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Re: Looking for advice on multi 277vac to a 24vdc relay...

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  • Dave Mucha
    ... is to ... feed that ... never heard it ... from the three ... they are in ... Did I miss something ? was this 3-phase 277 volts ? I have seen 277 VAC as
    Message 1 of 7 , Oct 3, 2004
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      --- In Electronics_101@yahoogroups.com, rgsparber@a... wrote:
      >
      >
      > In a message dated 10/3/2004 6:22:50 PM US Mountain Standard Time,
      > dave_mucha@y... writes:
      >
      > Once you use the voltage divider you an put that into
      > an AC opto.
      >
      >
      > You should not be using a voltage divider on the input. The idea
      is to
      > generate a current of a few mA directly from the 277V source and
      feed that
      > directly into what you call an "AC" opto (the term is fine, I just
      never heard it
      > before). Phase matters if you want to combine the opto outputs
      from the three
      > 277V sources and not rectify the incoming current. Fortunately,
      they are in
      > phase.
      >
      > Rick Sparber


      Did I miss something ? was this 3-phase 277 volts ?

      I have seen 277 VAC as typically a lighting circuit. higher voltage
      for less line losses for better efficency and all that.

      Lighting contactors as well as motor starters will have a huge
      current draw when closed and the lights are turned on.

      A single resistor to the opto, not a voltage divider. (good catch)

      H11AA1 - 6-Pin DIP AC Input Phototransistor Output Optocoupler
      http://www.fairchildsemi.com/pf/H1/H11AA1.html

      or

      MID400 8-Pin DIP AC Line Monitor Logic Output Optocoupler
      http://www.fairchildsemi.com/pf/MI/MID400.html

      Will have a continuous output and should not have any reaction to
      phase. Being an AC input or AC line monitor the dual photo sensors
      react to the ac signal and keep the output on hard.

      unlike a single diode that would only have half the AC wave, these
      optos have two led's internal that keep the output on when AC is
      present.


      Since I use the H11AA, I kinda choke on saying "AC Input
      Phototransistor Output Optocoupler" so, I just call them AC opto's.

      Dave
    • Chuck Waters
      Phase matters if you want to combine the opto outputs ... Well, actually the 277 is 2 legs of 480 3 phase mains voltage. What Im doing is taking the 6 fault
      Message 2 of 7 , Oct 3, 2004
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        Phase matters if you want to combine the opto outputs
        > from the three
        > > 277V sources and not rectify the incoming current. Fortunately,
        > they are in
        > > phase.
        > >
        > > Rick Sparber
        >
        >
        > Did I miss something ? was this 3-phase 277 volts ?
        >
        > Dave

        Well, actually the 277 is 2 legs of 480 3 phase mains voltage. What
        Im doing is taking the 6 fault signals from a spindle chiller panel
        and trying to generate a fault signal back to the machine control to
        display a message to the operator.

        The spindle chiller is a stand alone unit on a CNC 5 axis Cincinnati
        mill with 3-10,000 rpm spindles. All the 277 lines are from the same
        2 phases as far as I can tell. I don't have a schematic on the
        chiller and the company that made it folded along time ago.

        Chuck
      • JanRwl@AOL.COM
        In a message dated 10/3/2004 10:07:06 PM Central Standard Time, dave_mucha@yahoo.com writes: I have seen 277 VAC as typically a lighting circuit. higher
        Message 3 of 7 , Oct 3, 2004
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          In a message dated 10/3/2004 10:07:06 PM Central Standard Time, dave_mucha@... writes:

          I have seen 277 VAC as typically a lighting circuit.  higher voltage
          for less line losses for better efficency and all that.
          277 is the voltage to neutral, each leg, for a "480 VAC 3-phase" feed.
        • rtstofer
          And it is odd that the neutral would be extended to a machine tool. Normally the 3 phases are used for motors but control power is normally obtained with a
          Message 4 of 7 , Oct 3, 2004
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            And it is odd that the neutral would be extended to a machine tool.
            Normally the 3 phases are used for motors but control power is
            normally obtained with a small 480-120V single phase transformer.

