Induction heating element using separate coils - is to generate fundamental and third harmonic resonant circuits to provide uniform cylindrical type electro-magnetic field

摘要

An induction heating system, particularly suited for kilns handling a stack of plates, uses two separate coils to generate an approximation to a uniform cylindrical electromagnetic field. The stack of plates (1) is located within a concentric cylindrical coil (2) that coupled with a capacitor to form a resonating circuit operating at the fundamental harmonic frequency. Two counter-wound coils (2, 4) are diametrically located and are coupled to capacitors to operate at the third harmonic frequency. The resulting electromagnetic field is approx. cylindrical in form and results in a rapid heating period. A further improvement in the field structure may be achieved by using four coils for the third harmonic, each displaced by 90 degrees from each other.