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  • Honda EU2000 Transformer Problem

    One of our off-grid neighbors has a XW system. They bought a little Honda EU2000 so they can use it on generator support like we do to run their A/C system in the summer, and other heavy continuous loads at other times of the year, without running their big generator. Of course, being the the EU2000 is only 120V output it requires a transformer for split-phase to the inverter. They bought a Outback PSX-240 autotransformer.

    The problem is that the little EU2000's inverter faults on overload and doesn't seem to be able to handle the inrush when it magnetizes the transformer core. I fiddled with it for several hours yesterday and couldn't get it work. We brought the transformer over to our place thinking there might be a problem with it, and hooked it up to our system and tried it with our our little Honda EP2500CX. It works fine on our system. I put my Fluke meter on the transformer on capture mode and it looks like the transformer draws 80-90 amps on inrush when the core magnetizes. The conventional generator is able to handle this because it's only for a few milliseconds. But the inverter in the EU2000 is too quick on the trigger and faults because of it, thinking the transformer is a dead short.

    Any electrificution engineers got any good plans on how to overcome this little issue?
    off-grid in Northern Wisconsin for 14 years

  • #2
    Originally posted by ChrisOlson View Post
    One of our off-grid neighbors has a XW system. They bought a little Honda EU2000 so they can use it on generator support like we do to run their A/C system in the summer, and other heavy continuous loads at other times of the year, without running their big generator. Of course, being the the EU2000 is only 120V output it requires a transformer for split-phase to the inverter. They bought a Outback PSX-240 autotransformer.

    The problem is that the little EU2000's inverter faults on overload and doesn't seem to be able to handle the inrush when it magnetizes the transformer core. I fiddled with it for several hours yesterday and couldn't get it work. We brought the transformer over to our place thinking there might be a problem with it, and hooked it up to our system and tried it with our our little Honda EP2500CX. It works fine on our system. I put my Fluke meter on the transformer on capture mode and it looks like the transformer draws 80-90 amps on inrush when the core magnetizes. The conventional generator is able to handle this because it's only for a few milliseconds. But the inverter in the EU2000 is too quick on the trigger and faults because of it, thinking the transformer is a dead short.

    Any electrificution engineers got any good plans on how to overcome this little issue?
    Wire a death box (quad box, metal cover) into the center of a 12ga, 25' ext cord. In the death box, place a duplex outlet, in series with the hot wire only. Wire a incandescent rated wall switch across the outlet. Switch off.
    Plug in a 250W heat lamp & turn it's switch on. Start the generator, and plug in the death box cord. Plug the PSX-240 into the ext cord from the death box. Switch on the genset CB. The light bulb limits the power in the circuit till the core charges up (about 3 seconds maybe) Turn the death box switch to ON, bypassing the light bulb, and you should be good at 1.8Kw.

    This could all be hardwired after proven out, with a NO relay and a push-button switch) Change the light bulb wattage as needed (500w worklight)
    Last edited by Mike90250; 04-06-2014, 03:40 PM.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

    Comment


    • #3
      Mike, I've tried everything from light bulbs to a really long cord to even a run capacitor out of a single phase motor. I haven't been able to come up with a "poor man's soft start" yet that works.
      off-grid in Northern Wisconsin for 14 years

      Comment


      • #4
        I can fix you up. There are a few ways to getter done depending on how much time and money you want to spend. Easiest way is just to get a transformer that matches the source impedance.

        Option one is to use what is called a Inrush Current Limiter circuit. Sound fancy and complicated but very simple. All it amounts to is a temperature dependent resistor with a Negative Temperature Coefficient, and a relay to short it out after one second. When you initially apply power the resistance is high enough to start the saturation process. As current flows the resistor heats up and the resistance goes lower and lower fully saturating the core. Than about after one second you have a relay short it out thus removing it from the circuit and off you go.
        MSEE, PE

        Comment


        • #5
          Originally posted by Sunking View Post
          I can fix you up. There are a few ways to getter done depending on how much time and money you want to spend. Easiest way is just to get a transformer that matches the source impedance.

