Trains
Another interest I found in researching this system was the rolling stock themselves. This interest technically started in my most recent visits to Korea, when I started paying better attention to the complexity of the transport around me. With this project, it turned into a deep rabbit hole of information. This section is a comprehensive study on all the subway trains that ever ran the tracks in Seoul.
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You can read more about the trains running on each individual line by clicking its icon below.
Main metro lines
Commuter/named lines
Light rail lines
A Brief Intro on Numbering
I am going to use lots of numbers in this section. It's going to be a bit hard to keep track, so I decided to put this little intro here so I can give a little background on the train numbering system in Korea.
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Initially, both Korail and Seoul Metro trains followed the same numbering system. It consisted of a four-digit number.
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The first digit signifies the type, class, or series of train. For example, 2XXX means the 2000-series of trains.
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The second digit signifies the car number within the train. Going off of the example above, 21XX means car 1 of a 2000-series train.
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The last two digits signify the train number within the type, class or series. For example, 2143 means a 2000-series train, car 1, train 43.
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Seoul Metro trains are usually denoted by series. Korail uses class.
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In 2011, Korail decided to renumber all its trains on a new 6-digit system, presumably to prevent confusion and numbering conflicts with Seoul Metro trains and other rolling stock.
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The first digit signifies the type of service the train is meant for. In this case, all Korail subway trains have a first digit of 3, signifying "metro."
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The second and third digits signifies the class of train.
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The last three numbers remain the same as Seoul Metro's. The fourth digit is the car number within the train, and the last two digits denote the train number within the class.
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To eliminate confusion, I will write Korail trains as class-x-train (341x22) and Seoul Metro trains as series-train (2-43)
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Seoul Metro trains usually carry the numbers of trains they are inteded to replace. Korail trains usually carry a new number each time.
The Daegu Subway Fire and refurbishment of existing trains
The Daegu Subway Fire on February 18, 2003 killed 192 people when an arsonist set fire to a train, which quickly spread to another. Neither train, nor any train running in Korea at that time, had been fitted with fire-resistant materials. Stations themselves lacked sprinklers and emergency lighting, and the emergency equipment was inadequate.
The tragedy exposed the very inadequate safety measures, especially around fire, that were forgotten during South Korea's rapid industrialization. To address this, stations were refurbished with better fire suppressant systems, and all existing trains were refurbished with fire-resistant materials. All work was completed within a few years of the disaster. All subsequent trains built after this date were built with this updated code in mind.
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Electric Propulsion Systems
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Trains in South Korea use a variety of electric propulsion systems. Here is a short intro to each one.
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The first subway trains used rheostat, or resistance control propulsion systems. Rheostat devices can adjust an electric current by varying the resistance on a circuit. The dissipation of electric energy in the form of heat provides enough voltage for the motor to constantly produce a given current through the circuit.
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The next few trains used chopper controls. These take a fixed electric current and "chop" it at a variable frequency to create a variable output. This fast switching allowed for smoother acceleration and braking, and also allowed for regenerative braking to be used for the first time. Since the switching element is either fully on or fully off, losses are low and the circuit can provide high efficiency.
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All new trains or ones currently being built use VVVF (Variable voltage/variable frequency) inverters. VVVF inverters are a type of adjustable-speed drive that can control both input frequncy and voltage. They can be built for both DC and AC power. Benefits of this system include the use of auto-start, high efficiency in acceleration and braking, and energy savings.
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Currently, two types of VVVF inverters are used: VVVF-GTO and VVVF-IGBT.
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GTO (Gate Turn-off Thyristor) units require external devices to control its electric pulses. It also requires direct and active cooling. IBGTs (Insulated Gate Bipolar Transistor), on the other hand, do not require external devices to control electric pulses. As opposed to a active cooling system, IGBTs feature passive cooling through heat piping.
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Since VVVF-GTO units are no longer in production, spare parts are becoming increasingly difficult to find. It has become easier to simply retrofit existing trains with newer IGBT units rather than trying to maintain their original GTO units.
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Many VVVF-IGBT units have also been fitted with IPMs (Intelligent Power Module). It draws even greater performance by mounting a separate, dedicated drive circuit, and is also responsible for executing self-protection functions.
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Future trains will use PMSMs (permanent magnet synchronous motor). This system uses permanent magnets embedded in the rotors to create a constant magnetic field. The rotation of the shaft is also synchronized with the frequency of the supply current.
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