The LET-4000-R is designed for high DC current injection, used mainly in the railway industry to test extra fast relays protecting the locomotive’s DC motors. The set is split into two modules: the AC Regulation and Measurement Module and the AC/DC converter. The first module transforms the three-phase AC supply into a 2 VAC, 8 kVA output, adjustable by means of a variac. The second module performs the full-wave conversion to 2 Vdc with 8 kW powe