Abstract: A power system for a locomotive generally having an internal combustion engine coupled to drive a main alternator and an auxiliary alternator is provided. The main alternator is coupled to power one or more traction motors and the auxiliary alternator is coupled to power predetermined electrical equipment. The system includes a main power bus generally powered by the main alternator and an auxiliary power bus generally powered by the auxiliary alternator. A power interface unit is electrically coupled to the main power bus to capture and transfer electrical energy into the auxiliary power bus. The electrical energy may be generated during a predetermined mode of operation of the locomotive, such as during dynamic braking or self-load.