Difference between revisions of "AC vs. DC"
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AC vs. DC: The Struggle for Power
With the opening of the Pearl Street station in New York in September 1882, Thomas Edison ushered in the electric age. Ironically, however, the success of Edison’s original lighting system in some ways proved its undoing—or rather, its forced modification. Though Edison himself emphasized scale and distribution in his system, the demand for electricity soon led to the desire to build ever-larger power plants and transmit that power over greater distances. Additionally, with the rapid distribution of industrial electric motors came a strong demand for voltages other than the 110 volts used for lighting. The Edison system, which used direct current (DC), was ill suited to meet these new demands. The problem of transmission was even more difficult, since the long distance transmission of bulk quantities of DC at 110 volts was very expensive.
In 1886, George Westinghouse, a wealthy and respected inventor, but a newcomer in the electric power industry, founded Westinghouse Electric in order to compete with Edison. Westinghouse’s system relied on the discoveries and patents of Nikola Tesla, a Serbian (from Croatia) immigrant who passionately believed in the superiority of alternating current (AC) power. Power loss in transmission depends on voltage—the higher the voltage, the smaller the power loss. Unlike DC, the voltage of AC can be increased (stepped up) with a transformer at the generating station, and then it can be transmitted over long distances. Then, before it is delivered to customers, the voltage can be reduced (stepped down) to safe, usable levels again. Edison’s Pearl Street station was enormous, but lit only one square mile of New York City. Lighting up New York would take hundreds of Edison stations. Westinghouse’s AC system, on the other hand, made it possible to put large generating stations outside of cities and provide power to more customers.
Edison was less than thrilled with the emergence of Westinghouse’s technology, which threatened his own dominance in a field he virtually created. He also had genuine concerns about the safety of AC. The two men engaged in a public relations battle to determine which system would become the dominant technology. In an attempt to discredit AC power Edison stooped to some low tricks. He paid schoolboys a quarter for each dog or cat they delivered to him and then he electrocuted the animals in deliberately gruesome public experiments. In another desperate attempt to sway public opinion against AC, Edison recommended that the state of New York use electrocution by means of AC power as its method of capital punishment. He even suggested calling the electric chair the “Westinghouse Chair” and recommended that the verb “Westinghoused” be used to describe electrocution.
Edison’s theatrics notwithstanding, the superiority of AC became increasingly apparent to the public. And although Edison stubbornly defended DC, the use of AC equipment at the huge new Niagara Falls power facility in 1895 marked the rise of AC current.