Automatic Control for Variable Ratio Frequency Converters

An automatic switching equipment for the control of two 20,000-kw. frequency changer sets using the Scherbius method of load and power factor control has been in successful operation at the Page Avenue station of the Union Electric Light and Power Company of St. Louis, for almost a year. This equipment contains several new features in the automatic control of machines of this type. Besides being the first completely automatic switching equipment applied to machines of this type, it is unique in that it controls the largest rotating machines to which automatic switchgear has ever been applied. The Page Avenue station is one of the most important links in this Company's system of interconnecting plants. It is the point through which the two 25-cycle generating stations, Ashley Street and Keokuk, are tied. It will also be used as one of the ties for the recently completed Bagnell development, on the Osage River, to the 60-cycle generating system of the metropolitan area. These variable-ratio frequency converters are being used for the transfer of power between the 25-cycle and 60-cycle systems.