P&O Nedlloyd planned to build a fleet of large Post-Panamax container ships to operate between the Far East and Europe. These ships, of 80942 gross tonnage, have accommodation for 6700 containers, over 700 of which can be refrigerated containers-representing a substantial load on the ship's electrical supply. The ships are each propelled by a single 90000 HP (65 MW), 100 rev/min diesel engine. These ships are each designed with a 6.6 kV, 60 Hz main distribution system. During cruising at sea, up to 3.5 MW of electrical power is extracted from the ships' main diesel engine/propeller shaft via a salient pole shaft generator fitted to the main propeller shaft. Four diesel-engine driven, 3.6 MW generators are also installed to operate when power is not available from the shaft generator system, in port or during slow speed manoeuvring. Automatic no-break transfer between the generators is provided. The output of the shaft generator itself is at a low variable frequency, determined by the shaft speed. The output to the 6.6 kV system is changed up to a constant 60 Hz by a variable input frequency synchroconverter. The power system is supervised and controlled by a power management system employing a dedicated microprocessor controller. This paper describes the design of the rotating machine and variable speed drive components of this power system configuration. The following parts of the system are described: power system; shaft generator; variable frequency converter and its associated synchronous condenser; and control system.
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