Abstract :
Railway electrification has in the past been dominated by overhead contact wire and D.C. third/ fourth conductor rail electrification systems. The historical reasons for this have been the success of the D.C. traction motor and the necessity of a D.C. supply. Mercury arc rectifiers were originally used to provide rectification at substations with the D.C. power being transmitted to the traction equipment by the conductor rail or overhead wire. Success in producing mercury arc rectifiers capable of being operated on board the railway vehicle enabled railway A.C. electrification system to become a reality in the 1950/60´s.
