| Abstract |
Direct ac-ac frequency converters employed in induction heating applications are normally operated using one of three control schemes namely, the forced commutation scheme, the unclamped scheme and the clamped scheme. This paper reviews the basic performance characteristics of the six-pulse ac-ac frequency converter operating under the three control schemes. Ideal waveforms describing the operation of the converter with a resistive load and generalized analytical expressions derived from equivalent circuits of the converter are presented. On the basis of the waveforms and analytical expressions, the basic operating characteristics of the frequency converter are described for the three control schemes. The paper shows that the clamped scheme offers the advantages of reduced output current distortion and an output power control through frequency control as opposed to phase control. |
