Electric power system for electric induction heating and melting of materials in a susceptor vessel

A method of heating and melting a transition material in a vessel at least partially comprising a susceptor by supplying an alternating current to at least two induction coils surrounding different sections of the vessel, the method comprising the steps of:

• placing a charge of the transition material in the vessel;
• supplying a fixed frequency output alternating current from a separate power source to each of the at least two induction coils for at least one standard depth of current penetration into the interior volume of the vessel, an output voltage of each of the separate power sources operating with a phase synchronization;
• and
• varying a magnitude of electric power to each of the at least two induction coils by an independent pulse width control of the output voltage of each of the separate power sources operating with a phase synchronization.

A method of heating and melting a transition material in a vessel at least partially comprising a susceptor by supplying an alternating current to at least two induction coils surrounding different zones of the vessel, the method comprising the steps of:

• placing a charge of the transition material in a solid state in the vessel;
• supplying the alternating current at a susceptor inductive heating frequency from a separate power source to each of the at least two induction coils, an output voltage of each of the separate power sources operating with a phase synchronization, the susceptor inductive heating frequency selected for at least one standard depth of current penetration into the susceptor;
• varying a magnitude of electric power to each of the at least two induction coils by an independent pulse width control of the output voltage of each of the separate power sources operating with the phase synchronization;
• changing the susceptor inductive heating frequency of the alternating current from each of the separate power sources to a molten transition material inductive heating frequency, the molten transition material inductive heating frequency selected for at least one standard depth of current penetration into the transition material in the vessel;
• and
• establishing a mix stir phase shift between the output voltages of at least two of the separate power sources to electromagnetically stir the transition material in the vessel as the charge of the transition material transitions from the solid state to a molten state.

A method of heating, melting and directionally solidifying a charge of a silicon material in a vessel at least partially comprising a susceptor by supplying an alternating current to at least two induction coils surrounding different sections of the vessel, the method comprising:

• placing the charge of the silicon material in the vessel;
• supplying the alternating current at a susceptor inductive heating frequency from a separate power source to each of the at least two induction coils, an output voltage of each of the separate power sources operating with a phase synchronization, the susceptor inductive heating frequency selected for at least one standard depth of current penetration into the susceptor;
• varying a magnitude of electric power to each of the at least two induction coils by an independent pulse width control of the output voltage of each of the separate power sources to initially supply at least a 2 to 1 ratio of a total power to the one of the at least two induction coils located nearest to the bottom of the vessel relative to the one of the at least two induction coils located nearest to the top of the vessel, and decreasing the 2 to 1 ratio of the total power as the silicon material transitions from a non-electrically conductive solid state to an electrically conductive molten state;
• changing the susceptor inductive heating frequency of the alternating current from each of the separate power supplies to a molten silicon inductive heating frequency, the molten silicon inductive heating frequency selected for at least one standard depth of current penetration into the silicon material in the electrically conductive molten state in the vessel;
• and
• establishing a phase shift between the output voltages of at least two of the separate power sources to electromagnetically stir the silicon material in the vessel as the silicon material transitions from the non-electrically conductive solid state to the electrically conductive molten state.