Economical Equidistant Pulse Firing Scheme for Thyristorized DC Drives

From the literature published, six different gate firing schemes are available for three-phase thyristor Graetz bridge converters employing equidistant pulses. All these thyristor firing schemes have been developed with particular attention to the special control requirements of converters used in a high voltage dc transmission scheme. Herein is described a new simple equidistant pulse firing scheme intended to be economically quite competitive to the presently existing individual phase control circuits used in three-phase converter circuits for industrial applications. The princidple of operation and the circuit details of the firing circuit are described. Experimental results obtained on a laboratory dc drive of capacity 3 KVA are discussed.