The Electric Propulsion Of Ships PDF Download

Excerpt from The Electric Propulsion of Ships Much attention is now being given to propositions relating to the electric propulsion of ships. A study of the circumstances reveals a remarkable accordance of means and requirements. The case may be briefly outlined as follow's: - The double transformation of energy in the form of work into energy in the form of electricity and again from electricity into work, may often, when the operations are on a large scale, be effected at an overall efficiency of 90 per cent, and even higher. In other words, at the cost of a loss of 10 per cent, in energy and of the initial and maintenance cost of the electrical machinery, engineers can interpose an electric drive between the prime mover and the machinery to be driven. The object of interposing an electric drive is to obtain advantages of flexibility which will permit of securing greater efficiency both in the prime mover and in the driven machinery, which, in the case of ship propulsion, is the propeller. Further great advantages relate to the superior means of control rendered available with electric drive. In the case of ship propulsion, the prime mover has, until recently, almost always been a reciprocating engine. But during the last ten years, many ships have been fitted with steam turbines. As applied to ship propulsion, the steam turbine has not met with any approach to the almost unqualified success which has attended its use on land. This is chiefly because, in applying the steam turbine to ship propulsion, it has been necessary to adopt speeds several times lower than have been customary with land turbines. This has been necessary owing to the well-known circumstance that the efficiency attainable with the screw propeller is lower (for a given power) the higher the speed of revolutions. It was a realization of this circumstance, more than any other consideration, which first led to serious propositions for the electrical driving of large ships. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.