Induction heating utilizes the induced current (eddy current loss) generated in a conductor under the influence of a high-frequency magnetic field, along with the effect of the magnetic field within the conductor (hysteresis loss), to heat the conductor itself.
When a metallic conductor is placed in a high-frequency alternating electric field, according to Faraday's law of electromagnetic induction, an induced electromotive force will be generated within the conductor. Due to the conductor's very low resistance, a strong induced current is generated. According to Joule's law, the alternating magnetic field will cause the current in the conductor to flow towards the conductor's surface, causing the skin effect. The density of the alternating current is directly proportional to the frequency; the higher the frequency, the more concentrated the induced current density is on the conductor's surface, i.e., the more severe the skin effect. This reduces the effective conductive area, increases the resistance, and thus causes the conductor to heat up rapidly.
When current flows through a conductor, a magnetic field is simultaneously generated around it. The high-frequency current flows into an inductor coil wound into a loop or other shapes (usually made of copper tubing). This generates a strong magnetic flux with instantaneous polarity changes within the coil. When the metal to be heated is placed inside the induction coil, the magnetic flux penetrates the entire heated material, generating large eddy currents in the opposite direction to the heating current within the heated material. Due to the resistance of the heated metal material, Joule heating is generated, causing the temperature of the metal material itself to rise rapidly, thus completing the heating of the metal workpiece.