Grounding on Ships

[Walden]

I have a project to build a control panel for a ship. The incoming supply is 440 V: 3 phase: 3 wire: 60Hz. I need a 220 volt supply for the control circuit and some little single phase motors and other small single phase loads. I shall fit a double wound transformer to obtain the 220 volt supply. Do I ground one leg of the secondary winding of the transformer to the metal work of the control panel enclosure, and hence the hull of the ship, or leave it floating? In other words, is the sea a good enough ground? If the secondary leg is left floating, it will have to be protected with a fuse or MCB presumably?

 

[RajT]

I assume that the secod side of the Tx is star connected with a neutral which should be connected (earthed) to the ships hull.

Then you will have 220V ( 1 ph supply) between L-N for your small power distribution.
You must also ensure that all single phase supplies feeders have 2 core cable connection ie L-N.
You must not use the ships hull as the N return path.
loads such as motors/control panels may be earthed (bonded) locally to ships hull.

 

[jbartos]

Suggestion: Follow the project specifications and/or industry standards, e.g.
IEEE Std 45
Military Standards and Specifications
etc.

 

[Walden]

The incoming supply is 440V 3 phase 3 wire with no neutral. But we need a single phase supply for small loads. This supply we must provide from the control panel using a transformer. Do we ground one leg of the secondary winding?

jbartos thanks for tip on IEE STD45.

 

[tulum]

Kevd seems to be pretty informative on this subject...

See Earthing in Ships - thread238-51057...

 

[Walden]

Thank you all, I believe that between you,you have solved my query. I did search for previous threads but couldn’t find any. However, "tulum" pointed me in the right direction thanks!

“There’s none so blind as those who will not look!”