I don't really like my Surrettes

124

Comments

  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: I don't really like my Surrettes
    boB wrote: »
    As far as I have seen, all of the typical battery based inverters (Magnum, OB, Xantrex, SMA) use AC current
    transformers to measure current and derive the DC charging and inverting current from that.

    The SMA has the option of installing an external shunt on the batt negative cable, and when this is installed it overrides the internal current sensor.
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    I seen the CT's in there when I had the covers off that measures the L1 and L2 to loads.

    I've seen 4 CTs, which would suggest that it measures AC in and AC out. Why else would they have 4 CTs?

    Derivation would require knowing inverter efficiency. As they would assume certain efficiency and used it for calculations. If I use XW display, it comes to 85% peak efficiency. No way they used 85% for their calculations because the spec is 96%. So DC amps cannot be derived from AC amps unless they made some calculation errors. BTW: Actual efficiency is better than 85%.

    Very puzzling.
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    NorthGuy wrote: »
    I've seen 4 CTs, which would suggest that it measures AC in and AC out. Why else would they have 4 CTs?

    Derivation would require knowing inverter efficiency. As they would assume certain efficiency and used it for calculations. If I use XW display, it comes to 85% peak efficiency. No way they used 85% for their calculations because the spec is 96%. So DC amps cannot be derived from AC amps unless they made some calculation errors. BTW: Actual efficiency is better than 85%.

    Very puzzling.

    I've measured the actual efficiency, using my test equipment for generators, at ~97% at lighter loads of 300-500 watts. Actually, THE most efficient inverter I've ever tested at that power level.

    But it is very puzzling. If I get time later I'll pop the cover off the DC section again, take a photo of it and post it. Maybe somebody in the know can point out how they're measuring that DC current in the XW. But we got some walleye fishing to attend to and that's more important :cool:
    --
    Chris
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    But we got some walleye fishing to attend to and that's more important :cool:
    --
    Chris

    Glad you got your priorities correct! Any good Northern Pike and Muskie up that way?
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    solar_dave wrote: »
    Glad you got your priorities correct! Any good Northern Pike and Muskie up that way?

    Yessir. The world record muskie came from the Chippewa Flowage here in Wisconsin and the Fresh Water Fishing Hall of Fame is in Hayward, WI
    http://www.freshwater-fishing.org/

    Last year I caught this 38" northern that tried to steal that crappie off my hook. Got both fish in one shot - the crappie was still in the northern's jaws and he wouldn't let go of it.

    Attachment not found.

    --
    Chris
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    Yessir. The world record muskie came from the Chippewa Flowage here in Wisconsin and the Fresh Water Fishing Hall of Fame is in Hayward, WI
    http://www.freshwater-fishing.org/

    Last year I caught this 38" northern that tried to steal that crappie off my hook. Got both fish in one shot - the crappie was still in the northern's jaws and he wouldn't let go of it.

    Attachment not found.

    --
    Chris

    I remember back about 1960 on the Sable Lakes in mid Michigan with the old man taking a Wash tub full of crappie out in an afternoon. They were on the beds and would just hit a bare gold hook. The cleaning task was huge.

    We were out for a joy ride in the little rental boat and the old man had a Shakespeare rod and reel in the boat with a small hunk of dried night-crawler on it, as we approached an entrance to a channel connecting the lakes he he tossed it out and caught the biggest Bass I ever saw, got it to the side of the boat, It opened its mouth and my mother SCREAMED! He lost it and I think he never forgave her for that incident.

    Sorry didn't want to hijack the thread.
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    solar_dave wrote: »
    Sorry didn't want to hijack the thread.

    For sure - we'd better stay on topic. My wife and I LOVE fresh-water fishing. Get us going on that topic and we can't stop :D
    --
    Chris
  • Steve Higgins
    Steve Higgins Registered Users Posts: 13 ✭✭
    Re: I don't really like my Surrettes
    NorthGuy wrote: »
    How about XW6048?

    got an email confirming that the XW uses a CT on the DC side to measure current... should be relatively accurate.

