And, of course, Obama commutated her sentence in January 2017.
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Copulas have been used for quality ranking in the manufacturing of electronically commutated motors.
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812 In absence of such current reversal, the motor would brake to a stop. In light of improved technologies in the electronic-controller, sensorless-control, induction- motor, and permanent-magnet-motor fields, externally-commutated induction and permanent-magnet motors are displacing electromechanically-commutated motors.
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Bakshi et al., pages 8.1–8.3 Telemetry may be commutated to allow the transmission of multiple data streams in a fixed frame.
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Top view of a typical 91mm wafer Gate Commutated Thyristor with cathode segments arranged in 10 concentric rings and the gate contact placed between Ring 5 and Ring 6 Gate Commutated Thyristor (GCT) typical device structure and doping An IGCT is a special type of thyristor. It is made of the integration of the gate unit with the Gate Commutated Thyristor (GCT) wafer device. The close integration of the gate unit with the wafer device ensures fast commutation of the conduction current from the cathode to the gate. The wafer device is similar to a gate turn-off thyristor (GTO).
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Most of the HVDC systems in operation today are based on line- commutated converters (LCC). The term line-commutated indicates that the conversion process relies on the line voltage of the AC system to which the converter is connected in order to effect the commutation from one switching device to its neighbour.Arrillaga, Jos; High Voltage Direct Current Transmission, second edition, Institution of Electrical Engineers, , 1998, Chapter 2, pp 10-55. Line-commutated converters use switching devices that are either uncontrolled (such as diodes) or that can only be turned on (not off) by control action, such as thyristors.
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In a line- commutated converter, the DC current (usually) cannot change direction; it flows through a large inductance and can be considered almost constant. On the AC side, the converter behaves approximately as a current source, injecting both grid-frequency and harmonic currents into the AC network. For this reason, a line commutated converter for HVDC is also considered as a current- source inverter.
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A voltage-sourced converter can therefore feed power to an AC network consisting only of passive loads, something which is impossible with LCC HVDC. Voltage-source converters are also considerably more compact than line-commutated converters (mainly because much less harmonic filtering is needed) and are preferable to line- commutated converters in locations where space is at a premium, for example on offshore platforms. In contrast to line-commutated HVDC converters, voltage- source converters maintain a constant polarity of DC voltage and power reversal is achieved instead by reversing the direction of current. This makes voltage-source converters much easier to connect into a Multi-terminal HVDC system or “DC Grid”.
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Some types of voltage-sourced converters may produce such low levels of harmonic distortion that no filters are required at all. However, converter types such as the two-level converter, used with pulse-width modulation (PWM), still require some filtering, albeit less than on line-commutated converter systems. With such converters, the harmonic spectrum is generally shifted to higher frequencies than with line-commutated converters. This usually allows the filter equipment to be smaller.
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Hippolyte Pixii's dynamo. The commutator is located on the shaft below the spinning magnet. The first commutated dynamo was built in 1832 by Hippolyte Pixii, a French instrument maker. It used a permanent magnet which was rotated by a crank.
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Harmonic filters are necessary for the elimination of the harmonic waves and for the production of the reactive power at line commutated converter stations. At plants with six pulse line commutated converters, complex harmonic filters are necessary because there are odd numbered harmonics of the orders and produced on the AC side and even harmonics of order on the DC side. At 12 pulse converter stations, only harmonic voltages or currents of the order and (on the AC side) or (on the DC side) result. Filters are tuned to the expected harmonic frequencies and consist of series combinations of capacitors and inductors.
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Line-commutated converters have some limitations in their use for HVDC systems. This results from requiring the AC circuit to turn off the thyristor current and the need for a short period of 'reverse' voltage to effect the turn-off (turn-off time). An attempt to address these limitations is the capacitor-commutated converter (CCC) which has been used in a small number of HVDC systems. The CCC differs from a conventional HVDC system in that it has series capacitors inserted into the AC line connections, either on the primary or secondary side of the converter transformer.
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Most HVDC schemes using line- commutated converters operate with a SCR of at least 3, but the McNeill scheme was designed to operate with an Effective Short Circuit Ratio (ESCR – a measure which subtracts the harmonic filters from the evaluation of SCR and is more meaningful on very weak AC systems) of less than 1.0 on the Saskatchewan side.Burgess, R.P., Ainsworth, J.D., Thanawala, H.L., Jain,M., Burton, R.S., ,Voltage/Var control at McNeill Back to Back HVDC converter station, CIGRÉ session, Paris, 1990, paper reference 14-104. This is one of the lowest ESCR values ever achieved with a line-commutated HVDC converter.
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By way of comparison, AC harmonic filters of typical line-commutated converter stations cover nearly half of the converter station area. With time, voltage-source converter systems will probably replace all installed simple thyristor-based systems, including the highest DC power transmission applications.
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The main applications are in variable speed motor drives, high power inverter and traction. GTOs are increasingly being replaced by integrated gate-commutated thyristors, which are an evolutionary development of the GTO, and insulated gate bipolar transistors, which are members of the transistor family.
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Line-commutated converters (HVDC classic) are made with electronic switches that can only be turned on. Voltage-sourced converters are made with switching devices that can be turned both on and off. Line-commutated converters (LCC) used mercury-arc valves until the 1970s,Peake, O., The History of High Voltage Direct Current Transmission, 3rd Australasian Engineering Heritage Conference 2009 or thyristors from the 1970s to the present day. Voltage-source converters (VSC), which first appeared in HVDC in 1997,Asplund, G., Svensson, K., Jiang, H., Lindberg, J., Pålsson, R., DC transmission based on voltage source converters, CIGRÉ session, Paris, 1998, paper reference 14-302.
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For this reason, a line-commutated converter for HVDC is also considered as a current-source converter. Because the direction of current cannot be varied, reversal of the direction of power flow (where required) is achieved by reversing the polarity of DC voltage at both stations.
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The most efficient motors exceed 98% efficiency. These are brushless three-"phase" DC, electronically commutated, wheel motors, with a Halbach array configuration for the neodymium-iron-boron magnets, and Litz wire for the windings. Cheaper alternatives are asynchronous AC or brushed DC motors. A test chassis at Ford Proving Grounds in 1992.
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The phases of the elevation and azimuth signals are then compared with the sum signal to determine error polarity. These errors are detected, commutated, amplified, and used to control the antenna- positioning servos. A part of the reference signal is detected and used as a video range tracking signal and as the video scope display.
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PWM rectifier is an AC to DC power converter, that is implemented using forced commutated power electronic semiconductor switches. Conventional PWM converters are used for wind turbines that have a permanent-magnet alternator. Today, insulated gate bipolar transistors are typical switching devices. In contrast to diode bridge rectifiers, PWM rectifiers achieve bidirectional power flow.
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Electronically commutated (EC) motors are electric motors powered by direct- current (DC) electricity and having electronic commutation systems, rather than mechanical commutators and brushes. The current-to-torque and frequency- to-speed relationships of BLDC motors are linear. While the motor coils are powered by DC, power may be rectified from AC within the casing.
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Wellington Drive Technologies Ltd (WDT) is a New Zealand based company that supplies electricity-saving, electronically commutated (EC) motors and fans worldwide. Their focus is on advanced motors, electronics and software that save power. The company makes motors from industrial plastics, rather than from stamped metal parts. They claim that this provides advantages in costs, performance and reliability.
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DVRs use a technically similar approach as low voltage ride-through (LVRT) capability systems in wind turbine generators use. The dynamic response characteristics, particularly for line supplied DVRs, are similar to those in LVRT-mitigated turbines. Conduction losses in both kinds of devices are often minimized by using integrated gate- commutated thyristor (IGCT) technology in the inverters.
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If the rotor is well balanced the rotor will start itself with enough light. Even a candle light could start a very well balanced rotor. In a modification new constructors used one coil each supported by one opposite solar panel. Its easier to produce but this way of construction isn't that favorable as the light commutated version.
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As a result, IGBTs can be used to make self-commutated converters which are closer to a large inverter in operation. In such converters, the polarity of DC voltage is usually fixed and the DC voltage, being smoothed by a large capacitance, can be considered constant. For this reason, an HVDC converter using IGBTs is usually referred to as a voltage-source converter (or voltage- sourced converterHigh-voltage direct current (HVDC) power transmission using voltage sourced converters (VSC), IEC/TR 62543:2011.). The additional controllability gives many advantages, notably the ability to switch the IGBTs on and off many times per cycle in order to improve the harmonic performance, and the fact that (being self-commutated) the converter no longer relies on synchronous machines in the AC system for its operation.
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Valve hall at Henday converter station, part of the Nelson River DC Transmission System in Canada. The converter is usually installed in a building called the valve hall. Early HVDC systems used mercury-arc valves, but since the mid-1970s, solid state devices such as thyristors have been used. Converters using thyristors or mercury-arc valves are known as line commutated converters.
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Resonant inverters are electrical inverters based on resonant current oscillation. In series resonant inverters the resonating components and switching device are placed in series with the load to form an underdamped circuit. The current through the switching devices fall to zero due to the natural characteristics of the circuit. If the switching element is a thyristor, it is said to be self-commutated.
