Distribution networks

After much debate the system most favored is the three-phase, four-wire alternating-current network for the supply of light, power or the combination of light and power. Bur, unfortunately, most services and equipments are 110 volts or 220 volts today, and the electrical relations in the three-phase circuit make it possible only to obtain service at either 115 and 199 volts or 120 and 208 volts with simple transformation ratios. The relative merits of these combinations have been debated thoroughly and especially their effects on service using present standard equipment. No unanimous decision has been reached and both types of networks are in service. Both systems give satisfactory service when standard equipment is used, for, fortunately, lamps may be had at either 115 or 120 volts and single-phase and polyphase motors have tolerances whereby satisfactory operation may be had between, roughly, 110 and 120 volts single-phase and 200 and 240 volts three-phase. But, of course, when operated at points near the tolerance limits the margins of departure from the average motor characteristics are changed, and a design based on either system as a standard would have a wider field of satisfactory application. Electrical World.