Dummies Guide to Marine Electrical Systems

Suppose that you are stranded on a deserted island. All the residents of the island are already dead due to an epidemic outbreak of a deadly virus; a situation similar to what happens in the famous movie, Resident Evil. The residents of the island were in the process of constructing a beautiful ship when they were struck by the virus. The ship is almost complete but only the installation of the marine electrical system remains. You are the sole survivor and the ship is your only lifeline that will take you away from the island. Quite a hypothetical situation, but assume you are confronted with one. How will you install the marine electrical system?

You know this much - that to supply power to any system you need something that generates power. You got it!! Generators. What are the basic things you need to know about generators on ship?

Generators

The generator is the heart of the ship. The electrical system should be characterized in such a way that it supplies sufficient energy to all systems of the ship and for that it is extremely essential that the correct sizing of the generators is done. The correct sizing of the generator is the key to a safe, workable and economic electrical system. The size of the generator depends on the load. The load often varies or undergoes swings as the generator is connected to various other elements such as motors, heating elements and air conditioning systems. Therefore, considerable care should be taken for generators are susceptible to heavy system load swings.

Every ship must have at least two generators which have their individual diesel engines. But running them through out the voyage is expensive and uneconomical as far as fuel consumption is concerned. Thus every ship should have at least one generator that is attached to its propulsion system.

It’s always advisable that a ship should have three generators. One that is connected to its propulsion system and the other two having their own prime movers. That way if one fails the other two are sufficient to take the load with all the load swings.

So now you know what is the main thing you will require for an electrical system. Let’s chalk down what are the other important elements.

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The second important thing that we will require is motors and their controls. Motors are used onboard to run various auxiliaries such as fuel and lubrication oil services, ventilation systems, water circulation etc. All these motors are controlled from a group motor controller which is located at a convenient position such as a machinery control room or in the engine room itself. The most economical way is to provide local starters for each motor supplied from main power panels located in the same or adjacent rooms.

Nowadays most of the ships have a centralized machine control system where all the motors are connected to a machinery control room with the help of cables which are then connected to push button startups located on centralized machinery control console. This is the most efficient and user friendly arrangement which is used by almost all ships today.

This will provide you a bird’s eye view of how and where the motors and their controls need to be installed:

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click to enlarge

One more important thing is the main switch board. All the machineries on ship that consume electrical power should be connected to a main switch board. The system should be designed in such a way that under all normal conditions of operation, power should be distributed from main switch board.

The main switch boards are located in the center of the distribution or in engine control room. They should be installed in such an area that in time of emergency such as fire or flooding, they should be easily accessible. Thus they should be installed in spaces away from the main machinery spaces.

Read on to find out more about emergency power systems in on ships.

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click to enlarge

_{Image References}

^{engine room console - www.farm2.static.flickr.com}

^{motors arrangement- www.nafts.net}

^{shaft generator - www.rynoenterprises.us}

^{generator arrangement - www.boatnerd.com}

^{main switch board - www.ptpco.co.kr}