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Voltage drop – selection of cable in DC network

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cable cross-section:
[mm 2 ]
length of the cable from a source to the consumer:
[m]
maximum current:
[A] or power [W]
rated voltage:
12 V 24 V 230 V
calculated voltage drop:
_ [%]

The voltage drop is calculated in accordance with the following equation:
,where:

  • In, rated current [A],
  • l, length of cable [m],
  • σ, conductivity, for copper 58 [S*m / mm 2 ],
  • Un, rated voltage [V],
  • s, cable cross-section [mm 2 ],

Voltage drop on cables between generators and main switchboard is not to be more than 1%

Voltage drop is not to exceed:

  • 10% for lighting and signalling devices,
  • 10% for power consumers at short-time and intermittent service
  • 7% for power and heating devices,
  • 5% for navigation light circuit.

Permissible voltage drop is given in:

  • 6.8.5 and 16.8.3, Rules for the Classification and Construction of Sea-going Ships - Part VIII, Electrical Installations and Control Systems,
  • 6.3.8 and 13.8.13, Rules for the Classification and Construction of Small Sea-going Vessels - Part VII, Electrical Installations and Automation,
  • 6.5.7 and 14.6.3.2, Rules for the Classification and Construction of Inland Waterways Vessels - Part VII, Electrical Equipment and Automation,
  • 15.2.3.1, Rules for the Classification and Construction of Floating Docks - Part VI, Electrical Equipment,
  • 8.2.3, Rules for the Classification and Construction of Sea-going Yachts - Part V, Electrical Equipment,
  • 8.2.3, Rules for the Classification and Construction of Motor Boats - Part V, Electrical Equipment.
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