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Operating characteristics of battery for ships machinery spaces

How a battery circuit works ?: The battery is a convenient means of storing electricity. It is used on many ships as an instantly available emergency supply. It may also be used on a regular basis to provide a low-voltage d.c. supply to certain equipment. To provide these services the appropriate size and type of battery must be used and should be regularly serviced. Two main types of battery are used on board ship: the lead—acid and the alkaline type, together with various circuits and control gear.



When operating in a circuit a battery provides current and voltage and is itself discharging. Depending upon the capacity, it will provide current and voltage for a short or a long time. The capacity is measured in ampere hours, i.e. the number of hours a particular current can be supplied. Thus a 20 ampere-hour capacity battery can supply 2 A for 10 hours or 1 A for 20 hours. This is a reasonable assumption for small currents. The ampere-hour capacity does depend upon the rate of discharge and therefore for currents above about 5 A, a rate of discharge is also quoted.

Having been 'discharged' by delivering electrical power a battery must then be 'charged' by receiving electrical power. To charge the battery an amount of electrical power must be provided in the order of the capacity. Some energy loss occurs due to heating and therefore slightly more than the capacity in terms of electrical power must be provided. By charging with a low current value the heating losses can be kept to a minimum.

The different methods of charging include constant current, constant voltage and trickle charge. With constant current charging the series resistance is reduced in order to increase the charging voltage. This may be achieved manually or automatically. The constant voltage system results in a high value of current which gradually falls as the battery charges. The circuit resistance prevents the initial current from being too high. Trickle charging is used to keep a battery in peak condition—a very low current is continuously passed through the battery and keeps it fully charged.




Related Info:

  1. A.C. motors for ships machinery
  2. Supplying alternating current to a coil which is free to rotate in a magnetic field will not produce a motor effect since the current is constantly changing direction. Use is therefore made in an induction or squirrel cage motor of a rotating magnetic field produced by three separately phased windings in the stator. ...

  3. Use of A.C. generators
  4. A coil of wire rotating in a magnetic field produces a current. The current can be brought out to two slip rings which are insulated from the shaft. Carbon bushes rest on these rings as they rotate and collect the current for use in an external circuit. Current collected in this way will be alternating, that is, changing in direction and rising and falling in value. To increase the current produced, additional sets of poles may be introduced....

  5. D.C. motors for ships machinery
  6. When a current is supplied to a single coil of wire in a magnetic field a force is created which rotates the coil. This is a similar situation to the generation of current by a coil moving in a magnetic field. In fact generators and motors are almost interchangeable, depending upon which two of magnetic field, current and motion are provided.....

  7. Use of D.C. generators
  8. A current is produced when a single coil of wire is rotated in a magnetic field. When the current is collected using a ring which is split into two halves (a commutator), a direct or single direction current is produced. The current produced may be increased by the use of many turns of wire and additional magnetic fields....

  9. Emergency power supply for ships machinery operation
  10. In the event of a main generating system failure an emergency supply of electricity is required for essential services. This can be supplied by batteries, but most merchant ships have an emergency generator. The unit is diesel driven and located outside of the machinery space .

  11. Maintenance requirement for ships electrical equipment
  12. With all types of electrical equipment cleanliness is essential for good operation. Electrical connections must be sound and any signs of sparking should be investigated. Parts subject to wear must be examined and replaced when necessary. ...

  13. Choice of batteries for ships machinery spaces - Lead acid and alkaline batteries
  14. The battery is a convenient means of storing electricity. It is used on many ships as an instantly available emergency supply. It may also be used on a regular basis to provide a low-voltage d.c. supply to certain equipment.....

  15. Ships battery maintenance guidance
  16. The electrolyte level should be maintained just above the top of the plates. Any liquid loss due to evaporation or chemical action should be replaced with distilled water. Only in an emergency should other water be used. It is not usual to add electrolyte to batteries.....

  17. Operating characteristics of battery for ships machinery spaces
  18. Having been 'discharged' by delivering electrical power a battery must then be 'charged' by receiving electrical power. To charge the battery an amount of electrical power must be provided in the order of the capacity.....

  19. Insulation resistance measurement
  20. Good insulation resistance is essential to the correct operation of electrical equipment. A means must be available therefore to measure insulation resistance. Readings taken regularly will give an indication as to when and where corrective action, maintenance, servicing, etc., is required....

  21. Use of navigational light circuits
  22. The supply to the navigation lights circuit must be maintained under all circumstances and special provisions are therefore made. To avoid any possibility of accidental open circuits the distribution board for the navigation lights supplies no other circuit.....

  23. Ward—Leonard speed control system
  24. As a very flexible, reliable means of motor speed control the Ward-Leonard system is unmatched.The system is made up of a driving motor which runs at almost constant speed and powers a d.c. generator .....

  25. Danger of electric shock to human body
  26. The resistance of the human body is quite high only when the skin is dry. The danger of electric shock is therefore much greater for persons working in a hot, humid atmosphere since this leads to wetness from body perspiration.....




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