AC or DC That Was the Question

By the early 1880's Direct Electrical Current, DC, was already a developed and commercially used electrical power system in the USA. Thomas Edison was the first major inventor and big businessman to commercially produce, distribute, and supply electrical energy and power to customers for their own local use and he used Direct Electrical Current, DC to do it. Edison was also one the most major and prolific proponents leading the way to highly promoting Direct Current, DC, for widespread widescale commercial use throughout the USA. So prior to Alternating Electrical Current, AC, being chosen as the preferred mainstream elecrical power method and system of choice, to be used on a widescale widespread basis for home, public, govt, and business use throughout the USA for; lighting, appliances, machines, motors, refrigeration, A/C, electric heating, stoves, toaster ovens, radios, tvs, telephones, computers, and so much more.

An ongoing battle ensued during the 1880's between two sides of inventors, business leaders, and investors. One side wanted AC and the other side wanted DC to be the preferred mainstream method and system of choice. For producing, maintaining, supplying, distributing, delivering, applying, and using electrical power. During that time each side was competitively working against the other to be the first to further develop and promote their AC or DC type inventions, methods, systems, applications, and use. For and to the general public, govt, business and company owners. They did this in order to try and win the ongoing AC vs DC debate, argument, and battle. In order to be the one chosen over the other for that role, to be widely accepted as the preferred method and system of choice for using electric power on a widespread widescale basis for home, public, govt, and business use in the USA, Europe, Asia, and elsewhere.

Edison Promoter of the DC Electric System

One of the most technically advanced, accomplished, successful, famous, infamous, and controversial American inventors and businessmen from the late 19th and early 20th century was Thomas Edison, who was the inventor of the electric light bulb in 1879 and the phonograph in 1877, and 100's of other important ground breaking elictricity related inventions. In the late 1880's he and a highly accomplished railroad engineer, inventor and business investor, George Westinghouse, who in 1869, at age 22 successfully invented the railroad air-braking system using compressed air, that was thereafter widely accepted and used by all major railroads throughout the US, Europe, Asia, and elsewhere. They engaged in what would become an epic battle of competition to decide on which direction the US, Europe, Asia, and other nations would be going. Relating to choosing AC or DC electrical power systems for widespread widescale nationwide use. Between their two competing electric power companies, Edison's was promoting DC and Westinghouse's was promoting AC.

Edison DC vs Westinghouse AC

Edison's 1890's era DC electric energy generated and distributed electric power at the same amount of voltage as what was being used by the homeowner's and business owner's lighting, motors, and appliances, such as 110 volts for 100 volt light bulbs. So the current being transmitted and sent to power them up was quite large and required heavy conductors. At the time there was no practical method for transmitting and stepping down higher voltages of DC power for long distances. Because of an increase in the loss of electric power the farther away the customers destination was, DC electric power could only be transmitted over limited distances, up to around 1 mile maximum. Edison and his company had invested heavily in DC technology and was relentlessly defending its DC based patents when along came the invention of an efficient transformer that allowed high voltage to be used for AC electrical power transmission. An AC power plant could then serve more customers at large distances up to hundreds of miles away at alot lower costs. That also meant that alot less of these much larger power plants would be needed for AC, which lowered the costs even more.

Soon thereafter a practical AC motor was invented that increased alternating currents usefulness for powering machines. At that time George Westinghouse saw that if he was to own the most important patents to the inventions that comprised the main components of the Alternating Electric Current system he could have his own electric system to compete in the electric power generation and distribution business. He went on to set up the Westinghouse Electric Company to design and build the AC electric power system. In spite of Edison and his company's non-stop campaign against AC electric power, the much lower cost and ease of distribution on a much larger scale caused the AC electric system to prevail over DC for home, public, govt, business, and commercial use on a widespread widescale nationwide basis and level. Leading the way for Alternating Current, AC, being chosen and accepted as the preferred electric power system, was the technical and economic success of the 1893 Niagara Falls to Buffalo, New York AC electric power transmission project.

AC Research, Inventors, Patents, Investors

Each of their company's had their own teams of inventors, inventions, applications, licensed patents, methods and systems. Their battle was over whos method and system of electicity, AC or DC would be the one to lead the way for the future of widescale, home, public, govt, and business use. For producing, supplying, distributing, delivering, and maintaining, all kinds of popular applications and uses for electrical energy and power. By the industrialized nations, USA, Canada, Europe, Asia, and beyond. Westinghouse's main ally, inventor, project director and manager on the AC side, was an advanced Hungarian scientist, researcher, and inventor named Nikola Tesla.

Whos own pioneering groundbreaking and very valuable Alternating Current related inventions and patents were bought up from him by Westinhouse, among the other pioneering breakthrough AC related inventions and patents that he bought from some of the other leading top level European scientists, researchers, inventors, and developers. Businesses and companies in America and Europe lined up on either side of the ongoing AC DC argument, debate, competition, depending on which type of electrical power method and system, AC or DC, that their business's or company's products or services were based on, more related too, worked better with. Or based on which of the two electric methods and systems AC or DC that they were expecting, betting on, or investing in, to win the ongoing AC DC race to the finish argument, debate, competition.

Edison and His War Against AC

The high level of cold calculating and unethical competitive one upsmanship engaged in during this battle of AC vs DC, Alternating Electric Current vs Direct Electric Current on the part of Edison, in his desperate bid not to lose. Can hardly be pictured, and would not have been tolerated in later years, especially in recent times. In Edison's fight to win over the popular opinion of the general public on this matter, he wanted to try and prove to them that his preferred method and system of choice DC, for electricity, electrical power and energy production, distribution, maintenance, applications, and overall home, public, govt, and business use. Was so much safer than his opponent Westinghouse's preferred method of choice for electricity and overall electrical power and energy usage, AC, Alternating Electric Current. Unfortunately, Edison strangely, bizarrely, and wrongfully decided to go so low as to engage in setting up and carrying out cruel sadistic exhibitions of highly abusive animal cruelty and torture. With numerous demonstrations being carried out by Edison's employees for onlooking newspaper reporters.

Using AC-current on a high amount of unsuspecting innocent helpless animals of all kinds, even an elephant. All of those kinds of intentional deliberate incidents and acts of highly abusive animal cruelty and torture, that were carried out by Edison and his employees, would be felony level crimes today. Edison also used AC, Alternating Electrical Current on condemned prison inmates to demonstrate how potentially dangerous and unsafe AC could be if used as a widescale widespread power and energy producing method, system and source for nationwide commercial distribution. When compared to his much safer preferred method and system of choice, DC, Direct Current, for electric energy and power production, supply, distribution, delivery, maintenance, applications, and overall use. That was one of the main reasons that two of Edison's main company inventors were ordered to invent and build the AC driven electric chair in 1888 at Edisons company. It was widely accepted, acquired and used throughout the United States Federal and State prison systems.