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The type of motor is not critical to a servomotor and different types may be used. At the simplest, brushed permanent magnet DC motors are used, owing to their simplicity and low cost. Small industrial servomotors are typically electronically commutated brushless motors. For large industrial servomotors, AC induction motors are typically used, often with variable frequency drives to allow control of their speed.
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Due to steep voltage and current transient, the simulation becomes slow when switches are commutated. In most simplistic applications, switches are modelled as variable resistors that alternate between a very small and a very large resistance. In other cases, they are represented by a sophisticated semiconductor model. When simulating complex power electronic systems, however, the processes during switching are of little interest.
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For this reason the twelve-pulse system has become standard on most line-commutated converter HVDC systems built since the 1970s. With line commutated converters, the converter has only one degree of freedom – the firing angle, which represents the time delay between the voltage across a valve becoming positive (at which point the valve would start to conduct if it were made from diodes) and the thyristors being turned on. The DC output voltage of the converter steadily becomes less positive as the firing angle is increased: firing angles of up to 90° correspond to rectification and result in positive DC voltages, while firing angles above 90° correspond to inversion and result in negative DC voltages. The practical upper limit for the firing angle is about 150–160° because above this, the valve would have insufficient turnoff time.
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Estlink 2 will be a classic bidirectional monopolar high-voltage direct current connection with line-commutated converter thyristors. Its maximum transmission rate will be 650 MW and it will operate with a voltage of 450 kV. Its estimated cost is about €320 million, of which converter stations cost €100 million and cable €180 million. The European Commission has decided to allocate €100 million to the project.
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All of these devices function as rectifiers. it was expected that these high-power silicon "self- commutating switches", in particular IGBTs and a variant thyristor (related to the GTO) called the integrated gate-commutated thyristor (IGCT), would be scaled-up in power rating to the point that they would eventually replace simple thyristor-based AC rectification systems for the highest power- transmission DC applications.
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Therefore, a significant reduction of heat output will occur with a relatively small reduction in voltage. An incandescent lamp will dim due to lower heat creation in the filament, as well as lower conversion of heat to light. Generally speaking, no damage will occur but functionality will be impaired. Commutated electric motors, such as universal motors, will run at reduced speed or reduced torque.
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Networks of Power: Electrification in Western Society, 1880–1930. Baltimore, Maryland: Johns Hopkins University Press. , pages 120-121 Practical conversion of power between AC and DC became possible with the development of power electronics devices such as mercury-arc valves and, starting in the 1970s, semiconductor devices as thyristors, integrated gate-commutated thyristors (IGCTs), MOS- controlled thyristors (MCTs) and insulated-gate bipolar transistors (IGBT).
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The integrated gate-commutated thyristor (IGCT) is a power semiconductor electronic device, used for switching electric current in industrial equipment. It is related to the gate turn-off (GTO) thyristor. It was jointly developed by Mitsubishi and ABB. Like the GTO thyristor, the IGCT is a fully controllable power switch, meaning that it can be turned both on and off by its control terminal (the gate).
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Voltage sourced converters generally produce lower intensity harmonics than line commutated converters. As a result, harmonic filters are generally smaller or may be omitted altogether. Beside the harmonic filters, equipment is also provided to eliminate spurious signals in the frequency range of power-line carrier equipment in the range of 30 kHz to 500 kHz. These filters are usually near the alternating current terminal of the static inverter transformer.
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Motors for drive technology are, in part, also designed as internal rotor motors. In recent years, quiet, electronically commutated motors with increased energy efficiency have been finding use. These are available in versions for 1 or 3-phase alternating current and for direct current between 12 and 48 volts. By means of the already integrated electronics, EC motors have very good control characteristics, including integrated pressure, temperature or air flow control.
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However, HVDC requires power converters in order to connect to the AC grid. Both line commutated converters (LCCs) and voltage source converters (VSCs) have been considered for this. Although LCCs are a much more widespread technology and cheaper, VSCs have many more benefits, including independent active power and reactive power control. New research has been put into developing hybrid HVDC technologies that have a LCC connected to a VSC through a DC cable.
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A synchronous motor was chosen over a commutated motor or an asynchronous motor due to the reduced mass, simplicity of equipment, and price. Two locomotives SNCF BB 20011 and 20012 were used to develop and test the dual voltage traction system, microprocessor control systems and auxiliary motors, BB 20012 was used to develop and test the pneumatic and electrical braking system. The Paris-based industrial design group MBD Design contributed to the design of the locomotive.
