D.3 INDUSTRIAL APPLICATIONS
Industrial induction heating. Industrial induction systems use alternating magnetic fields to induce currents directly within electrically conductive workpieces. Applications include brazing, hardening, annealing, forging, shrink fitting, and metal melting. Small laboratory and precision-production units may provide about 0.5–10 kW, while ordinary manufacturing systems commonly operate from roughly 10 to 250 kW. Large forging, billet-heating, and melting installations may use several hundred kilowatts and, in exceptional cases, multiple megawatts. Operating frequencies range from a few kilohertz for deep heating of large metal sections to several hundred kilohertz for shallow or highly localized heating. Commercial equipment spans approximately 500 W to 1 MW, illustrating the very wide variation among applications. The quoted power normally refers to generator output delivered to the work coil, not radiated power. Most energy is magnetically coupled into the intended load, but strong localized magnetic fields and leakage fields may exist near the coil, feed conductors, matching network, and poorly shielded equipment.
Dielectric heating. Dielectric heaters apply strong alternating electric fields to insulating or weakly conducting materials, causing molecular polarization losses and internal heating. They are used for drying textiles, timber, paper, food, and ceramics, as well as for RF welding and sealing of plastics. Industrial RF systems commonly operate in designated ISM bands at 13.56, 27.12, or 40.68 MHz, with 27.12 MHz especially common. Small presses and laboratory systems may use a few hundred watts to several kilowatts, while production equipment commonly provides about 5–100 kW; individual high-capacity generators can exceed 100 kW. Textile-drying systems, for example, are available with outputs from about 5 to 105 kW, while particular industrial fabric dryers use 60 or 85 kW generators. Because the workpiece is placed between or close to energized electrodes, operator exposure is governed less by the nameplate power than by enclosure integrity, electrode geometry, shielding, access controls, maintenance condition, and the degree of field leakage.