Electric propulsion of ships is dominated by Electric Propulsion Technologies(VFD) technology based on power electronics converters.
The VFD converts the fixed line frequency power to variable-frequency power at the motor terminals. The frequency which may vary to match with the required propeller speed during various
phases of ship operations, such as approaching and leaving a port and while cruising at various speeds.
Electric propulsion in passenger cruise ships and navy warships offers minimum noise and vibration and maximum usable space for paying passengers or for combat weapons. It is fully developed in cruise ships, where it has opened up usable space for passenger cabins to bring greater revenue to owners.
A common electric propulsion package fitted on many cruise ships consists of a 21-MW gas turbine driving a 21-MW generator that powers a synchroconverter, cycloconverter, or pulse width
modulated (PWM) VFD with a 20-MW synchronous motor or an advance induction motor.
For warships, the electric propulsion technology that would meet military requirements on survivability and stealth is well under development.
The U.S. Navy is committed to electric propulsion for surface ships and is investing additional efforts to develop a common technology that is adaptable to submarines as well.
It is in this light that electric propulsion technology has become increasingly important to shipbuilders and operators.
The technology primarily involves highpower, high-voltage electric power systems, compact motors with high power and torque densities, and variable-speed power electronics motor drives.