page_title: Combined diesel-electric and gas
hierarchical_section_title: Combined diesel-electric and gas
caption_attribution_description: Working principle of marine CODLAG systems. Note that in reality, the clutches would be placed somewhere else (e.g. into the gearboxes). (Own work).
context_page_description: Combined diesel-electric and gas is a modification of the combined diesel and gas propulsion system for ships. A variant, called the combined diesel-electric or gas system, contains the same basic elements but will not allow simultaneous use of the alternative drive sources.
  A CODLAG system employs electric motors which are connected to the propeller shafts. The motors are powered by diesel generators. For higher speeds, a gas turbine powers the shafts via a cross-connecting gearbox; for cruise speed, the drive train of the turbine is disengaged with clutches.
  This arrangement combines the diesel engines used for propulsion and for electric power generation, greatly reducing service cost, since it reduces the number of different diesel engines and electric motors, requiring considerably less maintenance. Also, electric motors work efficiently over a wide range of revolutions and can be connected directly to the propeller shaft so that simpler gearboxes can be used to combine the mechanical output of turbine and diesel-electric systems.
context_section_description: Combined diesel-electric and gas (CODLAG) is a modification of the combined diesel and gas propulsion system for ships. A variant, called the combined diesel-electric or gas (CODLOG) system, contains the same basic elements but will not allow simultaneous use of the alternative drive sources. 
  A CODLAG system employs electric motors which are connected to the propeller shafts (usually 2). The motors are powered by diesel generators. For higher speeds, a gas turbine  powers the shafts via a cross-connecting gearbox; for cruise speed, the drive train of the turbine is disengaged with clutches.
  This arrangement combines the diesel engines used for propulsion and for electric power generation, greatly reducing service cost, since it reduces the number of different diesel engines and electric motors, requiring considerably less maintenance. Also, electric motors work efficiently over a wide range of revolutions and can be connected directly to the propeller shaft  so that simpler gearboxes can be used to combine the mechanical output of turbine and diesel-electric systems.
  Another advantage of the diesel-electric transmission is that without the need of a mechanical connection, the diesel generators can be decoupled acoustically from the hull of the ship, making it less noisy. This has been used extensively by military submarines but surface naval vessels like anti-submarine vessels will benefit as well.
caption: Principle of a CODLAG propulsion system
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