Skip to main content

High voltage

Voltages up to & Including 1000V is known as Low voltage system and Voltages 1001 and above is called as High Voltage system in maritime practice for ships.
Why High Voltage in Ships
  • Higher power requirements onboard vessels is the foremost reason for the evolution of HV in ships.
  • Higher power requirements have been necessitated by development of larger vessels required for container transort particularly for reefer containers.
  • Gas carriers needing extensive cooling electrical propulsion.
  • For ships with a large electrical power demand it is necessary to utilize the benefits of a high voltage HV installation.
  • The design benefits relate to the simple ohms law relationship that current (for a given power)is reduced as the voltage is increased. 
  • Working at high voltage significantly reduces the relative overall size and weight of electrical power equipment.
As per Ohms law, POWER = VOLTAGE x CURRENT
For a given Power, Higher the Voltage, Lesser is the Current
440 KW = 440,000 watts              
               = 440 Volts x 1000 Amps              
                -1100 volts x 400 Amps              
               -11000 volts x40 Amps 
When large loads are connected to the LV system the magnitude of current flow becomes too large resulting in overheating due to high iron and copper losses.
P= V I cosĪ¦
Copper Loss = I2 R
  • For a given power, Higher voltage means Lower current, resulting in Reduction in size of generators, motors, cables etc.
  • Saving of Space and weightEase of Installation
  • Reduction in cost of Installation
  • Lower losses — more efficient utilisation of generated power.
  • Higher Insulation requirements for cables and equipment used in the system.
  • Higher risk factor and the necessity for strict adherence to stringent safety procedures.
  • Trained crew.


Popular posts from this blog

Differences between MC/MC-C and ME/ME-C engines

The electrohydraulic control mechanisms of the ME engine replace the following components of the conventional MC engine: Chain drive for camshaft Camshaft with fuel cams, exhaust cams and indicator cams Fuel pump actuating gear, including roller guides and reversing mechanism Conventional fuel pressure booster and VIT system Exhaust valve actuating gear and roller guides Engine driven starting air distributor Electronic governor with actuator Regulating shaft Engine side control console Mechanical cylinder lubricators. The Engine Control System of the ME engine comprises: Control units Hydraulic power supply unit Hydraulic cylinder units, including: Electronically controlled fuel injection, and Electronically controlled exhaust valve activation Electronically controlled starting air valves Electronically controlled auxiliary blowers Integrated electronic governor functions Tacho system Electronically controlled Alpha lubricators

Why is a man hole door elliptical in shape?

Any opening in a pressure vessel is kept to a minimum and for a man entry an elliptical hole  is lesser in size than the corresponding circular hole. More over it is prime concern to have a  smoothed generous radius at the corners to eliminate stress concentration. Hence other  geometrical shapes like rectangle and square are ruled out.  To compensate for the loss of material in the shell due to opening, a doubler ring has to be  provided around the opening. The thickness of the ring depends on the axis length along the  dirrection in which the stresses are maximum and the thickness of the shell. It is important to  align the minor axis along the length of the vessel, as the stress in this direction is  maximum. Longitudinal stress: Pd/2t where P= pressure inside the vessel, d= diameter of the arc, t=  thickness of the shell plating  Circumferential stress: Pd/4t  More over a considerable material and weight saving is achieved as minor is along the  direction of maximum stress.

Shell Expansion Plan

It is a two dimensional drawing of a three dimensional surface of the ship’s hull form. This plan is very useful for the following information:It is used for marking the location of a hull Damage on this plan by identifying the strake number , letter and frame number so that the exact location of the damage and also suggested repairs are marked in a localised copy. The shell expansion can be used for finding areas of painting surfaces such as topside, boot topping and bottom areas by applying Simpsons rules directly.  In the shell expansion the vertical scale used is different from the horizontal scale and a suitable adjustment has to be made when calculating areas. This becomes useful in solving disputes concerning areas of preparation and painting. It gives information on the thickness of the original strake which is indicated by the number in the circle shown in the strake.  The quality of steel used is also shown by letters A,B,D E and AH, BH,DH, EH.