          Option one is to use what is called a Inrush Current Limiter circuit. Sound fancy and complicated but very simple. All it amounts to is a temperature dependent resistor with a Negative Temperature Coefficient, and a relay to short it out after one second. When you initially apply power the resistance is high enough to start the saturation process. As current flows the resistor heats up and the resistance goes lower and lower fully saturating the core. Than about after one second you have a relay short it out thus removing it from the circuit and off you go.
          Sunking - yeah, that would be like a typical soft start box for a big three-phase motor that starts under load. Without those soft-starts factories and plants that run big motors would cause brown-outs across entire neighborhoods when they fire 'em up.

          Now, I just have to figure out what commonly available stuff I can build a little one out of

          I had a 300uF run capacitor in the shop out of a single phase motor and tried that but it didn't even act like I had the capacitor inline. The reason the conventional generator can "soft start" that transformer is because when the core magnetizes, the corresponding voltage drop you get with a conventional generator limits the current so it just gently brings the transformer online (although the transformer still makes a big "thud" when it fires up). The inverter genset has virtually no surge power at all compared to a conventional generator. It's DC input is fed by a tiny little three-phase permanent magnet generator on the engine crankshaft that's rectified output, and that little generator and engine doesn't have anywhere near the surge capacity of a battery to keep within the inverter's operating limits. So it faults and shuts down.

          I'll have to go to the local electric motor rewinding shop (about a 60 mile drive) tomorrow and see if I can find a suitable resistor and timed contactor out of a junked out soft start. The trouble is, those resistors in even a small soft start for a three-phase motor are about 6" in diameter and 2 feet long and I doubt the little EU even puts out enough power to energize the contactor coil and close the contactor in one of those.

          But maybe old Bob there at the motor shop has something laying around that will work - he usually does
          off-grid in Northern Wisconsin for 14 years

          Comment


          • #6
            Originally posted by ChrisOlson View Post
            Mike, I've tried everything from light bulbs to a really long cord to even a run capacitor out of a single phase motor. I haven't been able to come up with a "poor man's soft start" yet that works.
            I'm sure a 100w bulb is too small. Maybe 250w heat lamp is too small. But a 500W quartz work light should be enough to "fill up" the transformer in a couple seconds, without crashing the genset.
            Inverters have trouble with large inductive / capacitive loads.

            My Honeywell 2KW inverter genset, was running just this last weekend, for a couple 5 hour runs, driving a 3.5KVA step-up transformer I rigged up as an auto-transformer.

            Maybe there is a fault in the transformer ? Try firing it up from another source and "bake it out" for a couple hours, in case some moisture got in there ?

            If the transformer is good, I just can't see how it's not working with a light bulb as a ballast.
            Last edited by Mike90250; 04-07-2014, 12:59 AM.
            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister

            Comment


            • #7
              Originally posted by Mike90250 View Post
              If the transformer is good, I just can't see how it's not working with a light bulb as a ballast.
              Mike, I think the transformer is OK. We brought it to our place because we thought there might be something wrong with it. We tested it on our EP2500CX and it worked fine. I measured the inrush with my Fluke and it's about 80-90 amps with the Fluke on high value capture. I verified that against our PSX-240 and got the same reading for inrush current.

              I agree that a big light bulb should work. However, we have never had a use for a 500 watt quartz lamp here and it would be a 60 mile drive to get one

              So we tried everything we had available at hand so far, including a long cord, and it didn't work. Today I have to run into town and then I'll see if I can find something to make a soft-start from.
              off-grid in Northern Wisconsin for 14 years

              Comment


              • #8
                Originally posted by Sunking View Post
                Option one is to use what is called a Inrush Current Limiter circuit. Sound fancy and complicated but very simple. All it amounts to is a temperature dependent resistor with a Negative Temperature Coefficient, and a relay to short it out after one second.
                Sunking - hey, the lightbulb came on over my head this morning when I re-read this. Your description is exactly how a soft start works - I just need the parts to build a little one for this tiny generator. So, I need a resistor. I got a 120V 2000 watt water heater element here. That heater measures 7.1 ohms. That should cause a pretty good voltage drop hooked in series on the hot leg going to the transformer to "soften" how fast the core builds a mag field around it. If one isn't enough I got two of 'em and can put 14 ohms in series.

