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  • 3 phase 220V generator

    HI Forum

    Back from holidays and already hit my first impasse! oh well, work is work.

    We have a client that wants to substitute his 3 phase 220V generator with a 2kW PV system. Fine, but he wants to be able to switch between the generator and PV. The trouble is that the circuits are mixed up between the phases of 220V. So he has one circuit L1-L2, one L2-L3 and another L1-L3.

    Is there any way we can keep the circuits as they are, yet switch between PV single phase and then to the 3-phase motor if the batteries are low?
    http://www.freelight.es

  • #2

    Re: 3 phase 220V generator

    Re: 3 phase 220V generator

    This may be a dumb question: can you not simply install a 3-phase inverter system? I know Outbacks can be wired this way.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

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    • #3

      Re: 3 phase 220V generator

      Re: 3 phase 220V generator

      Originally posted by Cariboocoot View Post
      This may be a dumb question: can you not simply install a 3-phase inverter system? I know Outbacks can be wired this way.
      I'll second that. SMA, Studer and Victron will also do 3-phase.
      2.8kW Yingli PV, 5kW SMA Sunny Island 5048, 900Ah 48V Forklift battery, 5kW Petteroid Indian diesel generator.
      Live data: https://xively.com/feeds/75889/ Blog: http://www.casanogaldelasbrujas.com

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      • #4

        Re: 3 phase 220V generator

        Re: 3 phase 220V generator

        Nope, 3 phase is a no can do- just one 5kVA inverter single phase, already bought. And anyway, they would give 380V 3 phase and the generator is 220V 3 phase
        http://www.freelight.es

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        • #5

          Re: 3 phase 220V generator

          Re: 3 phase 220V generator

          Originally posted by lazza View Post
          Nope, 3 phase is a no can do- just one 5kVA inverter single phase, already bought. And anyway, they would give 380V 3 phase and the generator is 220V 3 phase
          The motor could be handled either with a VFD which would generate the 3 phase required or with a rotary converter. The latter would probably only be about 50% efficient and would have to be run up to speed before the motor is started. Probably more reasonable to start the generator when the 3 phase motor has to be run.

          But before going deeper into this, I would like to know for sure just what the generator is providing!

          In the US, the POCO would supply 208 volts line to line and 120 volts line to neutral. Since your system is based on 220 volts with no neutral, the generator probably actually is configured to deliver 220 volts Line to Line. As such, there is no way that you can substitute a single phase 220 volt source from the inverter without making the transfer switch do a lot more reconnecting to maintain the single phase 220 volt loads, and the 3-phase motor would have to be completely disabled or else transferred to a separate 3-phase supply as I first mentioned.

          Assuming that you can do the required load shedding to not overload the inverter, and calling the two Inverter outputs A and B (220 volt w/o neutral), the transfer switch would have to connect L1 to A and L2 to B to provide power just to that one leg (L1 to L2) of the loads, and then disconnect the second leg (L2 to L3) L3 connection and transfer it to A. The third leg (L3 to L1) could then have its L1 side connected to A and its L3 side connected to B.

          The only other alternative that I can see would be to use a single-phase to three-phase converter running off the inverter output to power everything. This could NOT be a rotary converter, since they are not designed to handle separate single phase loads.
          Sunny Boy 3000US, 18 x BP Solar 175b panels, installed 2009.

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          • #6

            Re: 3 phase 220V generator

            Re: 3 phase 220V generator

            Thanks for your replies, yes it will require some form of complex switching, which may or may not be practical. The problem is he wants to switch between the two forms of power and this is difficult... without changing the generator setup..
            http://www.freelight.es

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            • #7

              Re: 3 phase 220V generator

              Re: 3 phase 220V generator

              Originally posted by lazza View Post
              Thanks for your replies, yes it will require some form of complex switching, which may or may not be practical.
              More than impractical, I think it'll be a costly nightmare, especially since you won't be able to switch between gen and inverter without dropping the loads.
              3 x single phase off-grid inverters will solve all this and provide a nice clean install, where the generator can be switched in without losing any power to the loads. You can configure them to be 230V 3 phase or 380V 3 phase.
              2.8kW Yingli PV, 5kW SMA Sunny Island 5048, 900Ah 48V Forklift battery, 5kW Petteroid Indian diesel generator.
              Live data: https://xively.com/feeds/75889/ Blog: http://www.casanogaldelasbrujas.com

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              • #8

                Re: 3 phase 220V generator

                Re: 3 phase 220V generator

                .. am I right in supposing that the generator has a Delta 3-phase wiring, which would give it 220V between phases without a neutral... if it were a Wye 3-phase wiring would it then give 380V ??
                http://www.freelight.es

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                • #9

                  Re: 3 phase 220V generator

                  Re: 3 phase 220V generator

                  Originally posted by lazza View Post
                  .. am I right in supposing that the generator has a Delta 3-phase wiring, which would give it 220V between phases without a neutral... if it were a Wye 3-phase wiring would it then give 380V ??
                  From the description of the load connections (phase-to-phase), it would have to be a delta application with 220 volts phase-to-phase regardless of how the generator is actually built and whether or not it has a neutral also.

