AC-DC single phase reversible converter with low loss snubber having a pair of entrance terminals (N1, N2) intended to be connected to a secondary of a transformer whose primary is connected to a high voltage AC supply, and a pair of output terminals (N3, N4) intended to be connected to a DC motor of a railway vehicle, said converter comprising a main bridge and a control unit, characterised in that - said main bridge is a force commutated fully controlled bridge having a first pair of opposite terminals connected to the entrance terminals of the converter and a second pair of opposite terminals connected to the output terminals of the converters, each branch (Bi) of the controlled bridge comprising a controlled power semiconductor device (Ti) in series with an uncontrolled power semiconductor electronic device (Di); - said main bridge is configured to transmit a power to the DC motor when said DC motor is in a traction mode and transmit a power to the secondary of the transformer when said DC motor is in a regenerative braking mode, with the same direction of current flow in the DC motor in both modes due to a reconfiguration of the converter by the control unit; - the converter further comprises a snubber bridge comprising a first pair of opposite terminals (N5, N6) connected to the entrance terminal of the converter and a second pair of opposite terminals connected together by means of a capacitor (Ks), each branch of the snubber bridge comprising a controlled power semiconductor device (Tsi); and - said controlled power semiconductor devices (Ti; Tsi) are configured to be switched on or off by the control unit so that said capacitor stores energy from the secondary and releases said energy to the motor at the end of the conductive period in traction mode or to the secondary at the beginning of the conductive period in a regenerative braking mode. - said main bridge is a force commutated fully controlled bridge having a first pair of opposite terminals connected to the entrance terminals of the converter and a second pair of opposite terminals connected to the output terminals of the converters, each branch (Bi) of the controlled bridge comprising a controlled power semiconductor device (Ti) in series with an uncontrolled power semiconductor electronic device (Di); - said main bridge is configured to transmit a power to the DC motor when said DC motor is in a traction mode and transmit a power to the secondary of the transformer when said DC motor is in a regenerative braking mode, with the same direction of current flow in the DC motor in both modes due to a reconfiguration of the converter by the control unit; - the converter further comprises a snubber bridge comprising a first pair of opposite terminals (N5, N6) connected to the entrance terminal of the converter and a second pair of opposite terminals connected together by means of a capacitor (Ks), each branch of the snubber bridge comprising a controlled power semiconductor device (Tsi); and - said controlled power semiconductor devices (Ti; Tsi) are configured to be switched on or off by the control unit so that said capacitor stores energy from the secondary and releases said energy to the motor at the end of the conductive period in traction mode or to the secondary at the beginning of the conductive period in a regenerative braking mode.