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Because thyristors can only be turned on (not off) by control action, the control system has only one degree of freedom – when to turn on the thyristor. This is an important limitation in some circumstances. With some other types of semiconductor device such as the insulated-gate bipolar transistor (IGBT), both turn-on and turn-off can be controlled, giving a second degree of freedom. As a result, they can be used to make self-commutated converters.
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An alternative is to use two high-voltage conductors, operating at about half of the DC voltage, with only a single converter at each end. In this arrangement, known as the symmetrical monopole, the converters are earthed only via a high impedance and there is no earth current. The symmetrical monopole arrangement is uncommon with line-commutated converters (the NorNed interconnection being a rare example) but is very common with Voltage Sourced Converters when cables are used.
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The Storebælt HVDC is a 600 MW Line Commutated Converter (LCC) HVDC at a voltage of 400 kV. It consists of the Fraugde converter station on Funen connected to an existing 400 kV substation and the new Herslev converter station on Zealand connected to an existing 400 kV overhead line. The converter stations are supplied by Siemens Power Transmission and Distribution. The interconnector includes long sea cable, long land cable on Funen and long land cable on Zealand.
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DC motors can be operated at variable speeds by adjusting the DC voltage applied to the terminals or by using pulse-width modulation (PWM). AC motors operated at a fixed speed are generally powered directly from the grid or through motor soft starters. AC motors operated at variable speeds are powered with various power inverter, variable-frequency drive or electronic commutator technologies. The term electronic commutator is usually associated with self-commutated brushless DC motor and switched reluctance motor applications.
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Genteq is a division of Regal-Beloit Corporation, one of the largest manufacturers of electric motors in the world. Genteq is the rebranding of Regal’s GE ECM, GE Capacitors and GE Commercial Motors divisions, which occurred in 2009.Regal Rebrands GE Businesses as Genteq, ACHR News, March 23, 2009 Genteq develops and manufactures electronically commutated motors (ECM) and capacitors for residential and light commercial heating and air conditioning (HVAC) systems. The company is based in Fort Wayne, Indiana, with manufacturing facilities in Mexico.
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The HVDC back-to-back facility Shin Shinano uses line-commutated thyristor converters. The station houses two converters, one of which opened in December 1977,Compendium of HVDC schemes, CIGRÉ Technical Brochure No. 003, 1987, pp100-103. the other in 1992. The original 1977 converter was one of the first thyristor-based HVDC schemes to be put into operation in the world and used oil-insulated, oil-cooled outdoor thyristor valves supplied by Hitachi (60 Hz end) and Toshiba (50 Hz end).
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Faraday disc The first homopolar generator was developed by Michael Faraday during his experiments in 1831. It is frequently called the Faraday disc or Faraday wheel in his honor. It was the beginning of modern dynamos -- that is, electrical generators which operate using a magnetic field. It was very inefficient and was not used as a practical power source, but it showed the possibility of generating electric power using magnetism, and led the way for commutated direct current dynamos and then alternating current alternators.
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Most of the HVDC systems in operation today are based on line-commutated converters. The basic LCC configuration uses a three-phase bridge rectifier or six-pulse bridge, containing six electronic switches, each connecting one of the three phases to one of the two DC rails. A complete switching element is usually referred to as a valve, irrespective of its construction. However, with a phase change only every 60°, considerable harmonic distortion is produced at both the DC and AC terminals when this arrangement is used.
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In such converters, the polarity of DC voltage is usually fixed and the DC voltage, being smoothed by a large capacitance, can be considered constant. For this reason, an HVDC converter using IGBTs is usually referred to as a voltage sourced converter. The additional controllability gives many advantages, notably the ability to switch the IGBTs on and off many times per cycle in order to improve the harmonic performance. Being self-commutated, the converter no longer relies on synchronous machines in the AC system for its operation.
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Air handlers in Europe and Australia and New Zealand now commonly use backward curve fans without scroll or "plug fans". These are driven using high efficiency EC (electronically commutated) motors with built in speed control. Multiple blowers may be present in large commercial air handling units, typically placed at the end of the AHU and the beginning of the supply ductwork (therefore also called "supply fans"). They are often augmented by fans in the return air duct ("return fans") pushing the air into the AHU.
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Direct drive thrusters have higher reliability, lower noise, and higher efficiency, but the prices are higher than geared thrusters. # Motor driver and electronics: Brushless motors need some electronics to be commutated and control their speed. In early versions the drivers were unreliable and this led to user dissatisfaction when compared with highly reliable hydraulic thrusters. More recently developments in power electronic technology have made the motor driver more efficient and reliable, cheap and small, to be fitted directly to the end of the motor.
