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The passengers were thrilled by the quietly humming boat which produced hardly any vibrations at all.
1840 kW double electric machine Planesman of a submarine,
to be clearly seen (from bottom to top) gyro compass, rudder angle indicator and telegraph.
U 226, type VII B submarine
The Elektra, the first electrically powered vessel, in 1886
The Permasyn motor optimizes the propulsion of submarines.
The boat. The challenge.
In the end, it was the submarine that made electricity into a necessity for watercraft propulsion. Because underwater travel with steam or combustion engines was impossible and because everything had to be concentrated in a very small space in below-surface vessels, the submarine became the great challenge for electrical engineers in the ship-building industry.
In Germany, the first submarines were built in 1904 – for the navy of the Russian
tsar. And Siemens was involved, with the Siemens factory in Petersburg
supplying the machines for all three boats. When German submarine
production started in 1906, Siemens played a major role in the
continuous improvements and, up to 1918, supplied almost 90 per cent of all electrical machines
and switchboards for the 374 German submarines.
Improved propulsion
Constant improvement and further development of submarine propulsion systems were greatly enhanced thanks to Siemens engineers in the following decades and right up to the present day.
Siemens developed the Permasyn motor, for example, first for the submarines of the German navy and later for submarines of foreign navies as well. This motor combines all the virtues that are so important underwater and can, indeed, be vital: it is relatively small and light, its output is infinitely variable and it runs very quietly; thanks to its high level of efficiency, it makes especially good use of the energy that is available and works reliably and steadily even under extreme conditions.
High temperature superconductors – New solutions
Even now, Siemens sets the pace in the development of new, even revolutionary ship's propulsion systems.
Most importantly, there is the high-temperature superconductor technology (HTS), which makes it possible to build motors and generators that are even lighter and more compact.
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8,100 kW direct-current double motor for driving the middle propeller on the Lenin, an icebreaker (1959).
The Moskva icebreaker with a direct-current propeller drive system of 16,200 kW, breaking an ice layer around 2 m thick (1962).
32,440 kW three-phase synchronous motor, 2.3 kV, speed 121 rpm, for a ship's propeller drive, 1938.
The driving force behind the scenes
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Electricity for icebreakers Outside of submarine construction, the electric motor as a means of ship propulsion always plays a specialist role.
This is not really surprising, given that propulsion is provided by diesel-electric and, rarely, steam-electric drives, which need diesel machines as primary and electrical machines as secondary motors (generator sets). This, however, is readily accepted since the diesel-electric drive has important advantages: the generator sets can be placed anywhere in the ship, separately from the drive motors. When the ship is moving slowly and therefore consumes little energy, individual generator sets are switched off. The degree of utilization and efficiency can thus be optimally adapted at any time. These advantages make them especially suitable for ferries, special ships, offshore vessels and icebreakers.
Motors for icebreakers are the biggest items of direct-current equipment that Siemens has ever supplied. In the nineteen-sixties, the Moscow, the Kiev and the Lenin – all Soviet icebreakers – were each fitted with an 8,100 kW motor from Siemens as well as two machines half this strength. The Deutschland, a ferry which belonged to German Rail (Deutsche Bahn AG) and was built in 1972, had two powerful motors from Siemens on board, each with 7,720 kW.
Today, modern three-phase synchronous motors are used. In the Grand Princess, a cruise ship, for example, two motors of this type with an output of 21,000 kW each provide an economically efficient drive system.
Quiet strength
In the nineteen-thirties, there were several passenger ships with an electric propulsion system. The French ship, the Normandie, with 79,000 gross register tons and four times 30,000 kW had one of the largest electric drive systems that had ever been built. In Germany, for example, the Potsdam and the cruise ship, the Robert Ley, had electric propulsion systems.
For some years now, electricity as a source of energy has been looked at in
Installation of a modern 21,000 kW three-phase synchronous motor One of the two 21,000 kW motors
on the Grand Princess
The Normandie, a cruise ship in 1940
a new light, especially for cruise ships. The reason is that, for luxury liners, extreme speed is not as important as comfort, the latter being achieved by motors that run with very little vibration and produce very little noise.
An ideal drive
The idea for “Pod” drives was not particularly new but Siemens engineers applied their imagination and know-how in order to develop this principle further.
Working with Schottel GmbH, they developed the Siemens-Schottel propulsor.
The electric drive motor is outside the ship in a pod that can rotate 360°. Cooling is provided by seawater flowing around it. For the drive motor, Siemens uses a permanently excited motor such as the Permasyn motor. This drive combines a series of advantages. The whole steering system, for example, can be dispensed with, the ship is more maneuverable as well as being safer and more comfortable and yet there are less vibrations. And
the operating costs are also low. An ideal propulsion system for passenger ships, ferries, tankers, special ships and so on.
Siemens is pleased to report that, once captains have maneuvered a ship with a pod, they never want any other kind of propulsion system for their ship.
The promising future of Elektra’s inheritors
The limited oil reserves and increasing environmental problems are forcing people to think about how the ubiquitous diesel motor can be replaced in ship-building. A lot speaks in favor of fuelcell technology as a source of energy. Direct electric current is produced which has to be converted into propulsion energy in the most efficient way possible – for example with the help of high-temperature superconductor technology (HTS). This still sounds some-what futuristic but Siemens has already helped to develop both technologies to the extent that they are now ready for use in practice. In the foreseeable future, the electric propulsion system for ships will be even more important than it is today.
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*Pod – Like a plane's thrust-unit pod, the pod drive is suspended underneath the ship's stern.