Methods and procedures for accurate induction heating load measurement and characterization

Current research topics in domestic induction heating field, such as the analytical description or the grey- box modelling of the impedance behaviour of the inductor- pot coupled system, require experimental measurements to be obtained in a variety of situations covering wideband frequency operation and output power conditions due to its nonlinear nature. Frequency values up to the MHz range and current levels as high as several tenths of amperes can be needed to get the required information to describe the operation in real-working conditions. While small-signal impedance measurements are easily achieved up to 1 MHz and above with commercial LCR meters, no commercial equipment provides the complete solution for the power, frequency and load quality factor ranges required under large-signal operation so a custom- made measurement testbench must be designed. The testbench design comprises the development of a specific hardware for load excitation and the definition of the characterization procedures to obtain accurate impedance measurements which are described in this paper using a high performance digital oscilloscope and standard power electronics probes.