CUVX Design Report - the AOE home page - Virginia Tech

CUVX Design – VT Team 2 Page 644.4.4 Endurance Fuel CalculationAn endurance fuel calculation is performed for the endurance range of 4000 nm at endurance speed inaccordance with DDS 200-1. The endurance range was selected in concept exploration. The 24 hour averageelectric load is used to estimate the fuel required for ship service electrical power. The endurance fuel calculation isshown in Figure 57.4.5 Mechanical and Electrical SystemsMechanical and electrical systems are selected based on mission requirements, standard naval requirements forcombat ships, and expert opinion. The Machinery Equipment List (MEL) of major mechanical and electricalsystems for CUVX HI3 including quantities, dimensions, weights, and locations is included in Appendix D.2. Themajor components of the mechanical and electrical systems and the methods used to size them are described in thefollowing two subsections. The arrangement of these systems is detailed in Section 4.9.4.5.1 Integrated Power System (IPS)Due to the Navy’s commitment in all-electric ships and the potential synergy with electro-magnetic catapults,integrated power system options were considered for CUVX and selected for CUVX HI3. Solid-state powerelectronics devices utilizing programmable microprocessor based digital control, such as silicon controlled rectifiers,thyristors, and more recently, isolated gate bipolar transistors (IGBTs), make it possible to utilize fixed frequencyalternating current generator sets supplying a common bus which feeds both propulsion and ship service loads. Theapplication of fixed frequency AC input, variable voltage DC output propulsion motor drives became common inicebreakers, tugs and offshore supply vessels in the 1970’s. In the early 1980’s, fixed frequency AC input, variablefrequency AC output propulsion motor drives began to be applied in icebreakers, ferries and passenger cruisevessels. It is this type of plant which has become increasingly popular in commercial and naval ships for both newconstruction and conversions, the most notable conversion being the 1987 re-powering of the Queen Elizabeth 2from geared steam-turbine propulsion to AC diesel electric propulsion utilizing two 60,000 HP propulsion motors.Major cruise lines such as Carnival, Royal Caribbean and P&O Princess Cruise Lines are ordering increasinglylarger ships with integrated AC electric propulsion plants.Figure 58 shows the one-line diagram for CUVX propulsion and ship service power. CUVX’s 5 main dieselengines (MGDs) and generators provide electrical power to the propulsion switchboards. The electric powerdistributed from the propulsion switchboards for propulsion is sent to propulsion power converters which control thespeed of the ship by varying the frequency to the 2 propulsion motors. Each propulsion switchboard is connected toboth propulsion motors for redundancy and survivability and the power converters have 3 parallel elements. Thepulse power for EMALS is taken from a switch at the power converters.To support the IPS power specified in the ELA, Table 35, the main diesel generator sets are rated at 7755 kWeach. The propulsion motors are AMS A/C synchronous motors from ABB rated at 14000 kW each as specified inSection 4.4.2. This satisfies the power requirement with a 1.25 margin on CUVX HI3’s shaft horsepower forsustained speed. There is one propulsion motor per shaft. Each MDG set provides 4160 volt, 3-phase, 60 Hz powerto its main switchboard. The ADG sets provide 480 volt, 3-phase, 60 Hz power to separate ship serviceswitchboards but this power may also be routed to the propulsion bus. The generator sets each have a generatorcontrol panel for local control, and may be automatically or manually started both locally and remotely from theEOS. Automatic paralleling and load sharing capability are provided for each set. The propulsion motors arecapable of infinite speed control from 0 to full rpm. Two shafts may be operated at all times thereby eliminating theneed for trailing a shaft during low speed operations. Each propulsion motor includes an integral thrust bearing;shaft lock; turning gear; and dual stator windings. Power to each propulsion motor is supplied from two 60 Hz fixedvoltage and frequency input, variable voltage and frequency output, IGBT propulsion drives with associatedisolation transformers. In addition, harmonic filters are provided for compliance with the ship service distributionsystem power quality requirements. The total efficiency of this electric propulsion system is estimated to be 93% atfull power.4.5.2 Service and Auxiliary SystemsTanks for lube oil, fuel oil, and waste oil are sized based on requirements from the Ship Synthesis model. Fuelservice tank requirements are based on a capacity to run for 18 hours. The pumps needed for fuel and lube oilservice and transfer are based on similar ships. Where necessary, two pumps are installed, one for use and anotherfor redundancy. These pumps are located either in the Main Machinery Rooms or the Auxiliary Machinery Room.