Westinghouse and AC Wins Edison Loses

All of Edisons poor decisions, unethical behavior, and actions that he engaged in during this epic battle for the direction and future of electricity in the US, Canada, Europe, Asia, and beyond, added and ended up being a very bad business strategy. These major careless and reckless mistakes that Edison made while working in the field of electricity within big industry and business, were going to soon cause him a lot of trouble. Resulting in his loss of control and running of his electricity related inventions and whole overall main business, Edison General. In 1892, E-G was renamed General Electric under a new Co President and GE board of directors. At that same time Edison's highly biased opinions and suggestions on the AC vs DC argument, debate, and competition were becoming more and more unpopular amongst those new GE Co owners and board of directors. so Edison's opinions and suggestions on the direction that GE should be taking were being pushed aside. Edison's constant claims of DC being better than AC as the nationwide widescale home, business, govt, commercial, electric power method and system of choice was being disproven so much on a day to day basis by 1892.

This was a direct result of the high level of ongoing AC research, development, advancements, breakthroughs, applications, and AC system implementation. Alot of major electric production and distribution field testing projects, involving alot of big electric power system development and provider Co's such as Westinghouse and other big Co's with their major backings and investments, were also underway. The AC electric power systems involved and being tested in these major projects were ending up being mostly highly successful. Thereby paving the way for AC to being chosen over DC as the electric power method and system of choice for home, business, govt, and commercial use on a widespread widescale nationwide level and basis. In that same year 1892 General Electric started to invest heavily in building its own AC methods and systems and acquiring AC related patents. GE hired many highly skilled electrical engineers to improve its own new designs of generators, transformers, motors and other electrical system devices.

It wasn't before too long that GE was able to catch up to Westinghouse's type of major level leadership in the Alternating Electric Current production and distribution field and big buisines. How ironic it was that the General Electric Co of which Edison was the original founder, had so quickly become one of the major top competitive big Co's in the AC electric production and distribution field and big business. DC electric power continued to be used in some highly populated urban areas where its use was considered economicly acceptable because of local DC electric power stations being able to bring alot of electric power to alot of people who were all closely located to eachother and the DC power station too. DC electric power continued to be used and newly developed in and for alot of established and newly developed compatible applications, such as building elevator DC electric power motor systems and numerous other types of much needed and useful commercial and business related electric power applications and uses.

AC Electric System Niagara Falls Test

In 1893, the Niagara Falls Power Co awarded a major contract for the NF electric generation project in which the power was to be generated and transmitted as alternating current, to Westinghouse after having first rejected General Electric and Edison's proposal on the project. Skeptics doubted that the system would be able to produce enough electricity to power Buffalo NY industry's electric power needs. Westinghouse's leading electrical engineer Nikola Tesla reassured the NFPC that it would work. Tesla added that “Niagara Falls could power the entire eastern United States.” The first Niagara River hydraulic tunnel that was completed had a capacity to produce an unprecedented 75 MW. Nov 16, 1896, Electrical power was transmitted to Buffalo NY's industries from Niagara Fall's Edward Dean Adams hydroelectric generator station. Westinghouse Electric Co had built these generators which had Nikola Tesla's name on the nameplates based on Tesla's AC system patents. NFPC appeased the interests of General Electric by awarding them the contract to construct the transmission lines to Buffalo NY, but as part of their contract they had to agree to use, abide and be guided by Tesla's patents while doing so.

Ac vs DC Argument Debate Outcome

Alternating Current electric power systems in Europe were being built by the Siemens and Halske Co who were the leading major big Co for AC power generating and distribution systems in Europe. Their method and system used 50-hz at 220-240 volts which became the EU's standard AC power system. In North America 60 Hz at 120 volts became the standard AC power system. Today AC electric power distribution networks provide consistent repeating paths and power lines for electric energy and power from any power plant to any load center, depending on the economic viability of the energy delivery's path, cost, and the importance of keeping certain load centers supplied with power at all times. AC Hydroelectric, gasoline, and coal fueled generator sites can also be located far away from the load stations. Even after AC electric power systems took over most of the electric energy and power markets in the USA, Europe, and Asia, some cities continued to use DC well into the 20th century. Until the late 1940s Finlands major city Helsinki still had a DC network in place and in use. In Sweden thecity of Stockholm's DC network was finally put out of use in the 1960s. After 1940 if a location still wanted to use one of these original type DC designed electric power systems that was already in place, they were then able to use AC electric power as the original electrical energy and power source, which had to then be converted over to DC electric power by a mercury-arc valve rectifier station.

Then that DC electric power could be distributed out to the DC electric systems still being used by the local towns in those cities. In 1942, New York City.s Greenwich Village was still using DC electric power. In the 1960s some parts of Boston, MA were still using 110 volts DC. Some Boston University students who were residing on and around Beacon Street and Commonwealth Avenue that ignored the warnings about the old style DC electricity supply that was still in place and use were having some of their small AC appliances such as hair dryers and phonographs destroyed. New York City building owners who had installed DC electric motor powered elevators early in the twentieth century continued to be supplied Direct Current by Consolidated Edison. They delivered their last DC to a customer in Nov 2007. The New Yorker Hotel (1929) in which AC pioneer Nikola Tesla spent his last years until 1943, had its own large Direct Current power plant and did not fully convert over to Alternating Current until well into the 1960s. Con-Edison started to end its DC service in Jan 1998 when they still had between 4 and 5 thousand DC customers left. There were only 60 Con-Ed customers still using DC electric energy and power in 2006, and on Nov 14, 2007, Con Ed's last Direct Current delivery account was shut down.

Con-Ed provided on-site AC to DC rectifiers for their customers who were still using DC electric energy and power. A DC power grid was still in use by the city of San Francisco, California in 2010, in order to supply electric energy and power for their old style DC powered winding-drum elevators (pre-1940s), that were still in use there. At the end of that sdame year, that DC power grid was divided into 171 islands, that supplied DC electric power for 7 to 10 customers each. In the UK as late as 1981 the Central Electricity Generating Board continued to maintain a 200 volt DC generating station at Bankside Power Station on the River Thames in London. It was used to power the UK's newspaper industry's DC printing machinery on Fleet Street. In 1981 the UK's newspaper industry started using modern AC powered printing equipment. So the DC generating station was put out of service, the building converted into an art gallery (Tate Modern), and the UK's newspaper industry moved farther down the river into the developing docklands area. Third rail systems used by electric railways utilize DC power between 500 and 750 volts. A number of power schemes are used by railways with overhead catenary lines, including both high voltage AC and high current DC.

