2. Technological development on the Yamanashi test line
(1) History of running tests
      In fiscal 2004, 164 days of running tests were performed for a total running distance of approximately 85,700km, with about 21,700 people experiencing test riding. After the start of running tests in fiscal 1997, the cumulative running distance reached 434,000km, including achievement of the targeted distance of over 200,000km with multiple trucks, and the number of test riders reached about 89,200.
      Figure 2 summarizes the yearly running distance and the number of test days since fiscal 1997. The running distance per test day, which was 107km in fiscal 1997, exceeded 400km in fiscal 2000 and reached 500km or more in fiscal 2003 and 2004.
      In fiscal 2004, the RTRI implemented special tests (such as tests with a flat tire, superconducting magnet (SCM) failure and operation of two train-sets coupled in tandem to simulate relief operation of a failed train-set) (Fig. 3) to check the system's ability to cope with abnormal situations and the soundness of landing wheels and other auxiliary devices.
      The RTRI also implemented tests to assess the rolling stock's kinetic characteristics using a guideway on which irregularities were set, and by subjecting the rolling stock to simulated lightning strikes and other abnormal situations.
      The RTRI ran vehicles for 1,000km or more on a daily basis for a period of 10 days to demonstrate the reliability of the system, and checked the behavior of two trains passing each other at a relative speed of as high as 1,026km/h (as per the running pattern in Fig. 4).

Fig. 2 Yearly running distance and number of test days

Fig. 3 Test of failed train-set relief operation

Fig. 4 Run curve in the high-speed in the test of two trains passing each other

(2) Improvement of ride comfort by zero-phase inductive power collection added with a strengthened truck vibration control function
      The RTRI has been developing an inductive power collection system to supply power to onboard equipment (Fig. 5), into which a zero-phase control technique is incorporated with the truck control function strengthened to improve ride comfort. This technique superimposes a zero-phase current (the sum of the currents in three phases, which is obtained by controlling the current in each phase separately) onto the three-phase AC current to be collected, which generates a large damping force. The results of testing on the Yamanashi line are as follows:
1) The profile of the power-collecting coil was devised to improve the power collection function. This enables collection of the targeted 25kW of power at a speed of 300km/h or more (Fig. 6).
2) Damping control reduces the up/down vibration of the truck, improving ride comfort in the vertical direction (Fig. 7).

Fig. 5 Inductive power-collecting coils installed on the vehicle

Fig. 6 Collected power versus speed

Fig. 7 Effect of damping control

(3) Characteristics confirmation test for the superconducting magnet for simplified ground coils
      To reduce the construction costs of the Maglev system, discussion is underway on the simplification of ground coils, such as the single-layer propulsion coils introduced on part of the Yamanashi test line and the coils for propulsion, levitation and guidance (PLG coils) now under development at the Kunitachi institute. If the ground coils are simplified, however, the electromagnetic exciting force working on the superconducting magnets (SCMs) during running will increase, thus intensifying the magnets' vibration and accelerating the evaporation of liquid helium. The RTRI has therefore promoted the technological development of an SCM that is free from these problems when used for simplified ground coils.
      The RTRI performed bench tests and analysis to investigate the effect of simplified ground coils on SCMs. Based on the results, the RTRI remodeled the SCMs now used on the Yamanashi test line to improve their vibration resistance by placing aluminum plates on the side of the SCM's outer vessel and reinforcing the vertical load supports for the superconducting coils.
      Running tests on the Yamanashi test line showed that this remodeling has shifted the SCM's vertical secondary bending resonance frequency outside the range of running speed (Fig. 8), and has decreased the volume of evaporated liquid helium. This demonstrates the feasibility of SCMs capable of coping with simplified ground coils.

Fig. 8 Effect of simplified ground coils on superconducting magnets

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