A microprocessor-based control method for a voltage-fed inverter with a tank load

A description is given of a microprocessor-based control scheme for a single-phase voltage-fed thyristor inverter with an induction heating tank load. The processor generates the gating signals for the inverter thyristors and uses the interval between given combinations of gating signals to perform two feedback control functions. One feedback loop maintains the power to the tank load at a desired constant value. The other feedback arrangement maintains the load power factor at unity by rapidly adjusting to zero any degree of detune between the natural tank load frequency and the inverter operating frequency. Effective protection of the inverter circuit components against load overvoltages and overcurrents are also provided. Some experimental waveforms showing the response of the control scheme to step changes in the tank load parameters are presented.<>