CHAPTER 5 20 KW SHIP AUXILIARY GENERATOR SET
SECTION I. Description and data
5-1. Description. The 20 kW SAG set supplies limited amounts of electrical power for the barge when ROWPU systems
are not in operation. It provides sufficient power for operating normal lighting, dayroom equipment, workshop equipment,
and battery chargers. It must never be used to provide power for any major system onboard.
This generator set consists of a Perkins Model 4.236M engine and a Newage Stamford SC144E generator
mounted, with vibration isolators, on a common base. It has free standing switching gear and is capable of parallel
operations. The set weighs 1300 pounds dry and 1451 pounds wet and is 74 inches long, 26 inches wide, and 40 inches
high. Installation is shown in engineering drawings listed in Appendix A.
The Perkins 4.236M engine is a 236-cubic inch inline, four cylinder, four-stroke diesel specifically built for use in a
maritime environment. It has direct injection, with a 16:1 compression ratio and is rated at 72 horsepower (hp) at about
2500 rpm. The engine has a heat exchanger using seawater to cool both engine coolant and engine oil and a 24 V electric
starter. The battery pack on the engine is charged by a battery charger built into the switchboard in the ROWPU space.
The Newage Stamford SC1 44E generator is a brushless, revolving field machine. It is based on a fabricated
frame and cast iron end brackets with a large sheet metal terminal box mounted on the non-drive end. The stator/rotor is
made from low loss electrical grade sheet steel laminations with special building techniques to provide an extremely rigid
core to withstand vibration and load impulses. A high-grade, precision-machined shaft carries the rotor assembly. For a
more detailed technical description, refer to manufacturers manuals listed in Section VI of this chapter.
5-2. Capabilities. This auxiliary generator set provides electrical power necessary for normal occupancy of the barge
when major ROWPU systems are NOT operating. It will provide continuous power under these conditions. For load
transfer purposes only, it may be operated, for a very short time, in parallel with either of the two SSGs.
5-3. Special limitations. This generator set cannot be operated in parallel with power from the shore power receptacle. It
cannot be used to provide power for any major systems onboard. It must be used only to provide power for normal
nonoperating occupancy and housekeeping equipment.
5-4. Performance characteristics. The auxiliary generators voltage regulation is maintained within the limits of t2 percent
from no load to a full load. This includes cold to hot variations at any power factor between 0.8 lagging and unity and
inclusive of a speed variation of 4.5%. Total distortion of the voltage waveform, with open circuit between phases or
between phases and neutral, is on the order of 2%. On a 3-phase, balanced, harmonic-free load, total distortion is on the
order of 3.5%. Electrical output characteristics at an 0.8 power factor are listed below: