Woodward 2301D, Инструкция по установке и эксплуатации, Страница: 96 / 130

2301D/2301D-EC Digital Control Manual 26247
88 Woodward
Isochronous Mode
Isochronous means repeating at a single rate or having a fixed frequency or
period. A generator set operating in the isochronous mode will operate at the
same set frequency regardless of the load it is supplying, up to the full load
capability of the generator set (see Figure 6-6). This mode can be used on one
generator set running by itself in an isolated system.
Figure 6-6. Isochronous Mode
The isochronous mode can also be used on a generator set connected in parallel
with other generator sets. Unless the governors are load sharing and speed
controls, however, no more than one of the generator sets operating in parallel
can be in the isochronous mode. If two generator sets operating in the
isochronous mode without load sharing controls are tied together to the same
load, one of the units will try to carry the entire load and the other will shed all of
its load. In order to share load with other units, some additional means must be
used to keep each generator set from either trying to take all the load or from
motoring.
Droop/Isochronous Load Sharing on an Isolated Bus
Droop/isochronous load sharing combines the first two modes. All generator sets
in the system except one are operated in the droop mode. The one unit not in
droop is operated in the isochronous mode. It is known as the swing machine. In
this mode, the droop machines will run at the frequency of the isochronous unit.
The droop and speed settings of each droop unit are adjusted so that each
generates a fixed amount of power (see Figure 6-7). The output power of the
swing machine will change to follow changes in the load demand. Maximum load
for this type of system is limited to the combined output of the swing machine and
the total set power of the droop machines. The minimum system load cannot be
allowed to decrease below the output set for the droop machines. If it does, the
system frequency will change, and the swing machine can be motored. The
machine with the highest output capacity should be operated as the swing
machine, so that the system will accept the largest load changes within its
capacity.