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Leyton 3-2 tranformer setup - found in old thread in this forum- very interesting

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    Leyton 3-2 tranformer setup - found in old thread in this forum- very interesting

    It's this question in italics below that's intriguing. It wasn't answered 3 years ago, and the setup seems great for stepping down.
    If it did something usable when stepping up, it would be even more useful.
    Anyone have any reasonable guess what would happen?
    I'm thinking you'd get one unique leg and the two other legs on the "3 phase" side would be... the same angle?
    I sent Mr. Leyton an email, hope to hear back from him.

    Just wondering if anyone besides the "inventor" has actually seen a setup like this used , in any capacity.

    http://forums.mikeholt.com/showthread.php?t=146298

    Q- Curious, what happens if it it back fed with single phase voltage?

    A- Interesting ! - You would not get 3-phase out of it unfortunatly. Not sure what would happen though.

    Here's another link for it:http://wpedia.goo.ne.jp/enwiki/User:Hugh_Leyton/sandbox

    #2
    Maybe I'm missing something but I don't see what's special about a transformer with multiple secondary windings or why it would be needed. We already get 1 phase power from 3 phase trannys: Most apartment buildings are fed that way.

    And no, it wouldn't work stepping back up from single phase to three phase. If it did, I agree, that would be invaluable.

    Comment


      #3
      Originally posted by big john View Post

      And no, it wouldn't work stepping back up from single phase to three phase.
      Sure it would. All you have to do is feed it three perfectly synchronized single phase waveforms of equal magnitude 120 degrees apart.

      Comment


        #4
        Originally posted by big john View Post
        1. Maybe I'm missing something but I don't see what's special about a transformer with multiple secondary windings or why it would be needed. We already get 1 phase power from 3 phase trannys: Most apartment buildings are fed that way.

        2. And no, it wouldn't work stepping back up from single phase to three phase. If it did, I agree, that would be invaluable.
        But that's 120/208V 1ph from 208/120V 3ph, right?
        When there's already an entire 120/240V wiring system in place (3 wire, split phase, 120V L-N, 240V L-L) with "highly variable" loads over 20kVA, this idea seems a lot more useful (more useful than boosting 20kVA of 240V loads up from 208V, maybe?)

        2. It wouldn't work wired at 480V delta/high side as described, but if you scratch that and look at it as 3 xfmrs being fed on the low side with the same 2 legs/phases of 120V and the neutral...
        or feed it something different, like ggunn said~!

        If fed 120/240V low side (wired as is by Mr. Leyton), and considered as three separate outputs on the 480V side...they'd all be the same single phase of 480V? Maybe?



        HughL
        If, for example, your Intake Transformer and or Generator are 100 KVA and your total 120/240V are 10 KVA or less, then stick with the Single phase transformer across two phases. If, on the other hand, your 120/240V loads are highly variable, and in the 20 KVA to say 80 KVA range, then this 3-phase to 120/240V transformer arrangement is the Best solution.

        Comment


          #5
          Based entirely on a symmetry argument, I would have to guess that with 120V or 240V applied to the appropriate output terminals you would have zero volts on all three of the primary phases.
          Applying a voltage in the correct phase relationship to the supplied 120 to any single input phase would then cause the other two matching phases to appear on the three phase side.
          But that is just a SWAG.

          Comment


            #6
            Originally posted by PVfarmer View Post

            2. It wouldn't work wired at 480V delta/high side as described, but if you scratch that and look at it as 3 xfmrs being fed on the low side with the same 2 legs/phases of 120V and the neutral...
            or feed it something different, like ggunn said~!
            I was joking. You cannot generate three waveforms displaced by 120 degrees from each other from a single phase waveform using only transformers.

            Comment


              #7
              http://forums.mikeholt.com/showthread.php?t=172825

              The arrangement described in the original post is a conventional 'double delta'. This is simply two delta secondaries placed electrically in series. You can greatly simplify the discussion and your understanding by considering what would happen to a single delta system.

              You can take a normal 3 phase delta secondary and just put a single phase load on it, connected to two of the phase terminals and a mid-coil tap. The third phase terminal is simply unused.

              If you were to connect a single phase _supply_ to the delta secondary, you will _not_ get 3 phase power developed on the primary side!

              -Jon

              Comment


                #8
                Originally posted by ggunn View Post
                I was joking. You cannot generate three waveforms displaced by 120 degrees from each other from a single phase waveform using only transformers.
                Originally posted by winnie View Post
                The arrangement described in the original post is a conventional 'double delta'. This is simply two delta secondaries placed electrically in series. You can greatly simplify the discussion and your understanding by considering what would happen to a single delta system.

