Marine Power Supply

Put a meter on it before you throw the switch.

We put a boat into a shipyard and replaced a lot of fuses and electronics after hooking up to shore power at the yard after we were assured that they were going to supply the correct voltage and phase to us---OOOPsie wrong S.O cord.

I would wait and read the advice that is sure to follow this post.

K T

The question is what is done with that power ?

If it is for any type of motors then

- 50 Hz will make motors run slower by thet % ie 50/60=83% that will have the effect on the efficiency and the connected load etc capacity (eg pumps etc)

-380 V will make these draw more current for the load but again in certain load (eg pumps) the load will decrease due to lesser RPM.

Resistive Loads - eg lighting etc will not have much effect only it will be a bit dimmer

Electronics: will most likely rectify the power and use DC- will have some minor problem with the filtering harmonics (the filters will be for 60Hz optimised)/ But should run if you step up the voltage.

The problem will not be much less likely with the Voltage (you can always step up) but the frequency - which you can not.

What the other ships do ? (If you dock in most of the areas I think you will land up with 50Hz only, there must be something other ships are doing ?)

Of course you take what you can get. For the lights that will be dimmer it is not a problem, but for other critical systems you will likely have problems. Motors will run slower at higher temps, and your electronics will be at risk. (Forgive me, I was a movie set electrician, but this is my suspicion.) I did spend some time working on scrapping a ship, and do remember it had a 480 generator. Does the ship have a generator that could somehow be run to power at hertz your electronics? Can your owner rent one at the port for supply to your electronics? A ship does have on it some things that will run alright, and some that won't do so well with the supply offered. You may need to ask your Bosun's mate what systems they would cut off from the shore supply. I'd certainly check with other ships who have the same supply setup as yours who have attempted to use the 380 50, instead of the 440 60. My suspicion is that the lights and the motors will not explode, but that the electronics would not like it. Better to tell the Captain what the risks are, than to say all will be fine, and things burn up.

motors will not like it either the loads at low voltage mayl draw excessive current.

I thought so, but figured the motors may run imperfectly without full breakdown. I did suggest renting a generator. Lights will be dim. Motors will run hot. Electronics will not work or burn up. Is that about right?

OP to answer. technically OK but whether he wants to spend in rentals ?

This is not an answer, but as someone else has said use a metter. If you value your equipment it would be advisable to find space some where to install on the line side of an isolator which controls the output of your shore supply, a complete set of instruments which will not be expensive, consisiting of a phase rotation meter, a voltmeter for each phase an ammeter for each phase ( current transformer meters can be used and are quite inexpensive for high loads- but be careful about leaving the CT secondaries unbridged when not required) and a frequency meter. Of course you can switch the meters if you only wish to spend the money for one meter for Three phases, but that may be costly, depending on where you supply comes from. I will stay out of the arguement for the electronics as that is not my strong point, but most other things will survive 10% variation indefinitely and a bit more for short to mid term.Motors of most types will last well but heavily loaded ones could be a problem especially single phase uits, with centrifugal switch gear. As I mentioned else where, most normal units with 3 phase motors will only be slightly affected by frequency changes and will work well going from 50 to 60 Hz. The biggest problem will be with over heating and on board a ship with good thermal conductivity I would be trying it out

Regards

Bill P.

As many have answered, its simply not a good idea at all, even if you do not lose any vital motors, they may become severely overheated and less reliable in the long run.

The supply you need is a standard NATO ship requirement and has been used on NATO ships for around 50 years. Any dockyard that CANNOT supply this nowadays, is just not up to the work quality required, go somewhere else or loan a portable diesel (BIG BUGGER!) that will do just that......

In my Navy days, we would use dockyard lighting hung throughout the ship and either shore mains for heavy machinery (if and when required) or many ships had an emergency diesel generator, somewhere near to the upper deck, that was entirely self contained, to supply mains when and where required....

Actually, very little mains is required in drydock as almost no motors need to run and firemains (water to fight fires) would be supplied directly from a shore based mains pump.

It could be that a relatively small DG would be enough for individual component testing onboard. A simpler way would be to carry such a generator onboard (either Turbine set up for Diesel fuel or a DG) at all times, just in case you have major generator problems when at sea......for the same reason that RN ships (used to?) carry one...

During dry dock I presume a large % of your machinery would be inoperative and only a domestic load required. I am surprised that the dry dock does not have a multi tap transformer for various voltages required for visiting ships. The lower frequency would not cause a great deal of trouble for motors unless they were running close to there maximum output which could cause some overheating. 380V is close to your +- 10% tolerance supply voltage so all resistive loads should be OK , I would observe your water pressure pumps and compressors if required you will probably find they will be OK.

Dry dock, every 5 years?

What is vessel's tonnage, and what type of vessel is it?

Is it a FOC vessel? (Where registered)

Although this is not really an answer to the question, could you please satisfy my curiosity?

The ships I sail on are tankers carrying crude oil, about three hundred thousand tonnes weight and 330 meters long. Hope I have satisfied your curiosity.

Thanks for that...........i am still interested in country of registration...........and again, out of interest, in what country are you dry docking the vessel.........would it be South Korea..........at a guess

NEGATIVE.... unless a transformer is used

Most systems on a ship are designed for a specific voltage range. If you go about 10% outside that range, you will get unpredictable results (plus possible equipment damage). I would recommend against it. See if you can arrange for a transformer to convert the input to 440.

It's true that during the refit the requirements are less severe. But towards the end you will need to test navigation and other equipment. You want standard conditions for that.