DC's Major Role in Electric Power

Direct current electric systems continued to be used for powering up highly populated urban areas well into the 20th century. Besides being used mostly for ligting applications it also continued to be used to power passenger and freight elevators that ran mostly on direct current motors. Direct current remained useful in streetcar, trolley, tram, and steamboat wheel type traction systems, inside vehicles and battery operated systems. Often rectifiers were used to convert AC power from the public grid over to Direct Current power, for customers who were still using DC electric energy at their homes, business, or public place. DC power is still commonly used for short distances and especially in applications where electric energy needs to be stored or converted. Such as with batteries and fuel cells for use in all kinds of electronic devices. For starting, running, and fully powering all types of engines and accessory systems, for all types of transportation and work performing vehicles and devices.

Starters, ignition systems, dashboards, full lighting systems, and all other onboard accessory electric power systems for; cars, trucks, buses, airplanes, warehouse fork lifts, farm tractors, and all types of big construction machinery. Isolated power installations (Off-grid) using wind or solar power use DC electric power over limited distances, between the source and application destination. Direct current is also seeing new application in big business computer data centers, where DC distribution within a building can provide useful energy savings. In such applications DC electric power systems replace current AC power systems in order to isolate and individually power the PCU's being used in the PC data centers computer networks PC's. That can save alot of energy costs while keeping the Co's whole PC system running better, more efficiently and reliably.

High Voltage Reduces Energy Loss

Alternating Current was the original electric energy method and system chosen over Direct Current for national widescale electric energy and power production and distribution. One of the main reasons was because the needed AC transformer technology had been invented and developed earlir than it had been for DC power systems. The AC power systems generators were also much more efficient and economical to run and use. Those early AC transformers allowed for AC to be distributed at much higher voltages compared to the voltages that DC could be distributed at, at the time. The Alternating electrical Currents voltage was then stepped down using the AC transformers to meet the much lower and variable amounts of voltages needed by the end users, customers, at their homes, business, govt, public places, and locations. Early on it was figured out that the distribution and routing of electric power at higher voltages reduced the amount of electricity lost in the resistance of the conductors which are the copper wires.

For a given amount of electrical energy, multiplying the volts will deliver the same quantity of electric power using only half the amount of electricity. A reduction of the electric power that is lost in transmission can also be achieved by increasing the conductors size, but larger conductors are heavier and more expensive. Since the power lost as heat in the wires is proportional to the square of the current for a given conductor size, but does not depend on the voltage, doubling the voltage reduces the power line losses per unit of electrical power delivered by a factor of 4. The high voltages being transmitted through the routed power lines must first be reduced before they can be used for electric lighting, motors, machinery, equipment, and other types of electrical devices. Transformers are used to change the voltage levels in alternating current, AC, circuits.

Converting ACV to DCV With Rectifiers

In 1901 an inventor Peter Cooper Hewitt who was the son of New York City Mayor Abram Hewitt and the grandson of industrialist Peter Cooper, invented and patented a mercury vapor gas discharge lamp, that used mercury vapor produced by passing current through liquid mercury. Soon thereafter he invented and patented a much improved and convenient way of lighting and using the lamp. It was an inductive ballast that is still in use today with the much improved version of his original lighting system. Although the color and kind of light which is described as a bluish-green colored light was not optimal for general use, it was highly credited for its reliability and very economical use of electricty when compared to the then current standard incandesant light bulbs much higher electricity use and cost. The original mercury vapor gas discharge lamp was very useful though for its everday use in specific professional fields, such as in the field of photography, where the color of the light that the lamp emitted was not an issue at a time where films were black and white. The mvg-discharge lamp was also commonly used along with a standard incandescant bulb for lighting spaces. When the two were used together the light it provided produced a more acceptable color and helped to lower electricity use and cost.

Hewitt's mercury vapor gas discharge lamp would later in the 1930s be only slightly modified but greatly improved by the engineers at the General Electric Co. They did this by simply adding a white diffuse coating to the inside of the lamps clear glass, which eliminated the bluish-green colored light that the original lamps clear glass had previously been emitting and replaced it with a very acceptable and usable clean and cool white colored light. Up until that time Hewitt's highly commendable, groundbreaking, and potential mass market success, mercury vapor gas discharge lamp, had eventually become considered antiquated, obsolete, and unusable for general lighting because of the odd bluish-green color that its light was emitting. That one simple but major improvement of a white coating on the inside of the lamps clear glass, that GE contributed to Hewitt's mercury vapor gas discharge lamp, transformed it into the modern day flourecent light bulb. Thereby enabling it to go on to being one of the most highly manufactured, distributed, and utilized types of commercial lighting, being used for and in all types of applications and installations everywhere.

In 1902 based off of similar technology and design that Hewitt had used for inventing and manufacting his highly successful mercury vapor gas discharge lamp in 1901, Hewitt invented a new breakthrough type of rectifier called a mercury-arc valve or mercury-vapor rectifier, or mercury-arc rectifier in the UK. A mercury-arc valve is a type of electrical device classified as a rectifier or converter, that is used for converting High Voltage or High Current, Alternating Current, AC, into Direct Current, DC. It is a type of cold cathode gas discharge tube, but it's unusual in that the cathode, instead of being solid, is made from a pool of liquid mercury, and is therefore self-restoring. This results in mercury-arc valves (a type of rectifier) being much more rugged, durable, long lasting, reliable, versatile, and being able to carry much higher voltages and currents, than most other types of gas discharge tubes. Mercury-arc valves were used to provide power for industrial motors, electric railways, locomotives, streetcars, radio transmitters and for high voltage Direct Current power distribution and transfer. Before the advent of semiconductor AC to DC converters such as diodes, thyristors and gate turn-off thyristors, GTOs, in the 1970s, Mercury-arc valves were the primary method of high power AC to DC electric power conversion.

Thermionic Diode Vacuum Tubes

The correct name for a Vacuum Tube which is a type of thermionic-valve device is a thermionic diode. It is sometimes referred to simply as a tube or valve. The basic principle of operation of thermionic diodes was discovered in 1873 by Frederick Guthrie. He discovered that a positively charged electroscope could be discharged by bringing a grounded piece of white-hot metal close to it, but not actually touching it. He also discovered that the current flow was only possible in one direction. Because when he tried discharging a negatively charged electroscope by again bringing a grounded piece of white-hot metal close to it, it didn't discharge. On Feb 13, 1880 Thomas Edison rediscovered the same principle on his own. Edison was investigating why the filaments of his carbon-filament light bulbs nearly always burned out at the positive-connected end. He had a special bulb made with a metal plate sealed into the glass envelope. Using this device, he confirmed that an invisible current flowed from the glowing filament through the vacuum to the metal plate, but only when the plate was connected to the positive supply.

Edison devised a circuit where his modified light bulb effectively replaced the resistor in a DC voltmeter. Edison was awarded a patent for this invention in 1884. Since there was no apparent practical use for such a device at the time, the patent application was most likely just a precaution, in case someone else did find a use for the so-called Edison effect. Edison was awarded a patent in 1884 for a device that he invented using that same modified light bulb to build a circuit that effectively replaced the resistor in a DC voltmeter. Since there was no apparent practical use for such a device at the time, the patent application was most likely simply a precaution in case someone else did find a use for the so-called Edison effect. in Nov 1904 a British inventor John Ambrose Fleming, who was a scientific adviser to the Marconi Co and a former Edison employee, realized that the Edison effect could be used as a precision radio detector. Fleming patented the first true thermionic diode, the Fleming valve, Nov 16, 1904, followed by another US Patent in Nov 1905.

