Induction Motor
The induction motor is one of the ideal candidates for drive
motors in ship propulsion applications due to advances in
induction motor technology over the last several years.
Converteam is presently among the leaders in industry in
induction motor development with their advanced induction
motor, or AIM. The AIM is a multi-phase, shock hardened,
and high torque density induction motor. It was specially
designed for converter starting, which allows for more
flexibility in operation and optimization of electromagnetic
design. This, in turn, enables improved efficiency and power
factor whilst allowing a larger air gap to be used to provide a
good shock withstand capability.
The AIM was primarily developed for applications where low
speed and high torque are required, such as in ship propulsion
drives, and has a very high power density that makes it ideal
for warship propulsion [10]. The UK Royal Navy’s Type 45
Daring Class destroyers are powered by two of Converteam's
20MW AIMs [11]. Further, the Royal Navy’s Queen Elizabeth
Class and Prince of Wales Class aircraft carriers, which are
due to enter service in 2014 and 2016, respectively, will each
be powered by four 20 MW AIM [11]. The U. S. Navy's
DDG1000 Zumwalt class destroyers are being installed with
two 34.6 MW (120 rpm) AIMs [12]-[13]. Initially, a more
advanced permanent magnet motor solution had been
envisioned, but technology risk led to the choice of the AIM
[13]. AIM technology can be considered to be most matured
of all propulsion motor technology. The full load efficiency of
this motor is about 97%. The US Navy plans to build at least
three DDG 1000s. Delivery of first ship is expected to be in
2014, and plan for its initial operating capability is expected to
be in 2016 [14].
The induction motor's simple construction leads not only
to its inherent reliability, but also permits a simple design for
3
shock requirements. It has low structure-borne noise, allowing
hard mounting of the motor to the hull of a surface combatant.
It has high power density, efficiency, low noise and vibration
levels, high shock withstanding capability, and low
maintenance and life cycle costs.
Propulsion system of an electric ship constitutes about
70%–90% of the total electric load. Surface combatants and
submarines have a need for quiet, efficient, high power dense
propulsion motors. Advanced induction motor employed in
DDG-1000, is adequate and affordable for normal power
density applications. When there is a need for higher power
density naval ships PMSM or HTSSM will be the solution.