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  • #16
    Originally posted by J Tiers View Post

    Does not work that way, you manually turn on the idler then the load. And his 3 HP is the idler, the 1 HP is the load. That should work. The box is for a 5 HP idler, and might need some adjustment.
    It certainly can work that way.

    On Edit:
    Some commercial statics don’t require idlers. They don’t “start” until you push the start button native to whichever machine is being powered.

    In my case I had a static converter suppling a 3phase buss that every machine in the shop ran on. Any start button on any machine in the shop would at least attempt to activate the static converter. (via. the potential relay in the converter box. )




    Last edited by SVS; 03-26-2021, 02:02 PM.

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    • #17
      Originally posted by SVS View Post

      It certainly can work that way.

      Actually, it would be complex. The idler does not start well with a load already on it. So you would have to add a contactor, as well as a sensor setup, to detect the load, then trigger the idler, and when it is "up" and online, close the contactor to start the load.

      Yes, it is doable, but few RPCs are set up like that.

      Old time house power systems were like that. You'd switch on a light, and that would trigger the prime mover (perhaps out in a shed) to start and spin up the generator, and when that was "up", switch it to the load. Certainly possible, just not done anymore.
      2730

      Keep eye on ball.
      Hashim Khan

      Everything not impossible is compulsory

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      • #18
        JT-I expanded on my post above. Maybe more clear now?

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        • #19
          Originally posted by SVS View Post
          JT-I expanded on my post above. Maybe more clear now?
          Static is a totally different animal.... same type deal as the starter on an RPC, so that, yes.
          2730

          Keep eye on ball.
          Hashim Khan

          Everything not impossible is compulsory

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          • #20
            Ok-bringing this full circle: Chief’s project hinges on wether his commercial “box” was intended to run an RPC (start button) or be a stand alone static converter. (potential relay)

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            • #21
              Originally posted by SVS View Post
              Ok-bringing this full circle: Chief’s project hinges on wether his commercial “box” was intended to run an RPC (start button) or be a stand alone static converter. (potential relay)
              I politely disagree.
              The only difference between a SPC and a RPC is where you load the 'load motor' from.
              example: if you got a RPC, and you put a pulley on the idler and take power right there, then, all you got is a motor running on a SPC
              If you remove said pulley and let the motor run as an idler, then, tap power (for a different motor) from the 3ph buss inside the control box, then you got a real RPC.

              My point is that a static converter in and of itself, is the same as a RPC control box.
              The difference is how you tap into power, either mechanically on the (so-called idler), or electrically on the 3ph buss

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              • #22
                Ringo-What shall we call it when a motor is sometimes the load and sometimes the idler for motors too small to run alone on the converter buss? You’re arguing a point that I didn’t make.

                Here is the one point I attempted to make:My GWM brand 7.5-10hp converter, which has a potential relay instead of a start button, made bad clicking sounds if I attempted to start 1-5hp motors without first starting a 7.5-10hp motor to act as an idler. This may or may not apply to Chief’s situation.






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                • #23
                  Static converters need to be matched to the motor HP-wise. That really means they need the correct start cap for the motor in question. SVS' 1 HP motors likely would not start well because the capacitor did not provide suitable phase shift, it was so big that it is closer to a piece of wire than to a capacitor shifting phase.

                  Ringo is 100% correct in principle. The difference between a static converter and an RPC control box is really just in the "balance capacitors", which a static converter normally does not have.

                  Phase-a-Matic has instructions on how to make an RPC with their type of static converter. They require a switch to isolate the generated leg from the static converter.

                  It seems the OP here has something that is intended to be an RPC. But An RPC with a larger (5 HP) idler than he has (3 HP). So some adjustment to the start capacitor size may be needed, but it ought to work OK as -adjusted.
                  2730

                  Keep eye on ball.
                  Hashim Khan

                  Everything not impossible is compulsory

                  Comment

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