Inverter output 66v

BarnstormerBarnstormer Registered Users Posts: 13
One of my inverters (Xantrex SW5548 ) has failed in a way that it is only outputting 66v. The display indicates that it is outputting 120v, but it is only putting out the 66.

Any comments on what has happened? Is the inverter toast?

Thanks for any ideas

Brian

Comments

  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Inverter output 66v

    What sort of meter are your useing to measure the 66V with ?

    What are the failure indications ? What's the voltage if you try to power a 100W incandescent bulb ?
    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 ,

  • BarnstormerBarnstormer Registered Users Posts: 13
    Re: Inverter output 66v

    I'm using an auto-ranging multi tester. It was tested at the AC out terminal in the inverter itself. The other inverter it is stacked with (both running from the same battery packs) is making 120v correctly. Everywhere downstream of the inverter shows the same 66v
  • BB.BB. Super Moderators, Administrators Posts: 32,997 admin
    Re: Inverter output 66v

    You may need a oscilloscope to figure out what is happening with the output wave form.

    Have you checked to see if it is still being repaired by Xantrex or anyone else?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BarnstormerBarnstormer Registered Users Posts: 13
    Re: Inverter output 66v

    Even if Xantrex is repairing these, I'm in the middle of Nowhere, Haiti. If it's not a reset or somewhat simple fix, I'm better off replacing it. I do have a spare inverter I can swap in, if needed. I'm just hoping to diagnose it before I pull it apart.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Inverter output 66v

    Replace it ...

    Sounds like one of the stepping transformers or the FETS that drive it has failed, its not a programing issue
  • BarnstormerBarnstormer Registered Users Posts: 13
    Re: Inverter output 66v

    Looks like replacing is my only feasible option. I've reset the inverter, etc.. and no help. Especially because the inverter doesn't actually see a fault- the display thinks it's making 120v- makes me think it has had an internal failure somewhere.

    Thanks!
  • RCinFLARCinFLA Solar Expert Posts: 1,477 ✭✭✭✭
    Re: Inverter output 66v

    Sounds like you have blown out one set of three H-bridge MOSFET drivers.

    There are three transformers, big, medium, and small, that are series connect on secondary to build the output stepped sinewave.

    Big transformer outputs approximately +135v, 0v, or -135v. based on H-bridge drive on primary winding.

    Medium sized transformer outputs approximately +45v, 0v, or -45v. based on H-bridge drive on primary winding.

    Small sized transformer outputs approximately +15v, 0v, or -15v. based on H-bridge drive on primary winding.

    These 27 possible voltage combinations make up the step voltages that build the sinewave. The actual number of steps used depends on battery voltage and line voltage.

    If your 66v reading is correct, I would guess the big transformer driver is blown.

    There are 52 MOSFET's on a PCB at lower right hand side of unit. These make up the 4 legs on each of three H-bridge drivers. There are multiple MOSFET's in parallel, particularly on large transformer driver since it carries most of the 48v battery current.

    I believe all the MOSFET's are N-ch, 40 amp, 80 volt breakdown rated devices. Original Fairchild parts are no longer made but they have 40 amp, 85v parts that should be a good substitute.

    Most service shops just replace the entire MOSFET PCB.
  • Solar GuppySolar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Inverter output 66v

    And the reason they change the PCB is almost 100% of the time when a FET fails, it shorts the drain to the gate and blows out the drive circuit. If you just change the FETS, its just blows up again as soon as you apply the power, not a DIY task
  • BarnstormerBarnstormer Registered Users Posts: 13
    Re: Inverter output 66v

    Is it possible that having a common connected to a ground in the AC wiring could create this situation? It is common down here (Haitian electricians are not familiar with 3 wire AC systems) to find commons and grounds tied together. I don't know when this 66v condition started, I've been chasing other problems and this is one of the less used parts of my "grid" here.
  • RCinFLARCinFLA Solar Expert Posts: 1,477 ✭✭✭✭
    Re: Inverter output 66v

    Not likely.

    The SW's have pretty good protection systems. They will release from grid if not right and shut down inverter if load gets too excessive.
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