Alternating Current System

A system of electric distribution employing the alternating current. For transmi ion in the open air or in conduits a high potential circuit is used, from 1,000 to 10,000 volts being maintained at the central station. Two leads unconnected at the end lead from the station. Where current is desired a converter or transformer (see Converter) is placed, whose primary is connected to the two leads bridging the interval between them. From the secondary the house leads are taken with an initial potential in some cases of 50 volts. The converters are thus all placed in parallel. By law or insurance rules the converters are generally kept outside of buildings. Where no secondary current is taken from the converters very little primary current pa es them on account of their counter-electromotive force. As more secondary current is taken the primary increases and this accommodation of one to the other is one of the interesting and valuable features. Street lamps are sometimes connected in series. Each lamp in such case is in parallel with a small coil with iron core. While the lamp is intact little current pa es through the coil. If the lamp is broken, then the converter impedes the current by its spurious resistance, q. v., just enough to represent and replace the resistance of the extinguished and broken lamp filament. (See Meter, Alternating Current; Motor, Alternating Current.)