Oscillation Valve Diode

The Fleming valve, also called the Fleming Oscillation valve was invented and patented 1904-1905 by John Ambrose Fleming. It was designed as a radio receiver, detecter and rectifier. It was the first of a type of thermionic diode vacuum tubes which led to alot of similar and different kinds of improved design variations of vacuum tubes, resulting in a wide variety of similar and different kinds of applications and uses. Some of which were widely used inside the power supplies of consumer electronic equipment, radios, tvs, portable devices, as radio receivers and voltage converting rectifiers. While Flemings diode did have an immediate practical use in its ability to detect messages sent by Morse code, it was more important as a precursor to a new kind of more advanced and versatile vacuum tube that were to be developed soon thereafter based on its original design. It was the forerunner of one of the most major and leading electronic devices and components.

After reading Fleming's 1905 paper on his oscillation valve, American engineer Lee De Forest in 1906 created a three element tube, a triode, which it turned out, could function as an amplifier, an oscillator, as well as a radio receiver detector. Through its initial and future applications, the Fleming valve laid the foundation for the field of electronics. Thermionic diodes and vacuum tubes had the monopoly on the electronic component and devices market well into the 1960s and 70's, when solid state semiconductor diode technology had finally been developed and advanced enough to start catching up to, equal, and eventually surpass, all of the different kinds of thermionic diodes and vacuum tubes, already being used in all kinds of home and business, consumer and commercial grade electronic equipment, components, and devices, such as the Fleming Oscillation valve. In ease of manufacture, greater efficiency, more conveneince, better performance, and with much lower overall costs.

Thermionic Diode Vacuum Tube Design

The Fleming valve consisted of an evacuated, sealed glass bulb containing two electrodes: a cathode in the form of a heated filament, a loop of carbon or fine tungsten wire similar to that used in light bulbs of the time, and a metal plate anode. In early versions this was a flat plate next to the filament, but in later versions it was changed to a cylinder of sheet metal surrounding the filament. In some versions, a grounded copper screen surrounded the bulb, to shield against external electric fields from nearby static charges. In operation, a separate current was sent through the filament and heated it until it glowed. The hot filament emitted electrons into the space of the tube, a process called thermionic emission. The alternating AC voltage to be rectified was applied between the filament and the plate. When the plate has a positive voltage with respect to the filament, the electrons are attracted to it, creating a current of electrons through the tube from filament to plate.

However, when the plate has a negative voltage, the electrons are not attracted to it, so there is no current through the tube; unlike the filament, the plate does not produce electrons. So current can only pass through the tube in one direction and it rectifies (converts) an AC voltage into a pulsing DC current. The load was connected in series with the tube and AC source. This simple design and setup was somewhat complicated by the presence of residual air in the tube, because the vacuum pumps of the time were not able to create as high a vacuum as exists in the more modern vacuum tubes that would follow. At high voltages, the tube could become unstable and oscillate, but this occurred at voltages far above those normally being used back then. The Fleming valve was the first practical application of thermionic emission, which was discovered in 1873 by Frederick Guthrie. As a result of his work on the incandescent light bulb, Thomas Edison made his own discovery of the phenomenon in 1880, which led to it being called the Edison effect.

Radio Signal Receiver Detecter

Edison was granted a patent for this device as part of an electrical indicator in 1884, but he did not find any practical use for it at the time. During that same time Professor Fleming of University College London was consulting for the Edison Electric Light Co, from 1881-1891, and thereafter for the Marconi Wireless Telegraph Company. In 1901 Fleming designed a transmitter for Guglielmo Marconi to attempt transmission of radio waves across the Atlantic from Poldhu, England, to Nova Scotia, Canada. The distance between the two points was about 2,200 miles. Although the contact, reported Nov 12, 1901, was widely heralded as a great scientific advance at the time, there is also some skepticism about the claim. Because the signal that was received, which was three dots of the Morse code letter “S”, was so weak that the primitive receiver had difficulty transmitting it clearly enough to tell if it was from atmospheric radio noise caused by static electricity or the actual morse code that was attempting to be sent. This later led to critics suggesting that it may have been nothing but random noise.

Regardless, it was clear that reliable transatlantic communication with the existing transmitter required more sensitive receiving apparatus. The receiver for the transatlantic demonstration employed a coherer, which had poor sensitivity and degraded the tuning of the receiver. This led Fleming to look for a detector which was more sensitive and reliable, while at the same time being better suited for use with tuned circuits. In 1904 Fleming tried an Edison effect bulb for this purpose, and found that it worked well to rectify high frequency oscillations and thus allow detection of the rectified signals by a galvanometer. On Nov 16, 1904, he applied for a US patent for what he termed an oscillation valve. This patent was subsequently issued as number 803,684 and found immediate utility in the detection of messages sent by Morse code.

Oscillation valves Power Applications

The Fleming valve proved to be the start of a technological revolution. After reading Fleming's 1905 paper on his oscillation valve, American engineer Lee De Forest in 1906 created a three element vacuum tube triode, the Audion, by adding a wire grid between the cathode and anode. It was the first electronic amplifying device, allowing the creation of amplifiers and continuous wave oscillators. De Forest quickly refined his Audion triode device into new even better, more advanced, and versatile types of triodes, that had much better performance and design characteristics. All of which became the basis of long-distance telephone and radio communications, radars, and early digital computers for 50 years, until the advent of the solid state transistor in the 1960s and 70s. Which used semi-conducter materials as the main innovation and basis of its design.

Fleming sued De Forest for infringing his valve patents, resulting in decades of expensive and disruptive litigation, which were not settled until 1943. When the US Supreme Court finally ruled that the US Patent that Fleming was defending in the case, was actually invalid. Because of US patent research showing that very similar US patents to his own that he was defending in the case, had already been granted to other inventors, prior to when his own US patent had been granted to him in 1905. Later, when vacuum tube equipment began to be powered from wall power by transformers instead of batteries, the Fleming valve was developed into a rectifier to produce the DC plate, anode, and voltage required by other vacuum tubes.

Around 1914 Irving Langmuir at General Electric developed a high voltage version of the called the Kenotron which was used to power x-ray tubes. As a rectifier, the tube was used for high voltage applications but its high internal resistance made it inefficient in low voltage, high current applications. Up until vacuum tube equipment was replaced by transistors in the 1970s, radios and televisions usually had one or more diode tubes. Alot of the different kinds of very useful specialized Thermionic diode valves that were invented from the 1930s to the 1970s were all derived from the original Fleming valve.

