Japan Railway & Transport Review No. 25 (pp.58–61)

Railway Technology Today 12
Magnetic Levitation (Maglev) Technologies
1. Superconducting Maglev Developed by RTRI and JR Central
Kazuo Sawada

The Tokaido Shinkansen began operations in 1964 and was an immediate success. Since then, Japan's shinkansen network has expanded considerably, and its success has prompted rapid development of high-speed railways in other countries as well, especially in the West.
In its early days, the shinkansen was considered the ultimate form of high-speed rail travel. But passengers in Japan now demand even faster rail service, as we can see in the preference they have recently shown for the Nozomi on the San'yo Shinkansen that runs at 300 km/h, or 70 km/h faster than the older Hikari.
The shinkansen uses a conventional train design, with motors and other equipment mounted on the rolling stock, electric power collected from overhead wires, and wheels running on rails. It is extremely difficult to modify this conventional design to increase speeds much more. Some inherent limitations are:
Greater size and weight of on-board equipment
Difficulty in collecting electric power
Reduced adhesion between wheels and rails at higher speeds, causing wheel slip

The shinkansen, and other similar high-speed trains in different parts of the world, have made rail travel faster than ever before, but the speed is reaching the maximum possible with present technology.
To break through this speed barrier, the Railway Technical Research Institute (RTRI) and JR Central are working together to develop technologies for a new type of railway that is ideal for high speed travel—the superconducting magnetically levitated train (maglev).

Advantages of Superconducting Maglev

Superconducting maglevs are also called linear motor cars. The motor is linear, not rotary. We can think of it as an ordinary electric motor that has been split open, spread out flat, and oriented in the direction of train travel (Fig. 1). The motor does not rotate; instead, it exerts a kinetic force in a straight line, or guideway.
One part of the linear motor is mounted on the train, the other on the guideway. The train has light but powerful superconducting magnets, and the guideway has energized coils along the sides. Thus, the train does not carry equipment such as transformers and inverters. As a result, it is very light and slim, but still capable of harnessing a large propulsive force. Another advantage is that there are no current collectors and electromagnetic force levitates the vehicles, so there are no wheels or rail adhesion problems.
Different types of linear motors have been developed, but the only other type that supplies electric power to a guideway for transport is Germany's Transrapid system.
As mentioned, superconducting magnets are used create a strong magnetic force to propel the vehicle. But they offer more than just propulsion—they also levitate the vehicles and guide them within the bounds of the guideway.
The system takes advantage of the naturally stabilizing effect provided by electromagnet induction. No controlling devices whatsoever are needed to keep the train on its guideway, and there is no risk of the train ‘derailing.’ The magnetic levitation force is ideal for supporting a train at very high speeds.

Figure 1: Different Propulsion Methods of Conventional Electric Railways and Superconducting Maglev Guideway

Development History

In the early development stages, superconducting magnet technology was considered an esoteric technical field and some people assumed that the technology could never be used for commercial train travel. But the former Japanese National Railways (JNR) was convinced that the technology held great potential for very fast rail travel, and began conducting maglev R&D in 1970.
In 1977, experiments began in earnest on the Miyazaki Test Track in southern Japan. In 1979, the prototype ML-500 test train reached an unmanned speed of 517 km/h on the 7-km track, proving the maglev's tremendous potential for high speed. The track was modified later into a more practical U-shaped guideway.
At this stage, the Japanese government started providing the project with financial assistance. The manned MLU001 was the first train set developed with government subsidies and had three cars.
Soon, the MLU002 and then the MLU002N were being used for a wide range of experiments on the Miyazaki Test Track. But the test track was too short and only had a single guideway with no tunnels and almost no gradients. Obviously, the experimental data from the track would be too limited to verify the maglev's commercial potential.
After JNR was split and privatized in 1987, the Tokaido Shinkansen experienced a dramatic increase in passengers, leading to more calls to build a commercial superconducting maglev as soon as feasible. As a result, the Yamanashi Test Line was constructed in Yamanashi Prefecture, 100 km west of Tokyo.

Photo: The ML-500 test reached a speed of 517 km/h in 1979
Photo: MLU001 Three-car train on Miyazaki Test Track