    Hi Bob... Hope all is well.
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    got an email confirming that the XW uses a CT on the DC side to measure current... should be relatively accurate

    Steve, OK - that I might have seen in our XW when I had the covers off. There was a single coil toroid type transformer in the DC side. I wasn't sure what it was for because it didn't look like it was in the right place to measure DC current.
    --
    Chris
  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    Steve, OK - that I might have seen in our XW when I had the covers off. There was a single coil toroid type transformer in the DC side. I wasn't sure what it was for because it didn't look like it was in the right place to measure DC current.
    --
    Chris

    Xantrex XW and Outback Radian and the other Outback inverters are mixed-frequency inverters. The initial switching is high frequency, the inductor coil (the toroid transformer-looking thingy) converts the high frequency to low frequency to go through the single low frequency transformer.

    Xantrex SW is a multi-branch (multiple transformers) low frequency inverter where multiple low frequency transformers are used to create the natural sine wave AC (a simple low speed switching transister and low frequency transformer creates square waves).

    Most straight (non-battery) grid tied inverters are straight high-frequency or solid-state.

    I learned this stuff out of a Home Power magazine. Actually I found the source. The links under 'Inside this article' have general flow/component diagrams. For Xantrex/Schneider brand lineage, it is Trace Engineering -> Xantrex -> Schneider Electric Connext.

    Low-Frequency Multistep Sine-Wave Inverter.

    Another solution that was developed to make the AC output closer to a true sine wave involves combining several low-frequency, inverters operating at different frequencies together in series. This allows multiple AC output voltage levels to be produced, creating a stepped sine-wave approximation of a sine wave form. This approach resulted in a surprisingly good sine wave, while still using low-frequency switching and transformers to maintain efficiency at low power levels while only modestly increasing the cost and complexity.

    The AC output sine wave allows some inverters using this topology to be tied to the grid, although few manufacturers are currently using this topology due to the high parts count and resulting high manufacturing cost.

    Brand Names: Trace Engineering SW & PS series; Sustainable Energy Technologies Sunergy series

    Mixed Frequency Sine-Wave Inverters.

    This topology combines the benefits of both low-frequency and high-frequency inverters. High-frequency switching transistors convert the DC source to a lower-voltage AC waveform. The transistors are switched at high frequency—hundreds of times per AC cycle or about 20,000 times a second. An inductor then smooths the choppy, high-frequency square wave form into a smooth, low-frequency wave form—creating a low-voltage sine wave. Then, a low-frequency transformer steps up the AC voltage to the required 120 or 240 VAC. This type of inverter is able to produce a “true” sine wave like a high-frequency inverter, but it is simpler to build and more reliable.

    Because the DC currents are being switched at high frequency, which causes electrical noise, a carefully designed output filter must be included to eliminate electrical interference with loads or clean up the power being sent into the utility grid.

    Like the low-frequency modified square-wave inverters, these types of inverters are also large and heavy. When used in a batteryless grid-tied PV application with high DC input voltages, efficiencies as high as 96% can be attained since the DC currents being switched are much smaller than with low-voltage battery systems.

    Brand Names: Apollo Solar TSW series; OutBack FX series; Xantrex GT and XW series; SMA Sunny Boy and Sunny Island series; PV Powered PVP series
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: I don't really like my Surrettes

    thanks for that second quote, most informative.
     
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    West Chilcotin, BC, Canada
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    Xantrex XW and Outback Radian and the other Outback inverters are mixed-frequency inverters. The initial switching is high frequency, the inductor coil (the toroid transformer-looking thingy) converts the high frequency to low frequency to go through the single low frequency transformer.

    Well, what do these two big yellow and white toroids do on the AC side? They look Real Important. I'm assuming there's one for each leg of the split phase. But maybe not?

    Attachment not found.

    --
    Chris
  • YehoshuaAgapao
    YehoshuaAgapao Solar Expert Posts: 280 ✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    Well, what do these two big yellow and white toroids do on the AC side? They look Real Important. I'm assuming there's one for each leg of the split phase. But maybe not?

    Attachment not found.

    --
    Chris

    Whats behind the main panel in the inverter? I'm sure the main transformer is there. I'm thinking if there are no inductor coils there (if there are, they may be larger), then these are converting the high frequency AC to low frequency AC prior to feeding the low frequency transformer. The clear boxes I believe are relays that are part of the automatic transfer switch (AC1 passthrough, AC2 passthrough, AC1 charge, AC2 charge, invert with or without passthrough (grid support / load shave)
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    Re: I don't really like my Surrettes

    But Current Transformers (CT's) don't measure DC current. Only AC current.

