1. A Study and Research on the use of Power Electronics and its Relationship on
Propulsion System
M. Haq Nuzul,M. Syazwan Abdullah BMEE
Abstract- This article is a study on the application of power
electronics on shipboards especially on propulsion system
and the various system developments currently being
followed to accomplish better power density. This paper
will also provide an explanation on why these developments
are mostly desired. The paper also reviews the power
electronics application on shipboards, their advantages and
drawbacks, types of electric propulsion and its basic
operating principle. The paper concludes by considering
the application of power electronics on board ships and its
relationship to the propulsion system.
Index Terms – Marine vessel electrical power system,
propulsion system, power electronics, drives, power
electronic applications, electric propulsion
I. INTRODUCTION
The evolution of marine propulsion system is rapidly changing
with a noteworthy drive towards the use of electrical propulsion
and the incorporation of auxiliary and propulsion power
systems. Whether the discussed vessel is a large cruise line
driven by external podded motors, a small highly powered
warship with inboard motors and shafts or an offshore oil
support vessel the need for very flexible, robust and compact
power systems has always been on the rise. This requirement is
being achieved through the most improvements, approaching
on uprising, in power electronic device assembly and their use
for power adaptation and control. The most recent development
of power electronics in marine propulsion system is the
Dynamic Positioning system.
II. POWER ELECTRONICS APPLICATION ON
SHIPBOARDS, THEIR ADVANTAGES AND
DRAWBACKS
Ship propulsion system can be either mechanical or electrical.
Mechanical propulsion system implies the use of the diesel
engine to drive the ship's propelling shaft, while electrical
propulsion is a system consisting of a prime mover ( a steam
turbine, diesel engine, etc.) and a generator, electric motor and
the appertaining equipment (measuring instruments,
converters) which are used to drive these components. Recently
significant advantage has been given to electrical propulsion
due to an easy control of speed and direction of propeller's
revolutions, as well as a possibility of remote control
being effected from several different locations, which
means that, apart from the duty officers, this task can be
performed by other authorized members of the crew. The
latter undoubtedly entails a higher level of personnel
education and training, which further increases the total
cost of operation. However, it has to be regarded as a part
of the overall level of personnel education which tends
to be increasing due to the fact that the same principle is
being applied aboard a ship as is being the case with
power plants ashore. Furthermore, concerning the safety
of navigation considerable advantage is being given to
electrical propulsion over mechanical one since a larger
number of engines and propellers has been proved to
guarantee greater safety of navigation ( in case of a
failure malfunction of one, the load can be distributed
among the others). In the application of the electrical
propulsion a significant role is played by electronic
components which give great possibilities of
management and regulating. These are only some of the
basic advantages which can be only viewed in relation to
the type and size of the ship, the choice of general electric
and power system and bearing in mind other important
parameters.
III. TYPES OF PROPULSION SYSTEM
The type of propulsion system used on a ship depends on
the vessel's requirement. The article describes the main
types of propulsion systems that have been used on ships.
The main engine of a ship is connected to its propeller
with the help of a shaft. This whole system, along with
other vital machineries is known as the ship propulsion
system. The type of propulsion system used in a ship
depends on several factors such as speed, power, ship
type etc.
Since the time man started using ships, various types of
propulsion systems have been used depending on the
ship’s requirement. Using propulsion forces, ships are
able to maneuver themselves in the water. Initially while
there were limited number of ship propulsion systems, in
the present era there are several innovative ones with
which a vessel can be fitted with. Today ship propulsion

2. is not just about successful movement of the ship in the water.
It also includes using the best mode of propulsion to ensure a
better safety standard for the marine ecosystem along with cost
efficiency.
 Diesel Propulsion: Diesel propulsion system is the
most commonly used marine propulsion system
converting mechanical energy from thermal forces.
Diesel propulsion systems are mainly used in almost
all types of vessels along with small boats and
recreational vessels.
