In the War of Currents era (sometimes, War of the Currents or Battle of Currents) in the late 1880s, George Westinghouse and Thomas Edison became adversaries due to Edison's promotion of direct current (DC) for electric power distribution over alternating current (AC) advocated by several European companies[1] and Westinghouse Electric based in Pittsburgh, Pennsylvania.
Contents  [hide]
1 Background
2 Electric power transmission
2.1 The competing systems
2.2 Early transmission analysis
2.3 Transmission loss
3 Current wars
3.1 Edison's publicity campaign
3.2 Willamette Falls to Niagara Falls
3.3 International Electro-Technical Exhibition
3.4 AC deployment at Niagara
3.5 Competition outcome
3.6 Remnant and existent DC systems
4 See also
5 References
6 Further reading
7 External links
[edit]Background



The Hungarian "ZBD" Team (Károly Zipernowsky, Ottó Bláthy, Miksa Déri). They were the inventors of the first high efficiency, closed core shunt connection transformer. The three also invented the modern power distribution system: Instead of former series connection they connect transformers that supply the appliances in parallel to the main line.
During the initial years of electricity distribution, Edison's direct current was the standard for the United States, and Edison did not want to lose all his patent royalties.[2] Direct current worked well with incandescent lamps, which were the principal load of the day, and with motors. Direct-current systems could be directly used with storage batteries, providing valuable load-leveling and backup power during interruptions of generator operation. Direct-current generators could be easily paralleled, allowing economical operation by using smaller machines during periods of light load and improving reliability. At the introduction of Edison's system, no practical AC motor was available. Edison had invented a meter to allow customers to be billed for energy proportional to consumption, but this meter worked only with direct current. The transformation efficiency of the early open-core bipolar transformers was very low. Early AC systems used series-connected power distribution systems, with the inherent flaw that turning off a single lamp (or the disconnection of other electric device) affected the voltage supplied to all others on the same circuit.[3] The direct current system did not have these drawbacks as of 1882, giving it significant advantages.
Alternating current had first developed in Europe due to the work of Guillaume Duchenne (1850s), Ganz Works (1870s), Sebastian Ziani de Ferranti (1880s), Lucien Gaulard, and Galileo Ferraris.


The prototype transformer is on display at the Széchenyi István Memorial Exhibition, Nagycenk, Hungary
A prototype of the high efficiency, closed core shunt connection transformer was made by the Hungarian "Z.B.D." team (composed of Károly Zipernowsky, Ottó Bláthy and Miksa Déri) at Ganz Works in the autumn of 1884.[4][5] The new Z.B.D. transformers were 3.4 times more efficient than the open core bipolar devices of Gaulard and Gibbs.[6] Transformers in use today are designed based on principles discovered by the three engineers.[7] Their patents included another major related innovation: the use of parallel connected (as opposed to series connected) power distribution.[8][9] Ottó Bláthy also invented the AC electricity meter to compensate the competition of AC and DC technology.[10][11][12][13][14] The reliability of the AC technology received impetus after the Ganz Works electrified a large European metropolis: Rome in 1886.[15]


George Westinghouse, American entrepreneur and engineer, financially backed the development of a practical AC power network.
In North America one of the believers in the new technology was George Westinghouse. Westinghouse was willing to invest in the technology and hired William Stanley, Jr. to work on an AC distribution system using step up and step down transformers of a new design in 1886.[16] After Stanley left Westinghouse, Oliver Shallenberger took control of the AC project. In July 1888, George Westinghouse licensed Nikola Tesla's US patents for a polyphase AC induction motor and transformer designs and hired Tesla for one year to be a consultant at the Westinghouse Electric & Manufacturing Company's Pittsburgh labs.[17] Westinghouse purchased a US patent option on induction motors from Galileo Ferraris in an attempt to own a patent that would supersede Tesla's. But with Tesla's backers getting offers from another capitalist to license Tesla's US patents, Westinghouse concluded that he had to pay the rather substantial amount of money being asked to secure the Tesla license.[18] Westinghouse also acquired other patents for AC transformers from Lucien Gaulard and John Dixon Gibbs.[19]


