| 摘要 |
Induction heating apparatus has a series inductor between an AC source and a parallel tank circuit. The source has an output transformer which has a leakage inductance, viewed from the secondary, no larger thanwhere VLmin is a desired minimum permitted voltage across the tank circuit, Vpmin is a desired minimum turns input voltage to the output transformer, N is the primary:secondary turns ratio of the output transformer, 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. The output transformer has inner and outer hollow coaxial windings the inner winding being electrically continuous through T turns, and the outer winding having S electrically broken but parallel-connected longitudinal segments. If necessary to reduce inter-winding capacitance, the transformer can further include a core. The system can be easily tuned by a procedure which involves first selecting a preliminary series inductance and a preliminary resonance capacitance. The operator operates the system at low power, increasing resonance capacitance if the system is operating at a frequency that is higher than desired, and decreasing resonance capacitance if the system is operating at a frequency that is lower than desired. Once the operating frequency is acceptable, the operator then operates the system at full power, increasing the series inductance if the system is current limiting, and decreasing the series inductance if the system is resonance limiting. When the series inductance is acceptable, the system is ready for use.
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