Abstract: A power converter apparatus for an electric train, including at least a first modular power converter unit having a main circuit formed of switch for interrupting power from a D.C. power source, a first D.C.-A.C. power converter connected to the switch, an isolation transformer connected between the D.C.-A.C. power converter and a rectifier and a second D.C.-A.C. power converter connected to the rectifier. The switch and the first D.C.-A.C. power converter are controlled by a control signal derived from the difference between the output voltage of the first D.C.-A.C. power converter and the sum of a delayed soft starting control signal and a settable reference signal. The second D.C.-A.C. power converter is pulse width modulated. Preferably a second modular power converter unit having the same construction as the first unit is provided and has inputs connected in series or in parallel with inputs of the first unit.