AZIPOD (Azimuthing Podded Drive)
Azipod® is the electrically driven propulsor with an AC motor incorporated in a streamlined azimuthing pod unit directly driving a fixed-pitch propeller. The motor is controlled by a frequency converter, which produces full nominaltorque in either direction over the entire speed range, including standstill. Over torque can also be utilized e.g. in ice-going vessels. Each Azipod propulsion system is individually designed and optimized to achieve maximum performance. The name “Azipod” is a registered trade mark of ABB.
The idea of placing an electric motor inside a submerged propulsion pod has been around for some time but it was not until the late 1980s the Kvaerner Masa-Yards teamed with ABB Stromberg Drives to develop the first practical podded main propulsion system. The 1.5MW Azipod propulsion unit was installed on the waterway service vessel, SEILI delivered in December 1990. In 1994 the existing propulsion installation of the 16,000dwt Arctic tanker UIKKU was replaced by a cycloconverter-controlled 11.4MW Azipod drive. Sea trial results were encouraging: the same trial speed at the same shaft speed was achieved as in the original trials, however, remarkable improvements were found in the manoeuvrability. See also Electric podded propulsors.
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HARMONY OF THE SEAS, the largest cruise ship in the world, is provided with three ABB 20 MW frequencyconverter-controlled Azipod propulsion units. This arrangement was chosen to provide improved efficiency, excellent manoeuvrability and less vibration operation. For the shipyard, fitting a pod drive system is a single lift operation instead of installing and checking thrust bearing, shaftlines, sterntubes, seals and possibly gearboxes.
- Compact Azipod – The propulsion system with a power range from 1000kW up to 7MW aimed at ferries, costal ships and offshore vessels. Unlike the ordinary single or double wound synchronous AC motor of conventional Azipod concept, the Compact Azipod unit incorporates a permanent magnet synchronous motor and therefore has no cooling on the rotor. Due to this the construction of Compact Azipod thruster is simpler and more compact, either not needing a separate cooling system at all when it is cooled completely by the surrounding sea, or having a hybrid cooling with surrounding sea and small air cooling system. Compact Azipod has also an option with asynchronous motor with hybrid cooling.
Among vessels provided with Compact Azipod there are:
- HMS ECHO & HMS ENTERPRISE, 2x1700kW,
- Platform Support Vessel VIKING AVANT 2x3000kW,
- UT 745-E Platform Supply Vessel NORMAND FLOWER, 2x2300kW.
- CRP Azipod – The combination of the shaft-driven main propeller and the podded propulsor located on the same axis, but without any physical connection. The arrangement works as the contra-rotating propellers and is said to give an improvement of over 10% in hydrodynamic efficiency for fast ferries and ultra-large containership. See also CRP-Azipod propulsion of the ferries AKASHIA and HAMANASU.