Cruise ship to retrofit permanent magnet tunnel thruster

JANUARY 15, 2015 — Rolls-Royce says that Norwegian Cruise Line has selected a Rolls-Royce permanent magnet tunnel thruster to upgrade the propulsion package onboard the 4,100 passenger cruise ship Norwegian Epic, delivered in 2010 by shipbuilder STX France.

According to Rolls-Royce, the permanent magnet tunnel thruster offers numerous advantages over traditional tunnel thrusters including significant reduction in noise and vibration, an increase in power output of around 25% from the same size propeller, and is removable underwater eliminating the need for dry docking.

“We are delighted that Norwegian Cruise Line is the first cruise customer to select our new permanent magnet tunnel thruster as an upgrade to an existing propulsion package,” said Jay McFadyen, Senior Vice President – Marine Services, Americas, Rolls-Royce. “Passenger comfort is a top priority for cruise lines, and the reduction of both noise and vibration, which our permanent magnet technology provides, is of paramount importance to successful cruise operators like Norwegian.”

Mr. McFadyen said the permanent magnet technology is suitable for a range of applications in both merchant and offshore vessels, where exceptionally low noise levels, high power output, and rapid response to power demand will benefit operators, crew and passengers.

“What we have seen so far through the experience of our first permanent magnet tunnel thruster in operation on the Rolls-Royce designed Olympic Octopus, a highly advanced offshore anchor handling vessel, is that a permanent magnet motor thruster is quiet, efficient and durable,” he said. “It is capable of running for thousands of hours in intensive dynamic positioning (DP) mode, where rapidly varying loads and alternating thrust directions are the norm.”

The permanent magnet tunnel thruster design concept comprises a permanent magnet motor in a rim, which drives the propeller in the center. The permanent magnet motor consists of two main parts – a stator that carries a number of electrical coil windings, and a rotor fitted with a number of very strong permanent magnets. A rotating magnetic field is created by the stator which interacts with the fields of the permanent magnets on the rotor, which generates force to drag the rotor around, providing the mechanical power.

Other benefits of permanent magnet technology include the freeing up of space directly above the thruster where traditional tunnel thruster motors are located, and a symmetrical design that gives equal thrust to port or starboard. It is available in 1,600mm and 2,000mm diameter.