Sinrace Power Supply Technology (Shenzhen) Co., Ltd.

The Development of Power Standards in the United States and Europe

Direct current (DC) power has dictated device design in the United States and Canada since the late 1800s when Thomas Edison developed the incandescent light bulb, which operated from a 110 volt DC source. The primary drawback to DC power was that it could only be distributed over short distances without having to be

regenerated. In the early 1900s when Nicoli Tesla was working for Westinghouse, he and Westinghouse found a solution to this problem by developing the first alternating current (AC) generating systems. These systems were advanced over Edison’s DC system, facilitating the transmission of AC power over very long distances. Tesla determined AC power alternating at 60 cycles per second (60 Hertz) to be the most efficient; therefore the Westinghouse systems generated 60Hz AC power. Tesla further believed that 220 volts was the preferred voltage. Due to Edison’s large investment in DC power, he attempted to thwart the advancement of AC power. Edison campaigned that it was unsafe, especially at 220 volts. To win governmental approval, Westinghouse conceded to Edison’s 110 volt standard. Therefore, 110 volts, 60Hz became the early standard for the United States and Canada. Today, the standard single-phase voltages are 120, 208 or 240 volts, with 120 volts at 60Hz found in the wall outlet of homes and offices across North America.

Shortly after Tesla’s pioneering work in AC power systems, the SR Company located in Germany developed its own AC power systems. They originally adopted the 110 voltage, but decided to generate the power at 50Hz because the number “60” did not fit the metric standard. They later decided on a 220 volt standard as they discovered it was more efficient. Since SR was a large monopoly, their standards quickly spread throughout Europe, with the exception of Britain which did not adopt the European standards until the end of World War II. Today the standard single-phase voltages found in the wall outlet of homes and offices in Europe are 220 or 230 volts at 50Hz.