Electrification of a major steel mill

This paper discusses the electrification of major steel mill. These mills were all to be electrically driven, and it was realized that the time had come to consider a serious expansion of the electric power system in the Bethlehem Works. Since the new mill drives were to use AC, and since it had been realized that the increasing size of the Bethlehem Works made power distribution using low-voltage DC more difficult, it was decided to begin the generation of AC instead. Alternators operating at 6,600 V were installed, and this voltage level was used for distribution as well. Transformers located in various buildings would then be used to lower this voltage to the level desired for actual use. A significant characteristic of ac power systems, of course, is the frequency in hertz, which is a function of the speed of rotation and of the number of poles in the alternators. However, a lower frequency of 25 Hz was still very much in use for situations where large, slow-speed rotating electrical machines, such as steam engine driven alternators for generation or large motors for heavy industrial uses, were involved.