7/21/2019 Bahan Kuliah Minggu 13 (Electric Propulsion) http://slidepdf.com/reader/full/bahan-kuliah-minggu-13-electric-propulsion 1/28 Electric Propulsion ELECTRIC PROPULSION IS SELECTED IN MANY SHIPS WHICH USED TO HAVE MECHANICAL PROPULSION! Typical DE vessels have been icebreakers, seismic exploration vessels, shuttle tankers, cable ships, pipe layers, cruise liners Pentti Häkkinen /Electric propulsion and systems Wärtsilä New Professionals 3.-7.11.2008 Higher freedom in location of main generator units Diesel engine load can be kept in the optimum range Suitable for ships with high auxiliary power demand; great variation in both propulsion and auxiliary power Electric pod propulsion is an option
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7/21/2019 Bahan Kuliah Minggu 13 (Electric Propulsion)
ELECTRIC PROPULSION IS SELECTED IN MANY SHIPSWHICH USED TO HAVE MECHANICAL PROPULSION!
Typical DE vessels have been icebreakers, seismic explorationvessels, shuttle tankers, cable ships, pipe layers, cruise liners
Pentti Häkkinen /Electric propulsion and systemsWärtsilä New Professionals 3.-7.11.2008
Higher freedom in location of main generator units Diesel engine load can be kept in the optimum range Suitable for ships with high auxiliary power demand; great variation in
both propulsion and auxiliary power Electric pod propulsion is an option
7/21/2019 Bahan Kuliah Minggu 13 (Electric Propulsion)
According to rules for electric propulsion,redundancy is required.i.e. tolerance to failure against short circuit(also fire and flood could be considered)
Normally distributed in 2, 3 or 4 compartments,depending on redundancy requirements andcosts.
System Components – Switchboards
Pentti Häkkinen /Electric propulsion and systemsWärtsilä New Professionals 3.-7.11.2008
Installed power affects normal current and shortcircuit currents. Physical limitations on handlingthermal and mechanical stresses in busbars,and swicthgear.
Various circuit breakers: air, vacuum, gas filled.Vacuum breakers may chop current and causespikes when breaking inductive load.Overvoltage protection maybe necessary.
7/21/2019 Bahan Kuliah Minggu 13 (Electric Propulsion)
• Cycloconverter consists of 3 thyristor bridges, supplied from propulsion switch-board. Bridges are needed to feed positive and negative current into winding
• Basic arrangement for has 36 switching devices (thyristors)• More commonly a propulsion motor has 2 sets of 3-phase windings, each with
its own network of 36 devices• Cycloconverter “constructs” the output voltage wave-form from sampledportions of the supply wave-form. Both 6 pulse and 12 pulse systems possible.
Pentti Häkkinen /Electric propulsion and systemsWärtsilä New Professionals 3.-7.11.2008
7/21/2019 Bahan Kuliah Minggu 13 (Electric Propulsion)
Thyristor controlled rectifier feeds DC link. Invertor side is fed by motor resultingin increased dimensions of motor.By controlling the switching of thyristor pairs, controlled current at variablefrequency is applied sequentially to the motor windings.
At low speeds (5-10 % of rated) EMF too low to perform natural commutation.
Pentti Häkkinen /Electric propulsion and systemsWärtsilä New Professionals 3.-7.11.2008
7/21/2019 Bahan Kuliah Minggu 13 (Electric Propulsion)
Numerical example for 40.000 GRT 1400 pax. cruise liner, 2 * 7.5 MW.Electric variant has 14 extra cabins => added income 1.330.000 USD/a...loses 45.000 USD/a as diesel engine fuel, saves 41.000 as heating fuel,
saves 20.000 as machinery maintenance. Total savings 15.000 USD/a
= > Electric propulsion investment is paid back in 2.2 years!
Electricpropulsion
Gearedpropulsion
Equipment
Pentti Häkkinen /Electric propulsion and systemsWärtsilä New Professionals 3.-7.11.2008