Locomotive is AC-DC transmission diesel locomotive which can undertake passenger and freight traction transport on trunk lines, secondary trunk lines in mountain areas and railways in extremely cold areas.
The locomotive is divided into three types:
1. mountain type double heading passenger and freight diesel locomotive;
2. cold-proof type double heading passenger and freight diesel locomotive;
3. standard type double-cab passenger and freight diesel locomotive.
Locomotive is equipped with 12V240/275 series diesel engine and its main components and parts are interchangeable with 16V240/275 series diesel engine of current trunk-line prime type passenger and freight diesel locomotive. DF7D diesel locomotive possesses excellent economy and advanced technology. Equipped with specially designed bogie, the mountain type locomotive has good dynamic curve negotiation performance upon service on small curves in mountainous areas. Equipped with reinforced cold-proof facilities, the cold-proof type locomotive is very applicable to extremely cold areas in the northeast.