                You can take a normal 3 phase delta secondary and just put a single phase load on it, connected to two of the phase terminals and a mid-coil tap. The third phase terminal is simply unused.

                If you were to connect a single phase _supply_ to the delta secondary, you will _not_ get 3 phase power developed on the primary side!

                -Jon
                ggunn- I wasn't sure if you were joking or saying rewire it and feed it 208/120V.

                winnie- I'm reading it as T2 and T3 are in series, and then those together are paralleled with T1. So T2 and T3 are creating the 180 degree leg of 120V (from 120 and 240 degree 480V) and T1 is the 0 degree leg when stepping down.
                In reverse...maybe two 120V legs of 120 and 240 degrees fed into the low side would... end up as 3 identical legs of single phase 480V? Or maybe as T1 at 0 degrees and T2 and T3 at 180 degrees, all 480V?

                A conventional double delta would just be two xfmrs with delta windings- this is three single phase xfmrs wired in...not quite double delta, but you can't call it triple either.
                This is from Mr. Leyton's .doc.

                Click image for larger version

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                Comment


                  #9
                  If you take a conventional delta-delta transformer, and supply _single_ phase between two terminals, then one of the coils will see _full_ applied voltage. The other two coils are electrically in series between the supply terminals, and act as a voltage divider. All things being equal, each would see half of the applied voltage. If this is a common core transformer, then things will not be equal, but you will still have a voltage divider.

                  So if you 'reverse feed' a 480/277V to 120/204 Leyton 3-2 configuration, then on the primary side you will get 480V between two of your (now output) terminals, and approximately 240V between the other terminals, with everything 'in phase'. Note: by 'in phase' I am including both exactly in phase or 180 degrees out of phase, which is the equivalent of inverted.

                  -Jon

                  Comment


                    #10
                    Originally posted by PVfarmer View Post
                    ggunn- I wasn't sure if you were joking or saying rewire it and feed it 208/120V.

                    winnie- I'm reading it as T2 and T3 are in series, and then those together are paralleled with T1. So T2 and T3 are creating the 180 degree leg of 120V (from 120 and 240 degree 480V) and T1 is the 0 degree leg when stepping down.
                    In reverse...maybe two 120V legs of 120 and 240 degrees fed into the low side would... end up as 3 identical legs of single phase 480V? Or maybe as T1 at 0 degrees and T2 and T3 at 180 degrees, all 480V?
                    So what is the point of all this? Yes, you can make 480V single phase from any other single phase AC voltage with a transformer, but you cannot make 480/277Y three phase from any single phase using transformers.

                    Comment


                      #11
                      Originally posted by ggunn View Post
                      So what is the point of all this? Yes, you can make 480V single phase from any other single phase AC voltage with a transformer, but you cannot make 480/277Y three phase from any single phase using transformers.
                      The point is curiosity, mainly. If it does something useful one way, maybe it has potential in reverse.

                      Say for instance you reverse feed it and change the xfmr voltages, with the same series/parallel "3-2" setup on the "high side" this time.
                      Make the high/Leyton side the same three 120V/240V inputs and the "low side" three 1ph 120/240V outputs.
                      Instead of 0 and 180 degrees 120V to the 3-2 side, apply 2 phases of 120V from 3ph 208/120V 3ph, one at 120 and the other 240 degrees- wouldn't you still get one 240V 1ph output and 2 120V 1ph outputs?


                      Originally posted by winnie View Post
                      If you take a conventional delta-delta transformer, and supply _single_ phase between two terminals, then one of the coils will see _full_ applied voltage. The other two coils are electrically in series between the supply terminals, and act as a voltage divider. All things being equal, each would see half of the applied voltage. If this is a common core transformer, then things will not be equal, but you will still have a voltage divider.

                      So if you 'reverse feed' a 480/277V to 120/204 Leyton 3-2 configuration, then on the primary side you will get 480V between two of your (now output) terminals, and approximately 240V between the other terminals, with everything 'in phase'. Note: by 'in phase' I am including both exactly in phase or 180 degrees out of phase, which is the equivalent of inverted.
                      Thanks-
                      How "approximate" are you being there?
                      And sorry- "240V between the terminals" ...so if the other 4 terminals are 240V L-L...then would you still have 120V L-N? If so...you'd have to have T1 be 240/480V and T2 and T3 be 120/240V on the non-Leyton side?

