8 · vacon
General
Tel. +358 (0)201 2121 • Fax: +358 (0)201 2121 205
1
1.4
Shaft Generator
The shaft generator is a system where the generator is connected to the main engine shaft that also
runs the main propulsion. The disadvantage is that the main engine must run at nominal speed even
if full power to the propeller is not necessary.
With the shaft generator system power goes through the drives. One converts power from the
generator to DC link, and the other makes a ship grid with constant 50 Hz or 60 Hz. Thus there is no
direct connection to generator. The main engine can run at a more efficient speed without changing
grid frequency.
One drive operates as an AFE on the generator side and the other operates on Island mode or Micro
Grid mode on the grid side.
-
The start command to generator side drive.
-
Both drives can make DC charging if powered by +24 Vdc.
-
When DC is at an 80% of nominal, the generator side and the grid side breakers close.
-
The generator side AFE is started to boost DC first.
-
The grid side Grid Converter is started and will synchronise to grid.
-
The drives take power from the bypass, and the PMS opens the SG contactor.
-
You can decrease the speed of the main diesel engine to be more economical.
NOTE! If it is necessary to have these systems in parallel, the system bus communication is
reserved for parallel Micro Grid units on the grid side. The control must be arranged separately for
each drive.
G1
T3
Auxilliary loads
including single
phase loads
T2
Sh
ip
G
ri
d
U4
U3
UDC
U2
=
~
=
~
Filter
Filter
ST
BT
G2
SG
U5
Q2
Q4
U5
Q1
Q3
D7
T1
Figure 5.