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35-513: The SD-100 began production in 1992, and is equipped with direct current traction motors and folding doors. It was succeeded in 2001 by the revised SD-160, which is equipped with alternating current motors and plug doors . The first orders for the SD-160 were placed in 2001, and production continued until 2013. A related design is the SD-400/SD-460 high-floor light rail vehicle, which

70-542: A conductor such as a wire, but can also flow through semiconductors , insulators , or even through a vacuum as in electron or ion beams . The electric current flows in a constant direction, distinguishing it from alternating current (AC). A term formerly used for this type of current was galvanic current . The abbreviations AC and DC are often used to mean simply alternating and direct , as when they modify current or voltage . Direct current may be converted from an alternating current supply by use of

105-510: A rectifier , which contains electronic elements (usually) or electromechanical elements (historically) that allow current to flow only in one direction. Direct current may be converted into alternating current via an inverter . Direct current has many uses, from the charging of batteries to large power supplies for electronic systems, motors, and more. Very large quantities of electrical energy provided via direct-current are used in smelting of aluminum and other electrochemical processes. It

140-543: A DC circuit. However, most such circuits have a DC solution. This solution gives the circuit voltages and currents when the circuit is in DC steady state . Such a circuit is represented by a system of differential equations . The solution to these equations usually contain a time varying or transient part as well as constant or steady state part. It is this steady state part that is the DC solution. There are some circuits that do not have

175-407: A DC solution. Two simple examples are a constant current source connected to a capacitor and a constant voltage source connected to an inductor. In electronics, it is common to refer to a circuit that is powered by a DC voltage source such as a battery or the output of a DC power supply as a DC circuit even though what is meant is that the circuit is DC powered. In a DC circuit, a power source (e.g.

210-453: A battery system to ensure power is maintained for subscriber lines during power interruptions. Other devices may be powered from the telecommunications DC system using a DC-DC converter to provide any convenient voltage. Many telephones connect to a twisted pair of wires, and use a bias tee to internally separate the AC component of the voltage between the two wires (the audio signal) from

245-423: A battery, capacitor, etc.) has a positive and negative terminal, and likewise, the load also has a positive and negative terminal. To complete the circuit, positive charges need to flow from the power source to the load. The charges will then return to the negative terminal of the load, which will then flow back to the negative terminal of the battery, completing the circuit. If either the positive or negative terminal

280-524: A direct current source . The DC solution of an electric circuit is the solution where all voltages and currents are constant. Any stationary voltage or current waveform can be decomposed into a sum of a DC component and a zero-mean time-varying component; the DC component is defined to be the expected value, or the average value of the voltage or current over all time. Although DC stands for "direct current", DC often refers to "constant polarity". Under this definition, DC voltages can vary in time, as seen in

315-462: A generator, regenerating power back to a city's electrical lines. The SD-160 has a passenger capacity of 236 passengers (standing) with 64 seats. Compared to its predecessor, the Siemens–Duewag U2 , the SD-160's driver's cabin is significantly larger, but its total length is still less than 25 metres (82 ft 1 ⁄ 4  in), allowing three vehicles to be combined and still be under

350-554: Is also used for some railways , especially in urban areas . High-voltage direct current is used to transmit large amounts of power from remote generation sites or to interconnect alternating current power grids. Direct current was produced in 1800 by Italian physicist Alessandro Volta 's battery, his Voltaic pile . The nature of how current flowed was not yet understood. French physicist André-Marie Ampère conjectured that current travelled in one direction from positive to negative. When French instrument maker Hippolyte Pixii built

385-482: Is an AC device which uses a rectifier to produce DC for battery charging. Most highway passenger vehicles use nominally 12  V systems. Many heavy trucks, farm equipment, or earth moving equipment with Diesel engines use 24 volt systems. In some older vehicles, 6 V was used, such as in the original classic Volkswagen Beetle . At one point a 42 V electrical system was considered for automobiles, but this found little use. To save weight and wire, often

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420-435: Is commonly found in many extra-low voltage applications and some low-voltage applications, especially where these are powered by batteries or solar power systems (since both can produce only DC). Most electronic circuits or devices require a DC power supply . Domestic DC installations usually have different types of sockets , connectors , switches , and fixtures from those suitable for alternating current. This

