Alternating-current feeder regulators

The sensitiveness of the incandescent lamp to changes in voltage, both with reference to candle-power and life of the lamp, demanded very early in the history of electric lighting a close control of the voltage on constant-potential circuits. With the small direct-current generators that were first used this was easily accomplished by the simple field adjustment of the generator, but when the size of the generators increased and several were operated in multiple, several circuits were usually operated from one station bus-bar. With the low voltage used in direct-current distribution, the feeders could not have a negligible drop; therefore an adjustable artificial loss, in the form of a rheostat, had to be inserted in each feeder and adjusted according to the load. We all remember the early direct-current stations in which these rheostats took up almost as much space as the generators, and consumed enough energy to increase materially the cost of operating the plant. In these rheostats is found the first elementary feeder regulator.