    I've been seeing quite a few XW6048s come through for pre-wiring lately
    and have not seen what looks remotely like a shunt but will look closer
    next time.

    And as an internal DC shunt does not measure actual battery current, an external
    DC shunt on the battery does not measure actual inverter/charger DC current
    unless those two are the only things connected to the system.

    Also, it is very difficult to accurately measure efficiency but they could
    use a very rough estimation of efficiency to semi-adjust the AC to DC
    current accuracy in software. Why should they care how accurate
    the DC current measurement is ? The main thing is to not trip breakers.

    boB
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    boB wrote: »
    But Current Transformers (CT's) don't measure DC current. Only AC current.

    Yeah, that's true. But they could use a hall effect sensor for DC measurement. If you look in my photo there, there's two CT's right to the left of the bottom two relays (they're black with about a 10 gauge piece of magnet wire running thru the hole). And there's two more up by the blue thing in the top. The transformer leads connect to that strip that's just to the right of the blue thing. And for some reason they got capacitors that are about the size of a silver dollar connected across the AC1 and AC2 inputs - it looks to me like one capacitor from each leg to the neutral.

    But with four CT's in there that I can see, I think they're measuring more than than AC out, like Schneider told me. I'm guessing they're measuring AC1 in/out for the grid-tie crap. And I'm also guessing that they're probably measuring the AC output on both legs. But I think the AC2 input is a calculated value and not measured.

    The DC side is still a mystery. You have to pull the information panel on the inverter to pull the DC side cover off. And I didn't feel like switching over to gen power and shutting the inverter down to do that today to take a photo of it.

    Well, actually, here it is. You can take the two screws out of the right side of the info panel and wangle that DC side cover off with the inverter hot and running. There's a big Ring Thing right down by the power studs mounted on a board and that's where they're measuring the DC power

    Attachment not found.
    --
    Chris
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes

    And look at this - we got another one on the wires going to the transformer or FET board.

    Attachment not found.

    I have no clue what this little cute one does - looks like a Star Gate

    Attachment not found.

    Both the positive and negative from the power studs goes thru that big Ring Thing on the bottom. And only the positive goes thru that hall effect sensor on the processor board. That Ring Thing looks like a hall effect sensor of some sort too. But I'm not sure how that works with both the positive and negative going thru it.

    But at any rate, there is no shunts in there. And there is no CT's on the DC side that I can see. They're using a hall effect sensor (or two).

    Edit:
    Upon closer examination of the whole unit and trying to figure it out, that big Ring Thing near the DC power studs is not where they're measuring DC power. I don't even know what that thing does. It's on a circuit board and it doesn't say on it what it does. There's some capacitors on that board and some other little magic components that I don't know what they are. Nor is it connected to the processor board with a ribbon cable. It ain't connected to anything that I can see, except that all the DC power flows thru that outfit. Looks to me like it was some spare parts they found laying under the workbench and they just screwed it in there because they didn't know else to do with it.

    They're measuring the DC power thru that hall effect sensor on the processor board. That makes sense to me as it's the processor that needs to know what the DC current is.

    The board to the lower right is the networking and fan control - it says that right on it.

    This an overview picture of the whole thing

    Attachment not found.

    The FET board and transformer and cooling fan is behind all them capacitors on the DC part there and the black cables go to the FET board thru that hole. The transformer is in the top and it's Big. Real Big. Probably about 12" across or so. It's what makes all the noise. There's four leads from the transformer that connect to that terminal block on the AC output board. I know when you switch a XW to 120V only output so you can stack three of them for 120/208 three-phase that you have to swap them transformer wires around in that terminal block.

    For what's in there, I can't figure out why it took two men and one woman to lift that confounded thing onto the wall bracket.
    --
    Chris
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: I don't really like my Surrettes
    boB wrote: »
    Why should they care how accurate
    the DC current measurement is ?

