Shows basic circuit configurations, control methods, operationmodes 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 andvoltage/current harmonics.