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The large brown molded-plastic piece in the foreground supports the brush guides and brushes (both sides), as well as the front motor bearing. The universal motor is a type of electric motor that can operate on either AC or DC power and uses an electromagnet as its stator to create its magnetic field. It is a commutated series-wound motor where the stator's field coils are connected in series with the rotor windings through a commutator. It is often referred to as an AC series motor.
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A set of data words, together with synchronization and ID or counter words, constitute a minor frame; a set number of minor frames are combined to form a major frame. Measurands occupy fixed positions within each major frame, with these positions defined in a database, allowing them to be extracted. Measurands may be sampled multiple times within each minor frame (supercommutation), or they may only be sampled once in several frames (subcommutation), depending on the required data rate for each measurand. Commutated frames may also contain asynchronous data, which require further processing to extract.
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The synchronous motor produces its rated torque at exactly synchronous speed. The brushless wound-rotor doubly fed synchronous motor system has an independently excited rotor winding that does not rely on the principles of slip-induction of current. The brushless wound-rotor doubly fed motor is a synchronous motor that can function exactly at the supply frequency or sub to super multiple of the supply frequency. Other types of motors include eddy current motors, and AC and DC mechanically commutated machines in which speed is dependent on voltage and winding connection.
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The cables are jointed in 120 km sections. Line commutated converter technology is used at each HVDC converter to maximise the amount of electrical power, generated predominantly by renewable sources in Scotland, which can be transferred across the B6 boundaryThe UK transmission grid is often analysed in terms of flows across fictitious "boundaries" which divide the network in two. Where the lines which across a boundary struggle to accommodate projected flows, the boundary needs strengthening. Though most boundaries do not correspond to geographic or political features, the B6 boundary runs along the England/Scotland border.
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In HVDC applications, the AC power system itself provides the means of commutating the current to another valve in the converter. Consequently, converters built with mercury arc valves are known as line-commutated converters (LCC). LCCs require rotating synchronous machines in the AC systems to which they are connected, making power transmission into a passive load impossible. Mercury arc valves were common in systems designed up to 1972, the last mercury arc HVDC system (the Nelson River Bipole 1 system in Manitoba, Canada) having been put into service in stages between 1972 and 1977.
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The task of suppressing such harmonics is still challenging, but manageable. Line- commutated converters for HVDC are usually provided with combinations of harmonic filters designed to deal with the 11th and 13th harmonics on the AC side, and 12th harmonic on the DC side. Sometimes, high-pass filters may be provided to deal with 23rd, 25th, 35th, 37th... on the AC side and 24th, 36th... on the DC side. Sometimes, the AC filters may also need to provide damping at lower-order, noncharacteristic harmonics such as 3rd or 5th harmonics.
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Stators with different winding topologies Because of the higher performance density, brushless EC drives (electronically commutated motors) with permanent magnet rotors are increasingly used instead of the asynchronous technology. Owing to the compact design, the copper content can be cut in half in the best-case scenario. The manufacturers of electric motors also demand more flexibility of the production technology. For producing asynchronous motors, drawing-in systems are usually used that are initially winding air-core coils only to draw them later into the stator with a tool.
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Simplified schematic of New Zealand HVDC scheme The New Zealand Inter-Island HVDC link is a long distance bipolar HVDC "Classic" transmission scheme that uses overhead lines and submarine cables to connect between the South and North Islands. It uses thyristor-based line-commutated converters at each end of the link for rectifying and inverting between AC and DC. The link includes ground electrode stations that enable the use of earth return current. This permits operation with unbalanced current between the two poles, and monopolar operation when one pole is out of service.
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In thyristor-based converters, many thyristors are connected in series to form a thyristor valve, and each converter normally consists of six or twelve thyristor valves. The thyristor valves are usually grouped in pairs or groups of four and can stand on insulators on the floor or hang from insulators from the ceiling. Line commutated converters require voltage from the AC network for commutation, but since the late 1990s, voltage sourced converters have started to be used for HVDC. Voltage sourced converters use insulated-gate bipolar transistors instead of thyristors, and these can provide power to a deenergized AC system.
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When line commutated converters are used, the converter station will require between 40% and 60% of its power rating as reactive power. This can be provided by banks of switched capacitors or by synchronous condensers, or if a suitable power generating station is located close to the static inverter plant, the generators in the power station. The demand for reactive power can be reduced if the converter transformers have on-load tap changers with a sufficient range of taps for AC voltage control. Some of the reactive power requirement can be supplied in the harmonic filter components.
