Chapter 3 AC Power Distribution System

CHAPTER 3 AC POWER DISTRIBUTION SYSTEM Almost every function performed aboard a naval ship depends upon electric power for its accomplish- ment From the launching of missiles against an aggressive force to baking bread for lunch, electric power is vital to a ship’s ability to accomplish its mission. The ship’s service electric plant is equipment that takes the mechanical power of a prime mover and converts it to electrical energy. The prime mover may be driven by steam, gas turbine, diesel, or motor. The mechanical energy of the prime mover is converted to electrical energy in the ship’s service generators. These generator sets supply power to the ship’s ac power distribution system for further distribution to the various electrical loads throughout the ship. The ac power distribution system aboard ship consists of the following: � Ac power plant. � Switchboards that distribute the power. � The equipment that consumes the power. The power distribution system is comprised of the following: � Ship’s service power distribution system. � Emergency power distribution system. � Casualty power distribution system. ELECTRICAL DISTRIBUTION SYSTEM The electrical distribution system is the link between the ship’s source of electrical power and the ship’s electrical loads. Power is normally supplied from the ship’s own generators but can be supplied from an external source through the shore power cables. Most ac power distribution systems in naval ships are 450-volt, three-phase, 60-Hertz, three- wire systems. Bus ties interconnect the ship’s service generator and distribution switchboards so any switchboard can be connected to feed power from the generators to one or more of the other switchboards allowing the generators to operate in parallel. In large installations (fig. 3-1), power from the generators goes through distribution switchboards or Figure 3-1.-Power distribution in a large combatant ship. 3-1