Figure 1: Diesel Propulsion Engine
 Wind Propulsion: Wind propulsion emerged as an
alternative to those systems which emit huge
quantities of CO2 gases in the marine atmosphere.
However, the usage of wind turbine marine propulsion
has not started extensively in large commercial ships
because of a requirement of constant windiness. Two
wind propulsion systems for ships that have become
lately are- kite propulsion and sail propulsion for
merchant ships.
Figure 2: Wind Propulsion
 Nuclear Propulsion: Naval vessels incorporate the
usage of nuclear maritime propulsion. Using the
nuclear fission process, nuclear propulsion is a highly
complex system consisting of water reactors and other
equipment to fuel the vessel. The nuclear reactors in
the ships are also used to generate electricity for the
ship. Several merchant ships are also being planned to
be constructed with this propulsion system
Figure 3: Nuclear Propulsion System
 Gas Turbine Propulsion: Gas turbine
propulsion is used for naval as well as non-
naval ships. In case of naval ships, the gas
turbine propulsion system aids in faster
movement of the ships which is necessary in
case of the ship coming under attack.
Figure 4: Gas Turbine Propulsion
 Fuel Cell Propulsion: Fuel cell propulsion
systems use hydrogen as the main fuel
component. Electricity is created in the fuel cell
without any combustion whatsoever. The
process is clean and therefore has been regarded
as a very important alternative marine
propulsion system. There are various types of
propulsion under the fuel cell propulsion head
like PEM (Photon-Exchange-Membrane) and
the molten-carbonate systems.

3. Figure 5: Fuel Cell Propulsion
 Biodiesel Fuel Propulsion: Biodiesel propulsion has
been deemed as a potential marine propulsion system
for the future. Currently tests are being carried out to
find out about the viability of this propulsion system
which is expected to be in full operation by the year
2017.
 Solar Propulsion: Solar propulsion for ships was
utilized for the first time in the year 2008. Solar
propulsion benefits include a high reduction in the
poisonous carbon dioxide emissions. Solar
propulsions are capable of generating a capacitance as
high as 40 kilowatts (kW).
Figure 6: Solar Propulsion
 Steam Turbine Propulsion: Steam turbine
propulsion involves the usage of coal or other steam-
generating fuels to propel the vessel. Steam turbine
maritime propulsion system was highly utilized
between the late 19th and the early 20th century.
Figure 7: Steam Turbine Propulsion
 Diesel-Electric Propulsion: In simple terms,
diesel-electric ship propulsion systems use a
combination of a generator operated by
electricity attached to a diesel motor. The
technology has been in use since the early
1900s. In today’s times, submarines and
merchant ships incorporate the diesel-electric
propulsion system to propel themselves.
Figure 8: Diesel Electric Propulsion
 Water-Jet Propulsion: Water-jet propulsion
has been used since the year 1954. The most
important advantage of water-jet propulsion is
that it does not cause noise pollution and offers
a high speed to the vessels. In contrast the
water-jet propulsion as a ship propulsion system
is costlier to maintain which can cause problems
to the user.
Figure 9: Water-Jet Propulsion
 Gas fuel or Tri Fuel Propulsion: LNG fuel is
now utilized to be burnt in the Main Engine
after adopting some modification in the
propulsion engine to reduce emission from the
ship. It is known as tri fuel because it can burn
gas fuel, diesel and heavy fuel.

4. Figure 10: Gas fuel or Tri Fuel Propulsion
The various types of propulsion systems offer their own unique
advantages to a vessel. Depending on the necessity and the
requirement, the best type of ship propulsion system needs to
be fitted. Only then the vessel will be able to offer its optimum
service capacitance.
IV. UNDERSTANDING ELECTRICAL
PROPULSION SYSTEM AND ITS
OPERATING PRINCIPLE
Electrical propulsion was used extensively during the days of
Second World War, when the ships had steam turbines as their
prime movers, along with electrical drives and large gearboxes.
