Simultaneous induction heating and stirring of a molten metal

An apparatus for simultaneous induction heating and stirring of an electrically conductive material in a vessel, the apparatus comprising:

• a plurality of induction coils disposed around the vessel, the plurality of induction coils connected together to form an at least one three-phase impedance network comprising an open delta circuit having a first and second open delta terminals and a first and second closed delta terminals;
• a heat circuit capacitor having a first capacitor terminal and a second capacitor terminal, the first capacitor terminal connected to the first open delta terminal;
• a single-phase ac power supply, the single-phase ac power supply having a first and a second output heat supply terminals, the first output heat supply terminal connected to the second capacitor terminal, and the second output heat supply terminal connected to the second open delta terminal, the single-phase ac power supply operating at a heat frequency;
• a plurality of stir circuit inductors, each one of the plurality of stir circuit inductors having a first inductor terminal and a second inductor terminal, the first inductor terminal of each one of the plurality of stir circuit inductors connected exclusively to the first closed delta terminal, the second closed delta terminal, and the second open delta terminal of the at least one three-phase impedance network;
• and
• a three-phase ac power supply having three output stir supply terminals, each of the three output stir supply terminals connected exclusively to the second inductor terminal of each one of the plurality of stir circuit inductors, the three-phase ac power supply operating at a stir frequency, the stir frequency less than the heat frequency,
• whereby the single-phase ac power supply provides inductive heat power to the at least one three-phase impedance network to heat the electrically conductive material and the plurality of stir circuit inductors substantially blocks heat power from the single-phase ac power supply. The three-phase ac power supply, and the three-phase ac power supply provides stir power to the at least one three-phase impedance network to stir the electrically conductive material and the heat circuit capacitor substantially blocks stir power from the three-phase ac power supply to the single-phase ac power supply.

An apparatus for simultaneous induction heating and stirring of an electrically conductive material in a vessel, the apparatus comprising:

• a plurality of induction coils disposed around the vessel, the plurality of induction coils connected together to form at least one three-phase impedance network comprising an open delta circuit having a first and second open delta terminals and a first and second closed delta terminals;
• a first heat circuit capacitor and a second heat circuit capacitor, the first and second heat circuit capacitors having approximately the same capacitance, each of the first and second heat circuit capacitors having a first and second terminals, the second terminals of the first and second heat circuit capacitors connected together to form a common capacitor connection;
• a single-phase ac power supply, the single-phase heating power supply having a positive dc bus and a negative dc bus, and a first and second output heat supply terminals, the first output heat supply terminal comprising the center of a half-bridge circuit of the single-phase ac power supply, the positive dc bus connected to the first terminal of the first heat circuit capacitor and the negative dc bus connected to the first terminal of the second heat circuit capacitor, the single-phase ac power supply operating at a heat frequency;
• a plurality of stir circuit inductors, each one of the plurality of stir circuit inductors having a first inductor terminal and a second inductor terminal, the first inductor terminal of each one of the plurality of stir circuit inductors connected exclusively to the first closed delta terminal, the second closed delta terminal, and the second open delta terminal of the at least one three-phase impedance network;
• and
• a three-phase ac power supply having three output stir supply terminals, each of the three output stir supply terminals connected exclusively to the second inductor terminal of each one of the plurality of stir circuit inductors, the three-phase ac power supply operating at a stir frequency, the stir frequency less than the heat frequency,
• whereby the single-phase ac power supply provides heat power to the at least one three-phase impedance network to heat the electrically conductive material and the plurality of stir circuit inductors effectively blocks heat power from the single-phase ac power supply to the three-phase ac power supply, and the three-phase ac power supply provides stir power to the at least one three-phase impedance network to stir the electrically conductive material and the heat circuit capacitors effectively blocks stir power from the three-phase ac power supply to the single-phase ac power supply.

