Type DF4B diesel-electric locomotive is equipped with AC-DC transmission and is used for passenger and freight traction on main lines. Locomotives for different services have the same structures except the gear ratios. The maximum operating power of the locomotive diesel engine is 2430kW.

    The engine drives a three-phase synchronous traction alternator. The AC generated is delivered to traction motor through the thyrestor and then traction motors drive the wheel sets via traction gears.

    The locomotive body is a box structure with sidewall loading. There is a cab on each end and the locomotive can be controlled by either of them. The power room is in the mid-locomotive and inside the room are diesel generator set and auxiliary equipment. Electric apparatus room and cooling room are located at both ends of the power room respectively. The fuel tank is suspended at the middle bottom of the main frame with the battery box by its both sides. The running gear of locomotive consists of two interchangeable three-axle bogies with a low four-rod mechanism traction and roller bearing journal box. The whole bogie is two-series suspension system which is composed of journal box springs and bearing rubber pads. The traction motor is suspended from the axle of the wheel set. In addition to electric resistance brake, Type JZ-7air brake is used for air brake system, which can brake the locomotive separately or brake the locomotive and train simultaneously. The means of three-stage filtering by V-type strainer mesh, high efficient air spin cleaner in form of multiple-eddying flow tube and paper element are employed for air filtering of the engine. The lubricating oil is filtered by the high-efficiency polypropylene fibre filter.

    DF4B diesel-electric locomotive is a major traction power unit on the main lines in China, and is characterized by good performance, low oil consumption, reliable operation, easy maintenance and comfortable working conditions.