A SIMPLE CORRECTION SCHEME FOR PHASE AND SEQUENCE OF 3-PHASE FIRING CIRCUIT IN PHASE-ANGLE CONTROL APPLICATIONS

A simple scheme for use in a four-wire AC voltage controller system is presented. This scheme automatically provides the correct firing puls es for the working thyristors irrespective of any mistake introduced w hile connecting the firing circuit. The scheme can also readjust the f iring circuit against any phase and/or sequence alterations. This feat ure leads to elimination of the manual adjustment usually needed in su ch cases. Another advantage of the scheme is the ability to detect if the system contains faulty thyristors. Experimental results are given to verify the principle of operation of the proposed scheme.