    It is used to calculate ending amps for the absorption. Few A difference in this measurement may translate into hours of difference in absorption.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: I don't really like my Surrettes
    NorthGuy wrote: »
    It is used to calculate ending amps for the absorption. Few A difference in this measurement may translate into hours of difference in absorption.
    A zero offset (like from a mis-calibrated Hall Effect sensor) can be a real problem. Difference between 50A and 52A at full Bulk is not much but the difference between 0A and 2A for end amps is very large.
    But if the error is proportional, like an error in the AC to DC efficiency estimate, then it will not be important. 50A versus 52A is again no big deal, and 2A versus 2.1A for end amps is also close enough.
    So you need to design the way of estimating DC current in a way appropriate to what that measurement will be used for.
    SMA SB 3000, old BP panels.
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    inetdog wrote: »
    A zero offset (like from a mis-calibrated Hall Effect sensor) can be a real problem.

    Hall effect sensors are reasonably accurate. So even if it's got 5% error at 10 amps, that's only .5 amps, which is nothing to worry about.

    I'm satisfied that they have a reasonably accurate way to measure the DC power in that inverter. And they are measuring AC in two places with CT's - AC Out and on AC1. The values for AC2 are calculated by the processor.

    So my investigation of the XW agrees with what Schneider told me, with the exception that I assumed that it was only measuring AC Out. But it's also measuring AC1, which I suppose it has to do for all the grid-tie stuff because that turns into an AC Out if the inverter is in Sell Mode.

    So there's no reason this inverter can't pretty accurately determine End Amps during Absorb, assuming you haven't mucked up the settings in the SCP.
    --
    Chris
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    Hall effect sensors are reasonably accurate. So even if it's got 5% error at 10 amps, that's only .5 amps, which is nothing to worry about.
    Hall effect sensors used for DC rather than for AC current measurement have a well known problem with zeroing. The effects of changing local magnetic fields and DC offset in the sense amplifier will both contribute to zero offset, and there are other factors with the same effect.
    Anybody who has used a clamp type DC ammeter has seen how bad this can be.
    Now, since the charger or inverter can just open the circuit any time the control computer wants, it is easy to re-zero the Hall Effect sensor regularly. Don't know if that is part of the actual design or not.
    SMA SB 3000, old BP panels.
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    inetdog wrote: »
    Now, since the charger or inverter can just open the circuit any time the control computer wants, it is easy to re-zero the Hall Effect sensor regularly. Don't know if that is part of the actual design or not.

    I've got a 500 amp 75mV shunt in the shop that I've been inclined to put on the negative cables to the inverter. But I haven't been able to find a meter that will read both ways (under load and charging) to go with it. When I get time I might put that shunt on there anyway and hook up my DVOM to it to see how close the XW's measurement actually is.
    --
    Chris
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    I But I haven't been able to find a meter that will read both ways (under load and charging) to go with it.

    Yeah, they used to make zero center mechanical meters, even DC millivolt meters, but they are definitely getting harder to find.
    The one exception is the DC ammeters being used for cars and other transportation applications. I think most if not all of them actually run the current through the meter coil or through an internal shunt in the meter case, but you may be able to adapt one of those.
    Once you go digital, it is easy to measure the absolute value of the shunt voltage and flip the sign bit with a separate circuit.
    SMA SB 3000, old BP panels.
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    And look at this - we got another one on the wires going to the transformer or FET board.

    Attachment not found.

    I have no clue what this little cute one does - looks like a Star Gate





    Edit:
    Upon closer examination of the whole unit and trying to figure it out, that big Ring Thing near the DC power studs is not where they're measuring DC power. I don't even know what that thing does. It's on a circuit board and it doesn't say on it what it does. There's some capacitors on that board and some other little magic components that I don't know what they are. Nor is it connected to the processor board with a ribbon cable. It ain't connected to anything that I can see, except that all the DC power flows thru that outfit. Looks to me like it was some spare parts they found laying under the workbench and they just screwed it in there because they didn't know else to do with it.

    They're measuring the DC power thru that hall effect sensor on the processor board. That makes sense to me as it's the processor that needs to know what the DC current is.

    --
    Chris


    Yep.. Looks like a LEM module (Hall effect) for DC current.
    These types of Hall effect sensors have feedback that linearizes them and
    much reduces the zero offset problem. That's the way to do it.
    It may be in the transformer primary rather than on the battery terminal
    side for other uses in addition to measuring the DC input. If so, it's not
    strictly for the battery current because it includes some other AC currents
    but probably works better than calculating DC from the AC CT side.

    Thanks for taking those pix.

