II. ELECTRIC DRIVE PROPULSION
AES unlocks propulsion power for use by other ship loads,
thereby, allowing a reduction in the number of installed prime
movers, which in turn increases fuel savings and improved
design flexibility. Power that is not used for propulsion can be
used for other purposes. Electric propulsion systems are
economical, environmentally friendly and reliable, offer
considerable comfort in terms of operation and control, have
optimal maneuvering and positioning properties, low vibration
and noise levels, in addition to enabling best possible
utilization of space.
A. Propulsion Systems
The most important advantage of using electric motor for
ship propulsion is that the naval engineers will no longer be
constrained by the placement of an in-line reduction gear and
shaft placement. Replacement of mechanical couplings
between the prime mover and propeller with an electrical
network offers potential benefits including reduced fuel
consumption, enhanced dynamic performance, increased
reliability, reduced maintenance cost, and greater flexibility in
ship layout [2]. By selecting appropriate drive motors, electric
drive propulsion can eliminate the need for a reduction gear,
and will significantly reduce the length of the shaft, or
eliminate it altogether, as is the case of podded propulsion.
Naval designers are investigating in-hull as well as podded
propulsion systems for use in future naval vessels.
In-hull Propulsion
In-hull propulsion configuration with electric propulsion
drives is similar to that of mechanical drives. Here, the prime
mover, located inside the hull of the ship, transfers torque to
the propeller using a shaft through the hull. A propeller
connected to the end of the shaft converts the torque
transferred into forward and reverse thrust. In-hull propulsion
requires additional equipment, such as shaft bearings at
bulkhead penetrations, shaft seals at hull penetrations, and a
rudder to provide steering control for the ship. Compared to
mechanical propulsion, significant reduction in shaft length is
possible due to flexibility of location of the drive motor.