Triode Three Element Vacuum Tube

In 1906 Lee De Forest invented the first triode vacuum tube. It was also the first electrical device which could amplify a weak electrical signal and make it stronger. The Audion and other assorted varieties of vacuum tubes that developed from that first design founded the field of electronics and encompassed the leading technology in that field until the 1960s and 70s, making radio broadcasting, tv, and long distance telephone service possible, among many other applications and uses. De Forest is also credited with one of the principal inventions that brought sound to motion pictures. In 1919 he invented the Phonofilm sound-on-film process. Because of these kinds of electronics related enhancing inventions amongst his over 180 patents, he has been called one of the 1906 Audion triode vacuum tube fathers of the “electronic age”. De Forest was a charter member of the Institute of Radio Engineers. DeVry University was originally named De Forest Training School by its founder Dr Herman A DeVry, who was a friend and colleague of his.

De Forest named himself the “Father of Radio,” with this famous quote, “I discovered an Invisible Empire of the Air, intangible, yet solid as granite,” He was involved in several patent lawsuits, and spent a substantial part of his income from his inventions on legal bills. He had four marriages and 25 Cos. He was indicted for mail fraud, but later was acquitted. Lee De Forest was born in 1873 in Council Bluffs, Iowa, the son of Anna Margaret née Robbins and Henry Swift De Forest. On his religious views LDF was an agnostic. De Forest was a direct descendant of Jessé de Forest who was the leader of a group of Walloon Huguenots who fled Europe due to religious persecutions. His father was a Congregational Church minister who hoped that his son One of the First Audion Radio Receivers 1914 would also become a minister. Henry Swift De Forest accepted the position of President of Talladega College, a traditionally African American school, in Talladega, Alabama, where Lee spent most of his youth.

Many citizens of the white community resented his father's efforts to educate African Americans. Growing up, De Forest had several friends among the black children of the town. De Forest attended Mount Hermon School, and in 1893 enrolled at the Sheffield Scientific School of Yale University in Connecticut. As an inquisitive young inventor, he tapped into the electrical system at Yale one evening and completely blacked out the entire campus, causing his suspension. He was eventually allowed to complete his studies, receiving his bachelor's degree in 1896. He paid part of his tuition with the income from his mechanical and gaming inventions. De Forest earned his PhD degree in 1899 with a dissertation on radio waves, supervised by theoretical physicist Willard Gibbs. For the First Audion AM Radio Transmitter April 1914 next two years, he was on the faculty at Armour Institute of Technology and Lewis Institute, which merged in 1940 to become the IL Technology physics dept, and conducted his first long-distance broadcasts from the university.

Audion Wireless Telegraphy

In 1901 De Forest fell into competition with Guglielmo Marconi at the New York Intl Yacht Races, each working for rival news services, and using their own inventions. Marconi used his patented wireless telegraphy and De Forest used his transmitter and receiver, which was not yet patented. They sat on separate boats and transmitted the highlights of the race live. They ended up jamming each other's signals so neither of the two men were able to transmit any news of the race. De Forest ended up angrily throwing his transmitter overboard. Jammed frequencies were a common problem in the very early years of radio. De Forest's interest in wireless telegraphy led to his invention of the Audion in 1906. He then developed an improved wireless telegraph receiver. On Oct 25, 1906, De Forest filed a patent for a diode vacuum tube detector, a two electrode device for detecting electromagnetic waves, a variant of the Fleming valve invented two years earlier. One year later, he filed a patent for a three electrode device that was a much more sensitive detector of electromagnetic waves.

It was granted US Patent No 879,532 in Feb 1908. The device was also called the De Forest valve, and since 1919 has been known as the triode. De Forest's innovation was the insertion of a third electrode, the grid, between the cathode or filament and the anode or plate of the previously invented diode. The resulting triode or three electrode vacuum tube could be used as an amplifier of electrical signals, notably for radio reception. The Audion was the fastest electronic switching element of the time and was later used in early digital electronics, such as computers. The triode was vital in the development of transcontinental telephone communications, radio, and radar until the 1948 invention of the transistor. De Forest had, in fact, stumbled onto this invention, the triode, via tinkering and did not completely understand how it worked. De Forest had initially claimed that the triodes operation was based on ions created within the gas in the tube.

When in fact, it was shown by others to operate with the vacuum in the tube. The device was subsequently carefully investigated by H D Arnold and his team at Western Electric, now AT&T, and Irving Langmuir at the General Electric Corp. Both of them correctly explained the theory of operation of the triode device and added significant improvements to its design and construction. In 1904, a De Forest transmitter and receiver were set up aboard the steamboat Haimun and operated on behalf of The Times. It was the first broadcast of its kind. On July 18, 1907, De Forest broadcast the first ship to shore message from the steam yacht Thelma. The communication provided quick, accurate race results of the Annual Inter Lakes Yachting Assn, I-LYA, Regatta. The message was received by his asst, Frank E Butler of Monroeville, Ohio. In the Pavilion at Fox's Dock located on South Bass Island on Lake Erie. De Forest didn't like the term “wireless” so he chose a new one, “radio.”

De Forest is credited with the advent of public radio broadcasting. On Jan 12, 1910, he conducted an experimental broadcast of part of the live performance of Tosca and, the next day, a performance with the participation of the Italian tenor Enrico Caruso from the stage of NYC's Metropolitan Opera House. De Forest came to San Francisco CA in 1910 and worked for the Federal Telegraph Co, which began developing the first global radio communications system in 1912. CA Historical Landmark No-836 is a bronze plaque at the eastern corner of Channing St and Emerson Ave in Palo Alto, CA, which memorializes the Electronics Research Lab at that location and De Forest for the invention of the three element triode radio vacuum tube. In April 1923, the De Forest Radio Telephone & Telegraph Co, which manufactured De Forest's Audions for commercial use, was sold to a coalition of automobile makers who expanded the co's factory to cope with rising demand for radios. The sale also bought the services of De Forest, who was focusing his attention on newer innovations.

First Ship To Shore Raadio Broadcast 1907 Ohio Plaque Electronics Research Lab California Historical Landmark No 836

Phonofilm Sound-on-Film Process

In 1919, De Forest filed the first patent on his sound-on-film process, which improved on the work of Finnish inventor Eric Tigerstedt and the German partnership Tri-Ergon, and called it the De Forest Phonofilm process. Phonofilm recorded sound directly onto film as parallel lines of variable shades of gray, and later became known as a “variable density” system as opposed to “variable area” systems such as RCA Photophone. These lines photographically recorded electrical waveforms from a microphone, which were translated back into sound waves when the movie was projected. From Oct 1921 to Sept 1922, De Forest lived in Berlin, meeting with the Tri-Ergon developers and investigating other European sound film systems. He announced to the press in April 1922 that he would soon have a workable sound-on-film system. On March 12, 1923, De Forest presented a demonstration of Phonofilm to the press. On April 12, 1923, De Forest gave a private demonstration of the process to electrical engineers at the Engineering Society Building's Auditorium at 33 W-39th St NYC. This system, which synchronized sound directly onto film, was used to record stage performances, such as in vaudeville, speeches, and musical acts.

