The induction heating power supply converts AC line power to a higher frequency alternating current, delivers it to a work coil and creates an electromagnetic field within the coil. Your work piece is placed in that field which induces eddy currents in the workpiece. The friction from these currents generates precise, clean, non-contact heat. A water cooling system is generally required to cool the work coil and induction system.
The size of the work piece and the heating application dictate the operating frequency of the induction system. Generally the larger the work piece the lower the frequency, and the smaller the work piece the higher the frequency. The operating frequency is determined by the capacitance of the tank circuit, the inductance of the coil and the material properties of the work piece.
If your work piece material is magnetic, such as carbon steel, it will be heated easily by induction’s two heating methods, eddy current and hysteretic heating. Hysteretic heating is very efficient up to the Curie temperature (for steel 600°C (1100°F)) when the magnetic permeability reduces to 1 and the eddy current is left to do the heating. Induced current in the work piece will flow at the surface where 80% of the heat produced in the part is generated in the outer layer (skin effect). Higher operating frequencies have a shallow skin depth, while lower operating frequencies have a thicker skin depth and greater depth of penetration.
The relationship of the current flow in the work piece and the distance between the work piece and the coil is key; the closer the coil, the more current in the work piece. But the distance between the coil and the work piece must first be optimized for the heating required and for practical work piece handling. Many factors in the induction system can be adjusted to match to the coil and optimize the coupling efficiency.
Induction heating efficiency is maximized if your work piece can be placed inside the coil. If your process won’t allow your work piece to be placed inside the coil, the coil can be placed outside of the work piece. The size and shape of the water-cooled copper coil will follow the shape of your work piece and be designed to apply the heat to the correct place on the work piece.
The power required to heat your work piece depends on: