Feature 1
Converteam leads by example
A new electrical control system for NCL cruiseships.
W
ork is progressing on The PWM MV7000 converter allows variation. Thus, no converter oversizing
the cruiseship industry’s electrical energy to be converted from is required linked to motor power factor
f i rst c om m it me nt to one level of voltage/current/frequency design.
Converteam’s new advanced digital to another by using high level switching Propulsion plant efficiency is high
electrical control system, with the components: the press-pack IGBT. (around 94%) and no harmonic filters
installation of high-torque density The ability to adjust, automatically and are necessary to be compliant with the
induction motors onboard two new during operation, both PWM patterns maximum Total Harmonic Distortion
4200 passenger capacity vessels under and frequency allows the control to (THD) allowed by classification
construction for NCL at Aker’s St keep drive output active power constant, societies. In addition, generator sizes are
Nazaire yard. regardless of the motor power factor reduced (power factor up to 0.9). NA
Including MV7000 converters, the
PAGINA-115x164TRACCIA 7-01-2008 18:45 Pagina 1
contract also specifies 12 generators
C M Y CM MY CY CMY K
(six per ship) with a total power of
160MW, to be supplied by Converteam
Ltd (UK), and 12 electric motors for
thrusters (six per ship) with a total
power of 30MW, to be manufactured
at Converteam Motors’ Nancy plant
(France).
The first 325m long, 150,000gt vessel
will be delivered at the end of 2009 and
the second in 2010. An option exists for
a third ship.
Each vessel will be powered by two
shaftlines, directly driven by two 24MW
slow-speed induction motors. Supplied
through four MV7000 converters using
press-pack IGBT (Insulated Gate Bipolar
Transistor) technology, Converteam says
these motors will help make propulsion
more reliable, more efficient, and more
compact. The induction motor rotor
has no components, such as insulated
windings, exciter, rotating diodes, or
permanent magnets. Rather, it only has
copper bars short-circuited by rings.
Thus, the reliability and the availability
of induction motors are naturally
increased.
Furthermore, the induction motor has
a reduced acoustic noise and vibration
level, improving passenger comfort, and
its simplicity reduces maintenance time
and cost.
Converteam has designed a dedicated
marine HTD (High Torque Density)
induction motor with optimised
cooling, a large air gap, a low resistance
rotor cage to decrease rotor losses,
and a low frequency machine with a
dedicated number of poles.
The Naval Architect February 2008
Colori compositi
37
NA Feb 08 -
p37.indd 37 05/02/2008 09:36:35
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