Nikola Tesla, inventor, physicist, and electro-mechanical engineer, who held several instrumental patents in the Westinghouse AC system.
The "War of Currents" is often personified as Westinghouse vs. Edison.[citation needed] However, the "War of Currents" was much larger than that: It involved both American and European companies whose heavy investments in one current type or the other led them to hope that use of the other type would decline, such that their share of the market for "their" current type would represent greater absolute revenue once the decline of the other current type enabled them to expand their existing distribution networks.[20][citation needed]
[edit]Electric power transmission

[edit]The competing systems
Edison's DC distribution system consisted of generating plants feeding heavy distribution conductors, with customer loads (lighting and motors) tapped off them. The system operated at the same voltage level throughout; for example, 100 volt lamps at the customer's location would be connected to a generator supplying 110 volts, to allow for some voltage drop in the wires between the generator and load. The voltage level was chosen for convenience in lamp manufacture; high-resistance carbon filament lamps could be constructed to withstand 100 volts, and to provide lighting performance economically competitive with gas lighting. At the time it was felt that 100 volts was not likely to present a severe hazard of fatal electric shock.
To save on the cost of copper conductors, a three-wire distribution system was used. The three wires were at +110 volts, 0 volts and −110 volts relative potential. 100-volt lamps could be operated between either the +110 or −110 volt legs of the system and the 0-volt "neutral" conductor, which carried only the unbalanced current between the + and − sources. The resulting three-wire system used less copper wire for a given quantity of electric power transmitted, while still maintaining (relatively) low voltages. However, even with this innovation, the voltage drop due to the resistance of the system conductors was so high that generating plants had to be located within a mile (1.2 km) or so of the load. Higher voltages could not so easily be used with the DC system because there was no efficient low-cost technology that would allow reduction of a high transmission voltage to a low utilization voltage.


Westinghouse Early AC System 1887 (U.S. Patent 373,035)
In the alternating current system, a transformer was used between the (relatively) high voltage distribution system and the customer loads. Lamps and small motors could still be operated at some convenient low voltage. However, the transformer would allow power to be transmitted at much higher voltages, say, ten times that of the loads. For a given quantity of power transmitted, the wire cross-sectional area would be inversely proportional to the voltage used. Alternatively, the allowable length of a circuit, given a wire size and allowable voltage drop, would increase approximately as the square of the distribution voltage. This had the practical significance that fewer, larger generating plants could serve the load in a given area. Large loads, such as industrial motors or converters for electric railway power, could be served by the same distribution network that fed lighting, by using a transformer with a suitable secondary voltage.
[edit]Early transmission analysis
Edison's response to the limitations of direct current was to generate power close to where it was consumed (today called distributed generation) and install large conductors to handle the growing demand for electricity, but this solution proved to be costly (especially for rural areas which could not afford to build a local station[21] or to pay for massive amounts of very thick copper wire), impractical (including, but not limited to, inefficient voltage conversion) and unmanageable. Edison and his company, though, would have profited extensively from the construction of the multitude of power plants required to make electricity available in many areas.
Direct current could not easily be converted to higher or lower voltages. This meant that separate electrical lines had to be installed to supply power to appliances that used different voltages, for example, lighting and electric motors. This required more wires to lay and maintain, wasting money and introducing unnecessary hazards. A number of deaths in the Great Blizzard of 1888 were attributed to collapsing overhead power lines in New York City.[22][23]
Alternating current could be transmitted over long distances at high voltages, using lower current, and thus lower energy loss and greater transmission efficiency, and then conveniently stepped down to low voltages for use in homes and factories. When Tesla introduced a system for alternating current generators, transformers, motors, wires and lights in November and December 1887, it became clear that AC was the future of electric power distribution, although DC distribution was used in downtown metropolitan areas for decades thereafter.
Low-frequency (50–60 Hz) alternating currents can be more dangerous than similar levels of DC since the alternating fluctuations can cause the heart to lose coordination, inducing ventricular fibrillation, a deadly heart rhythm that must be corrected immediately.[24] However, any practical distribution system will use voltage levels quite sufficient for a dangerous amount of current to flow, whether it uses alternating or direct current. As precautions against electrocution are similar for both AC and DC, the technical and economic advantages of AC power transmission outweighed this theoretical risk, and it was eventually adopted as the standard worldwide.


