High frequency inverter design for large-signal characterization of domestic induction heating load

Current research topics in the field of domestic induction heating entail analytical study of inductor-pot coupling behavior which must be verified with experimental results. Small-signal measurements are easily achieved up to 1 MHz with commercial LCR meters. On the other hand, large-signal experimentation requires a custom made measurement test bench. Whatever the approach selected to design this system, the instrumentation will be divided into a signal generator, a data acquisition block and a post-processing method for model parameter extraction. In order to separate influence of main factors determining load electrical parameter values a good solution could be sinusoidal current excitation with selectable frequency and amplitude. The scheme proposed is the utilization of a high frequency resonant half-bridge inverter operating slightly above resonance under zero voltage switching conditions to acquire near sinusoidal current. Output power control is carried out through of a variable DC bus and resonant conditions are fixed by means of an adjustable resonant capacitor. This paper enumerates the design challenges that such inverter involves in this application and which are the solutions adopted. Final prototype covering the required operation range has been designed, constructed and evaluated up to 1.5 MHz for a given active power of 3.5 kW at resonance with power capability of 16.8 kVA at Megahertz frequencies