive material, the crucible having a circular bottom;

a bottom support structure to support the bottom of the crucible;

a magnetic flux concentrator disposed below the bottom support structure, the magnetic flux concentrator comprising an inner central ring element, an outer perimeter ring element, and a plurality of transverse elements, the plurality of transverse elements spaced radially between and connected to the inner central ring element and the outer perimeter ring element; and

an at least one induction coil disposed between the bottom support structure and the magnetic flux concentrator, whereby a magnetic field generated by a flow of an ac current through the at least one induction coil passes through at least the openings between the plurality of transverse elements of the magnetic flux concentrator and penetrates the electrically conductive material to induce an eddy current in the electrically conductive material that heats the electrically conductive material.

7. An induction furnace for heating an electrically conductive material, comprising:

a crucible to contain the electrically conductive material;

a bottom support structure to support the bottom of the crucible;

a magnetic flux concentrator disposed below the bottom support structure; and

an at least one induction coil disposed between the bottom support structure and the magnetic flux concentrator, the at least one induction coil comprising;

an at least one active induction coil section, each of the at least one active induction coil section connected to an ac power supply; and

an at least one passive induction coil section connected to a capacitor to form a resonant circuit, whereby a magnetic field generated by a flow of an ac current through the at least one active induction coil section penetrates the electrically conductive material to induce an eddy current in the electrically conductive material, and the magnetic field couples with the at least one passive induction coil section to induce a secondary current flow through the at least one passive induction section to generate a secondary magnetic field that penetrates the electrically conductive material to induce an eddy current in the electrically conductive material that heats the electrically conductive material.

8. The induction furnace of claim 7 wherein the at least one active induction coil section and the at least one passive induction coil section are disposed interior and exterior to each other.

9. The induction furnace of claim 7 wherein the at least one active induction coil section and the at least one passive induction coil section are interspaced with each other.