Electric induction heating, melting and stirring of materials non-electrically conductive in the solid state

A method of heating and melting a transition material, the method comprising the steps of:

• depositing the transition material in a non-electrically conductive state in a susceptor vessel lined with a liner material to form a lined susceptor vessel, the lined susceptor vessel having a lower section surrounded by at least one active induction coil connected to an output of a variable frequency power supply, and an upper section above the lower section surrounded by at least one secondary induction coil connected to at least one resonance capacitor to form a passive coil circuit;
• supplying power from the output of the variable frequency power supply to the at least one active induction coil at a start frequency so that a standard depth of penetration is not greater than a wall thickness of the lined susceptor vessel to electromagnetically heat the lined susceptor vessel and transition the transition material in the lined susceptor vessel to an electrically conductive state by conduction heating supplied from the lined susceptor vessel;
• limiting the supplied power from the output of the variable frequency power source to a maximum of the thermal withstand density of the liner material;
• and
• reducing the frequency of the output of the variable frequency power supply from the start frequency to an intermediate frequency responsive to the transition of the transition material in the lined susceptor vessel from the non-electrically conductive state to the electrically conductive state.

A method of heating and melting a transition material, the method comprising the steps of:

• depositing the transition material in a non-electrically conductive state in a susceptor vessel having a lower section surrounded by at least one active induction coil connected to an output of a variable frequency power supply, and an upper section above the lower section surrounded by at least one secondary induction coil connected to at least one resonance capacitor to form a passive coil circuit;
• supplying power from the output of the variable frequency power supply to the at least one active induction coil at a cold frequency, fcold, to heat and melt the transition material in the susceptor vessel to an electrically conductive state wherein the cold frequency, fcold, is determined from the equation,
• f
• cold
• =
• 2.53
• ·
• 10
• 5
• ·
• ρ
• SV
• t
• 2
• ,
• where ρsv is the resistivity of the susceptor vessel and t is a wall thickness of the susceptor vessel;
• adjusting the cold frequency of the output of the variable frequency power supply from the cold frequency to an intermediate frequency responsive to the transition of the transition material in the susceptor vessel to the electrically conductive state, the intermediate frequency in a range less than the cold frequency;
• and
• adjusting the frequency of the output of the variable frequency power supply from the intermediate frequency to a hot frequency, fhot, the hot frequency being less than the intermediate frequency and determined from the equation,
• f
• hot
• =
• 1
• 2
• ⁢
• ⁢
• π
• ⁢
• L
• pas
• ·
• C
• TUNE
• where Lpas is the inductance of the at least one secondary induction coil and CTUNE is the capacitance of the at least one resonance capacitor when the transition material in the region of the at least one secondary coil is in the electrically conductive state to establish a running electromagnetic wave in the transition material for circulating the transition material from a bottom of the susceptor vessel upwards along an interior wall of the susceptor vessel and then downwards through a central vertical region of the transition material in the susceptor vessel.