INDUCTION HEATING APPARATUS AND TRANSFORMER

摘要

Induction heating apparatus has a series inductor (Ls) between an AC source (110) and a parallel tank circuit (118). The source (110) has an output transformer (150) which has a leakage inductance (Ll), viewed from the secondary, no larger than Lmax =(Vlmin Vpmin PFmin) / (2)(3.1416) (N fmax Pmax) where Vlmin is a desired minimum permitted voltage across the tank circuit (118), Vpmin is a desired minimum rms input voltage to the output transformer, N is the primary:secondary turns ratio of the output transformer (150), PFmin is a desired minimum permitted power factor, fmax is a desired maximum frequency of operation, and Pmax is a desired maximum power output into the induction heating coil (Lw). The output transformer (150) has inner and outer hollow coaxial windings having S electrically broken but parallel-connected longitudinal segments. If necessary to reduce inter-winding capacitance, the transformer (150) can further include a core. The system can be easily tuned by a procedure which involves first selecting a preliminary series inductance (Ls) and a preliminary resonance capacitance (122).