PDF《Case story | VACON? NXP Liquid》

Case story | VACON? NXP Liquid Cooled Drive 38% reduction in fuel consumption Fuel savings with Danfoss Drives at the heart of electric hybrid ferries drives.

danfoss.com CMAL is the asset owner for the ferries operated by CalMac Ferries Limited, the company that provides almost all of the ferry services to Scotland'

s offshore islands. Following confirmation of funding from the Scottish Government and the European Regional Development Fund in 2011, CMAL embarked on a project to develop electric hybrid ferries that would create new benchmarks for fuel economy and low environmental impact. After carrying out detailed evaluations of several alternative approaches to the project, which included high-efficiency diesel-mechanical and diesel-electric systems, the CMAL team concluded that the solution that offered the greatest benefits would be an electric hybrid propulsion system. Essentially this comprises diesel engines driving generator sets to produce power for electric motors that drive the vessel'

s propulsion units, just like a conventional diesel-electric propulsion system. A key feature of the hybrid arrangement, however, which sets it apart from traditional diesel-electric systems, is that the propulsion motors can be powered not only from the generator sets, but also from high- capacity energy storage batteries. In the CMAL vessels, these batteries are charged overnight from shore supplies while the vessels are in dock, which means that advantage can be taken of low-cost off-peak electricity. To turn this concept into reality in the form of an innovative ferry with high-efficiency hybrid diesel-electric- battery propulsion, CMAL worked with Ferguson Shipbuilders of Port Glasgow, ship design specialists Seatec, and electrical specialists Tec-Source. The initial contract covered the design, construction and fitting out of two ferries C the MV Hallaig, destined for use on the Sconser-Raasay route, and the MV Lochinvar, for the Tarbert to Portavadie route. As part of its commitment to supporting Scotland'

s target of achieving a reduction in environmentally damaging emissions by 2020, Caledonian Maritime Assets Limited (CMAL) has developed a groundbreaking diesel-electric hybrid propulsion system for its newest roll-on/roll-off (RORO) ferries. Equipped with variable speed drives from Danfoss, this system is achieving fuel savings of up to 38% with a commensurate reduction in emissions.

2 The propulsion system devised for the ferries has three diesel-driven

368 kVA three-phase generator sets operating at

400 V,

50 Hz. These feed the vessel'

s main switchboard, which also has provision for connection of a shore supply when the vessel is in port. The switchboard provides power for two VACON? NXP-series liquid-cooled variable speed drives from Danfoss. Each of the drives controls one of the vessels'

two propulsion motors, which are rated

375 kW and have an operating speed range of

0 to

615 rpm. The motors drive Voith Schneider Propellers that combine propulsion and steering in one unit. To make provision for pollution-free operation of the propulsion motors from batteries, each of the VACON? NXP variable speed drives has a

350 kWh lithium-ion battery bank connected to its DC link. This arrangement is particularly convenient and cost- effective as, with NXP-series drives, no additional electronics or control circuitry is needed for the batteries. We had many reasons for choosing Danfoss drives for this flagship project, said John Salton, Fleet Manager and Project Director at CMAL. They'