In Nov 1922, De Forest established his De Forest Phonofilm Co at 314 E-48th St in NYC, but none of the Hollywood movie studios expressed any interest in his invention. De Forest premiered 18 short films made in Phonofilm on April 15, 1923 at the Rivoli Theater in NYC. He was forced to show his films in independent theaters such as the Rivoli, since Hollywood movie studios controlled all major theater chains. De Forest chose to film primarily short vaudeville acts, not features, limiting the appeal of his process to Hollywood studios. Max Fleischer and Dave Fleischer used the Phonofilm process for their Song Car-Tune series of cartoons—featuring the “Follow the Bouncing Ball” gimmick—starting in May 1924. De Forest also worked with Freeman Harrison Owens and Theodore Case, using Owens's and Case's work to perfect the Phonofilm system. However, De Forest had a falling out with both men. Due to De Forest's continuing misuse of Theodore Case's inventions and failure to publicly acknowledge Case's contributions, the Case Research Lab proceeded to build its own camera. That camera was used by Case and his colleague Earl Sponable to record President Coolidge on Aug 11, 1924, which was one of the films shown by De Forest and claimed by him to be the product of “his” inventions.

Seeing that De Forest was more concerned with his own fame and recognition than he was with actually creating a workable system of sound film, and because of De Forest's continuing attempts to downplay the contributions of the Case Research Lab in the creation of Phonofilm, Case ended his ties with De Forest in the fall of 1925. Case then negotiated an agreement for his patents with studio head William Fox, owner of Fox Film Corp, who marketed the system as the Fox Movietone process. Shortly before the Phonofilm Co filed for bankruptcy in Sept 1926, Hollywood introduced a new method for sound film, the sound-on-disc process developed by Warner Bros as Vitaphone, with the John Barrymore film Don Juan, released Aug 6,1926. In 1927 and 1928, Hollywood began to use sound on film systems, including Fox Movietone and RCA Photophone. Meanwhile, a theater chain owner, Isadore Schlesinger, acquired the UK rights to Phonofilm and released short films of British music hall performers from Sept 1926 to May 1929. Almost 200 short films were made in the Phonofilm process, and many are preserved in the collections of the Library of Congress and the British Film Institute.

Solid State Semiconductor Diodes

German scientist, physicist, and inventor Karl Ferdinand Braun who shared the 1909 Nobel Prize in Physics with Guglielmo Marconi, discovered the “unilateral conduction” of crystals in 1874. Braun patented the crystal rectifier in 1899. Copper oxide and selenium rectifiers were developed for power applications in the 1930s. Indian scientist Jagadish Chandra Bose was the first to use a crystal for detecting radio waves in 1894. The crystal detector was developed into a practical device for wireless telegraphy by Greenleaf Whittier Pickard, who invented a silicon crystal detector in 1903 and received a patent for it on Nov 20, 1906. Other experimenters tried a variety of other substances, of which the most widely used was the mineral galena, lead sulfide. Other substances offered slightly better performance, but galena was most widely used because it had the advantage of being cheap and easy to obtain. The crystal detector in these early crystal radio sets consisted of an adjustable wire point-contact, the so-called “cat's whisker.”

Which could be manually moved over the face of the crystal in order to obtain optimum signal. This troublesome device was superseded by thermionic diodes by the 1920s, but after high purity semiconductor materials became available, the crystal detector returned to dominant use with the advent of inexpensive fixed-germanium diodes in the 1950s. Bell Labs also developed a germanium diode for microwave reception but Bell Labs did not develop a satisfactory thermionic diode for microwave reception. AT&T used these in their microwave towers that criss-crossed the nation starting in the late 1940s, carrying telephone and network tv signals. At the time of their invention, such devices were known as rectifiers. In 1919, the year tetrodes were invented, William Henry Eccles coined the term diode from the Greek roots di, from δί, meaning “two”, and ode from ὁδός, meaning “path”. However, the word diode itself, as well as triode, tetrode, penthode, hexode, was already in use as a term of multiplex telegraphy; “The telegraphic journal and electrical review, Sept 10, 1886.

Cathode Ray Tube and CRT-Oscilloscope

In 1897 Physisist Jarl Ferdind Braun built the first cathode-ray tube, CRT, and cathode ray tube oscilloscope. After long years of service CRT technology has finally been replaced by flat screen technologies, such as liquid crystal display, LCD, light emitting diode, LED, and plasma displays, on television sets and computer monitors. The CRT is still called the “Braun tube” in German-speaking countries, Braunsche Röhre, and in Japan, Buraun-kan. During the development of radio, he also worked on wireless telegraphy. In 1897 Braun joined the line of wireless pioneers. His major contributions were the introduction of a closed tuned circuit in the generating part of the transmitter, and its separation from the radiating part, the antenna, by means of inductive coupling, and later on the usage of crystals for receiving purposes. Wireless telegraphy claimed Dr Braun's full attention in 1898, and for many years after that he applied himself almost exclusively to the task of solving its problems.

Dr Braun had written extensively on wireless subjects and was well known through his many contributions to the Electrician and other scientific journals. In 1899, he would apply for the patents, Electro telegraphy by means of condensers and induction colls and Wireless electro transmission of signals over surfaces. Around 1898, he invented a crystal diode rectifier or cat's whisker diode. Pioneers working on wireless devices eventually came to a limit of distance they could cover. Connecting the antenna directly to the spark gap produced only a heavily damped pulse train. There were only a few cycles before oscillations ceased. Braun's circuit afforded a much longer sustained oscillation because the energy encountered less losses swinging between coil and Leyden Jars. And by means of inductive antenna coupling the radiator was better matched to the generator. The resultant stronger and less bandwidth consuming signals bridged a much longer distance. Braun invented the phased array antenna in 1905. He described in his Nobel Prize lecture how he carefully arranged three antennas to transmit a directional signal.

This invention led to the development of radar, smart antennas, and MIMO. Braun's British patent on tuning was used by Marconi in many of his tuning patents. Guglielmo Marconi used Braun's patents, among others.Marconi would later admit to Braun himself that he had “borrowed” portions of Braun's work. In 1909 Braun shared the Nobel Prize for physics with Marconi for “contributions to the development of wireless telegraphy.” The prize awarded to Braun in 1909 depicts this design. Braun experimented at first at the University of Strasbourg. Not before long he bridged a distance of 42 km to the city of Mutzig. In spring 1899 Braun, accompanied by his colleagues Cantor and Zenneck, went to Cuxhaven to continue their experiments at the North Sea. On Sept 24, 1900, radio telegraphy signals were exchanged regularly with the island of Heligoland over a distance of 62 km. Lightvessels in the river Elbe and a coast station at Cuxhaven commenced a regular radio telegraph service.

