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Economy, No.26  Jun. 5, 2015

Superconducting Maglev Technology: Future and Development

UMEHARA Jun, Railway journalist

UMEHARA Jun, Railway journalist

The journey toward realizing superconducting magnetic levitation (maglev) that achieves speeds of up to 500 kilometers an hour has come one step closer to its end, with the emergence of a train known as the linear motor car. JR Central, which is responsible for the operation of the Tokaido Shinkansen line, started work on the construction of the Chuo Shinkansen line for use by the superconducting maglev at the end of last year. The occasion was marked with a ceremony held on December 17, 2014 to pray for safe construction of the line, which will run between JR Central’s Shinagawa Station in Minato Ward, Tokyo and Nagoya Station in Nagoya, Aichi Prefecture. If all goes well, service is scheduled to begin in 2027, when linear motor cars will connect the 285.6-kilometer distance between Shinagawa and Nagoya in as little as 40 minutes.

“Superconducting maglev” refers to railways that use superconductivity to levitate and push linear motor cars forward. Electric power with extremely strong magnetic force can be obtained externally by feeding electric power from the outside after eliminating electrical resistance by lowering the temperature of metals or alloys to -273.16 degrees Celsius, or absolute zero. Superconducting magnets installed in linear motor cars create repulsive and attractive forces between ground coils that are built into guideway panels on either side of a railroad track. This levitates the train by 10 centimeters, and the repeated repulsive and attractive force propels the train forwards at speeds of up to 500 km/h.

L0-series (L zero) trial linear motor car (Photo: PIXTA)

L0-series (L zero) trial linear motor car (Photo: PIXTA)

Niobium titanium is currently used as the material for superconducting magnets. This material creates superconductivity at a comparatively high temperature of -269 degrees Celsius. Superconducting magnets are installed in a low-temperature receptacle that has an outstanding thermal insulation quality and are cooled down to nearly 300 degrees Celsius using a Gifford-McMahon cycle cooler which utilizes liquid helium as a refrigerant. The ground coils, which are the source of the power generated by superconducting magnets, are fed with three-phase alternating currents from a power conversion station. Linear motor cars, after the initial start, gradually accelerate using a mechanism that changes the voltage and the frequency of the three-phase power supply.

Ground coils are used as a brake for linear motor cars. Electromagnetic force attracts superconducting magnets through a change in the way the three-phase alternating currents flow, and thus the brake is powerful without having to rely on friction.

One surprisingly little known fact is that linear motor cars are driverless: operation is conducted entirely by remote control.

JR Central has already announced the route for the Chuo Shinkansen line and its stations as well as the location of the rail yard. The shortest radius of the curve of the guideways is 8,000 meters, which is dramatically less rounded than that for the 2,500 meters for the Tokaido Shinkansen. This serves to ease the centrifugal force that can be felt on a train when it is cruising at 500 km/h.

Meanwhile, a 100-meter incline of a slope generates a 4% gradient, which creates a difference in elevation of 4 meters. This means that there is less allowance than the 2% gradient for the Tokaido Shinkansen. The levitated linear motor car can operate under more advantageous conditions than rolling stock used for the Tokaido Shinkansen, which experiences resistance when there is a steep gradient due to friction between the wheels and the railroad track. 

The Chuo Shinkansen runs from Tokyo to Aichi Prefecture by way of Kanagawa, Yamanashi, Nagano and Gifu Prefectures. In addition to Shinagawa Station and Nagoya Station, it has been decided that each of these prefectures is to have one station, namely Kanagawa Prefecture Station, Yamanashi Prefecture Station, Nagano Prefecture Station and Gifu Prefecture Station.

Shinagawa Station will be located virtually right below JR Central’s Tokai Shinkansen station, so that the lines run parallel with each other. The direction in which the guideways are laid out is also the same as that for the Tokaido Shinkansen. Two platforms will be created, just like those at other stations, with two guideways to be laid on either side of the platforms for a total of four guideways. This allows a linear motor car consisting of a maximum of four cars to arrive at and depart from the station.

The Nagoya Station will be located underground and intersect JR Central’s Nagoya Station more or less at a right angle. This is a terminus on the line at this point, but it should become an intermediate station down the line as the Chuo Shinkansen is planned to extend toward Osaka by around 2045.

L0-series (Photo: PIXTA)

L0-series (Photo: PIXTA)

The Chuo Shinkansen will run through 43 tunnels, which together extend 246.6 kilometers long and make up 86% of the entire line. The line runs through an underground tunnel for about 35 kilometers both in central Tokyo and Nagoya, with the No. 1 Metropolitan Tunnel that runs between Shinagawa Station and Kanagawa Prefecture Stations being the longest on the Chuo Shinkansen, measuring 36.9 kilometers. Massive mountain tunnels successively extend between the Kanagawa Prefecture Station and the Gifu Prefecture Station. Of the tunnels, not only does the Southern Alps Tunnel (25.0 kilometers) run between the Yamanashi Prefecture Station and the Nagano Prefecture Station as well as the Central Alps Tunnel (23.3 kilometers) between the Nagano Prefecture Station and the Gifu Prefecture Station, but also the altitude of the mountains is high, making it necessary for the tunnel structure to be able to withstand pressure from hefty amounts of soil.  

The decision on the Chuo Shinkansen route has sparked expectations in regions where intermediate stations are to be set up. Local government agencies located near the train line are pushing forward with formulating city planning projects, with some already unveiling renderings of the areas surrounding their respective station. The challenge for both stations in Yamanashi Prefecture and Nagano Prefecture is access to city centers due to a lack of connections with existing railways, and thus setting up new roads is being considered.

In terms of construction, the key point is whether the excavation and construction of tunnels are successful or not and will enable the line to start operating in 2027. Specifically, construction is expected to be difficult as many unknowns exist regarding the quality of soil and underground water veins when it comes to laying tunnels at an extremely deep level of 40 meters underground in city centers, as well as for both tunnels that are to run through the Southern and Central Alps.

JR Central has laid a trial Yamanashi line that extends 42.8 kilometers and is currently conducting tests with an L0-series (L zero) trial linear motor car. A trial run opened to the general public in the fall of 2014. This has proven to be so popular that the chance of getting a trial ride in the lottery is low.

The trial Yamanashi line will be incorporated into guideways that will run between Kanagawa Prefecture Station and the Yamanashi Prefecture Station simultaneous to the Chuo Shinkansen. The results of this trial will pay dividends at some point, ultimately leading to the day when a dream railroad becomes a reality. Twelve years remain until JR Central’s anticipated railroad. It is no exaggeration to say that superconducting maglev is in the world’s spotlight.

Translated from an original article in Japanese written for Discuss Japan. [March 2015]