Abstract: The switching aid device includes, in the case of a main static switch, (1), a switching aid capacitor (10), parallel connected to the main static switch (1) via a loading diode (11) and, parallel connected to the latter, a series set up formed by an anti-return diode (12), primary winding (13) of transformer (14) of which secondary winding (15) is connected to an energy recovery circuit on an electrical power source (4) via diode (16) and an auxiliary static switch (17) fitted with control means (20) for closing the auxiliary switch in presence of an inverse voltage at the terminals of loading diode (11) and for opening the auxiliary switch in absence of such voltage.

Abstract: A thyristor (TR) is used to switch over between traction and braking states. Rather than supply a special extinction circuit for the switch-over thyristor, it is connected to make use of the extinction circuit already provided in the chopper circuit (H).