Since the advent of railway vehicles with the three-phase drive system in the 1970s, power semiconductors used for electric railway vehicles have been changed from thyristors to GTO thyristors and IGBTs. As for traction motor control, vector control has come into wide use in place of slip frequency control and vector control without speed sensor is now at a trial stage for commercial trains. Anti-slip and readhesion control of railway vehicles has greatly progressed by utilizing wheel axle speed information. Locomotives and electric multiple units with the vector control system without speed sensor in the future should have at least the same adhesion performance as that of the alternatives with speed sensor.

Copyright (c) 2002 Railway Technical Research Institute