            In fact, in 40 years of electrical work, I have never seen the
            neutral extended to a machine tool. I haven't even seen the neutral
            present in panels serving machine shop loads unless, perchance,
            there was a lighting circuit on the same panel.

            Anything is possible, I suppose; but this situation seems a little
            odd. This isn't a case where the phase is being referenced to
            ground (instead of a grounded neutral) by any chance? That is a
            very dangerous condition.

            --- In Electronics_101@yahoogroups.com, JanRwl@A... wrote:
            >
            > In a message dated 10/3/2004 10:07:06 PM Central Standard Time,
            > dave_mucha@y... writes:
            >
            >
            > I have seen 277 VAC as typically a lighting circuit. higher
            voltage
            > for less line losses for better efficency and all that.
            >
            >
            >
            > 277 is the voltage to neutral, each leg, for a "480 VAC 3-phase"
            feed.
          • Dave Mucha
            ... Fortunately, ... to ... Cincinnati ... same ... OK, whole different animal. If you want a phase to phase relationship, you can use the current
            Message 5 of 7 , Oct 4, 2004
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              --- In Electronics_101@yahoogroups.com, "Chuck Waters"
              <weallbecrashin@y...> wrote:
              >
              > Phase matters if you want to combine the opto outputs
              > > from the three
              > > > 277V sources and not rectify the incoming current.
              Fortunately,
              > > they are in
              > > > phase.
              > > >
              > > > Rick Sparber
              > >
              > >
              > > Did I miss something ? was this 3-phase 277 volts ?
              > >
              > > Dave
              >
              > Well, actually the 277 is 2 legs of 480 3 phase mains voltage. What
              > Im doing is taking the 6 fault signals from a spindle chiller panel
              > and trying to generate a fault signal back to the machine control
              to
              > display a message to the operator.
              >
              > The spindle chiller is a stand alone unit on a CNC 5 axis
              Cincinnati
              > mill with 3-10,000 rpm spindles. All the 277 lines are from the
              same
              > 2 phases as far as I can tell. I don't have a schematic on the
              > chiller and the company that made it folded along time ago.
              >
              > Chuck


              OK, whole different animal.

              If you want a phase to phase relationship, you can use the current
              transformers and get an analogue output of current.

              with current and voltge you can calculate watts so you can know what
              each leg is doing in relation to each other.

              Lots more work, but lots more information.

              Dave
            • Dave Mucha
              ... tool. ... neutral ... Funny how things work. I used to sell air curtains or air doors, the long blowers that sit over doors to keep the cold and bugs out.
              Message 6 of 7 , Oct 4, 2004
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                --- In Electronics_101@yahoogroups.com, "rtstofer" <rstofer@p...>
                wrote:
                >
                >
                > And it is odd that the neutral would be extended to a machine
                tool.
                > Normally the 3 phases are used for motors but control power is
                > normally obtained with a small 480-120V single phase transformer.
                >
                > In fact, in 40 years of electrical work, I have never seen the
                > neutral extended to a machine tool. I haven't even seen the
                neutral
                > present in panels serving machine shop loads unless, perchance,
                > there was a lighting circuit on the same panel.
                >
                > Anything is possible, I suppose; but this situation seems a little
                > odd. This isn't a case where the phase is being referenced to
                > ground (instead of a grounded neutral) by any chance? That is a
                > very dangerous condition.

                Funny how things work.

                I used to sell air curtains or air doors, the long blowers that sit
                over doors to keep the cold and bugs out.

                we would regularly get warehouses with 277 all over the place for
                lighting, their largest load. And, they wanted to use 277 for a 3 hp
                motor to run the blowers.

                I have never been involved in the 3 phase motor side outside of
                controling the units they were hooked to.

                Dave
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