Marine Transformer Question

[ksavoie]

I was tasked to add a 240/120v single phase transformer and panel on a marine vessel. I have access to 440V 3 phase. I have no marine experience. Is there a special type of transformer I will need? A vendor mentioned to me that nothing should be grounded on a marine vessel. Can someone guide me in the right direction?

Thanks in advance.

 

[itsmoked]

The right direction would be to find a competent electrician knowledgeable in marine power.

You want to add a 240/120 transformer but have 440V.

What power do you need out of the transformer.
Both 120 and 240?

You will supply the other(primary) side with this 440?

You need to make sure of what you have. People throw around 440,460,480 interchangeably. It will make a difference.

Otherwise you need the VA rating that will be required. You need to make sure the transformer is protected properly from overloads.

Otherwise normal transformers do not connect any part of their frame to power so keeping the ground free is just a matter of correct wiring.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ksavoie]

My source is 440V. So I need a 440V to 240/120V, 40KVA Transformer. It sound like you are telling me that as long as I keep my neutral and ground seperated I should be OK on a marine vessel?

On this same vessel there is a 690V to 230V, 3 phase, 150KVA Transformer. The vector group indicates that it is a Dyn11. Doing a little research the Dyn11 means Delta connected HV winding, star connected LV winding with neutral brought out, LV is leading HV with 30°

Does neutral pulled out me that I can use the neutral?

So from one phase to neutral I should have 230/1.73 = 132V?

 

[rovineye]

Maybe your voltage will be as described. It depends on primarily on voltage drop before the transformer at full load.

You are correct as to what your line to neutral voltage will be.

Normally correct that you are keeping neutral and ground isolated. There are a few exceptions, but very few.


Be careful with the load balancing esp of the neutral!

Special requirements? Is it a Classed vessel? ABS will require 40 or 45 deg C ambient rating depending on location. If forced cooling it must have temp alarm. If liquid immersed there are special requirements. Test certificates required. Enclosure IP rating will depend on location. IEEE Std 45 would also invoke ANSI C57 or IEC 60726.

 

[waross]

The standard voltage on shore is 120/208 volts.
A lot of boats use 220/127 volts, or 230/133 volts.
223/129 is also popular on board ship.
A lot of ships burn out a lot of lights.
I can't remember ever seeing a ship running at the onshore standard of 120/208, even when I set it there a week previous.
Go for it, everyone else does.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

The neutral is generally isolated from ground, but all exposed non current carrying parts should be grounded to prevent touch potentials. The problems arise when a vessel is connected to shore power and the ground path shares some of the neutral current. Serious hull corrosion, fast. There are also personal and equipment safety issues that are addressed by isolating the neutral from ground.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rovineye]

True waross. I have large distribution transformers, and depending on what the ship is doing my voltage is all over the place due to the voltage drop variance. No easy answer for that other than pick a tap that won't have damaging voltages at low loads. Bigger problem for me is shore power. My big demand is too much for most pier facilities. Even if they have the capacity the voltage drop at their end can be huge (I draw over 2MW). Sometimes we jack the xfmr up to well over 500 volts unloaded to get 460 on the swbd loaded. Then we wait until we smoke their xfmr or cabling and go back on engines.

We list distribution at 120v and user at 110. We have some 208 or 220, but use dedicated panels and xfmrs, very few center tap wye (specialized).

Not sure I can picture your shore power description however. I have never seen a shore power neutral (maybe small boat?) . But if it is marine, anything can and will be tried.

 

[itsmoked]

What kind of ship? Doesn't sound like enough for a cruise ship I'm guessing.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[rovineye]

Ships are Sealift cargo. Biggest draw are the cargo freeze decks. What I cited as shore power draw was wrong above. I plugged in my EDG MW for some twisted reason. My shore power draw is almost 8MW.

That is right in line with cruise ship shore power needs. Ports are starting to provide facilities for them and some are completed. And now that my memory is jogged thay do bring a seperate neutral to the ship, but I really don't know what they do with it. The big difference is that the shore power feed is 6.6kV or 11kV, and aircraft carriers use 4160V. I need 480 volts which is problematic at those loads. And put two of my ships on one pier? Forget it.

 

[davidbeach]

8MW at 480V is not reasonable. That would be over 12000A at 0.8 pf. Best to find a reasonable voltage/load combination.

 

[rovineye]

davidbeach,
Of course it isn't reasonable, that is why we rarely go on shore power, and when we can it is at reduced capacity. The piers we go to don't have 6.6 kV and we don't have 4160 distribution. I do have a spare breaker cubicle waiting for the day more piers have 6.6kV shore power available and then I can add that ability. I have a few piers that can give me 8000 amps, but that is about it, so we still can't meet peak demand in some environments, and those were designed just for us.