                I'm going to try this this morning with a light switch wired to bypass it like Mike's Death Box and see if it works. If it does, all I need is a timed 1 second delay contactor from the motor shop.

                Thanks!
                off-grid in Northern Wisconsin for 14 years

                Comment


                • #9
                  14 Ohms on a 120 volt circuit should be more than enough and limit start up current to around 9 amps. Might have to play with time settings to find the sweet spot but 1 to 2 seconds should getter done.
                  MSEE, PE

                  Comment


                  • #10
                    Just got back from the neighbor's place. One water heater element worked. But it make the generator grunt and the overload light flashed on for a brief instant before I flipped the switch. The transformer load is only about 10 watts once the core gets magnetized but the heater load is 2,000 watts which is all the little generator can put out on surge initially. Once I flip the switch the transformer is fired up and online and the heater is out of the circuit. And we got 240.6V at the inverter input.

                    The neighbor said forget the timed contactor. He has to manually start the little generator anyway, and he said he'll just throw the switch after it starts and that's no big deal.

                    Now I just have to build a nice box for him with the element mounted on an aluminum heat sink (the element does get pretty hot almost immediately before you can flip the switch) so it's safe and somewhat professional looking. A water heater element clamped in a vice and a switch dangling by some wires is not going to cut it long term........

                    Thanks guys!
                    off-grid in Northern Wisconsin for 14 years

                    Comment


                    • #11
                      Originally posted by ChrisOlson View Post
                      Thanks guys!
                      Your Welcome.

                      Told you I could fix it.
                      MSEE, PE

                      Comment


                      • #12
                        Originally posted by Sunking View Post
                        Your Welcome.

                        Told you I could fix it.
                        Yeah, it's "fixed". I formed up a nice stainless steel box and made an aluminum heat sink for the element to mount on in it. I have to TIG the corners on the box and make a cover for it yet. I don't think there's much danger of him overheating the element if he forgets to throw the switch because the generator will only put out enough power to run that element in the circuit for maybe 10-15 seconds before it overload faults. So I'm not going to drill any ventilation holes in the box. He doesn't have a nice generator house like we got. His generators are in an old pole shed with dust and dirt and cobwebs and bugs and birds and stuff. Be good to keep dust and bugs out of the box.
                        off-grid in Northern Wisconsin for 14 years

                        Comment


                        • #13
                          Originally posted by ChrisOlson View Post
                          Yeah, it's "fixed". I formed up a nice stainless steel box and made an aluminum heat sink for the element to mount on in it. I have to TIG the corners on the box and make a cover for it yet. I don't think there's much danger of him overheating the element if he forgets to throw the switch because the generator will only put out enough power to run that element in the circuit for maybe 10-15 seconds before it overload faults. So I'm not going to drill any ventilation holes in the box. He doesn't have a nice generator house like we got. His generators are in an old pole shed with dust and dirt and cobwebs and bugs and birds and stuff. Be good to keep dust and bugs out of the box.
                          Sounds like a good place for a fire.
                          MSEE, PE

                          Comment


                          • #14
                            Originally posted by Sunking View Post
                            Sounds like a good place for a fire.
                            Well, that's why I want to keep dust and bugs out of the box. If he forgets to throw the switch sometime and gets the element really hot at least it's contained inside the stainless steel box.

                            He's got a Perkins diesel generator in there sitting on a pallet with a piece of flex pipe going thru the wall for the exhaust. And now he's got a Honda EU2000 sitting on an old steel work table. And, of course, the rest of the shed is full of "stuff" too. Old boards that he cuts up for kindling for the fireplace. Couple old tractors. 1947 Chev truck cab sitting on a couple pallets. Several old rusted V-8 engines from the 60's and 70's sitting on their side on the dirt floor leaking oil out.

                            Yep. She's quite a place
                            off-grid in Northern Wisconsin for 14 years

                            Comment


                            • #15
                              don't get too fancy, the heater elements are going to fail from the thermal shock pretty quickly. I think the big light bulb as ballast, will be the better load.
                              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                              solar: http://tinyurl.com/LMR-Solar
                              gen: http://tinyurl.com/LMR-Lister

                              Comment

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