Electronic frequency changer

IN 1943, A 6,667-KW ELECTRONIC frequency changer, using mercury-arc rectifiers, was installed in the Gary Sheet and Tin Mill of the United States Steel Company, at Gary, Ind., to provide a nonsynchronous tie between the 25-cycle and 60-cycle power systems for the controlled flow of power in either direction. A non-synchronous interconnection had to be used because of the frequency variations on the 25-cycle system. In 1949 the capacity of the installation was increased to 16,000 kw by raising the capacity of the first unit to 8,000 kw and adding a second 8,000-kw unit. The installation has a 2-hour rating of 20,000 kw.