Publication Detail

Slip Ring Motors for Ship Propulsion

James Kirtley
7 pp.

Electric propulsion is now recognized as a means for improving performance and affordability of a wide range of naval vessels. In surface ships the improvements to efficiency of propulsion equipment lead to reductions in displacement and fuel requirements, making ships more affordable. Flexibility in arrangement arising from decoupling of the shaft line from prime mover to propulsor lead to better use of ’real estate’. In submarines the use of electric propulsion can result in lower propulsor speed and therefore reduction in acoustic emissions.

At the present time, the ’baseline’ motor for what is likely to be the first modern generaiton of
electric warship, DD-X, is a permanent magnet synchronous motor. A substantial amount of work
has been done on large induction machines for this application as well, and the current fallback
position is to use an advanced induction motor similar to the machine that has been tested at the
Land Based Test Facility in Philadelphia. Both of these machine types require an adjustable speed
drive that covers their full power range, which means that the rating of the drive system must be at least as large as the propulsion power of the ship. For a warship, which has quite high propulsion power for its displacement, this amounts to a lot of power electronics.

What we propose in this white paper is a drive system based on the doubly wound machine,
called variously according to application, the ’wound rotor induction motor’ or ’slip ring machine’.
We will argue here and attempt to show that use of such a machine can reduce the required power
electronics rating, resulting in a smaller and more efficient propulsion system for a high power ship.

type: Technical reports

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