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Combining 2 AC power suppy

  1. Nov 2, 2016 #1
    As per the diagram, how do i change the wiring of the equipment on the outside to achieve my desired setup?

    ac.jpg
     
  2. jcsd
  3. Nov 2, 2016 #2

    davenn

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    there's no point if the power outlets are on the same phase, you wont double the current
     
  4. Nov 2, 2016 #3

    rbelli1

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    This also causes a safety issue in two ways. First if you plug only one branch in you will have live prongs exposed on the other. Second if one breaker is opened for some reason the circuit will be energized through your death cord.

    BoB
     
  5. Nov 3, 2016 #4
    Why wouldn't the current be doubled if the two sources are switched on at positive zero crossing, so that there is no phase difference between the two sources?
     
  6. Nov 3, 2016 #5

    dlgoff

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    What would the current be in the bottom circuit?
    twowires.jpg
     
  7. Nov 3, 2016 #6
    The current would be 16A, but that's cause there is only 1 voltage source. But in the OP's picture there are 2 voltage sources so each can provide 8A current.
    Isn't that how parallel operation of transformer or generator works? Each transformer or generator provides with half the load current?
    Untitled-6-min.png
    parallel_gens.gif
    I'm confused. When should the voltage sources be in series and when in parallel?
    Sorry OP for hijacking your thread. Not sure if I should start a new thread or the mod will allow discussion here.
     
  8. Nov 3, 2016 #7
    OP is not clear - but I am reading Power Supplies to mean a piece of equipment, not just an outlet.

    1) For an AC source - the Power supplies need a way to synchronize their outputs ( be in phase with one another)-otherwise they may get damaged or as one "competes" with the other - they both shut down under a current fault, or get damaged.

    2) To Share the Load 8 A each to supply the 16A Load they need to have a load sharing feature, they need to communicate. Otherwise one Power supply will typically carry all of the load, or if regulated, will put out it's 13A limit, and then go into a current limit - as the other one only has 3A - this could damage the 13 A - or the system could oscillate.

    Basically - if the two PS are not made, and configured to load share load current they wont.

    Jaus -- in the 2 transformer case, very slight differences in the transformers can lead to circulating current, but paralleling Transformers is possible when properly matched. In the generator case - the generator controls must be equipped to be tied to the grid, or to another generator - primarily to carry out the two functions Synchronization and Load Sharing, I mention above.
     
  9. Nov 3, 2016 #8

    NascentOxygen

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    There may be a solution using a pair of isolation transformers, but these are heavy and very expensive so expect the cost to exceed $1000. Still interested?
     
  10. Nov 3, 2016 #9

    CWatters

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    Tell us more about the 16A and the 13A power supplies and the appliance itself. How much power does it actually draw? What is the wattage stated on the rating label?

    It sounds like you might be moving country from somewhere that has 16A plugs/sockets to somewhere that has 13A plugs/sockets. In which case there might be an easy solution if the power/wattage is below 3kW.

    In some countries you can replace a 13A socket with a 16A socket. There is a bit more to it but that might be a valid solution.
     
  11. Nov 3, 2016 #10

    davenn

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    NO, as I said, it's the same source because it's most likely two AC outlets off the same mains phase
     
  12. Nov 3, 2016 #11

    rbelli1

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    That is the assumption I made as well due to the ends of the cables being terminated in something that looks like a British wall plug and 13A which also matches British style wall plugs. This configuration *MIGHT* work as it parallels two 13A fuses inside the plugs. But it creates an electrical death hazard. Locally if one plug comes unplugged due to exposed prongs and possibly longer distance if two circuits are bridged with this thing.

    Do not do this. It is dangerous and probably illegal.

    BoB
     
  13. Nov 3, 2016 #12

    CWatters

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    I can see a way to prevent the danger with two plugs but I'm not going to suggest it because it would only take a single device to fail and the hazard would return. Way too dangerous.
     
  14. Nov 4, 2016 #13
    One question:
    What if instead of power outlets they are batteries (separate power sources)? Can i connect batteries in series to increase the power output? In network problems I've seen voltage sources in series. But then only the voltage output would increase. Not the current capacity of each battery.

    Say i have two power sources and one load. I guess the voltage output of both power sources much match the require load voltage. and the power sources must be connected in parallel to supply the required load current, and yes, there must be care(a lot lot lot lot of it) to make sure no circulating current flows between the sources. Am i right?
     
  15. Nov 4, 2016 #14

    CWatters

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    If you connect two batteries in series the voltage will increase. _IF_ the current is limited by the battery that will not change.

    Only certain types of battery can be connected in parallel. If you connect two batteries in parallel the voltage will stay the same. _If_ the current is limited by the battery then that will double.
     
  16. Nov 4, 2016 #15

    Baluncore

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    It might help if we knew what the equipment was so we had some idea of the variation in energy demand over time.

    Two AC or DC supplies could be merged with bridge rectifiers, but that is not safe to try unless you know exactly what you are doing.
    Consider for example a 6 kW variable frequency drive with three phase input. You might run that on the two outlets since the 3PH bridge on the VFD input could isolate an unplugged input.

    On the other hand, could the equipment run on DC? Or does it have AC motors?
     
  17. Nov 4, 2016 #16

    CWatters

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    The OP seems to have disappeared.
     
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