China Shipbuilding Industry Corp said its Wuhan Institute of Marine Electric Propulsion finalized its integrated electric propulsion technology in mid-July. It said the in-house development will help the nation wean itself off the longstanding dependence on imported parts in manufacturing ships.
Most surface vessels in China use mechanical transmissions and are propelled by a motor or an engine spinning a propeller. Many Western countries have adopted integrated electric propulsion, in which gas turbines or diesel generators produce electricity that powers electric motors.
The development of integrated electric propulsion may resolve engine problems that have long haunted the nation and its navy. One of the major issues has been a lack of domestic companies who can make gas turbine engines to support long distance voyages.
Without domestically developed gas turbine engines, the Chinese navy has been forced to import foreign engines for its ships, said a military expert who did not want to be named. And until an electric propulsion engine is more widely available in China, most ships must run on an engine fueled by diesel and gas.
“Compared with other drive methods, integrated electric propulsion has many advantages. It can save more space and is easier to control. It helps reduce a ship’s weight and noise,” Wang said. “It also enables ships to cruise at a faster speed and for a longer time.”
The British navy’s HMS Queen Elizabeth aircraft carrier and the United States navy’s Zumwalt-class destroyers, which are all under construction, will use the new electric propulsion technology, which means we must accelerate our development (of the technology) if we don’t want to fall behind in building advanced ships.”
The HMS Queen Elizabeth, which is scheduled to commence sea trials in 2017, will be the first carrier in the world to adopt integrated electric propulsion.
Integrated electric propulsion (IEP) or full electric propulsion (FEP) or integrated full electric propulsion (IFEP) is an arrangement of marine propulsion systems such that gas turbines or diesel generators or both generate three phase electricity which is then used to power electric motors turning either propellers or waterjets. It is a modification of the combined diesel-electric and gas propulsion system for ships which eliminates the need for clutches and reduces or eliminates the need for gearboxes by using electrical transmission rather than mechanical transmission of energy.
Eliminating the mechanical connection between the engines and the propulsion has several advantages including increased freedom of placement of the engines, acoustical decoupling of the engines from the hull which makes the ship less noisy, and a reduction of weight and volume. Reducing noise is particularly important to naval vessels seeking to avoid detection and to cruise ships seeking to provide passengers with a pleasant voyage, but is of less benefit to cargo ships. Because ships anyway require electricity even when not underway, having all of the engines produce electricity reduces the number of engines needed compared to more traditional arrangements in which one pool of engines provides electricity and another pool of engines provides propulsion, reducing capital costs and maintenance costs.
On a strictly motor-to-motor comparison, the advanced motor technologies may be 50-75% less massive and occupy 20 – 70% less volume than the state-of-the-art motors. However, when ALL system changes necessary to incorporate the advanced motor technologies are accounted for, the total power systems based upon advanced motor technologies may be 10 – 20% less massive and occupy up to 10% less volume than the total power systems based upon state-of-the-
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