However, nowadays most electrical drives have medium or
high speed diesel engines as their prime movers. The only
disadvantage of the electrical drive is that it is extremely
expensive in the first cost when compared with geared drive.
This is mainly because of lower mechanical efficiency, which
leads to more fuel consumption and cost.
In earlier times, DC motors were used with the electrical drives
and the ships used to have completely separate electrical system
for propulsion and other purposes. But after the invention of
marine type thyristor converters the ships are able to connect
all their machineries to one single electrical system, just as in a
power station. Thus the power for the propulsion system,
marine auxiliary machineries, and ship’s hotel load all comes
from a common energy pool. Generators are also used with the
main engine to get the near peak efficiency.
Also, combining all the electrical power sources into one
system has drastically helped in reducing the extra costs and
method is chosen for almost all the ships now. The system is
suitable especially for ships with high power requirements such
as large cruise liners and specialist ships such as research
vessels, ice breakers, fish factory ships, oil production and
drilling vessels, cable laying ships etc. An electrical drive is
thus advantageous for a ship that has a large non propulsion
electrical load or for a ship wherein the number of propulsion
devices are installed throughout the ship e.g. dynamically
positioned offshore vessel.
Apart for this, advantages of electrical propulsion also include
drastic reduction in noise and vibration levels, power for the
occasional use of bow thrusters without the help of any
other power source, and smooth operate on very low
speeds with high level of reliability. Moreover, an
electrical propulsion system can be easily maintained
and repaired. It provides the facility of using all
machineries on one fuel type. The requirement of spares
is also absolutely low. The system can work on low grade
fuels, increasing the cost efficiency of the whole
operation.
The shipping industry has come a long way as far as
R&D for reducing costs of propulsion without increasing
marine pollution is concerned. The conventional
propulsion system of the ship is efficient but requires
high operating costs and increases the marine pollution.
Among all the prospective alternate power sources,
electrical propulsion system is one of the best tried out
alternative in today’s time.
1. UNDERSTANDING THE SYSTEM
The electric propulsion system consists of a prime mover
which may be of two types:
 Diesel driven
 Turbine or steam driven
Both the systems produce less pollution as compared to
conventional marine propulsion system, which involves
burning of heavy oil. The propeller shaft of the ship is
connected to large motors, which can be D.C or A.C
driven and are known as propulsion motors. Power for
propulsion motor is supplied by the ship’s generator and
prime mover assembly.
Figure 11: Electrical Propulsion System
2. ARRANGEMENT OR OPERATION
The generator can be direct or alternating current type
with diesel or steam driven prime mover, depending
upon the requirement or demand of the owner/ship.
In the electrical propulsion system, the direction of the
rotation of propeller is governed by either the electrical
control of the motor itself or by changing the electrical
supply. Normally variable speed electrical motor is used

5. for fixed pitch propeller system and constant or variable can be
used for variable pitch propeller or CPP.
Figure 12: example of design
3. APPLICATIONS
Normally electrical propulsion is used in small vessel but now
a day shipping companies are adopting this system for big size
cargo vessel as well. Generally electrical propulsion is fitted in;
 Tugs and trawlers
 Dredgers
 Dynamic Positioning Vessels
 Cable laying ship
 Ice breakers
 Research ship
 Floating cranes
 Vessels for offshore industries
V. CONCLUSION
The development of marine electrical power systems has been
extremely rapid over the last two decades and this has been due
to developments in the topology and construction of both power
electronic switches and power converter themselves.
These under-pinning device and equipment
developments have formed the enabling technology for
the implementation of power electronic in propulsion
systems in both warship and commercial vessels. As
such, the power electronic community has exerted a
revolutionary effect on marine engineering resulting in a
common development thread and ambition across the
world.
ACKNOWLEDGEMENT
This research has been carried out at Universiti Kuala
Lumpur Malaysian Institute of Marine Engineering
Technology (UniKL MIMET). UniKL MIMET and the
respective lecturers are acknowledged as without their
assistance this paper could not have been achieved.
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