5. Method for estimating magnetic fields on railway vehicles

A method was proposed to calculate magnetic field distribution on railway vehicles in operation.
This method makes it possible to calculate the magnetic fields in the vicinity of ferromagnetic material, and verify the efficacy of magnetic shields.

Social concern has been rising over recent years about magnetic fields. Therefore, aside from measuring actual magnetic fields on railway vehicles, increased effort has been invested into establishing a method to predict magnetic field distribution during train operation. Magnetic shields and the carbody of trains both have a shielding effect against magnetic fields, and finding a simple theoretical formula to calculate magnetic fields is difficult. Consequently, a model of the magnetic field on a railway vehicle was produced and a method was proposed to estimate actual magnetic field distribution using numerical analysis modeling (Fig.1).　

Confirmation of the validity of this analytical method was obtained by comparing measurements made inside the test train on the RTRI test track with results from magnetic field analysis on a railway vehicle and close to the filter reactor (FL) (Fig.2). Results from the above comparison revealed that this method could be used for estimating the magnetic field on a railway vehicle even in the area just above ferromagnetic material, such as the magnetic shield.

The analytical model can be adjusted to take into account the shape, material quality and thickness of the magnetic shield and the car body, therefore the proposed method can be used to evaluate the effectiveness of measures taken to reduce DC and AC magnetic fields.

Fig.1 Model for analysis of magnetic fields on railway vehicles
Fig.2 Example of analysis of magnetic fields on a railway vehicle, and results of a comparison between analytical values and measured values (close to Filter Reactor)