• PTO/GCR
(Power Take Off/Gear Constant Ratio):
Generator coupled to a constant ratio stepup
gear, used only for engines running at constant
speed.
The DMG/CFE (Direct Mounted Generator/Con-
stant Frequency Electrical) and the SMG/CFE
(Shaft Mounted Generator/Constant Frequency
Electrical) are special designs within the PTO/CFE
group in which the generator is coupled directly
to the main engine crankshaft or the intermediate
propeller shaft, respectively, without a gear. The
electrical output of the generator is controlled by
electrical frequency control.
Within each PTO system, several designs are
available, depending on the positioning of the
gear:
• BW I:
Gear with a vertical generator mounted onto the
fore end of the diesel engine, without any con-
nections to the ship structure.
• BW II:
A freestanding gear mounted on the tank top
and connected to the fore end of the diesel en-
gine, with a vertical or horizontal generator.
• BW III:
A crankshaft gear mounted onto the fore end of
the diesel engine, with a sidemounted genera-
tor without any connections to the ship struc-
ture.
• BW IV:
A freestanding stepup gear connected to the
intermediate propeller shaft, with a horizontal
generator.
The most popular of the gear based alternatives
are the BW III/RCF type for plants with a fixed
pitch propeller (FPP). The BW III/RCF requires no
separate seating in the ship and only little atten-
tion from the shipyard with respect to alignment.
Introduction
Next to power for propulsion, electricity produc-
tion is the largest fuel consumer on board. The
electricity is produced by using one or more of the
following types of machinery, either running alone
or in parrallel:
• Auxiliary diesel generating sets
• Main engine driven generators
• Exhaust gas- or steam driven turbo generator
utilising exhaust gas waste heat (Thermo Effi-
ciency System)
• Emergency diesel generating sets.
The machinery installed should be selected on the
basis of an economic evaluation of first cost, ope-
rating costs, and the demand for man-hours for
maintenance.
In the following, technical information is given re-
garding main engine driven generators (PTO), dif-
ferent configurations with exhaust gas and steam
driven turbo generators, and the auxiliary diesel
generating sets produced by MAN Diesel & Turbo.
Power Take Off
With a generator coupled to a Power Take Off
(PTO) from the main engine, electrical power can
be produced based on the main engine’s low
SFOC/SGC. Several standardised PTO systems
are available, see Fig. 4.01.01 and the designa-
tions in Fig. 4.01.02:
• PTO/RCF
(Power Take Off/Renk Constant Frequency):
Generator giving constant frequency, based on
mechanicalhydraulical speed control.
• PTO/CFE
(Power Take Off/Constant Frequency Electrical):
Generator giving constant frequency, based on
electrical frequency control.
Electricity Production
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