                  If it were a wye with 220 from phase to neutral, then yes, the phase-to-phase would be 380. But we do not know how the generator is actually wired. We just know how it is intended to be used.

                  It will be far easier to change or supplement the inverter to make 3 phase power available than to reconfigure all of the loads and the generator itself!

                  Regardless of how the failover occurs in terms of switching and reconnection, either there will be a short drop as the relay contacts transfer or there will have to be a full-time UPS in the process somewhere. Doing the complex connection rearrangement with contactors and relays will not leave the loads disconnected for much (if at all) longer than just transferring 3 line connections via simple relays.

                  One critical requirement for safety though is that all three phase wires have to be interrupted in one operation and that operation must complete before any of the phase wires are reconnected to a power source. The consequences of one phase hanging on the generator while the others transfer to the inverter or vice-versa could be really bad.
                  Sunny Boy 3000US, 18 x BP Solar 175b panels, installed 2009.

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                  • #10

                    Re: 3 phase 220V generator

                    Re: 3 phase 220V generator

                    Originally posted by stephendv View Post
                    More than impractical, I think it'll be a costly nightmare, especially since you won't be able to switch between gen and inverter without dropping the loads.
                    3 x single phase off-grid inverters will solve all this and provide a nice clean install, where the generator can be switched in without losing any power to the loads. You can configure them to be 230V 3 phase or 380V 3 phase.
                    Not all single phase off-grid inverters have synchronizing capabilities which would allow them to work together to generate three proper phases. Not all of the loads are single phase, there is also a motor involved. Even if there were not, the delta connection of the loads demands that the three inverters be synchronized.
                    Sunny Boy 3000US, 18 x BP Solar 175b panels, installed 2009.

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                    • #11

                      Re: 3 phase 220V generator

                      Re: 3 phase 220V generator

                      Originally posted by inetdog View Post
                      Not all of the loads are single phase, there is also a motor involved.
                      Don't see where the OP said clearly that there was a motor load. I think he could be referring to the generator when he said motor in his first post.

                      Even if there were not, the delta connection of the loads demands that the three inverters be synchronized.
                      Has he told us that the loads have a delta connection? I have no idea what the wiring in Spain is likely to be like. If it is a wye, and there are no multiwire branch circuits where all three phase conductors share a neutral (or they could be rewired), then conceivably two legs could be hooked up to one single phase inverter.

                      Originally posted by lazza View Post
                      .. am I right in supposing that the generator has a Delta 3-phase wiring, which would give it 220V between phases without a neutral... if it were a Wye 3-phase wiring would it then give 380V ??
                      No, you have it backwards. If the phase-to-phase voltage (delta) is 380, the phase-to-neutral voltage (wye) will be 220V. If the phase-to-phase voltage is 220V, the phase-to-neutral would be 127V. Phase-to-phase is 1.73 of phase-to-neutral for the same generator.

                      You haven't told us whether the 220V is phase-to-phase or phase-to-neutral for the generator your client has.

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                      • #12

                        Re: 3 phase 220V generator

                        Re: 3 phase 220V generator

                        Originally posted by inetdog View Post
                        Not all single phase off-grid inverters have synchronizing capabilities which would allow them to work together to generate three proper phases. Not all of the loads are single phase, there is also a motor involved. Even if there were not, the delta connection of the loads demands that the three inverters be synchronized.
                        Which is why in the first response I mentioned the Outbacks which can be configured this way.
                        1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

                        Ohm's Law: Amps = Volts / Ohms
                        Power Formula: Watts = Volts * Amps

                        Comment


                        • #13

                          Re: 3 phase 220V generator

                          Re: 3 phase 220V generator

                          Originally posted by jaggedben View Post
                          Has he told us that the loads have a delta connection? I have no idea what the wiring in Spain is likely to be like. If it is a wye, and there are no multiwire branch circuits where all three phase conductors share a neutral (or they could be rewired), then conceivably two legs could be hooked up to one single phase inverter.
                          I think that the very first post stated that if the three busses in the panel are named L1, L2 and L3, some loads are connected L1-L2, some L2-L3 and some L3-L1. That can only be accomplished if the loads are wired in delta. That is what made it impossible for him to connect L1, L2 and L3 all to the single phase generator output when operating the transfer switch.

                          Yup:

                          The trouble is that the circuits are mixed up between the phases of 220V. So he has one circuit L1-L2, one L2-L3 and another L1-L3.
                          I think that you are right that motor was a reference to the generator, so there may not be any three phase loads (unless there is a heating appliance like a stove which leverages the 127 volt phase to neutral voltage via a cross-connection of resistive elements over all three phases to get different outputs. Not at all likely!)
                          Sunny Boy 3000US, 18 x BP Solar 175b panels, installed 2009.

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