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In 25kv ac main line traction system the traction transformer located in the engine are repeatedly switched off and on during the normal run of the train due to presence of neutral section in the contact wire. The transformer draws inrush current several times the full-load value. Its enegization creates severe power quality problem in each time. The inrush current may be reduced to the full-load value either by using point-onwave switching device or by connecting an external resistor in series with the primary circuit. The resistor is shorted within a few cycles of energization of the transformer to avoid voltage drop and losses during the steady-state operation of the transformer. Simulation results illustrate the effect of voltage and frequency variation on the production of inrush current. Only one circuit breaker with a delayed contact closing may be used for resistance switching. Index Terms--External resistor, inrush current, point-onwave switching, traction power supply, traction transformer Dr. K. P. Basu (M'99 and SM'02) received his B.E.E., M.E.E. and Ph.D.(Eng.) degrees from the Jadavpur University, Kolkata, India in 1961, 1967 and 1974 respectively. His research interest is power system operation, control, protection, and electric drives. He has authored and co-authored more than 70 journal and conference papers.

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This research article proposes the speed control of a separately excited DC motor (SEDM) in the constant torque region. The novelty of this article lies in the application of artificial neural network-based model reference controller (MRC) for the speed control of SEDM. This paper also discusses and compares the speed control systems of SEDM using PI-controlled and fuzzy logic-controlled chopper circuit with MRC. The entire system has been modeled using MATLAB 7.0/SIMULINK toolbox. It has been observed that chopper-controlled speed control system could be eliminated by the use of MRC and the performance of the proposed system is comparable with speed control system using chopper circuit.