A new three-phase to single-phase AC to AC frequency converter

A new ac to ac frequency converter which uses two six-pulse fully controlled bridge rectifiers and converts three-phase power frequency to a single-phase higher frequency is introduced in this paper. The power elements in the bridge rectifiers may be power transistors or thyristors provided with external means of commutation. The basic operation of the system with variable frequency and variable voltage is described for a resistive load. Analytical expressions for the frequency converter with a resistive load are presented and the results are compared with the existing three-pulse frequency converter. The operation of the system with a series RLC load is described and experimental results are presented from which pertinent characteristics of the frequency converter are discussed. Compared with the existing three-pulse frequency converter, the six-pulse frequency converter provides the advantages of improved input power factor and hence reduced input filter size and a wider range of power control without an increase in the KVA per unit output power rating of the power devices.