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This particular motor is an outrunner, with the stator inside the rotor. DC brushless ducted fan. The two coils on the printed circuit board interact with six round permanent magnets in the fan assembly. A brushless DC electric motor (BLDC motor or BL motor), also known as electronically commutated motor (ECM or EC motor) and synchronous DC motors, are synchronous motors powered by direct current (DC) electricity via an inverter or switching power supply which produces electricity in the form of alternating current (AC) to drive each phase of the motor via a closed loop controller.
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15, 2004 As part of that acquisition, Regal acquired the rights to use the GE brand through 2009. Nearing the end of that licensing period, Regal rebranded these divisions as Genteq in February 2009. General Electric developed an Electronically Commutated Motor (also called Electronically Controlled Motor), or ECM, technology for use in residential and light commercial heating and air conditioning systems in North America in the mid-1980s.The ECM Motor Story , Nailor Industries web site The GE ECM motor was the first ultra-high efficiency motor for home heating and air conditioning systems, providing greater home comfort and energy efficiency.
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The motor consists of a rotor shaft with an array of (typically four to eight) solar panels and electromagnetic coils arranged in a barrel shape around the centre of the shaft; this rotor is horizontally mounted in a frictionless radial bearings over a central magnet on the base plate of the motor. The final 6th degree of freedom, the axial or thrust direction, is not levitated, but rather supported by a steel ball point of contact (low friction). An original Mendocino Motor is a light commutated motor. Two opposite solar panels are connected plus to opposite minus and minus to opposite plus.
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Widely used in motor drives since the 1980s, voltage-source converters started to appear in HVDC in 1997 with the experimental Hellsjön–Grängesberg project in Sweden. By the end of 2011, this technology had captured a significant proportion of the HVDC market. The development of higher rated insulated-gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs) and integrated gate- commutated thyristors (IGCTs), has made smaller HVDC systems economical. The manufacturer ABB Group calls this concept HVDC Light, while Siemens calls a similar concept HVDC PLUS (Power Link Universal System) and Alstom call their product based upon this technology HVDC MaxSine.
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All power electronic converters generate some degree of harmonic distortion on the AC and DC systems to which they are connected, and HVDC converters are no exception. With the recently developed Modular Multilevel Converter (MMC), levels of harmonic distortion may be practically negligible, but with line-commutated converters and simpler types of voltage-source converters, considerable harmonic distortion may be produced on both the AC and DC sides of the converter. As a result, harmonic filters are nearly always required at the AC terminals of such converters, and in HVDC transmission schemes using overhead lines, may also be required on the DC side.
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Although HVDC converters can, in principle, be constructed from diodes, such converters can only be used in rectification mode and the lack of controllability of the DC voltage is a serious disadvantage. Consequently, in practice all LCC HVDC systems use either grid-controlled mercury-arc valves (until the 1970s) or thyristors (to the present day). In a line-commutated converter, the DC current does not change direction; it flows through a large inductance and can be considered almost constant. On the AC side, the converter behaves approximately as a current source, injecting both grid-frequency and harmonic currents into the AC network.
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A brushed DC electric motor is an internally commutated electric motor designed to be run from a direct current power source. Brushed motors were the first commercially important application of electric power to driving mechanical energy, and DC distribution systems were used for more than 100 years to operate motors in commercial and industrial buildings. Brushed DC motors can be varied in speed by changing the operating voltage or the strength of the magnetic field. Depending on the connections of the field to the power supply, the speed and torque characteristics of a brushed motor can be altered to provide steady speed or speed inversely proportional to the mechanical load.
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An example is the 2,000 MW Quebec - New England Transmission system opened in 1992, which is currently the largest multi-terminal HVDC system in the world.ABB HVDC Transmission Québec – New England website Multi-terminal systems are difficult to realize using line commutated converters because reversals of power are effected by reversing the polarity of DC voltage, which affects all converters connected to the system. With Voltage Sourced Converters, power reversal is achieved instead by reversing the direction of current, making parallel-connected multi-terminals systems much easier to control. For this reason, multi- terminal systems are expected to become much more common in the near future.
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This parallel holder distributes current evenly across all the brushes, and permits a careful operator to remove a bad brush and replace it with a new one, even as the machine continues to spin fully powered and under load. High power, high current commutated equipment is now uncommon, due to the less complex design of alternating current generators that permits a low current, high voltage spinning field coil to energize high current fixed-position stator coils. This permits the use of very small singular brushes in the alternator design. In this instance, the rotating contacts are continuous rings, called slip rings, and no switching happens.
