Device for supplying at least one series-excitation motor (M1, M2, M3, M4) with electric current, comprising - a chopper (11, 13, 15, 12, 14, 16) having a mid-point linked to the field coil of said motor and to which there are connected: - at least one first controlled static switch (11, 13, 15) further connected to a voltage source for applying to said at least one electric motor (M1, M2, M3, M4) a supply current during traction and - at least one second controlled static switch (12, 14, 16) further linked to ground for closing a linking circuit connecting a load to the motor (M1, M2, M3, M4) when operating as a generator during braking, and - switching means comprising reverse-biased diodes (32, 44, 35, 45, 31, 43, 34, 39) for allowing, respectively: - the supply current of the motor (M1, M2, M3, M4) delivered by the or each first controlled static switch (11, 13, 15) to pass in a first direction when said first switch is conducting and - the current delivered to a load of a linking circuit by the motor when operating as a generator to pass in a second direction through said second controlled static switch (12, 14, 16) when said second switch is conducting, characterised in that the common point of the chopper is connected to at least one series-excitation motor (M1, M2) installed in a first branch, comprising a rotor (25, 26) and a field coil (37, 38) of said motor and the associated switching means comprising diodes (32, 44, 31, 43), and to at least one series-excitation motor (M3, M4) installed in a second branch connected in parallel with the first branch and comprising a rotor (27, 28) and a field coil (41, 42) of said motor and the associated switching means comprising diodes (35, 45, 34, 39), the load for said motors when operating as generators being common to the first and second branches; and in that the switching means comprising diodes biased in a second direction comprise two third diodes (31, 34) connected, respectively, between the rotor (25, 26, 27, 28) of a motor (M1, M2) arranged in one branch and the field coil (41, 42, 37, 38) of the motor (M2, M3) arranged in the other branch and two fourth diodes (43, 39) interposed, respectively, between the field coils of the two motors and the load, said third and fourth diodes (31, 34, 43, 39) being biased to conduct the braking current delivered by the motors operating as generators when the second controlled static switch (12, 14, 16) is conducting, the first controlled static switch (11, 13, 15) being off. - a chopper (11, 13, 15, 12, 14, 16) having a mid-point linked to the field coil of said motor and to which there are connected: - at least one first controlled static switch (11, 13, 15) further connected to a voltage source for applying to said at least one electric motor (M1, M2, M3, M4) a supply current during traction and - at least one second controlled static switch (12, 14, 16) further linked to ground for closing a linking circuit connecting a load to the motor (M1, M2, M3, M4) when operating as a generator during braking, and - at least one first controlled static switch (11, 13, 15) further connected to a voltage source for applying to said at least one electric motor (M1, M2, M3, M4) a supply current during traction and - at least one second controlled static switch (12, 14, 16) further linked to ground for closing a linking circuit connecting a load to the motor (M1, M2, M3, M4) when operating as a generator during braking, and - switching means comprising reverse-biased diodes (32, 44, 35, 45, 31, 43, 34, 39) for allowing, respectively: - the supply current of the motor (M1, M2, M3, M4) delivered by the or each first controlled static switch (11, 13, 15) to pass in a first direction when said first switch is conducting and - the current delivered to a load of a linking circuit by the motor when operating as a generator to pass in a second direction through said second controlled static switch (12, 14, 16) when said second switch is conducting, - the supply current of the motor (M1, M2, M3, M4) delivered by the or each first controlled static switch (11, 13, 15) to pass in a first direction when said first switch is conducting and - the current delivered to a load of a linking circuit by the motor when operating as a generator to pass in a second direction through said second controlled static switch (12, 14, 16) when said second switch is conducting,