Tesla's US390721 Patent for a "Dynamo Electric Machine"
[edit]Transmission loss
The advantage of AC for distributing power over a distance is due to the ease of changing voltages using a transformer. Available electric power is the product of current × voltage at the load. For a given amount of power, a low voltage requires a higher current and a higher voltage requires a lower current. Since metal conducting wires have an almost fixed electrical resistance, some power will be wasted as heat in the wires. This power loss is given by Joule's first law and is proportional to the square of the current. Thus, if the overall transmitted power is the same, and given the constraints of practical conductor sizes, high-current, low-voltage transmissions will suffer a much greater power loss than low-current, high-voltage ones. This holds whether DC or AC is used.
Converting DC power from one voltage to another requires a large spinning rotary converter or motor-generator set, which was difficult, expensive, inefficient, and required maintenance, whereas with AC the voltage can be changed with simple and efficient transformers that have no moving parts and require very little maintenance. This was the key to the success of the AC system. Modern transmission grids regularly use AC voltages up to 765,000 volts.[25] Power electronic devices such as the mercury arc valve and thyristor made high-voltage direct current transmission practical by improving the reliability and efficiency of conversion between alternating and direct current, but such technology only became possible on an industrial scale starting in the 1960s.
Alternating-current transmission lines have losses that do not occur with direct current. Due to the skin effect, a conductor will have a higher resistance to alternating current than to direct current; the effect is measurable and of practical significance for large conductors carrying thousands of amperes. The increased resistance due to the skin effect can be offset by changing the shape of conductors from a solid core to a braid of many small (isolated) wires. However, total losses in systems using high-voltage transmission and transformers to reduce the voltage are very much lower than DC transmission at working voltage.
[edit]Current wars