An apparatus for simultaneous induction heating and stirring an electrically conductive material in a vessel, the apparatus comprising:

• a plurality of induction coils disposed around the vessel, the plurality of induction coils connected together to form at least one three-phase impedance network comprising a wye circuit having a common.terminal for all of the plurality of induction coils, and a first, second and third terminals;
• a plurality of heat circuit capacitors, each one of the plurality of heat circuit capacitors having a first capacitor terminal and a second capacitor terminal, the first capacitor terminal of each one of the plurality of heat circuit capacitors connected exclusively to the first, second and third terminals of the at least one three-phase impedance network;
• a single-phase ac power supply, the single-phase ac power supply having a first and second output heat supply terminals, the first output heat supply terminal connected to the second capacitor terminal of all of the plurality of heat circuit capacitors, and the second output heat supply terminal connected to the common terminal of the at least one three-phase impedance network, the single-phase ac power supply operating at a heat frequency;
• a plurality of stir circuit inductors, each one of the plurality of stir circuit inductors having a first inductor terminal and a second inductor terminal, the first inductor terminal of each one of the plurality of stir circuit inductors connected exclusively to the first, second and third terminals of the three-phase impedance network;
• and
• a three-phase ac power supply having a three output stir supply terminals, each of the three output stir supply terminals connected exclusively to the second inductor terminal of each one of the plurality of stir circuit inductors, the three-phase ac power supply operating at a stir frequency, the stir frequency less than the heat frequency, whereby the single-phase ac power supply provides inductive heat power to the at least one three-phase impedance network to heat the electrically conductive material and the plurality of stir circuit inductors substantially blocks heat power from the input to the three-phase ac power supply, and the three-phase ac power supply provides stir power to the at least one three-phase impedance network to stir the electrically conductive material and the plurality of heat circuit capacitors substantially blocks stir power from the three-phase ac power supply the single-phase ac power supply.

An apparatus for simultaneous induction heating and stirring an electrically conductive material in a vessel, the apparatus comprising:

• a plurality of induction coils disposed around the vessel, the plurality of induction coils connected together to form at least one three-phase impedance network comprising a wye circuit having a common terminal for all of the plurality of induction coils, and a first, second and third terminals;
• a plurality of heat circuit capacitors, each one of the plurality of heat circuit capacitors having a first capacitor terminal and a second capacitor terminal, the first capacitor terminal of each one of the plurality of heat circuit capacitors connected exclusively to the first, second and third terminals of the three-phase impedance network;
• a single-phase ac power supply, the single-phase ac power supply having a first and second output heat supply terminals, the first output heat supply terminal connected to the second capacitor terminal of all the plurality of heat circuit capacitors, and the second output heat supply terminal connected to the common terminal of the three-phase impedance network, the single-phase ac power supply;
• a plurality of stir circuit inductors, each one of the plurality of stir circuit inductors having a first inductor terminal and a second inductor terminal, the first inductor terminal of each one of the plurality of stir circuit inductors connected exclusively to the first, second and third terminals of the three-phase impedance network;
• and
• a three-phase ac power supply having three output terminals, each of the three output terminals connected exclusively to the second inductor terminal of one of the plurality of stir circuit inductors, the three-phase ac power supply operating at a stir frequency, the stir frequency less than the heat frequency,
• whereby the single-phase ac power supply provides heat power to the at least one three-phase impedance network to heat the electrically conductive material and the plurality of stir circuit inductors effectively blocks heat power from the single-phase ac power supply to the three-phase ac power supply, and the three-phase ac power supply provides stir power to the at least one three-phase impedance network to stir the electrically conductive material and the heat circuit capacitor effectively blocks stir power from the three-phase ac power supply to the single-phase ac power supply.

A method of simultaneously heating and stirring by magnetic induction an electrically conductive material in a vessel having a plurality of induction coils disposed around the vessel, the plurality of induction coils connected together to form at least one three-phase impedance network, the method comprising the steps:

• providing a single-phase ac power source having an output operating at an inductive heating frequency;
• providing a three-phase ac power source having an output operating at an inductive stirring frequency, the inductive stirring frequency less than the inductive heating frequency,
• connecting the output of the single-phase ac power source to the plurality of induction coils by at least one capacitive element to form a heating circuit operating at or near resonant frequency to supply an ac heating current to the plurality of induction coils, the ac heating current creating a heating magnetic field, the heating magnetic field inductively coupled with the electrically conductive material to heat the electrically conductive material;
• and
• connecting the output of the three-phase ac power source to the plurality of induction coils by at least one inductive element to form a stirring circuit operating at or near resonant frequency to supply an ac stirring current to the plurality of induction coils, the ac stirring current creating a stirring magnetic field, the stirring magnetic field inductively coupled with the electrically conductive material to stir the electrically conductive material;
• whereby the at least one capacitive element substantially blocks the output of the three-phase power supply from the output of the single-phase ac power supply and the at least one inductive element blocks the output of the single-phase supply from the output of the three-phase supply.