| This paper is devoted to the synthesis of the power control loop for a single-phase resonant inverter controlled by phase shift and used in an induction heating system. It starts from the assumption that, if the inverter control frequency is close to the resonance frequency of the assembly consisting of the compensation capacitor, inductor and heating piece, the current supplied by the inverter contains almost only the active component that determines directly the power transmitted to the inductor. After establishing the structural scheme and highlighting the transfer function, a PI controller is adopted for the control of the current through the inverter. The inverter active current is achieved by a Proportional-Integral controller tuned in accordance with the Modulus Optimum criterion in Kessler variant. Next, different experimental tests are presented in order to determine the performances of the induction heating system. The objectives of the tests were: the verification of the proper operation of the current through inverter control loop, the achievement of zero-current switching, the control of the power transmitted to the load by adjusting the inverter frequency and the determining the efficiency of the converter-inductor-pipe system. |
 |