In the late nineteenth century, the inventor Thomas Alva Edison (left, 1847-1931) and inventor/engineer/industrialist George Westinghouse (below, 1846-1914), both American, were engaged in a heated conflict concerning whether AC or DC power would become the dominant technology.
At the time, Edison was vastly wealthy and controlled a great deal of industry, including his companies Edison Machine Works, the Electric Light Company, and the Sprague Electric Railway; as well as running a research lab in Menlo Park, New Jersey, that was developing more new technologies and generating more patents than any group of people ever had. Edison and his company had invented the electric light, electric motors, dynamos and many other products, all of which ran on DC power (the light bulb can also run on AC).
George Westinghouse was a comparative newcomer to the electric power industry. However, he was a substantial businessman and inventor. He had made a great deal of money on inventions associated with the operation of railroads, and had founded the Westinghouse Air Brake Company, founded in 1869, and the Union Switch and Signal Company, in 1881. In 1886, he and several investors founded Westinghouse Electric in order to compete directly with Edison.
Edison had the initial advantage that the technology for generating DC was well established and DC worked well over short distances but it could only be generated and distributed at the voltages at which it was used by consumers. This meant that currents in conductors were large, leading to huge and expensive energy losses over distances of more than a few kilometres. To supply a large city required many power stations throughout the city and an unattractive proliferation of wires to carry the required current.
A further disadvantage was that DC power could not be easily stepped up or down as easily as AC, which will be expanded upon next.
The great advantage of AC was that, through the use of transformers, the voltage could be stepped up or down as required. Energy is conserved (almost) in the transformers, so the power in equals the power out. Power is V multiplied by I, so if the voltage is stepped by a factor of 100, the current is stepped down by the same amount. While transmitting the power, the loss is given by P=I2R. Thus, if the current is reduced by 100, the loss is reduced by a factor of 10,000! Transmissions over great distances could suffer insignificant energy losses by stepping up the voltage while local transmission only required the stepping down of voltage. Power stations could be fewer and further apart. Westinghouse also could harness the Niagra Falls and other natural sources of power, a feature that DC power lacked.
As aforementioned, Edison was heavily invested in DC power, and many of his inventions relied on it. However, these facts alone cannot explain his resistance to AC technology. Edison's company had bought the rights to European designs for transformers and other technology, but it seems that Edison mistrusted AC. Some people have argued that he did not understand AC, since it is less intuitive and he was in many ways a "gut level" designer. However, this is by no means certain.
For whatever reason, Edison went to great lengths to discredit Westinghouse and AC power. He frequently claimed that it was unsafe, and he conducted a highly publicized series of "experiments" in which he electrocuted hundreds of animals from mice and rats to dogs and horses. Edison also lobbied various state legislatures to pass laws prohibiting the use of voltages above certain levels (he recommended 800 V DC or 250 V AC as safe levels). He wrote a Letter to the Editor published in the New York Post in which claimed DC was perfectly safe and said "AC can be described by no adjective less forcible than damnable."
In a final, desperate attempt to make AC power unpalatable to the public, Edison recommended that New York state adopt electrocution by means of AC power as its method of capital punishment. He recommended AC voltages and suggested the name "Westinghouse Chair" for the instrument. He even recommended the use of the phrase "condemed to be Westinghoused." Unfortunately, when this process was first used (with many dignitaries and reporters in attendance) it was done very badly. Some onlookers thought they saw the body move, so the current was turned on and off several times. The executed man was partially burned and his body was too hot to be removed from the chair for a long period of time (poor bugger). This whole ghastly affair was widely reported in the press, and Edison lost a great deal of prestige over it.
In conclusion, George Westinghouse came out victorious and AC power eventually became the dominant form in which electricity is generated worldwide. The backfiring of his electric chair argument was the final nail in the coffin for Thomas Alva Edison and Edison Electric Company.
Other stuff regarding �stiff upper lip� ACDC (from Surfing):
AC advantages
� Is easy to transform
� Can be transmitted at high voltage, low current and transformed to low voltage, higher current
� Energy losses in transmission can be minimised by high voltage transmission
� Motors and generators have fewer moving parts so more reliable and easier to maintain
� Three phase motors (huh?) powerful for industry use
AC disadvantages
� Back emf due to eddy currents lowers power
� Emitted electromagnetic radiation interferes with other electronic equipment
� Requires thick insulation to minimise interference from other cables
DC advantages
� Does not need as much insulation as it has no electromagnetic radiation output
� No back emf
� No high frequency radiation to cause interference in other equipment or signals
� Transmission has no energy loss due to induction in adjacent lines and metal structures
DC disadvantages
� Can�t be transformed!
� More difficult to supply to houses by line distribution
� Equipment not as reliable due to sparking and wear across split ring commutator
� Sparking causes interference
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