[edit]Edison's publicity campaign
Edison carried out a campaign to discourage the use[26] of alternating current, including spreading disinformation on fatal AC accidents, publicly killing animals, and lobbying against the use of AC in state legislatures. Edison directed his technicians, primarily Arthur Kennelly and Harold P. Brown,[27] to preside over several AC-driven killings of animals, primarily stray cats and dogs but also unwanted cattle and horses. [28] Acting on these directives, they were to demonstrate to the press that alternating current was more dangerous than Edison's system of direct current.[29] He also tried to popularize the term for being electrocuted as being "Westinghoused". Years after DC had lost the "war of the currents," in 1903, his film crew made a movie of the electrocution with high voltage AC, supervised by Edison employees, of Topsy, a Coney Island circus elephant which had recently killed three men.[30]
Edison opposed capital punishment, but his desire to disparage the system of alternating current led to the invention of the electric chair. Harold P. Brown, who was being secretly paid by Edison, built the first electric chair for the state of New York to promote the idea that alternating current was deadlier than DC.[31]
When the chair was first used, on August 6, 1890, the technicians on hand misjudged the voltage needed to kill the condemned prisoner, William Kemmler. The first jolt of electricity was not enough to kill Kemmler, and only left him badly injured. The procedure had to be repeated and a reporter on hand described it as "an awful spectacle, far worse than hanging." George Westinghouse commented: "They would have done better using an axe."[32]
[edit]Willamette Falls to Niagara Falls
In 1889, the first long distance transmission of DC electricity in the United States was switched on at Willamette Falls Station, in Oregon City, Oregon.[33] In 1890 a flood destroyed the Willamette Falls DC power station. This unfortunate event paved the way for the first long distance transmission of AC electricity in the world when Willamette Falls Electric company installed experimental AC generators from Westinghouse in 1890. That same year, the Niagara Falls Power Company (NFPC) and its subsidiary Cataract Company formed the International Niagara Commission composed of experts, to analyze proposals to harness Niagara Falls to generate electricity. The commission was led by Sir William Thomson (later Lord Kelvin) and included Eleuthère Mascart from France, William Unwin from England, Coleman Sellers from the US, and Théodore Turrettini from Switzerland. It was backed by entrepreneurs such as J. P. Morgan, Lord Rothschild, and John Jacob Astor IV. Among 19 proposals, they even briefly considered compressed air as a power transmission medium, but preferred electricity. But they could not decide which method would be best overall.
[edit]International Electro-Technical Exhibition
The International Electro-Technical Exhibition of 1891 featured the long distance transmission of high-power, three-phase electric current. It was held between 16 May and 19 October on the disused site of the three former “Westbahnhöfe” (Western Railway Stations) in Frankfurt am Main. The exhibition featured the first long distance transmission of high-power, three-phase electric current, which was generated 175 km away at Lauffen am Neckar. It successfully operated motors and lights at the fair.
When the exhibition closed, the power station at Lauffen continued in operation, providing electricity for the administrative capital, Heilbronn, making it the first place to be equipped with three-phase AC power.
Many corporate technical representatives (including E.W. Rice of Thomson-Houston Electric Company (what became General Electric)) attended.[34] The technical advisors and representatives were impressed.
[edit]AC deployment at Niagara
In 1893, NFPC was finally convinced by George Forbes to award the contract to Westinghouse, and to reject General Electric and Edison's proposal. Work began in 1893 on the Niagara Falls generation project: power was to be generated and transmitted as alternating current, at a frequency of 25 Hz to minimize impedance losses in transmission (changed to 60 Hz in the 1950s).
Some doubted that the system would generate enough electricity to power industry in Buffalo. Tesla was sure it would work, saying that Niagara Falls could power the entire eastern United States. None of the previous polyphase alternating current transmission demonstration projects were on the scale of power available from Niagara:
The Lauffen-Neckar demonstration in 1891 had the capacity of 225 kW
Westinghouse successfully used AC in the commercial Ames Hydroelectric Generating Plant in 1891 at 75 kW (Single phase)
The Chicago World's Fair in 1893 exhibited a complete 11,000 kW polyphase generation and distribution system with multiple generators, installed by Westinghouse [35]
Almirian Decker designed a three-phase 250 kW AC system at Mill Creek California in 1893 [36]
On November 16, 1896, electrical power was transmitted to industries in Buffalo from the hydroelectric generators at the Edward Dean Adams Station at Niagara Falls. The generators were built by Westinghouse Electric Corporation using Tesla's AC system patent. The nameplates on the generators bore Tesla's name. To appease the interests of General Electric, they were awarded the contract to construct the transmission lines to Buffalo using the Tesla patents.[37]
[edit]Competition outcome
As a result of the successful field trial in the International Electro-Technical Exhibition of 1891, three-phase current, as far as Germany was concerned, became the most economical means of transmitting electrical energy.
In 1892, General Electric formed and immediately invested heavily in AC power (at this time Thomas Edison's opinions on company direction were muted by President Coffin and the GE board of directors). Westinghouse was already ahead in AC, but it only took a few years for General Electric to catch up, mainly thanks to Charles Proteus Steinmetz, a Prussian mathematician who was the first person to fully understand AC power from a solid mathematical standpoint. General Electric hired many talented new engineers to improve its design of transformers, generators, motors and other apparatus.[38]
In Europe, Siemens & Halske became the dominant force. Three phase 60 Hz at 120 volts became the dominant system in North America while 220-240 volts at 50 Hz became the standard in Europe.
Alternating current power transmission networks today provide redundant paths and lines for power routing from any power plant to any load center, based on the economics of the transmission path, the cost of power, and the importance of keeping a particular load center powered at all times. Generators (such as hydroelectric sites) can be located far from the loads.
[edit]Remnant and existent DC systems
Some cities continued to use DC well into the 20th century. For example, central Helsinki had a DC network until the late 1940s, and Stockholm lost its dwindling DC network as late as the 1970s. A mercury arc valve rectifier station could convert AC to DC where networks were still used. Parts of Boston, Massachusetts along Beacon Street and Commonwealth Avenue still used 110 volts DC in the 1960s, causing the destruction of many small appliances (typically hair dryers and phonographs) used by Boston University students, who ignored warnings about the electricity supply. New York City's electric utility company, Consolidated Edison, continued to supply direct current to customers who had adopted it early in the twentieth century, mainly for elevators. The New Yorker Hotel, constructed in 1929, had a large direct-current power plant and did not convert fully to alternating-current service until well into the 1960s.[39] This was the building in which AC pioneer Nikola Tesla spent his last years, and where he died in 1943. In January 1998, Consolidated Edison started to eliminate DC service. At that time there were 4,600 DC customers. By 2006, there were only 60 customers using DC service, and on November 14, 2007, the last direct-current distribution by Con Edison was shut down. Customers still using DC were provided with on-site AC-to-DC rectifiers.[40]
The Central Electricity Generating Board in the UK continued to maintain a 200 volt DC generating station at Bankside Power Station on the River Thames in London as late as 1981. It exclusively powered DC printing machinery in Fleet Street, then the heart of the UK's newspaper industry. It was decommissioned later in 1981 when the newspaper industry moved into the developing docklands area further down the river (using modern AC-powered equipment). The building was converted into an art gallery, the Tate Modern.
Electric railways that use a third-rail system generally employ DC power between 500 and 750 volts; railways with overhead catenary lines use a number of power schemes including both high-voltage AC and high-current DC.
High-voltage direct current (HVDC) systems are used for bulk transmission of energy from distant generating stations, or for interconnection of separate alternating current systems. These HVDC systems use electronic devices like mercury arc valves, thyristors, or IGBTs that were unavailable during the War of Currents era. Power is converted to and from alternating current at each side of the HVDC link. An HVDC system can transmit more power over a given right-of-way than an AC system, which is an advantage in overall cost. HVDC systems allow better control of power flows in transient and emergency conditions, which helps prevent blackouts. HVDC is an alternative to AC systems for long-distance, high-load transmission, see List of HVDC projects for example projects.
DC power is still common when distances are small, and especially when energy storage or conversion uses batteries or fuel cells. These applications include:
Electronics, including integrated circuits, high-power transmitters and computers
Vehicle starting, lighting, and ignition systems
Hybrid and all-electric vehicle propulsion with internal power-supply
Telecommunication plant power (wired and cellular mobile)
Uninterruptible power for computer systems
Utility-scale battery systems
"Off-grid" isolated power installations using wind or solar power
In these applications, direct current may be used directly or converted to alternating current using power electronic devices. In the future, this may provide a way to supply energy to a grid from distributed sources. For example, hybrid vehicle owners may rent the capacity of their vehicle's batteries for load-levelling purposes by the local electrical utility company.

