War of Currents
In the "War of Currents" era in the late 1880s, Nikola Tesla and Thomas Edison became adversaries due to Edison's promotion of direct current (DC) for electric power distribution over the more efficient alternating current (AC) advocated by Tesla.
During the initial years of electricity distribution, Edison's direct current was the standard for the United States and Edison was not disposed to lose all his patent royalties. From his work with rotary magnetic fields, Tesla devised the system for transmission of power over long distances. He partnered with George Westinghouse to commercialize this system. Westinghouse had previously bought the rights to Tesla's polyphase system patents and other patents for AC transformers.
Electric power transmission
The direct current electric power transmission system had many limitations that were recognized and solved by Tesla's alternating current. High loads of direct current melted copper wires and could rarely be transmitted for a distance of greater than a mile. Edison's response to this argument was to generate power near to where it was consumed and install more wires to handle the growing demand for electricity, but this solution proved to be impractical and unmanageable.
However, the single strongest argument against the DC system was that, because it maintained a constant voltage, it could not be stepped up or down with a simple transformer. This meant that separate electrical lines had to be installed in order to supply power to appliances that use different voltages, which led to an even greater number of wires to lay and maintain, wasting money and introducing unnecessary hazard. A number of deaths from the Great Blizzard of '88 were attributed to collapsing DC power lines that cluttered cities running DC power grids.
When Tesla introduced alternating current after filing seven patents for alternating current generators, transformers, motors, wires and lights in November and December of 1887, it became clear that AC was the future of electric power distribution. Distance ceased to be a problem and high-voltage AC could carry the same amount of power that would normally melt wires using direct current. Most importantly, alternating current could be easily manipulated with a transformer to change voltage and current. A lamp needing five volts could draw power from the same source as a machine using twenty volts, unlike with the DC system. High voltage alternating current was sent from source to destination without melting wires and then stepped down to low voltages in homes and factories for local use.
AC vs. DC
The advantage of AC for distributing power over a distance is due to the fact that power is given by voltage × current (P = VI). For a given power, a low voltage requires a higher current and a higher voltage requires a lower current. However, since metal conducting wires have a certain resistance, some power will be wasted as heat in the wires. This power is given by P = I2R, or by P = V2/R (where V is the voltage drop along the wire, not the overall voltage). As such, low-voltage, high-current transmissions will suffer a much greater power loss than high-voltage, low-current ones, even though the overall transmitted power is the same. This holds whether DC or AC is used. However, it is very difficult to transform DC power to a high voltage, low current form efficiently, whereas with AC this is a matter of a simple and very efficient transformer. This is the key to the success of the AC system. Modern distribution grids use AC voltages in the 330,000–500,000 volt range, but currents of only 90 amperes or so.
Niagara Falls
Experts announced proposals to harness the Niagara Falls for generating electricity. Against General Electric and Edison's proposal, Tesla's AC system won the international Niagara Falls Commission contract. The commission was led by Lord Kelvin and backed by entrepreneurs such as J. P. Morgan, Lord Rothschild, and John Jacob Astor IV. Work began in 1893 on the Niagara Falls generation project and Tesla's technology was applied to generate electromagnetic energy from the falls.
Edison's FUD
Edison went on to carry out a campaign to discourage the use of alternating currents, what today would be commonly referred to as FUD. Edison did preside personally over several executions of animals, primarily stray cats and dogs, for the benefit of the press, to demonstrate that his inferior system of direct current was safer than that of alternating current. Edison's series of animal executions peaked with the electrocution of Topsy the Elephant. Ironically, Edison was against capital punishment, but his desire to disparage the superior system of alternating current led to the invention of one of the world's most recognizable killing devices.
Edison (or, reportedly, one of his employees) used AC to construct the first electric chair for the state of New York in order to promote the idea that alternating current was deadly. Popular myth has it that Edison invented the electric chair solely as a means of impressing the public that AC was more dangerous than DC, and would therefore be the logical choice for electrocutions. In fact, the chair was primarily invented by a few of his employees, in particular Harold P. Brown, working at Menlo Park.
The Falls to Buffalo
Some doubted that the system would generate enough electricity to power industry in Buffalo. Tesla was sure it would work, saying that Niagara Falls had the ability to power the entire eastern U.S. On November 16, 1896, the first transmission of electrical power between two cities was sent from Niagara Falls to industries in Buffalo from the first commercial two-phase power plants (known as hydroelectric generators) at the Edward Dean Adams Station. The hydroelectric generators were built by Westinghouse Electric Corporation from Tesla's AC system patent designs. Tesla's system designs alleviated the limitations of the previous DC methods. The nameplates on the generators bear Tesla's name. He also set the 60 hertz standard for North America. It took five years to complete the whole facility.
Outcome
Edison's inventions using DC ultimately lost to AC devices proposed by others: primarily Tesla's polyphase systems, and also other contributors, such as Charles Proteus Steinmetz (of General Electric). With the financial backing of George Westinghouse, Tesla's AC replaced DC, enormously extending the range and improving the safety and efficiency of power distribution. Tesla's Niagara Falls system marked the end of Edison's roadmap for electrical transmission. Eventually, Edison's General Electric company converted to the AC system.
See also