The Yamanashi Test Line

The 18.4-km Yamanashi Test Line supports a wide range of tests to determine the commercial viability of superconducting maglev transport. It was built by JR Central, which hopes to operate a maglev between Tokyo and Osaka, and RTRI, which took over superconducting maglev development from the former JNR. The Japanese government provides considerable financial assistance.
Tunnels make up 16 km of the line and there is one open section 1.5-km long almost in the middle of the line. A substation for power conversion, and other facilities are located at the test centre on the open section. Part of the line is double-tracked to simulate actual operating conditions. This makes it possible to conduct tests with trains travelling in opposite directions and passing each other at high speed. The maximum gradient is 40 per mill, while conventional shinkansen lines are 30 per mill at most.
A total of 7 cars have been developed for two train sets. The head cars are 28-m long, and the middle cars are 22 to 24 m. The 20-tonne cars are only half the weight of the latest shinkansen carriages because they use a linear motor system with excellent propulsive power.
Another special feature of the maglev car is the articulated system used to connect cars. We chose this system in order to reduce the height of the carriage body and to facilitate installation of magnetic shielding in passenger compartments. The shield reduces the magnetic field at seats closest to the superconducting magnet to about 4 gauss. For the sake of comparison, hospitals recommend 5 gauss as the maximum permissible exposure for a pacemaker wearer.

Results from Yamanashi Test Line

Trial runs were begun on the Yamanashi Test Line in April 1997. The first train set of three cars was powered by a linear motor but driven at low speed. In early tests, the cars were not levitated; instead, they ran on rubber tyres. Once tests verified that there were no defects in the vehicles or guideway, levitation runs began at the end of May 1997. Thereafter, speed was increased in very small increments over a considerable period of time, with continual monitoring to measure car movement and verify braking performance. On 12 December 1997, a new world record of 531 km/h was set for manned train travel. Then, a maximum speed of 550 km/h was achieved on 24 December for an unmanned run, thereby achieving one of the original objectives of the Yamanashi Test Line.
Only one problem remains to be solved—air vibration that rattles the windows of buildings near tunnel portals when a maglev train enters or leaves a tunnel at high speed. We are presently attempting to solve this problem by installing air baffles at tunnel portals, and by modifying the opening design (JRTR 22 pp. 48–57).
There are no other environmental problems—ground vibration measurements indicate values well within acceptable limits and noise levels are also within acceptable limits. Aerodynamic noise can probably be reduced further by making the cars even more streamlined. Measurements of the magnetic field, at ground level directly under the standard 8m-high elevated guideway show a magnetic field of only 0.2 gauss caused by Maglev trains imposed on the constant terrestrial magnetism of 0.4 gauss.
A second train set was completed at the end of 1997, making it possible to conduct various tests with two trains, such as one train passing a stationary train or a train moving slowly in the same direction, or two trains travelling in opposite directions at high speed.
In February 1999, to more closely simulate future commercial operations, the 3-car train set was changed to a 5-car configuration for performance tests at speeds in the 500-km/h range. No problems were observed and on 14 April 1999, this manned 5-car train set registered a record speed of 552 km/h.
In May 1999, the cars were rearranged in their original configuration of two 3-car train sets and high-speed tests are continuing to confirm dependability. The trains run up to 44 times a day at around 500 km/h, and results are good.
After reducing aerodynamic vibration in autumn 1999, we conducted high-speed runs on the open section of the guideway. The vibration of trains passing at relative speeds as high as 1003 km/h was so small that it was felt only by someone actually expecting it.

Photo: This five-car train set registered a record speed of 552 km/h on 14 April 1999

Future Tests

Test runs on the Yamanashi Test Line were planned for a period of 3 years (1997–99). No major problem was experienced during this time, and we have achieved all of our original objectives, including a maximum speed of 550 km/h and relative passing speeds of 1000 km/h.
The Ministry of Transport established the Maglev Technical Performance Evaluation Committee to verify the technical merits of the system. The Committee report said, ‘Although further study is required to evaluate long-term durability and cost effectiveness, it appears that the superconducting maglev system is technically ready to be used commercially as a very high speed, large-capacity transportation system.’
During the next 5 years we will continue to conduct test runs and develop the system further, while focusing on these three objectives:
Verifying long-term durability
Finding ways to reduce costs
Achieving more aerodynamic car design


The superconducting maglev is an entirely new type of railway that combines the latest technologies in power electronics (e.g., superconducting magnets), communications and other high-tech fields. Maglev development sets a new course for rail transport and is a significant milestone in the 170 years of railway history. Air resistance is the only factor limiting the speed of this system, so there is every reason to believe that speeds will be raised dramatically by, for example, using maglev technology in a vacuum. This innovative made-in-Japan technology is about to revolutionize train travel for several centuries to come.

Kanji Wako
Mr Kanji Wako is Director in charge of Research and Development at the Railway Technical Research Institute (RTRI). He joined JNR in 1961 after graduating in engineering from Tohoku University. He is the supervising editor for this series on Railway Technology Today.
Kazuo Sawada
Mr Sawada is General Manager of Technology in the Maglev System Development Department of RTRI. He graduated in electronic engineering from the University of Tokyo in 1971 and then joined JNR. He has worked on the maglev project since 1974, holding various senior posts at the Miyazaki Test Track and RTRI.