Dieselmoottorivaunujen

Dieselmoottorivaunut, known in English as diesel multiple units (DMUs), are self-propelled railway coaches powered by diesel engines. They are a common form of rail traction, particularly on routes where electrification is not economically viable or where flexibility in service is required. A diesel multiple unit typically consists of two or more carriages permanently or semi-permanently coupled, with at least one carriage containing a diesel engine and transmission system to propel the train. Other carriages may be unpowered trailers or can also be powered.

The design of diesel multiple units allows for efficient operation on lines with lower traffic density, as individual units can be coupled together to form longer trains during peak hours and separated for off-peak services. This flexibility reduces operational costs compared to fixed-formation trains or locomotives. They are widely used for regional and commuter services, as well as for intercity routes in many countries.

The power transmission in diesel multiple units can be either mechanical, hydraulic, or electric. Mechanical transmission is less common in modern units, while hydraulic and electric transmissions are more prevalent. Electric transmission involves a diesel engine driving a generator, which then supplies power to electric traction motors. This configuration offers advantages in terms of acceleration and adhesion. Maintenance and fuel efficiency are key considerations in the operation of diesel multiple units.