Shows basic circuit configurations, control methods, operation modes and behaviour of electric power convertors for rolling stock such as external commutated rectifiers, self-commutated rectifiers, choppers and inverters. Describes typical charts and methods, but does not claim to be exhaustive. The main purpose of this specification is to calculate power quantities such as input/output voltage, input/output current, frequency spectrum of voltage/current, voltage/current ripple and voltage/current harmonics.