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  1. #11

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    Just asking, could there be a bad winding in one of the pots?

  2. #12

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    Labor, if it was a straight 480 power bank shouldn't there be one secondary leg grounded down? I have only built one but have ran into several and they always have a secondary leg grounded down.

  3. #13
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    Yes Charlie, you're right, straight power bank USSUALLY has one of the sec legs grounded.
    "It is not the critic who counts:The credit belongs to the man who is actually in the arena" Teddy Roosevelt

  4. Default 240/480 wye delta bank issue

    Quote Originally Posted by Orgnizdlbr View Post
    Yes Charlie, you're right, straight power bank USSUALLY has one of the sec legs grounded.
    I have a few questions also, are you checking voltage under load or with the consumer off? If the xformers don't have secondary taps, the primary coming in could be running low voltage on the phase that is going to one of the xformers. A voltage check at the metering point may be in order also. The transformer name tag is always good to get information from.

  5. #15
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    Is this bank feeding underground? If so how about a partial fault?

  6. #16

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    We have a couple of 240/ 480 volt banks that are not tied down. we can not read the voltage from phase to ground b/c it jumps all over the place. No point of reference but we can read phases to phase.

  7. Default Grounded leg

    You don't have to ground a leg....you can ground any one of them if you choose to do so, but only one can be grounded. Out in the oil patch the customer would have to sign off liability if for whatever reason they chose to have an ungrounded service.

    For whatever reason I have seen before at least on a open delta bank some screwy voltages on an existing bank feeding a lift pump and the problem was corrected by rolling the primary phases on the high side of the xfmr cutouts.

  8. #18

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    Quote Originally Posted by rcdallas_ View Post
    You don't have to ground a leg....you can ground any one of them if you choose to do so, but only one can be grounded. Out in the oil patch the customer would have to sign off liability if for whatever reason they chose to have an ungrounded service.

    For whatever reason I have seen before at least on a open delta bank some screwy voltages on an existing bank feeding a lift pump and the problem was corrected by rolling the primary phases on the high side of the xfmr cutouts.
    I believe they were McGraw Edison pots,3 phase straight power,no neutral,no low side taps,15 KVA pots.The meter was on the 3 phase bank pole which we dont allow anymore.Below the meter was a 3 phase breaker.Like I said the voltage was fine phase to phase but to ground,265,280,280 volts.Dont know why 265 on the one leg and i believe their using this pot to get a voltage for a step down xformer on there side,this is where the problem is occurring.When you have a Delta bank like this i guess you never know what voltage you can get trying to measure to ground.
    Birdog37: "Remember we're all on a journey in life, the only difference is, some people know it and some people don't."

  9. #19
    Join Date
    Dec 2010
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    Ontario, Canada
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    That’s the screwy part of delta voltages, the phase to ground readings will jump around as they stabilize the phase to phase voltage, it doesn’t matter if it’s primary or secondary. Around here we have a lot of 27.6 distribution which we can rubber glove in class 4’s, but 27.6 delta has to be sticked , barehanded , or killed!

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