Much of what the public knows about America’s most celebrated  inventor is riddled with misconceptions. Among other things, the shrewed businessman Thomas Alva Edison, did not invent the light bulb. Following is a list of inventions that are often attributed to Edison, but were in fact not his making.

1. The Electric Bulb or Incandescent Lamp




Ask any child who invented the light bulb, and the answer is likely to be "Thomas Edison". Contrary to what schools have taught for years, the American icon, Thomas Edison, neither invented the light bulb, nor held the first patent to the modern design of the light bulb. In reality, light bulbs used as electric lights existed 50 years prior to Thomas Edison’s 1879 patent date. In fact, Edison lost all patent rights to the light bulb both in Britain and the United States.

2. The Electric Chair

The first practical electric chair was invented by Harold P. Brown. Brown was an employee of Thomas Edison, hired for the purpose of researching electrocution  and for the development of the electric chair. Since Brown worked for Edison, and Edison promoted Brown’s work, the development of the electric chair is often erroneously credited to Edison himself. Furthermore, Brown’s design was based on George Westinghouse’s alternating current (AC), which was then just emerging as the rival to Edison’s less transport-efficient direct current  (DC), which was further along in commercial development.

3. The Movie Camera




As with the Electric chair, the invention of the movie camera should accurately be attributed to William Dickson, an Edison employee. Edison had absolutely no concept of how the movie industry would take off. Interestingly, even before Edison’s work on movies, the basic idea had already been developed by a British photographer named Eadward Muybridge. He wanted to prove that when a horse ran, all four of its legs could be up in the air at once. By taking several photos very fast, Muybridge proved his point.

