Xantrex SW5548 in series issue

5320Ferrari5320Ferrari Registered Users Posts: 6
I have 2 Xantrex sw5548 inverters connected in series that I have been using since 11/06. In that time I have used a couple gas generators as back ups with out any issues as long as the load was set within range of the generator so the voltage didn't drop out. Now I have found a good deal on a MultiQuip 6Kw diesel that will give me the ability to remote start from the inverters. The issue is when I plug in the MultiQuip I cannot keep both inverters connected. Either one or the other immediately drops out if it is the second to try and connect and without any errors. I can connect either pole of the generator to either inverter and no issue if kept single. The generator tested OK at an authorized shop. If I go back to my 8Kw welder/generator no issue. Any ideas?

Comments

  • VicVic Solar Expert Posts: 3,113 ✭✭✭✭
    Re: Xantrex SW5548 in series issue

    Welcome to the Forum,

    As you probably know, there are a number of settings that involve generators. There are those for qualification of the genset power, and those that involve the amount of charging current taken by each inverter, and those that govern the additional power needed for AC loads that are seen by the inverters, that must be carried when the genset is qualified and charging the batteries.

    Have you tried reducing the AC Charger current setting in each inverter?

    Sounds like the genset is being qualified with only inverter on-line but fails when the second connects and starts drawing additional AC current from the genset.

    Disqualification COULD be either the Vin minimum spec or the Input Frequency (Hz) spec is being violated, and there disqualified.

    Would first try reducing the AC Charger current settings (a bit) on each inverter.

    Am using SW Plus inverters which are very similar, yet different. Little time now, but will check back.

    If the inverters are trying to Bulk the batts, then there is little likelihood that the genset AC V is being dragged upward beyond the Max AC Vin spec, which can happen with smallish genserts as the inverters try to regulate to Vabsorb.

    EDIT: Furthermore, that genset is really a bit small, when considering that all loads on the Inverter AC outs plus Charger AC current must be supplied by the generator. Believe that your location is around 4000 feet elevation. Generators generally need to be de-rated for altitude at 3% per 1000 feet elevation above 500 or 1000 feet, depending on the manufacturer's spec. So that could easily be a 10% reduction in the output, plus any reduction due to wear on the engine, etc. It IS true that this de-rating would have applied to your previous, somewhat larger gensets as well ... back to work ..

    Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • 5320Ferrari5320Ferrari Registered Users Posts: 6
    Re: Xantrex SW5548 in series issue

    Vic,
    Thank you for your comprehensive reply. My first generator during construction was smaller so I learned early on not to have the 'Gen amps AC' to high. I immediately dropped the setting down to 10 amps to eliminate that issue and would then work it back up if it was the problem but no go. I seldom have to use the generator so the size works fine for me to keep the batteries from suffering. I am now retired and will soon be living there and can manage loads but needed the auto start capability for insurance against damaging the batteries like I did on the first set, only got six years on them. I am leaving to go up right now so I will play with the other settings you noted to see if I can isolate the issue that way. Looking at the manual I do not have an Input Frequency (Hz) setting, just 'lower' & 'upper limit VAC' of which only the lower set at 108 could be a problem when adding the second inverter load. When the shop tested the lower limit it was at 112VAC at 25 amps on both poles. Maybe it drops for just a split second until the generator revs up a little.
    Thanks again,
    Bruce
  • VicVic Solar Expert Posts: 3,113 ✭✭✭✭
    Re: Xantrex SW5548 in series issue

    OK Bruce,

    In the Charger menu, there should be a setting for AC Charge Amps, try cutting back on this setting on each inverter. The DC charge current will be about 2.5 times this value. You may not have too many items in the Meters menu, the SW +es have a Frequency DISPLAY, which might give you an idea of what the generator's frequency is when the generator has been qualified (if you do have that display)

    Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • 5320Ferrari5320Ferrari Registered Users Posts: 6
    Re: Xantrex SW5548 in series issue

    Vic,
    Just like anything else if you play with it long enough you get to know how to get around fast and respond to what the meters menu is telling you. I first set my multimeter to record minimum generator AC In and found it went down to 107 on one so I changed the lower limit to 106 and both connected and settled at around 110VAC from the generator at 60Hz. It is a cloudy day so the inverter pulled around 25 amps each for about an hour when I heard one disconnect. That's when I really got into looking at the meters of the inverter and found the generator output jumping all over the place. At one point I had 109VAC on one and 133VAC on the other and that is why it disconnected. Later the one leg that was high went low. I now think I need to price a winding for the generator. The inverters seem to be doing what they are supposed to.

    Thanks for all the input,
    Bruce
  • VicVic Solar Expert Posts: 3,113 ✭✭✭✭
    Re: Xantrex SW5548 in series issue

    OK, Bruce,

    Thanks for the update. One of the issues with the SW and SW Plus inverters when Series Stacked (and perhaps in parallel), when charging, is that they do not pull current from each side AV input source in unison. So, especially on smaller gensets, this can cause voltage requlation problems on the AC input with lower current. This sensitivity will depend on how well the generator regulates voltage with asymmetrical load currents.

    Your genset may not have any issue at all, may just be the nature of the way it regulates voltage with large asymmetric load currents.

    It is possible that the Bulk charge stage is fine (the first hour t 25 A you mentioned (?)), as the inverters are not trying to regulate voltage. When Absorb V is reached, then there can be that situation where the inverter's charger will dump some current INTO the generator's output in order to keep the voltage near its set point. This can drag the generator's output out of regulation, causing disqualification, and dropping of that side of the AC input.

    This stuff can be difficult to diagnose while using only the built-in Meters in the inverters, as they may not update quickly enough to see what is going on during the above-noted voltage regulation scenario.

    Smallish gensets can be dragged around a bit with these fairly large inverters, especially when paired. Just my opinions. IMHO, these inverter/chargers are very stout indeed. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • 5320Ferrari5320Ferrari Registered Users Posts: 6
    Re: Xantrex SW5548 in series issue

    Sounds very similar as the one that was disconnecting was trying to go to float while the one that was still on bulk stayed connected. With that I will finish the auto start wiring from the inverter and have it shut the generator off after bulk since it is backup anyway. Might even play with offsetting the bulk volts between the two to get them to switch about the same time and avoid the imbalance. The genset doesn't have a voltage regulator just a capacitor and RPM governor so probably very susceptible to this issue. That is probably why I didn't have any issues with the XW system.

    Thanks for keeping me on track,
    Bruce
  • mike95490mike95490 Solar Expert Posts: 9,363 ✭✭✭✭✭
    Re: Xantrex SW5548 in series issue

    Maybe a Balancing Transformer would help, equalizing the load on each leg ? Could be a simple step-up/down transformer with a CtrTap 240V winding.
    Powerfab top of pole PV mount | 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 ,

  • 5320Ferrari5320Ferrari Registered Users Posts: 6
    Re: Xantrex SW5548 in series issue

    Well here I go, just ordered an Outback balancing transformer FW-X240. Reads like it is made for this issue.
  • 5320Ferrari5320Ferrari Registered Users Posts: 6
    Re: Xantrex SW5548 in series issue

    So the balancing transformer is installed and has solved the problem where the SW5548 would disconnect due to out of range voltage. I also finished installing and testing the Atkinson Generator Start Control Module with great satisfaction and set the SW5548 on Auto so now I can go on winter vacations and not worry about the batteries. Thanks for all the helpful comments.
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