Man B&W S50ME-B9.3-TII, Project Manual

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MAN B&W 4.03
Page 6 of 6
MAN Diesel
198 43 156.3 MAN B&W 98
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50MC/MC-C/ME/ME-C/ME-B/-GI
In such a case, the problem is solved by installing
a small, elastically supported bearing in front of
the stator housing, as shown in Fig. 4.03.05.
As the DMG type is directly connected to the
crankshaft, it has a very low rotational speed and,
consequently, the electric output current has a
low frequency – normally of the order of 15 Hz.
Therefore, it is necessary to use a static frequency
converter between the DMG and the main switch-
board. The DMG/CFE is, as standard, laid out for
operation with full output between 100% and 75%
and with reduced output between 75% and 40%
of the engine speed at specified MCR.
Static converter
The static frequency converter system (see Fig.
4.03.06) consists of a static part, i.e. thyristors and
control equipment, and a rotary electric machine.
The DMG produces a threephase alternating
current with a low frequency, which varies in ac-
cordance with the main engine speed. This alter-
nating current is rectified and led to a thyristor in-
verter producing a threephase alternating current
with constant frequency.
Since the frequency converter system uses a DC
intermediate link, no reactive power can be sup-
plied to the electric mains. To supply this reactive
power, a synchronous condenser is used. The
synchronous condenser consists of an ordinary
synchronous generator coupled to the electric
mains.
Extent of delivery for DMG/CFE units
The delivery extent is a generator fully builton
to the main engine including the synchronous
condenser unit and the static converter cubicles
which are to be installed in the engine room.
The DMG/CFE can, with a small modification,
be operated both as a generator and as a motor
(PTI).
Yard deliveries are:
1. Installation, i.e. seating in the ship for the syn-
chronous condenser unit and for the static
converter cubicles
2. Cooling water pipes to the generator if water
cooling is applied
3. Cabling.
The necessary preparations to be made on the
engine are specified in Fig. 4.03.01a and Table
4.03.01b.
SMG/CFE Generators
The PTO SMG/CFE (see Fig. 4.01.01 alternative 6)
has the same working principle as the PTO DMG/
CFE, but instead of being located on the front end
of the engine, the alternator is installed aft of the
engine, with the rotor integrated on the intermedi-
ate shaft.
In addition to the yard deliveries mentioned for the
PTO DMG/CFE, the shipyard must also provide
the foundation for the stator housing in the case
of the PTO SMG/CFE.
The engine needs no preparation for the installa-
tion of this PTO system.