Different Types and Funtions of Diodes

A diode is a two-terminal electronic component with asymmetric conductance; it has low or zero resistance to current in one direction, and high or infinite resistance in the other. Semiconductor or solid state diodes which are the most common type in use today, utilize semiconductor material that is composed of a piece of crystal with a p–n junction connected to two electrical terminals. A vacuum tube diode has two electrodes, a plate anode and a heated cathode. The first semiconductor electronic devices were semiconductor diodes. The rectifying abilities of crystals was discoved by German physicist Ferdinand Braun in 1874. Cat's whisker diodes Swedish crystal radio with galena cat's whisker detector were the first semiconductor diodes, they were developed around 1906. They were made of mineral crystals such as galena. Most diodes are now made of silicon, but sometimes selenium or germanium semiconductors used.

Diodes are the electronic version of a check valve. They allow an electric current to pass in one direction, in the diodes forward direction, while blocking current in the opposite or reverse direction. This unidirectional action is called rectification, which is the conversion of Alternating Current, AC, over to Direct Current, DC. So, diodes are forms of rectifiers. They also extract modulation from radio signals in radio receivers. Due to diodes nonlinear current-voltage characteristics, diodes can have more complicated behavior than just this simple on–off action. Electricity can only flow through a semiconductor diode if a certain threshold voltage or cut-in voltage is present, in a forward  Semiconducter Diode biased direction. The voltage drop across a forward-biased diode varies only a little with the current, and is a function of temperature; this effect can be used as a voltage reference or temperature sensor.

By varying the semiconductor materials the current–voltage characteristics of Semiconductor Diodes can be changed. Doping and introducing impurities into the materials are the other ways that the current–voltage characteristics of Semiconductor Diodes can also be changed, such as in produccing special-purpose diodes that perform many different functions and tasks. Zener diodes are used to regulate voltage, avalanche diodes are used to protect circuits from high voltage surges, varactor diodes are used to electronically tune radio and TV receivers, Gunn diodes, IMPATT diodes are used Retrofit LED Lamp, bulb shape, aluminium heat sink, light diffusing dome, on board power supply to generate radio frequency oscillations as are tunnel diodes, which also exhibit negative resistance, which makes them useful in some other types of circuits, and light emitting diodes, called LED's.

Thermionic diode Rectifiers

A thermionic diode consists of a sealed evacuated glass envelope containing two electrodes: a cathode heated by a filament, and a plate called an anode. Early examples of these thermionic-valve devices were similar in appearance to ordinary incandescent light bulbs. The way that they work is by a process called thermionic emission. The cathode is heated to 800–1000°C red-hot by a separate current running through the heater filament, which is a high resistant wire made of nichrome, causing the cathode to release electrons into the vacuum. The cathode is coated with oxides of alkaline earth metals such as barium and strontium oxides, which have a low work function, to increase the number of electrons emitted. Some valves use direct heating, in which a tungsten filament acts as both the heater and the cathode.

The alternating voltage to be rectified is applied between the cathode and the concentric plate electrode. When the plate has a positive voltage with respect to the cathode, it electrostatically attracts the electrons from the cathode, so a current of electrons flows through the tube from cathode to plate. However when the polarity is reversed and the plate has a negative voltage, no current flows, because the cathode electrons are not attracted to it. The unheated plate does not emit any electrons itself. So current can only flow through the tube in one direction, from cathode to plate. In a mercury-arc valve, an arc forms between a refractory conductive anode and a pool of liquid mercury acting as cathode. Such units were made with ratings up to 100s of kilowatts and were important in the development of HVDC power transmission.

Some types of smaller thermionic rectifiers sometimes had mercury vapor fill to reduce their forward voltage drop and to increase current rating over thermionic hard-vacuum devices. Throughout the vacuum tube era, valve diodes were used in analog signal applications and as rectifiers in DC power supplies in consumer electronics such as radios, televisions, and sound systems. They were replaced in power supplies beginning in the 1940s by selenium rectifiers and then by semiconductor diodes by the 1960s. Today they are still used in a few high power applications where their ability to withstand transients and their robustness gives them an advantage over semiconductor devices. The recent 2012 resurgence of interest among audiophiles and recording studios in old valve audio gear such as guitar amplifiers and home audio systems has provided a market for the legacy consumer diode valves.

Long Distance High Voltage Direct Current

In the 1930's European inventors applied DC for high voltage direct durrent electric distribution and transfers. They developed HVDC to be used as a suitable alternative to AC electric systems for high capacity energy and power transfers. Which was being used to connect power plants to distant customers homes, business and buildings. HVDC power systems are used for high level electric power delivery from generating stations at long distances, and for connecting separate Alternating Current electric power systems. The electricity that is stored, transferred and flowing within a HVDC electric Power system can be converted to and from Alternating Current, AC, at each side of the HVDC connection by using a device called a mercury-arc valve. HVDC systems have an advantage in overall lower costs and can transmit more electric energy over a power line than an AC system can. HVDC systems allow better control of power flows and help prevent blackouts in variable use and quick response applications, situations, and conditions.

Starting in 1932, General Electric was doing tests with mercury-vapor valves using a 12-kV DC transmission line, which was also used to convert 40 Hz energy production over to serve 60 Hz end-line-use at Mechanicville, New York. In 1941, the Elbe Project going on in the German city of Berlin that was trying to develop buried cable technology was utilizing a 60-MW, 200-kV, 115-km buried cable link and mercury arc valves. The project was never finished and the equipment was moved to the Soviet Union and was put into service there as the Moscow Kashira HVDC system. The Moscow–Kashira system and the 1954 connection by ASEA between the mainland of Sweden and the island of Gotland marked the beginning of the modern era of HVDC transmission. Mercury arc valves require an external circuit to force the current to zero and thus turn off the valve.

In HVDC systems the AC power system itself provides the way for commutating the current to another valve in the converter. That is why rectifiers (converters) built with mercury-arc valves are known as line-commutated converters. LCCs require rotating synchronous machines in the Alternating Current systems which they are connected to, thereby making it immpossible to transfer power into a passive load. Mercury-arc valves were common in HVDC systems designed up to 1972. The last of these type of Mav-HDVC systems was the Nelson River Bipole 1 system in Manitoba, Canada, which had been put into service in stages between 1972 and 1977. Since then, all mercury-arc HDVC power systems have either been converted to use solid state devices or shut down. HVDC systems using mercury-arc valves were last used at the Inter-Island HVDC-link between the North and South Islands of New Zealand, which had been using them on one of its two poles. On Aug 1, 2012, the mercury-arc valves being used there were put out of service and they were replaced with thyristor converters.

