External Stack Controller-598G/599G could build up to 1440A External DC Drive in oneframe size. The equipment described is intended for an industrial (non-consumer) userfor the control of an external thyristor controlled bridge. The design assumes that a 2-phase field semi-controlled Rectifier Bridge and a fully controlled 3-phase Six PulseConverter exists, which is complete with Thyristor Suppression, Current FeedbackTemperature Monitoring and suitable fusing.