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The large brown molded-plastic piece in the foreground supports the brush guides and brushes (both sides), as well as the front motor bearing. A commutated electrically excited series or parallel wound motor is referred to as a universal motor because it can be designed to operate on AC or DC power. A universal motor can operate well on AC because the current in both the field and the armature coils (and hence the resultant magnetic fields) will alternate (reverse polarity) in synchronism, and hence the resulting mechanical force will occur in a constant direction of rotation. Operating at normal power line frequencies, universal motors are often found in a range less than .
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The idea of a light-commutated motor, where solar cells power the individual coils of a motor, was first described by Daryl Chapin in an experiment kit from 1962 about solar energy. The kit was distributed by Bell Labs, where Chapin together with his colleagues Calvin Fuller and Gerald Pearson had invented the modern solar cell eight years earlier, in 1954. Chapin's version of the motor uses a vertical glass cylinder on a needle point as a low-friction bearing. A magnetic suspension of the rotor was added in 1994 by eccentric inventor Larry Spring to create "Larry Spring's Magnetic Levitation Mendocino Brushless Solar Motor" \- more commonly called "Mendocino Motor" with a horizontal rotor.
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In contrast to AC systems, realizing multi-terminal systems is complex (especially with line commutated converters), as is expanding existing schemes to multi- terminal systems. Controlling power flow in a multi-terminal DC system requires good communication between all the terminals; power flow must be actively regulated by the converter control system instead of relying on the inherent impedance and phase angle properties of an AC transmission line. Multi-terminal systems are rare. As of 2012 only two are in service: the Hydro Québec – New England transmission between Radisson, Sandy Pond, and Nicolet and the Sardinia-mainland Italy link which was modified in 1989 to also provide power to the island of Corsica.
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The basic building- block of a line-commutated HVDC converter is the six-pulse bridge. This arrangement produces very high levels of harmonic distortion by acting as a current source injecting harmonic currents of order 6n±1 into the AC system and generating harmonic voltages of order 6n superimposed on the DC voltage. It is very costly to provide harmonic filters capable of suppressing such harmonics, so a variant known as the twelve-pulse bridge (consisting of two six-pulse bridges in series with a 30° phase shift between them) is nearly always used. With the twelve-pulse arrangement, harmonics are still produced but only at orders 12n±1 on the AC side and 12n on the DC side.
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These motors are sometimes called DC motors, sometimes called EC motors and occasionally EC/DC motors. DC stands for Direct Current and EC stands for Electronically Commutated. DC motors allow the speed of the fans within a Fan Coil Unit to be controlled by means of a 0-10 Volt input 'Signal' to the motor/s, the transformers and speed switches associated with AC Fan Coils are not required. Up to a signal voltage of 2.5 Volts (which may vary with different fan/motor manufacturers) the fan will be in a stopped condition but as the signal voltage is increased, the fan will seamlessly increase in speed until the maximum is reached at a signal Voltage of 10 Volts.
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Development and type tests of HVDC ±250 MIsubmarine cable system, Tae-ho Lee et al, Proceedings of the 16th International Symposium on High Voltage Engineering. Two of the high-voltage cables are normally used as the respective high-voltage conductors for the two converter poles and the medium- voltage cable is normally used as the neutral return conductor, but the third high-voltage cable is capable of being connected in parallel with, or instead of, any of the other three cables, giving a large number of possible operating modes.Project Overview , LS Cable and System. The converter stations use Line- Commutated Converters with a conventional arrangement of a single Twelve-pulse bridge per pole.
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Use of passive natural ventilation is an integral component of passive house design where ambient temperature is conducive — either by singular or cross ventilation, by a simple opening or enhanced by the stack effect from smaller ingress with larger egress windows and/or clerestory-operable skylight. When ambient climate is not conducive, mechanical heat recovery ventilation systems, with a heat recovery rate of over 80% and high-efficiency electronically commutated motors (ECM), are employed to maintain air quality, and to recover sufficient heat to dispense with a conventional central heating system. Since passively designed buildings are essentially air-tight, the rate of air change can be optimized and carefully controlled at about 0.4 air changes per hour. All ventilation ducts are insulated and sealed against leakage.
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Although classed as a "bipolar" HVDC scheme, the NorNed scheme is unusual for a Line-Commutated (thyristor-based) HVDC scheme since there is just one 12-pulse converter at each end of the scheme, midpoint-grounded at Eemshaven. With voltage-source converter-based HVDC systems, this arrangement with the two high voltage cables at equal and opposite voltages but only a single converter at each end is referred to as a Symmetrical monopole. Consequently, with a DC voltage of ±450 kV, the converter for the NorNed project has a terminal to terminal DC voltage rating of 900 kV, making it (as of 2012) the highest voltage rating of any HVDC converter in the world. The connection has a loss of 4.2% (95.8% efficiency).