Modern HVDC Thyristor valves

Since 1977, new HVDC systems have been using mostly solid-state devices called thyristor valves. A connection to an external AC circuit is required in HVDC applications using thyristor valves to turn them on and off. This was also the case with HVDC systems that used mercury arc valves. HVDC systems that use use thyristor valves are also called line-commutated converter, LCC, HVDC. Thyristor valves for HVDC began to be developed in the late 1960s. The Eel River project in Canada which was built by General Electric was the first complete HVDC system based on thyristor valves, it went into service in 1972. A thyristor based HVDC connection (1920-MW) that was built between Cabora Bassa and Johannesburg South Africa (895 miles) was energised on on March 15, 1979. AEG, and Brown Boveri Company, BBC, and Siemens were partners who were in the project built the conversion equipment in 1974. A civil war in thecountry was the cause off the late completion date. It was transmitting a voltage of ±533-kV which was the highest in the world at the time.

Capacitor-commutated Converters

Requiring the AC circuit to turn off the HVDC Thyristor current and the need for a short period of reverse-voltage to apply the turn-off (called turn-off time) cause a limited use situation for Line-commutated converters (thyristor valves) for HVDC systems. The development of the Capacitor-Commutated Converter, CCC, was an attempt to address these limitations. Unlike conventional HVDC systems, CCC systems have a series capacitors inserted into the AC powerline connections, either on the primary or secondary side of the converter transformer. The commutating inductance of the converter is partially offset by the series capacitors, which help to reduce fault currents and reduce the need of reactive power support for the converter and inverter, because a smaller extinction angle can be used. The widescale use of the newly advanced CCC HVDG system was soon bypassed though because of the new development of Voltage-source converters, VSC, HVDC systems, which eliminated the need for an extinction (turn-off) time altogether.

Voltage-source Converters

Voltage-source converters had been widely used in motor drives since the 1980s, The first time they started to appear in HVDC was in 1997 in the experimental Hellsjön–Grängesberg project in Sweden. By 2011 Voltage-source converter technology had gone on to capture most of the HVDC market. More versatility was added to HVDC systems applications and use when smaller HVDC systems became more economical to use because off the development of higher rated insulated-gate bipolar transistors, IGBTs, gate turn-off thyristors, GTOs, and integrated gate-commutated thyristors, IGCTs. Manufacturers Using this latest HVDC technology such as the ABB Group calls this concept HVDC Light, Alstom calls their product based upon this technology HVDC MaxSine. Siemens calls a similar concept HVDC PLUS, Power Link Universal System. Electric component systems manufacturers such as those mentioned above have extended the use of HVDC down to blocks as small as less than 50-megawatts and overhead power lines as short as less than 2 miles.

Several different types and varieties of VSC technology have been developed. Up until 2012 most of these kinds of advanced HVDC applications and installations were using pulse width modulation in a circuit that is effectively an ultra-high-voltage motor drive. More current HVDC applications and installations, including HVDC MaxSine and HVDC PLUS are based on variations of a converter called a Modular Multi-Level Converter, MMC. AC harmonic filters of typical line-commutated converter stations (thyristor valves) cover nearly half of the converter station area. In comparison Multilevel converters have the added advantage of allowing harmonic filtering equipments to be reduced or eliminated altogether, thereby saving and freeing up alot of overused open space that can be used for other needed purposes and uses. Voltage-source converter systems will probably be replacing all simple thyristor-based systems, including the highest DC power transmission applications.

HVDC Advantages Over AC

HVDC electric power systems were and are chosen over AC electric power systems based primarily on the fact that HVDC gets the same job done and is overall more cost effective to implement, utilize and maintain, compared to AC for long distance transmission of large amounts of point-to-point electric energy and power. There are many factors that add up to large transmitting line related cost reductions with HVDC electric power systems used over long distances. HVDC needs fewer conductors than an AC line, as there is no need to support three phases. Also, thinner conductors can be used since HVDC does not suffer nearly as much as AC does from the high conductor resistance related power loss that occurs from the effects of long distance electric power line routing. Generally, a long distance high power HVDC transmission system will have lower monetary costs with lower losses of electric power than an AC transmission line will have.

The overall savings in monetary cost is due to the highly reduced costs of routing electric power over long distance routes using HVDC power systems. Even though the initial costs of HVDC conversion equipment at the terminal stations is high, it is still overall much more cost effective when compared to transmitting large amounts of electric energy and power through AC power transfer systems. HVDC transmission losses are dependent on voltage level and construction details. They are quoted as being about 3.5% per 642 miles, which is less than typical losses in an AC electric power transfer system. An HVDC electric power transmitting system may also be selected because of other technical benefits that it provides for the power system. Such as transfering power between separate AC networks, automatically controlling the support provided for either network during an out-of-state system condition, but without risking a major power system shut-down in both networks, because of one of them being in an out of service condition.

The management teams that overlook energy production and storage centers, that are located far away from the main local-end-user electric energy and power distribution centers, have found that HVDC power transfer systems combined economic and technical benefits are a suitable choice for those type of long distance connections. Some notable applications of HVDC electric power and transfer technology that provide and utilize those kinds of benefits are; Undersea cables for electric power transfer systems, such as the 373 mile NorNed cable between Norway and the Netherlands, the 160 mile Baltic Cable between Sweden and Germany, and the 192 mile Basslink cable between the mainland of Australian and Tasmania. Endpoint to endpoint long-haul bulk power type transfers, without intermediate taps, usually to connect a remote electric energy and power producing plant to the main-grid. Such as the Nelson River DC Transmission System in Canada.

HVDC electric power systems can be used for increasing the capacity of an existing power grid in situations where additional wires are too difficult or expensive to install. Providing assistance with Power transmission and stabilization between AC networks that are not in sync with eachother. Being able to stabilize an Alternating Current type power-grid, without increasing fault levels or prospective short circuit current. Also in the remote chance that it is called for, the ability to transfer power between countries that use AC at different frequencies which can occur in either direction, increases the stability of both networks by allowing them to draw on each other in emergencies and failures.

DCV to ACV Power Inverters

A device that performs the opposite function of a rectifier (AC to DC converter) by converting Direct Current to Alternating Current, called a power inverter, is an electronic device or circuitry that changes DC to AC. It is a more complex device than a rectifier with more complicated circuitry. The input voltage, output voltage, frequency and overall power handling, are dependent on the design of the specific device or circuitry. A power inverter can be entirely electronic or may be a combination of mechanical effects, such as a rotary apparatus and electronic circuitry. Static inverters do not use moving parts in the DC to AC conversion process.

Typical applications for power inverters include being able to connect and use a battery, batteries, or battery pack with an AC driven portable device, in order to power it. Being able to produce AC power to run different kinds of electrical devices such as lights, radios, tvs, fans, power tools, kitchen and other home appliances. They can also be Used in energy and power production systems, such as electric utility co's or solar energy producung systems, to convert the DC output power over to AC power. And can also be used with large electronic systems where there is a need for to convert AC elecric power over to a DC source of power.

Science | Electrical Engineering

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