POWER SUPPLY ASSEMBLY

A power supply assembly comprising a load supply converter system (8) and energy saving transfer route (457) both connected electrically to a load connection (71). The energy saving transfer route (457) bypasses the load supply converter system (8), and comprises a bypass switch system (5) having a first bypass switch (51) and second bypass switch (52) connected in series. A control system (909) of the power supply assembly is adapted to provide a system diagnostic operation comprising providing a diagnostic state for the bypass switch system (5) by controlling the first bypass switch (51) into a non-conducting state, and controlling the second bypass switch (52) into a conducting state, generating a diagnostic voltage in an output of the load supply converter system (8), and detecting a short circuit incident if an electric current flowing through the bypass switch system (5) exceeds a predetermined short circuit threshold value.