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As the brush and commutator wear down, the spring steadily pushes the brush downwards towards the commutator. Eventually the brush wears small and thin enough that steady contact is no longer possible or it is no longer securely held in the brush holder, and so the brush must be replaced. It is common for a flexible power cable to be directly attached to the brush, because current flowing through the support spring would cause heating, which may lead to a loss of metal temper and a loss of the spring tension. When a commutated motor or generator uses more power than a single brush is capable of conducting, an assembly of several brush holders is mounted in parallel across the surface of the very large commutator.
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Volker Leiste: 1867 – Fundamental report on dynamo-electric principle before the Prussian Academy of Sciences The invention of the dynamo principle (self-induction) was a huge technological leap over the old traditional permanent magnet based DC generators. The discovery of the dynamo principle made industrial scale electric power generation technically and economically feasible. After the invention of the alternator and that alternating current can be used as a power supply, the word dynamo became associated exclusively with the commutated direct current electric generator, while an AC electrical generator using either slip rings or rotor magnets would become known as an alternator. A small electrical generator built into the hub of a bicycle wheel to power lights is called a hub dynamo, although these are invariably AC devices, and are actually magnetos.
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A major drawback of HVDC systems using line-commutated converters is that the converters inherently consume reactive power. The AC current flowing into the converter from the AC system lags behind the AC voltage so that, irrespective of the direction of active power flow, the converter always absorbs reactive power, behaving in the same way as a shunt reactor. The reactive power absorbed is at least 0.5 Mvar/MW under ideal conditions and can be higher than this when the converter is operating at higher than usual firing or extinction angle, or reduced DC voltage. Although at HVDC converter stations connected directly to power stations some of the reactive power may be provided by the generators themselves, in most cases the reactive power consumed by the converter must be provided by banks of shunt capacitors connected at the AC terminals of the converter.
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Both converter stations of Bipole 2 and the Araraquara converter station of Bipole 1 use single-phase, two-winding converter transformers with the thyristor valves arranged in double-valves, but the Porto Velho Bipole 1 converter station used single-phase three-winding converter transformers (because the river made the transport of larger transformers feasible than was the case at Araraquara) and valves arranged in quadrivalves. Because the 230 kV network in Rondônia and Acre is very weak, the back-to-back converters are implemented as Capacitor Commutated Converters (CCC). The thyristor valves being much smaller than those of the transmission bipoles, it was possible to arrange each back-to-back converter as just three valve stacks of eight valves each (octovalves). The design of certain aspects of the two bipoles (which were supplied by different manufacturers) needed to be coordinated in order to avoid adverse control interactions or harmonic filtering problems.
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One of the first documents signed by Ilham Aliyev was the Decree "On measures to accelerate the social and economic development of the Republic of Azerbaijan", as well as "On the approval of social and economic development of the regions of the Republic of Azerbaijan (2004-2008)." In the second document, in the first year of the program, 27 large and medium-sized enterprises were opened, and over 135,000 work places. In 2004, approved the law "Long-term strategy for managing oil and gas revenues (2005-2025 gg.)", which provided for the allocation of income from the oil sector to the development of the non-oil sector. On October 26, 2005, he signed the Order on approval of the "Employment Strategy of the Republic of Azerbaijan (2006-2015)", which provided for the rational use of all resources, in particular labor resources for building an economically strong society. In 2007, he signed a decree to pardon a number of convicted persons, as a result of which more than 200 prisoners were released or their punishments were commutated.
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The motors are supplied by traction converters with integrated gate-commutated thyristor (IGCT) rather than silicon-controlled rectifier (SCR) components as in the KTX-I. IGCT was the most advanced version of the Gate turn-off thyristor (GTO) used for control of high-power applications at the time, and the use of ABB- supplied IGCTs as the switching element in the rectifier and inverter modules of HSR-350x converters was a world's first in rail vehicles. However, testing found limited improvements in efficiency and noise levels, and problems with reliability. Each traction converter consists of two parallel-switched four- quadrant converters, which function as rectifier modules by converting single- phase alternating current (AC) from one main transformer winding each to direct current (DC), a 2,800 V DC intermediate circuit, one inverter module converting the DC supply to the three-phase AC supply for traction motors, an auxiliary inverter for the supply of motor and converter cooling fans, and resistors for rheostatic braking that are also connected to the DC circuit.
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