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Shorepower: 480 VS 100amp three phase, or 100 single

Discussion in 'Technical Discussion' started by Pascal, Sep 2, 2023.

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  1. chesapeake46

    chesapeake46 Senior Member

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    This confuses me.
    IF you run 480 v single, the adapter you made to go to three phse is not correct.

    480 single phase would be two phase pins, one neutral pin and one ground or a three pole four wire cord end.

    208 volt three phase would be three phase pins, one neutral, one ground, or four pole 5 wire male cord end.

    If you are using three pole four wire 480 volt cord end ( 480 single ) into four pole , 5 wire ( 208 v three ph. ) you are missing eithe the neutral on the 208 or the ground on the adapted cord.
  2. chesapeake46

    chesapeake46 Senior Member

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    Also, if the system was designed well, there should not be a great voltage drop.

    In most systems 3 % is acceptable.

    Utilities often pretend 10 % is acceptable.
  3. Capt Ralph

    Capt Ralph Senior Member

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    I'm reading ; your not using all 3 phases, Just one leg (phase) of the three per cable.
    Neutral is not needed from the dock, the Atlas makes that itself.
    The boat does well on a single phase 480Vac(48Kw), not well on 2 x 208Vac (41.6Kw).

    I feel the atlas is getting 2 different phases (of the 3).
    One cable getting Vac from Black-Red the other cable getting VAc from Red-Blue.
    The Atlas is using its transformer to make work. In doing so, your drawing a lot of of shore current and popping the breaker.
    Probably an old/abused dock breaker & outlet also.

    Your 208/460 converter could be re-strapped to get both lines on the same phase.
    Improving the in-efficiency of phase correction at the Atlas transformer.

    Fly me in, I can do it for you. :D
    I'll bring my O scope and show you the 120° phase delay between the legs.
    Last edited: Sep 3, 2023
  4. rtrafford

    rtrafford Senior Member

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    Atlas takes incoming AC, be it 3 phase or single phase, converts it to DC and then discharges 60 Hertz of 120 per line. The voltage drop isn't relative to what is happening within Atlas, and Atlas does use some, but rather out on the dock.

    The dock is delivering 480 to the pedestal, but from a meaningful distance, and then the shore connection and cable aboard create more loss. In many single phase dockside setups, they are fed 480 but deliver 208 per line to the pedestal because they use a straight transformation of 480 to 208 delta setup rather than to boost the output to 240 per line. Why? Because neither the marina nor the power company want to pay the amp hour cost of making that boost conversion. They want the customer to pay for it.
  5. rtrafford

    rtrafford Senior Member

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    Atlas uses two of the dockside lines or legs. It converts them into 600v DC, then transforms the DC back into 60 Hertz and 120v AC per line for load. This both provides flexibility of voltage input as well as cycles and delivers clean power to the ship. You can plug her into 480-3, 277-3, 208-3, 240-1, 208-1, etc and get teh desired useful outcome.

    Like any other device, it doesn't car much for low power, and these big loads are often interpreted as low incoming voltage. Atlas is pulling amps through the dockside breaker necessary to both provide the power as well as the voltage outcomes. I find myself at some marinas where I just default to genny when time to fire up the kitchen as to not stress the system nor to trip the dockside breaker.
  6. Pascal

    Pascal Senior Member

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    I looked at my notes, the 480 has three hots and a ground. No neutral. I have 480v between any two hot and 270v between the arch hit and ground

    no neutral since we have an isolation transformer.
  7. Capt Ralph

    Capt Ralph Senior Member

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    Yep, 270 to ground that would be at neutral potential.
    Your tied to 2 of the hots that make one of the 3 phases.

    The 208 works the same way.
  8. Capt Ralph

    Capt Ralph Senior Member

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    Questions for all;
    What happens to the boat when that one pedestal breaker pops?

    Are there two separate input transformers converting the two leads to DCv?

    I fear only one lead is in use and the other (out of phase) is rejected. This theory may be re-enforced if Pascal reports the boat goes dark.
    I'm thinking you can not combine (stack) two out of phase inputs on the same Atlas transformer primary.
  9. chesapeake46

    chesapeake46 Senior Member

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    Got it. Thanks
  10. chesapeake46

    chesapeake46 Senior Member

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    Utilities most common, commecial three phase transformers today are 120/208 Y secondary.

    230 or 240 volt three phase transformers are a Delta configuration on the secondary.

    120/ 208 volt is a " Y " secondary & has a neutal tap called a center tap
    The neutral is derived fron the center of the Y where one end of each of the three windings all terminate together.

    There is no center tap in a 240 Delta secondary.
    The windings are connected like a triangle.
    No center tap
    The neutral in a delta is connected "mid-winding" between two ends of the tri angle.
    A delta secondary has a " high leg " or a "Wild leg " on one phase. Meaning only 2 of the three phases will give you 120 to neutral.
    The third phase ( The high leg ) too high a voltage to neutral to use and if used to feed a 120 load, all the factory smoke will be released instantly

    This is why utilies use 120/ 208 v, Y. secondary transformers.

    You can use any of the three phases to neutral and have 120 volts.
    This keeps the overal sytem more in balance load wise.

    A Delta system ( 240 v. 3 ph ) has only 2 usable phases .
    That can male an inbalane on the overall system.
    This can be overcome by careful tracking of terminatuons on the utity ( medium voltage ) side but its a P.I.T.A.

    So much easier to keep the overall system more balance with 120/ 208 volt transformers regardless of the primary voltage

    And the price of replacement factory smoke is off the charts.

    The above disertation applies to the US of A only.
    I do not know the factory smoke costs elsewhere in the world.
  11. Pascal

    Pascal Senior Member

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    Myers it all shuts down when one breaker trips on the dock.

    As long as both cords are 3 phases or single phase, the system will do its thing. What you can not do is use a single phase and a three phase cord together, if you do the system doesn’t kick and flashes a red “cord not compatible” light.

    back home and plugged in 480v. Heaven.

    ocean reef is a pita. They had us on a med mooring with the moorings too close to the boat, they were actually under the bow. Luckily there was piling next to us closer to the stern so I could put a spring to keep off the dock
  12. Capt Ralph

    Capt Ralph Senior Member

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    So, How do you know your drawing from both leads? I'm still worried you were drawing only from one pole.
    This just messed me up; Your not consuming all 3 phases, only one of the three.

    Do you have a PDF of your Atlas model, theory or tech manual I could read.
    I really need to get my mind in phase.
    I'm not in sync with you kids or I have took a wrong turn in Albuquerque again.
  13. Pascal

    Pascal Senior Member

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    Three phase fives me a headache everytime I think about it.

    I know we were pulling from both cables because the meters on the cord selector boxed showed voltage and amps on both cords.

    here it is, connected to a single 480 so only the stbd cord is active. Yesterday I had both active cord green lights on and voltage / amps registering in both

    the only selector that affects operation is the Cord A/B selector. Switching from one to the other shuts the system down while it reconfigures and a bunch of relays engage. The other two only change voltage / amps on the meters but do not affect operation

    I don’t have a PDF of the manual. It’s pretty light on details anyway, mostly explains the various screenshots.

    Attached Files:

  14. chesapeake46

    chesapeake46 Senior Member

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    I see Strbrd Cord and Port cord.

    Does that mean you can only use one or the other depending on the side the shore power is on ?

    Or does the switch simply swap the meters from A to B ?
  15. Pascal

    Pascal Senior Member

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    No, the system is designed to use one or both cords at the same time. The control power switch (center) selects the cord used if only one is used. The other two switches select what is being read by the meters