    Most of the other toroids you show like the yellow ones are common mode chokes for EMI reduction.
    Same for those 2 black ferrite rings near the battery terminals.
    It's all for FCC and CE EMI reduction.

    boB
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: I don't really like my Surrettes
    inetdog wrote: »
    A zero offset (like from a mis-calibrated Hall Effect sensor) can be a real problem. Difference between 50A and 52A at full Bulk is not much but the difference between 0A and 2A for end amps is very large.
    But if the error is proportional, like an error in the AC to DC efficiency estimate, then it will not be important. 50A versus 52A is again no big deal, and 2A versus 2.1A for end amps is also close enough.
    So you need to design the way of estimating DC current in a way appropriate to what that measurement will be used for.

    The problem with that is that the DC current gets subracted from SCC output. So, you may get 70A of solar and 50A to inverter, thus 20A coming to batteries. If it now measures 55A instead of 50A, the result is only 15A to batteries - time to finish the absorption, but in reality it may be another two hours to go.
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    I've got a 500 amp 75mV shunt in the shop that I've been inclined to put on the negative cables to the inverter. But I haven't been able to find a meter that will read both ways (under load and charging) to go with it. When I get time I might put that shunt on there anyway and hook up my DVOM to it to see how close the XW's measurement actually is.

    Thank you for posting pictures Chris!

    You can use two meters, one connected one way and the other connected other way.

    Or, you can simply measure voltage accross the shunt with Fluke in mV range - it measures both ways.

    Waveform may be highly unusual, so some meters may freak out.
  • RSHobson
    RSHobson Registered Users Posts: 8
    Re: I don't really like my Surrettes

    Craftsman (Sears) makes a pretty good Clamp-On DC Ammeter. I use one to measure loads on Aircraft Battery Chargers, Inverters. Ect. I don't remember what it cost, but it was not expensive and it calibrates every year.

    Steve
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: I don't really like my Surrettes

    One we have been recommending here from Sears is this guy:

    http://www.sears.com/shc/s/p_10153_12605_03482369000P

    Usually costs ~$60 but sometimes $5-$10 less on sale.

    Mine has worked well, except for the Thermal Couple plug in broke--I think the meter (in thermal probe mode) still works. But I have an inexpensive IR Meter that works fine for my usage--So I have not worried about fixing/replacing the probe assembly.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: I don't really like my Surrettes
    NorthGuy wrote: »
    Thank you for posting pictures Chris!

    Say, one thing I wanted to mention for other folks that got XW's - don't be pulling that DC side cover off with the inverter hot and running, or even connected to the DC power, like I did. It's kind of like the FPS Russia guy on YouTube that I always get a big laugh over - he says (with Russian accent), "Don't try this at home. I can do it because I'm Professional Russian" (which means he's an idiot).

    Some of the high-amp DC bars in that capacitor bank, and the connections that go to the FET board and transformer primary are VERY close to that cover. One slip removing or installing that cover with power hooked up, and you'll probably look like Wile E. Coyote when one his ACME devices that he's trying to get the Roadrunner with goes haywire.
    --
    Chris
  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: I don't really like my Surrettes
    ChrisOlson wrote: »
    Some of the high-amp DC bars in that capacitor bank, and the connections that go to the FET board and transformer primary are VERY close to that cover. One slip removing or installing that cover with power hooked up, and you'll probably look like Wile E. Coyote when one his ACME devices that he's trying to get the Roadrunner with goes haywire.

    That's why pictures are pictures are so useful. I've always wanted to look inside, but I didn't want to turn the inverter off ;)
  • GENX
    GENX Registered Users Posts: 3
    Re: I don't really like my Surrettes

    Gentlemen, hello all. New member here. I have been researching equipment for my off grid home in Colorado and stumbled onto the forum here. I am leaning to an XW 6048 with the MPPT 80-600.
    I am learning (solely thanks to you guys) that an offgrid system is going to be anything but set it and forget it. I currently live and work in TX. With the thought of retiring/snow birding in CO. ---Sorry for the life story. Just am thinking that without constant care and continual monitoring my absence will undoubtedly shorten the life of the battery bank. Unless there is some type off absence setting. Perhaps I should buy a very small battery system until we are there full time to monitor/ or perhaps there is a more qualified RE inverter MPPT (forgive me if I have opened a can of worms) just don't know how to proceed and am wary about saddling up with thousands of dollars of products that over promise and under deliver. Recommendations?