455-427: Is disconnected, the circuit will not be complete and the charges will not flow. In some DC circuit applications, polarity does not matter, which means you can connect positive and negative backwards and the circuit will still be complete and the load will still function normally. However, in most DC applications, polarity does matter, and connecting the circuit backwards will result in the load not working properly. DC

490-412: Is distributed to a substation, which utilizes a rectifier to convert the power to direct current. The term DC is used to refer to power systems that use only one electrical polarity of voltage or current, and to refer to the constant, zero-frequency, or slowly varying local mean value of a voltage or current. For example, the voltage across a DC voltage source is constant as is the current through

525-708: Is estimated that they will end in 2026 or 2027), the arrival at the Mendoza International Airport and the department of Luján de Cuyo stands out. In addition, due to its speed compared to other means of transport, it is increasingly chosen and presents a greater demand for people, which is why it is also planned to join two pairs to increase passenger capacity. The SD-160's dimensions are 24.802 metres (81 ft 4 + 1 ⁄ 2  in) by 2.654 metres (8 ft 8 + 1 ⁄ 2  in) by 3.811 metres (12 ft 6 in) and can be joined together to form trains of up to six cars in length. It

560-447: Is mostly due to the lower voltages used, resulting in higher currents to produce the same amount of power . It is usually important with a DC appliance to observe polarity, unless the device has a diode bridge to correct for this. Most automotive applications use DC. An automotive battery provides power for engine starting, lighting, the ignition system, the climate controls, and the infotainment system among others. The alternator

595-538: Is powered by four AC motors which provide a maximum of 580 kW . In most applications, the SD-160 has a maximum speed of 80 kilometres per hour (50 mph). Some SD-160 trains, such as those operated in Denver, are configured to reach higher speeds of 90 kilometres per hour (56 mph). It accelerates at 1.07 m/s (3.5 ft/s) and decelerates at 1.31 m/s (4.3 ft/s), with emergency braking deceleration of 2.63 m/s (8.6 ft/s). The brakes also serve as

630-747: The 75-metre (246 ft 3 ⁄ 4  in) maximum length of a German streetcar train assembly. Each vehicle also features an onboard closed-circuit TV security camera system for increased passenger safety. Unlike the Siemens SD-100, the Siemens SD-160 does not use the bi-folded doors, instead using sliding doors similar to designs featured on the Siemens S70 . In addition, both can be used together in mixed trains consisting of SD-100s and SD-160s. The new, streetcar-length S70 cars ordered for San Diego are designed to be compatible with

665-604: The S200 , the successor to the SD-160. Along with some electronic improvements, they have been upgraded to be compatible with Calgary's newer SD-160s, which were previously incompatible due to software differences. The refurbished fleet will eventually start to run with the newer units once the software has been adjusted to allow seamless operation. Since 2022, 39 retired San Diego SD-100s were transferred to Metrotranvía Mendoza to supplement its existing fleet of Siemens–Duewag U2 which had also been purchased from San Diego. Currently,

700-767: The San Diego Metropolitan Transit System ordered 52 SD-100 cars as the San Diego Trolley system was expanded with a new line, these entered service in 1995. As of 2021, they are currently being phased out and replaced by Siemens S700 cars. The final order for the SD-100 came in 1996, when the Utah Transit Authority , located in Salt Lake City placed an order for 23 vehicles that were delivered before

735-448: The DC component of the voltage between the two wires (used to power the phone). High-voltage direct current (HVDC) electric power transmission systems use DC for the bulk transmission of electrical power, in contrast with the more common alternating current systems. For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses. Applications using fuel cells (mixing hydrogen and oxygen together with

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770-634: The Metropolitan Transportation System (MTS) of San Diego, California is in the process of donating its Siemens SD100 pairs to the Mendoza Transportation Society, which has an urban metro-tram service that connects four departments (Las Heras, Ciudad , Godoy Cruz and Maipú) of the Province of Mendoza, Argentine Republic. The donation consists of 39 pairs of the mentioned model, until June 2023 9 of

805-746: The SD-100 was launched in 1992 when the Regional Transportation District , located in Denver, Colorado placed an order for 49 vehicles. The physical design was derived from the U2A car that was built between 1985 and 1991, but built with more modern mechanical equipment. The first vehicles rolled off the production line at the Siemens facility in Florin, California in 1994, in time for the start of Light Rail service in Denver. In 1993,

