Naval History Forums

Other than the US Navies use of turbo-electric plants, why was Diesel / Electric propulsion not used more in major warship designs between 1936 - 1944 ?

Issues that I have researched so far that may have limited the use of this type?

For what reason did the USN discontinue the use of turbo/electric type?

Phase & Frequency issues in AC units when varying motor speed.?

Availability of copper and any fallbacks replacing copper with Aluminum?

The need to convert DC to AC for other hip boardship requirements?

Failure of RM to follow up it's research with merchant ship experiments?

Can anyone expand on and enlighten on this subject?

sineatimorar wrote:Other than the US Navies use of turbo-electric plants, why was Diesel / Electric propulsion not used more in major warship designs between 1936 - 1944 ?

Issues that I have researched so far that may have limited the use of this type?

For what reason did the USN discontinue the use of turbo/electric type?

Phase & Frequency issues in AC units when varying motor speed.?

Availability of copper and any fallbacks replacing copper with Aluminum?

The need to convert DC to AC for other hip boardship requirements?

Failure of RM to follow up it's research with merchant ship experiments?

Can anyone expand on and enlighten on this subject?

Hybrid drive systems, either turbo or diesel electric, have very poor power to weight ratios compared to a direct drive system. The between wars naval treaty environment ensured that warship propulsion would have to achieve very high power to weight ratios to release displacement for armament, armour and hull volume.

Another point as well is the newer compact turbines of the 1930s, more efficient boilers, and double reduction gearing adopted by the USN was nearly as economical in terms of fuel usage as Turbo electric drive, while providing more power per ton of machinery. As far as Germany was concerned, the rapid expansion of the Kriegmarine prohibited lengthy R & D necessary to develop TE and DE systems for large military ships without delaying new construction. Raeder himself made the decision to go with standard turbine drive. There was also the matter of fears over shortages of copper, which for the Germans was strategic material, the majority of which had to be imported. Likewise, although aluminium could be substituted, it too was in short supply and was necessary for the rapid build up of the new Luftwaffe.

Had a thought. Why was a hydraulic drive never considered? Or am l suffering from modern day hind sight?

Out if my mind. There was a arms race between Diesel und turbines in Germany. For scharnhorst Raeder waited ti the latest moment take the decision between both concepts. Only electric drive systems were disregarded for weight reasons. A second point was that Siemens. reported problems with speed control and change of turning direction

From what I have seen since posing the questions is as indicated weight of any Dc system & limited practical max power output. The more powerful Ac system had phase shift issues related to variation in revolutions. Something beyond WW2 tech to solve ?

old school ac motor control was pretty much limited to wound rotor induction motors which were both heavy and ran hot at reduced speeds. dc motors could be varied easier but still were usually limited in fine control since most used resistor banks and either stepper switches or drum controllers. this meant that you got speed control in steps instead of a smooth curve. you could use reactors to fake ac control with series wound motors and get a smooth curve but the system loses were rather high . its much easier today with all the different solid state controls. the other issue was that really high horsepower motors were kind of big and heavy. changing ac to dc or dc to ac was really the easy part. motor generator sets were widely used for this. motors could be connected in tandem on the shafts to increase hp but the control got a bit more complicated

Further research suggests a. DC limit of 10Mw per motor. So to achieve the approximate 40,000 shp per shaft would indicate multiple electric motors per shaft. Also as AC power was more desirable for RPC gunnery control units AC power would make more sense.