4. The Power Generator

In the early 1880s, Nikola Tesla invented the AC generator, which allowed electricity to be transmitted over greater distances than could be done with DC power, which required a generator every few miles. Edison was making good money off of DC power, and didn’t want to change, or worse, have someone else move in on his turf. Not surprisingly, Tesla and Edison had a long standing feud over this and many other inventions[1] . Edison did not invent the first electrical power station. Ultimately, though, he did improve the designs of existing generators and regulators to create the first commercially successful power station capable of delivering affordable power for electric lighting.

5. X-Ray Photographs (fluoroscope)




In 1887, Nikola Tesla, not Edison, was among the first to investiage the nature of X-Ray’s using designs based on the Cathode Ray Tube. Eight years later, Thomas Edison began investigating materials’ ability to fluoresce when exposed to x-rays. The fluoroscope he developed became the standard for medical X-ray examinations. Nevertheless, Edison dropped X-ray research around 1903 after the death of Clarence Madison Dally, one of his glassblowers. Dally had a habit of testing X-ray tubes on his hands, and acquired a cancer in them so tenacious that both arms were amputated in a futile attempt to save his life.

6. The Storage Battery

What invention made Edison the most money? The alkaline storage battery. Ironically, though, Edison did not invent the first storage battery, but combined new materials to create a storage battery suitable for practical use. By the time he perfected the alkaline storage battery, electric-powered cars had lost out in the competition with gas-powered cars that could be driven far greater distances. A failure as the motive force for automobiles, the alkaline storage battery was ultimately a great commercial success as the power source for train lights, marine appliances, and miners’ lamps. Prior to this invention, miners used candles or small oil lamps attached to their hard hats as their light source.

7. The Record Player


Thomas Edison did not invent the record player. Rather, he invented the phonograph, which was intended for making recordings. The phonograph was first marketed as a dictation machine and only later modified for use in musical devices. The ability to record sounds had been invented much before Edison’s phonograph. The gramophone, invented by Emile Berliner, was actually the first record player as we know it. To compete with the success of the record player, Edison and his company later devised the "disk" phonograph.

8. Wax Paper

Although Edison claimed to have invented wax paper, he did not. Waxed paper was invented by Gustave Le Gray in 1851. Used for hand-colouration, it allowed the colour from the back of the photograph to be seen from the front. The wax paper revolutionized photography and also became a commercially successful household product for, among other things, wrapping food.

9. The Telegraph

The telegraph had been invented while Edison was still a child. Due to his partial deafness, Edison learned the art of telegraph at an early age. And later on, spent a considerable time devising inventions that relied on the telegraph system, such as the stock ticker. Nevertheless, he did not invent the telegraph. To his credit, he did invent the first duplex and multiplex telegraphy systems, enabling telegraphs to send and receive messages at the same time over the same wire.
–
Thomas Edison himself did not invent major breakthroughs. He often took credit for the ideas and inventions of others and most of his patents were little more than improvements on already existing products. He was an astute businessman, and as such, had greater impact on innovating existing products than inventing new ones. To quote himself, "I always invent to obtain money to go on inventing."




Update

Received an email from Greg Farmer: “Near the end, you say that Edison did invent the first duplex and multiplex telegraphy systems. Not so. Moses G. Farmer demonstrated duplex telegraphy between New York and Philadelphia in 1856 and patented a duplex telegraph in 1859. Edison patented an “improved duplex telegraph” in 1874, 15 years after Farmer. There are other internet articles claiming that Edison invented duplex telegraphy, but they are all based on misconceptions caused by the huge publicity that surrounded Edison’s inventions.”

Notes

1: When it was clear that AC power was a threat, Edison started a propaganda campaign against AC power, claiming that it was much more dangerous than DC power. Besides distributing pamphlets, he also set up demonstrations where he electrocuted dogs and cats to show the power of AC. He also convinced the authorities at Sing Sing to carry out death sentences not by hanging, but by AC power. Despite all of this, AC power ‘won’, and is what we use today.