Special-purpose cargo vessel delivered

Designed to offer exceptional capacity and high stowage flexibility, the newbuilding and the sister ship “Jaguar” are said to represent a major advance in diesel-electric propulsion systems as they use DC current for enhanced versatility and efficiency as one of the first operational commercial vessels. Alewijnse Marine Systems was responsible for the design, the installation and the commissioning of the complete electrical installations on both vessels, including the third-generation DC diesel-electric propulsion systems. The 107m-long “Abis Dover” is owned by Abis Shipping and operated by Amasus Shipping BV. It has a dwt of 6,000 tonnes and is equipped with a dynamic position system (DP). All diesel engines are replaced with six, much smaller, Scania diesel generators, positioned at the aft end of the hull in convenient locations. Instead of propeller shafts the propulsive power comes from steerable Z-drive thrusters.
Alewijnse Marine Systems together with Vacon developed a diesel-electric system that uses DC current. These generators can run at different speeds simultaneously, giving a larger flexibility in selecting overall power outputs and as a consequence the possibility of better fuel economy. It also removes the requirement for complex control apparatus. To address the issue of harmonics, Vacon designed an AFE (active front end) AC/DC rectifier into the system feeding into a 750 Volt DC bus. This in turn feeds variable frequency AC/DC inverters to power the Z-drive thrusters and bow thrusters, all of which are AC motors.
Only one or two of the six generators will be needed in DP-mode while all are required for full propulsion at maximum tonnage. All remaining motors for pumps, winches and other onboard systems are fed by either fixed or variable speed inverters depending on their design. A power management system designed and installed by Alewijnse, along with the remaining onboard electrics, is said to ensure that the optimum number of generators delivers the correct amount of current at any time.
The “Abis Dover” has just completed a series of sea trials and is now on her maiden commercial voyage.