Takashi Sasakawa

Linear eddy current brake for railway vehicles using dynamic braking

One type of braking system for railway vehicles is the eddy current brake. Because this type of brake has the problem of rail heating, it has not been put to practical use in Japan. Therefore we proposed using a linear induction motor (LIM) for dynamic braking in eddy current brake systems. It reduces rail heating and uses an inverter for the self-excitation function. In this paper, we estimated the performance of an LIM from experimental results of a fundamental test machine and confirmed that the LIM under constant current excitation has an approximately constant braking force regardless of frequency for relatively low frequencies, and the reduction ratio of rail heating is approximately proportional to the frequency. These characteristics are convenient for the realization of the LIM rail brake system.

Preliminary design of magnetic shielding by FEM

In this paper, we propose an optimization method for magnetic shielding. Our main purpose is the weight reduction of shield material. Assuming that the permeability of shield material is infinite, we simplify the magnetic shielding problem. Under this assumption, we design optimal passage for magnetic flux through the shield. We apply this method to designing the magnetic shielding for Maglev and show the effectiveness of this method by experimental and numerical data.

Reduction of magnetic field in vehicle of superconducting maglev train

For EDS (electrodynamic suspension) maglev trains, magnetic shielding is an important task. We have attained a field of less than 2 mT. In this study, we tried to reduce the magnetic field level in vehicles further (less than 0.5 mT) by suitable choice of shielding material and shielding structure according to each part on vehicles.

Study on Electromagnetic Force Characteristics Acting on Levitation/Guidance Coils of a Superconducting Maglev Vehicle System

Superconducting Maglev has been developed as a high-speed transport system. Superconducting coils (SC coils) are installed on the vehicle, and levitation/guidance coils (LG coils) are installed on the ground. A null-flux-type electrodynamic suspension system provided by electromagnetic interaction between SC coils and LG coils serves as the levitation and guidance functions of the vehicle system. Electromagnetic forces acting on SC coils are related to levitation and guidance functions of the vehicle. These forces were studied in previous research, and characteristics of levitation and guidance forces were revealed with respect to parameters of the design of the vehicle. On the other hand, electromagnetic forces acting on LG coils also exist as action–reaction pairs with the forces acting on SC coils. The forces act on LG coils in every levitated run of the vehicle, and stress is applied on the conductor and molded resin of the LG coils. In conventional studies, the vehicle design has been decided mainly by the electromagnetic forces acting on SC coils, and not by the forces acting on LG coils. The aim of the study is to establish an improved method to design the vehicle system with the objective of not only optimization of characteristics of the vehicle, but also consideration of stress on LG coils. As a preliminary study to establish the improved method, a study by computer simulation on characteristics of electromagnetic forces acting on LG coils with respect to the parameters of the vehicle is described in this paper.

Preliminary study of HTS magnet using 2G wires for maglev train

There are several advantages by applying a high temperature superconducting wire to an on-board superconducting magnet for the maglev train. At first, an increase of thermal capacity of superconducting coils contributes a stability of the superconducting state of the coils. In addition, a reliability of superconducting magnet improves by simplification of the magnet structure. And the weight of the superconducting magnet and the energy consumption of the on-board cryocooler will decrease. Therefore, we examined the possibility on application of the 2G wire with a high critical current density in a high magnetic field. We performed numerical analysis regarding the weight of a superconducting magnet and the energy consumption of an on-board cryocooler in consideration of the characteristics of the 2G wire. Furthermore, we have carried out the Ic measurement for the commercial 2G wires under various experimental conditions such as temperature, magnetic field strength and angle. We also performed the trial manufacture and evaluation of Ic characteristics for the small race track-shaped superconducting coil.