                      Also- any thoughts on this?

                      This time staying with stepping up to 480V.
                      "Instead of 0 and 180 degrees 120V to the 3-2 side, apply 2 phases of 120V from 3ph 208/120V 3ph, one at 120 and the other 240 degrees"...

                      Would you still get 480V from T1 and 240V from T2 and T3, but... T1 at 120 degrees and T2 and T3 at 240 deg.?

                      Comment


                        #12
                        Originally posted by ggunn View Post
                        So what is the point of all this?
                        Let me change my answer there- the point isn't about reverse feeding it at all, that's just the curiosity part.

                        I was hoping for someone to say "yes, I've tried it" or "no, that's a waste of time", by that I mean stepping down and using it for "messy" 120/240V loads.

                        Seems like winnie answered the question I meant to ask:
                        So if you 'reverse feed' a 480/277V to 120/204 Leyton 3-2 configuration,

                        Assuming it'll do the same thing stepping down to 120/240V "split" phase, whether the supply is either 480V L-L or 277V L-N, this is in fact the answer to all those Tripower questions I keep asking!
                        A 45kVA bank of 3 single phase 15kVA, 277V to 120/240V xfmrs makes 30kVA of 120/240V for a ~20kVA max load.
                        What more could I want?

                        Comment


                          #13
                          If you have a Tripower inverter lying around and you wanted to use it on a single phase 120/240 three wire service, the Leyton 3-2 would NOT do you any good since it will not supply the necessary three phase reference voltage to the Tripower to get it started.
                          If the inverter were an off-grid inverter with its own internal phase reference instead, then you could use the 3-2 configuration to get split phase output from it and distribute that load over all three inverter output phases.

                          Comment


                            #14
                            I think that if you analyze the phase angle of the current flowing in the Leyton arrangement, you will see that you still only have single phase loading.

                            In a normal step down transformer, the primary is a delta and the secondary is a wye. If you instead have a transformer with a delta primary and a 'Leyton' secondary, you will load all 3 coil sets, but the phase angle of the load currents would mean you are placing a _single phase_ load on the supply. A 3 phase supply is connected, and all three phases supply magnetizing current, but only 2 phases would actually supply power.

                            You asked about using three 277 to 120/240V transformers. This implies a wye primary and a 'Leyton' secondary. This _would_ put loading on all three phases, but I think if you look at the power factor of that loading you would find that it _still_ presents a single phase (line-line) load upstream.

                            -Jon

                            Comment


                              #15
                              Originally posted by GoldDigger View Post
                              1. If you have a Tripower inverter lying around and you wanted to use it on a single phase 120/240 three wire service, the Leyton 3-2 would NOT do you any good since it will not supply the necessary three phase reference voltage to the Tripower to get it started.
                              2. If the inverter were an off-grid inverter with its own internal phase reference instead, then you could use the 3-2 configuration to get split phase output from it and distribute that load over all three inverter output phases.
                              1. I get that. The service in this one case will be 480/277V- because the PV will be over the POCO limit on single phase PV output around here (50kVA), but all the premises wiring/equipment is 120/240V. Since the only "common" option is a 480/277V to 208/120V xfmr, this seems better.

                              2. Yes. It would create 120/240V from 480V, 240V or 208V three phase off-grid inverters, which is why I think it's neat!

                              Originally posted by winnie View Post
                              I think that if you analyze the phase angle of the current flowing in the Leyton arrangement, you will see that you still only have single phase loading.

                              In a normal step down transformer, the primary is a delta and the secondary is a wye. If you instead have a transformer with a delta primary and a 'Leyton' secondary, you will load all 3 coil sets, but the phase angle of the load currents would mean you are placing a _single phase_ load on the supply. A 3 phase supply is connected, and all three phases supply magnetizing current, but only 2 phases would actually supply power.

                              You asked about using three 277 to 120/240V transformers. This implies a wye primary and a 'Leyton' secondary. This _would_ put loading on all three phases, but I think if you look at the power factor of that loading you would find that it _still_ presents a single phase (line-line) load upstream.
                              Right, the two in series are acting as one xfmr. So as described by Mr. Leyton and reverse fed with 10 amps of 120/240V, you'd get... 5 amps of 480V from T1 and 2.5 amps each of 240V from T2 and T3, all at 0 and 180 degrees? Is that what you were getting at in your previous comment?
                              Thanks.

                              Comment

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