840-568: The SD-100, allowing the SD-100 to operate in a mixed consist, sandwiched between two S70 cars. The SD-160NG for Calgary have been taking over some features from the SD-460 series including IGBT equipment. Other Siemens light rail vehicles for the American market: Direct current Direct current ( DC ) is one-directional flow of electric charge . An electrochemical cell is a prime example of DC power. Direct current may flow through

875-467: The SD-160 was updated in 2005 with a new end cap that changed the look of the front/rear of the train. The Edmonton Transit Service ordered 57 of the redesigned SD-160 vehicles and Calgary Transit ordered 38. Starting in late 2017, Calgary has been sending SD-160s to Siemens' facility in Florin for mid-life refurbishment. The refurbished units contain several components and electronics already present on

910-407: The circuit voltages and currents are independent of time. A particular circuit voltage or current does not depend on the past value of any circuit voltage or current. This implies that the system of equations that represent a DC circuit do not involve integrals or derivatives with respect to time. If a capacitor or inductor is added to a DC circuit, the resulting circuit is not, strictly speaking,

945-654: The first dynamo electric generator in 1832, he found that as the magnet used passed the loops of wire each half turn, it caused the flow of electricity to reverse, generating an alternating current . At Ampère's suggestion, Pixii later added a commutator , a type of "switch" where contacts on the shaft work with "brush" contacts to produce direct current. The late 1870s and early 1880s saw electricity starting to be generated at power stations . These were initially set up to power arc lighting (a popular type of street lighting) running on very high voltage (usually higher than 3,000 volts) direct current or alternating current. This

980-512: The metal frame of the vehicle is connected to one pole of the battery and used as the return conductor in a circuit. Often the negative pole is the chassis "ground" connection, but positive ground may be used in some wheeled or marine vehicles. In a battery electric vehicle , there are usually two separate DC systems. The "low voltage" DC system typically operates at 12V, and serves the same purpose as in an internal combustion engine vehicle. The "high voltage" system operates at 300-400V (depending on

1015-428: The raw output of a rectifier or the fluctuating voice signal on a telephone line. Some forms of DC (such as that produced by a voltage regulator ) have almost no variations in voltage , but may still have variations in output power and current. A direct current circuit is an electrical circuit that consists of any combination of constant voltage sources, constant current sources, and resistors . In this case,

1050-621: The start of the TRAX light rail service in 1999. In 2001, Siemens launched the SD-160 light rail vehicle, which used alternating current motors instead of direct current motors and outward sliding doors. Calgary Transit ordered 72 vehicles for its CTrain service, while the Utah Transit Authority ordered 17 vehicles as it expanded the TRAX light rail service. Deliveries to both agencies started in 2003. The physical design of

1085-490: The total pairs that are operating and providing regular service in Mendoza, Argentina have arrived, while for the remaining 30 MTS is expected to withdraw them from their service between this year and the next in order to coordinate the shipping logistics of these pairs between the two cities. The arrival of these formations is important for Mendoza since it is carrying out works to double the route of its metro-tram service (it

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1120-464: The vehicle), and provides the power for the traction motors . Increasing the voltage for the traction motors reduces the current flowing through them, increasing efficiency. Telephone exchange communication equipment uses standard −48 V DC power supply. The negative polarity is achieved by grounding the positive terminal of power supply system and the battery bank. This is done to prevent electrolysis depositions. Telephone installations have

1155-406: Was followed by the widespread use of low voltage direct current for indoor electric lighting in business and homes after inventor Thomas Edison launched his incandescent bulb based electric " utility " in 1882. Because of the significant advantages of alternating current over direct current in using transformers to raise and lower voltages to allow much longer transmission distances, direct current

1190-569: Was initially built by a Siemens– Duewag joint venture. Siemens purchased Duewag in 1999, and assembled the SD-460 model alongside the SD-100/SD-160 in Florin, California. The SD-100, SD-160, SD-400, and SD-460 were succeeded in the 2010s by newer LRV designs from Siemens, including the low-floor S700 and S70 and the high-floor S200 . As of 2024, most SD-100 and SD-160 vehicles remain in service with their original operators. Production of

1225-477: Was replaced over the next few decades by alternating current in power delivery. In the mid-1950s, high-voltage direct current transmission was developed, and is now an option instead of long-distance high voltage alternating current systems. For long distance undersea cables (e.g. between countries, such as NorNed ), this DC option is the only technically feasible option. For applications requiring direct current, such as third rail power systems, alternating current

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