Jim

I'm interested in what Dry Dock our friend is headed to. What Transformer do you actually have in mind? One time I flew in a DC 6 to Schnectity NY from FLL with a Kuboki Generator for something Amerati Hess was doing. Captain let me fly the DC6 for two hours left seat on the way back. Was a very nice work day. (my job was to load and unload the generator.) I could give the name of a freight company that did such stuff by air at best costs out of FLL.

Hi Jimtaylor,

I appreciate your concern perhaps I should have stated that the motors should have a 1.15 service factor to allow for 50Hz running with a 10% reduction in HP.

I do not think they would dry dock for navigation equipment repairs or any other electronic equipment which would be sensitive to a reduced power supply. Once dry dock repairs are complete they would be out of there like a shot, The ships electrical officer should be capable of isolating any equipment which should not be operated whilst under shore supply.

Sorry make that a 20% reduction inHP

Hi Garth,

In my experience (USN), during a refit, electronics repairs proceed in parallel with mechanical. You also have the after undocking restoration and testing period when you still need shore power.

I think maybe for a quick docking for painting or underwater repairs, there would not be any impact. I don't know enough about merchant practices to say for sure. My experience has been with naval ships in a couple of different yards as overhaul project manager/ship superintendent. I know that when we lived in Japan, we had 50cycle power and ran 60cycle motors without any problems.

zenthil100,

Can you give use more info on the types of work to be done and which systems are mandatory operations during the docking period? Will you have a period in the yard after undocking?

Jim

Well, when we drydock a ship, generally we will be in the dock for couple of weeks to finish the hull work, painting of hull, the ship side valves etc and then refloat the ship in the dock to check for leaks and come out as soon as possible cos it costs alot to be in a dock. Most of the jobs in the machinery space as well gets done in that two week period. As for the running machinery, its only the AC and the Fridges which needs to be run and ofcourse the lighting. Rest all of the machinery will be stopped. My doubt regarding this subject is cleared, as correctly said by some of the people in this forum, even the books say that if we supply a reduced frequency then we also need to reduce the voltage accordingly to prevent the motor to draw more current. The book also give a formula which says voltage of ship up on frequency of ship equals to voltage shore up on frequency shore. Thats gives us a calculated voltage of 366 volts in our case, which closer to the standard 380 volts 50 hz, that can be accepted. By doing so the through put of the pumps will be reduced, and we definitely have to keep and eye on the temperatures of the motor windings.

Zenithil100,

You are perfectly right about the ratio voltage/frequency in case of motors and transformers. The ratio for 440V and 60 Hz would be 7.3 V/Hz while for 380 V and 50 Hz it would be 7.6 V/Hz.

You may not be able to load the machines up to their rated power, but for lower power requirements supplying them at 380V/50Hz will work. Definitely other stated parameters (efficiency, power factor, etc) will not be met.

With regard to electronic equipment, this type of equipment uses AC/DC converters anyway, so they should not be affected.

Hi jimtaylor,

The USN has a lot more money than stingy merchant marine ship owners. I would expect a fully fitted out dockyard for USN ships , lots of electronic equipment to test etc and quick turn around which would simulate war time conditions. Every thing to be done ASP.

I am surprised at the over site of a 330,000 Ton tanker not being fitted with it own transformer for shore supply [ also a good safety method] the designers were penny pinching. As I said before the domestic load would not be that large.

Yes, the Navy spends big bucks on overhauls. I can understand the merchant point of view though. Anytime you're not carrying cargo, it's a drain on money.

Hi All,

From a lot of experience with US yachts (up to 150 ft / 200t) the problems that you will suffer will be with 60hz spec'd transformers which may run hot. The same applies to motors. On the basis that only a small amount of the total load will be running then connect them and test for undue temp rise. The other alternative is to hire a shore based mobile generator which is set to 60Hz. Obviously if the dock is in a 50hz area all the mobiles will be 50Hz also but to change them is usually only a little work(<1hr) and would attract a small charge.

Yachts, per ton have a much higher budget than commercial and the usual way to solve the problem is to fit a shore-power converter. See http://www.mastervolt.com/view_product.php?lang=2&section=marine&prggr_id=1034&prg_id=1105&pro_id=5537

And http://www.abb.com/product/seitp322/9040033fd45d1f88482574a90081ede1.aspx

These are not the only ones but they are ones we deal with.

Regards

Chas

tell that bunch of cheap bastards you work for to spring the few extra bucks to go to a US shipyard. You will be glad that you did.

zenthil100; burned out a 380 volt 3 phase 50 Hz. asked them to rewind it for 60 Hz, 440 volt 3 phase the company rewinding said that the number of turns of copper was the same for both frequencies, you would need to change transformer taps on equipment with them. perry

I wouldnt suggest mastervolts unit. it has been bought out by Imtech NL major problems but they are working on it. A/SEA is a good proven unit. couple hundred grand investment and you can plug into anything, anywhere. it uses an auto tap input tranformer rectifies it into DC then using VFD technology, ei scr switching, it converts the DC back into AC at the vessels required output via an output isolation transformer. I also work in yachting business and although there is much more expendable income it is much cheaper then renting a shore side generator.

I dont care what all these knuckleheads say DO NOT plug a 440 DELTA system into a 380 volt WYE!!!!!!!!!!!!!!!!!!! I have not heard one person even mention the difference. Being on these yachts where 380v 50 hz is common remember it is a wye 220v to neutral. being a 440v delta you require transformers to make 208v 3 phase. What happends to those outputs when you plug straight into 380v????????