Environmental low-frequency magnetic field due to direct-current electric railcars.

Biomagnetic signals are very weak compared with those of the environmental magnetic field due to trains and motorcars. Trains, especially direct-current electric railcars, seem to be one of the main urban magnetic noise sources of low frequency in Japan, as indicated by comparing the fluctuation of the magnetic field during the day when there are many trains with that at night when there are no trains. In this paper, the relationship between the environmental magnetic field and the electric current of the direct-current electric railcar of the personal track is discussed. Next, the fluctuation of the magnetic field is calculated from that of the unbalanced electric current between feeder line and railroad, which could be obtained as the leakage electric current to the ground. The validity of the calculation is verified by comparison with measurements. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 10–21, 2001 [ABSTRACT FROM AUTHOR]