CHAPTER 4 155 KW SHIP SERVICE GENERATORS
4-1. Description. Two diesel powered generator sets, each rated at 155 kW, serve as primary electrical power sources
for the barge. When shore power is not used, one SSG must be online when any of the ROWPU major systems are being
operated. These SSGS, number 1 in void 4 port and number 2 in void 4 starboard, are Caterpillar diesel engine driven
generator sets. Each SSG consists of a Caterpillar 3306TA diesel engine and a Caterpillar Model SR4 generator mounted,
with isolation isolators, on a common base. The set weighs 3960 pounds dry and 4180 pounds wet and is 118 inches long,
39 inches wide, and 59 inches high. The third generator set, rated at 20 kW, supplies power for the barge when ROWPU
major systems are not operating and there is a lower demand for electrical power. Information on the SAG is in Chapter 5.
Generator set installation and electrical hookups are shown on drawings listed in Appendix A.
3306TA diesel engine. This engine is a 6cylinder inline, 638-cubic inch displacement, four-stroke cycle diesel.
Turbocharged and after cooled, it provides its maximum output at 1800 rpm. It has a 24 Vdc electric starter and battery
bank. A battery charger mounted in the switchboard keeps the SSG batteries charged. A heat exchanger provides
seawater cooling for both engine coolant and engine lubricating oil. Instrumentation includes an engine service meter
calibrated in hours and protective cutoffs that activate in the event engine coolant temperature or oil pressure exceed
maximum allowable limits.
SR4 generator. This generator has a revolving field and is statistically regulated with a rotating brushless
exciter. It has no brushes or commutator and uses a solid-state automatic voltage regulator. For a more detailed technical
description, refer to manufacturers manuals listed in Section VI of this chapter.
4-2. Capabilities. Either SSG is capable of providing all electrical power for barge operations. For load transfer purposes
only, SSGs can be operated in parallel with each other or either one can be operated in parallel with the auxiliary
generator. With full barge fuel tanks, the SSGs can operate nonstop for 7 days. The supply of other consumables used
by the electrical power system, such as lubricating oil, will last 30 days.
4-3. Special limitations
The SSGs consume fuel at about 12.7 gph at 100 percent of power at 1l80 rpm and as low as 4.2 gph at25
percent of power at the same rpm.
SSGs will not operate in parallel with an external power source.
SSGs are designed to operate at ambient temperatures of -22 to 1 220F
4-4. Performance characteristics. The voltage level can be adjusted within ±5 percent of rated voltage. Voltage droop is
adjustable for proper division of reactive kVA when operating in parallel with other generators. Voltage gain is adjustable to
compensate for engine speed variation when operating with a speed droop governor. Full load rpm is 1800; low idle is
1200 rpm. Electrical output characteristics at an 0.8 power factor are listed below:
4-5. Equipment specifications. Engine and generator specifications are outlined in paragraphs 4-5.1 and 4-5.2.
Additional information is in manufacturers' manuals provided in Appendix B.