How to Convert 120V Single Phase to 440V Three Phase for a Diving Tender Boat?

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Discussion Overview

The discussion revolves around the technical challenges and considerations involved in converting 120V single-phase power to 440V three-phase power for a diving tender boat. Participants explore various methods for this conversion, including the use of rotary and static phase converters, while also addressing the implications of power draw and the feasibility of using marina power sources.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • Scott seeks advice on converting 120V single-phase power to 440V three-phase for a diving tender boat, expressing concerns about power requirements and potential solutions.
  • Some participants suggest that a mechanically rotating motor-three-phase generator or a static converter could work for the conversion.
  • There is a concern about the high amperage required for the conversion, with calculations indicating that drawing 30.5 kW from a 120V supply would necessitate impractically high current levels.
  • Participants discuss the importance of conducting a proper power budget to assess the total power consumption of all equipment running alongside.
  • Questions arise regarding whether the 40 amps mentioned by Scott refers to the three-phase or single-phase power, and the implications of this distinction for the conversion process.
  • One participant suggests that despite marinas claiming to provide only single-phase power, there may be three-phase supply available that is not advertised, prompting further investigation.
  • There is a suggestion that single-phase power might suffice for the boat's needs, with the possibility of running the generator intermittently if three-phase power is only required occasionally.
  • Some participants share anecdotes about equipment that operates effectively on single-phase power despite being rated for three-phase, highlighting potential flexibility in power requirements.

Areas of Agreement / Disagreement

Participants express a mix of viewpoints, with some agreeing on the feasibility of certain conversion methods while others raise concerns about power requirements and the practicality of the proposed solutions. The discussion remains unresolved regarding the best approach to take for the conversion and the actual power needs of the boat.

Contextual Notes

Participants note the importance of verifying the actual power supply available at marinas and the potential for hidden three-phase connections. There are also discussions about the implications of high amperage on wire size and handling, which could affect the feasibility of the conversion.

buckland23
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Hi there,
i'm trying to do a technical paper on converting 120 volt single phase to 440 volt 3 phase for a diving tender boat. Does anyone know what things i should be concerned about when trying to convert the power. The boat usually runs in generators alongside but, i was hoping to hookup marina 120 volt power into the boat. The boat usually draws around 30-45 amps alongside.
Would a rotary phase or static phase converter work? Any help would be greatly appreciated

thanks
Scott
 
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A single phase 120V input mechanically rotating motor-three phase generator would work.
Also a static converter could work. I would use Google and Amazon to search out companies that make them.

Here's one: http://www.dtims.com/products/obvp/
 
The amperage might be prohibitively high though...
 
True, the amprerage draw may be high. I did not do any calculations. The OP did mention the dockside power source supplied 30-45 Amps at 120V. For this project a proper power budget must be done.
 
whats a power budget? Is it a power consumption total of all the things running alongside
 
"""The boat usually draws around 30-45 amps alongside.
""

is that forty-ish amps from the three phase 440 or from the single phase marina power?

3 phase power is Volts X Amps X √3
and of course single phase is just Volts X Amps.

be aware also that rotating machinery will have an advantage during brief overloads , such as in starting a big compressor motor.
electronic inverters of the 1980's had substantially less stout overload characteristics than generators. i would guess they still do.
 
right now the boat is just running on one of its big generators alongside. I was hoping to come up with a way to supply the 440v 3 phase from the marina/docks 120v supply. This would probably be cheaper than paying for fuel to run a big generator all night

thanks again for all your help
 
Can you verify here that the dockside power source you intend to use for your power converter is single phase, 120 Volts?
 
a technical paper? sure sounds real.

you mentioned 40-ish amps

well, 440 volts 3 phase at 40 amps is 30.5 kw

and to get 30.5 kw from a 120 volt supply would take 254 amps. the wire size gets impractical to manhandle.
you ought to get current measurements,
and see if the marina has three phase.
A 40 amp 440 volt three phase extension cord is not unheard of.
 
  • #10
all the marinas i spoke to along the east coast of vancouver island were 120v single phase. The amperage ratings were mostly 30 amp up to 100 amp. Campbell River did have 3 phase but they were the only one. Thanks for the info regarding wire size. Thats why i wanted to get some advice before i started my paper. I just thought they could be a better way than to run on the ships generators all night when we are alongside a marina. Not only does the noise bother the neighbours but we are burning lots of fuel. I might have to do another topic for my paper

thanks again
scott
 
  • #11
buckland23 said:
all the marinas i spoke to along the east coast of vancouver island were 120v single phase. The amperage ratings were mostly 30 amp up to 100 amp. Campbell River did have 3 phase but they were the only one.
Please bear with me while I labour the point here. Despite the marina saying they only have single phase, examination of the supply cables may reveal that they are indeed supplied with 3 phases. It may be worth pursuing this further. The marina may just be reporting that there are no 3 phase sockets for you to plug into to. You'll need to ask them how many overhead wires they are supplied from, if overhead; or some other revealing question.

The power company may have put 33% of the single phase power outlets on each phase for load balancing. I don't know whether they routinely do this; I'm just saying it's conceivable that they may. Where there are a host of power outlets, including 100A outlets, I'd be surprised if the place isn't using all three phases.

If you find they do have 3 phases, all you'll need are 3 transformers 100v:250v and some switches and breakers, etc. That is so much easier than what you are otherwise looking at.
 
  • #12
I just re-read your post. I see it's not just one marina, but multiple marinas, where you wish to dock. My other question is--what does the boat use/need 3 phase power for? I'm wondering whether single phase might suffice, and while docked power all GPOs from a single phase, and run the boat's generator for 1 or 2 hrs a day if three phase is needed only intermittently or for only a few hours? Though that might be a bit tricky to arrange.
 
  • #13
indeed see what the boat does with that 3 phase
and whether that 40 amps is all the time or just when something big is running

i saw a computer system once where manufacturer demanded it be supplied 3 phase 230 volt power
but one of the terminals wasn't even connected to anything inside the chassis
and it ran fine on good ol' 230 centertapped housepower.

Nascent's suggestion is common sense.
 
  • #14
jim hardy said:
i saw a computer system once where manufacturer demanded it be supplied 3 phase 230 volt power
but one of the terminals wasn't even connected to anything inside the chassis
and it ran fine on good ol' 230 centertapped housepower.

Sounds like my former boss. I suggested he run a new 230 volt single phase circuit out of a certain breaker box. His reply was: "You can't do that! That's 3 phase!" Of course it was three phase delta, but he somehow thought legs A and B were somehow different in that box than legs A and B in the box on the other side of the wall which didn't contain the C leg.
 
  • #15
Well, Av'SuperNova -- thanks!

i helped a friend with that one.
his boss had just contacted the power company to have a new pole pig installed and three phase brought into the building for the computer. when my buddy called him and said we'd got it going already, he was ecstatic.

needless to say we got a nice steak dinner ...
 

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