The Electronic Converter for Exchange of Power

The installation of the first 20,000-kw electronic power converter was made in December 1943 at the Edgar Thompson plant of the Carnegie-Illinois Steel Corporation to exchange power between their 25-cycle 44-kv and 60-cycle 69-kv systems, the latter being connected to a large public utility. The converter operates in parallel on both systems with normal generators. This type of converter was selected to obtain its ease and simplicity of control, low contributions to faults, light weight of indoor equipment, high efficiency, and ability to transfer a fixed value of power regardless of departure from normal frequency ratio between the two systems. The converter may have its power output controlled manually or by a power regulator or may reduce the demands for power taken from the 60-cycle utility system. Controls also may be supplied to a typical electronic converter to cause it to share the total load of the receiving system in a predetermined proportion with prime movers. Inherently transferring power in a preselected direction in relation to the departure from normal voltage ratios of the two systems, automatic phase control of grid excitation rapidly compensates for changes in this ratio. The reactive kilovolt-amperes needed for commutation, harmonics, and transformer magnetizing current of both rectifier and inverter is supplied by the synchronous machinery in the steel company's systems. Faults such as arc-backs and ``shoot-throughs'' in the electronic equipment are suppressed in a very short time period. The rectifier cannot furnish current to a fault in its supply system.