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  • #31
    Originally posted by DaveDE2 View Post

    Nonsense.

    A 2-3% voltage drop results in power/voltage loss in the wires from the panels to the inverter and nothing more. It in no way affects the inverter other than producing slightly less voltage into it.

    Wire sizing above and beyond NEC requirements is a tradeoff for the end user, going bigger saves a little power, going smaller wastes a little power.
    Actually I have to agree with ncs55 concerning SMA. I did find an early document for a Sunny Boy SB 700U showing a chart for wire size and distances for voltage drops. There was a note that SMA recommends a max voltage drop of 1.5% for the wire used. I did not find anywhere in this manual what would happen if the 1.5% VD was exceeded or if SMA would void any warranty if that happened.

    Comment


    • foo1bar
      foo1bar commented
      Editing a comment
      1% vs 3% voltage drop (at max current) will not result in even close to a full year's worth over 25 years.
      At most it would be 2% * 25 = 50% of a year.
      But since you would not be at max current the vast majority of the time the overall impact would be even less.
      (ex. if it's 5kW system, when the system is doing only 500W of power instead of 5000W you would have ~0.1% voltage drop instead of ~0.3% voltage drop instead of 1% vs 3%. It wouldn't be linear - but it's close enough that you can see how you're going to be significantly less than a year's worth of production)

    • ncs55
      ncs55 commented
      Editing a comment
      foo1bar, consider this. Assume a 50 kW PV system at 400 Vdc with 1,000 feet from combiner box to inverter. The minimum dc output-circuit conductor is 4/0 for ampacity, resulting in 3.8% voltage drop, or 1,900 watts of lost power at full-power conditions. Upsizing to 300-kcmil conductors would result in 2.68% voltage drop, or 1,340 watts of lost power, which is a net gain of 560 watts under full power. full power can be all day long if the modules are mounted on trackers.

    • foo1bar
      foo1bar commented
      Editing a comment
      Ok - 50kW system producing 50kW most of the day because it's using trackers (not what you would actually see for someone's offgrid system or even any residential system - but sure let's use the numbers you supplied)

      0.56kW extra lost to voltage drop (comparing the two possible configurations.)

      Let's say a day is 8 hours and 365 days in the year - so 2920 hours per year

      50kW * 2920 = 146000kwh
      0.56kW * 2920 = 1635kwh

      In 25 years the total losses are 0.56kW * 2920 * 25 = 40880 kwh

      And 40880kwh is 28% of one year's production (146MWh)

      BTW you can use whatever number of hours per year you want - it cancels out and comes out that still only 28% of a year's worth of production is lost over that 25 year span.

      So in short - 1% of production loss is *AT MOST* ~25% of a year's production when looking at a 25 year span.
      2% of production lost is *AT MOST* 50% of a year's production when looking at a 25 year span.
      And most likely it will be significantly less because most people don't use trackers and most of their power generation is not at that max current condition. (Even with trackers, you're not going to be at that spot most of the year - but you will certainly be a lot closer to it for a much larger amount of time)

  • #32
    DaveD2, First of all 0.5% VD is excellent and your reasoning of not wasting power is spot on my friend. However, you need to understand that inverters are very sensitive to voltage drop and their algorithms sense the voltage drop and adjust the performance partly based on voltage drop.
    en-phase says this about voltage drop:
    The total VRise in the AC wiring should be less than 2% in all wire sections from the point of common coupling (PCC) to the last microinverter on each branch or sub-branch circuit as described in Voltage Rise by Wire Section on page 3. A good practice is to maintain less than 1% VRise in the Engage Cable. https://enphase.com/sites/default/fi...Vdrop_M250.pdf Please read the whole article as it goes into more depth.
    SMA has this note at the bottom of their voltage drop calculator.
    IMPORTANT: SMA America, Inc., recommends a maximum of 1% to 1.5% voltage drop from the Main Service panel to the inverter. This calculator, like the String Sizing Program, is intended to provide an estimate of system performance, and should not be used to guarantee or imply any guarantee about system performance. The code that forms the basis of this Calculator was used with permission from the Computer Support Network.
    I read a tech brief from Schneider that talked specifically about voltage drop and how the inverter senses and adjusts to the rise and fall of voltage drop throughout the day. there was a reference in that paper about voltage drop and what happens inside of the inverter when the voltage drop is out of the range of the inverter. Too much drop will cause the internal components to run hotter and the inverter will produce less. when the internals run hotter than optimal it is obvious that in a hotter environment internals will fail sooner and shorten the life of the equipment. I cannot find that paper right now as I read it when going through training for repair of these units. Considering that I repair utility scale inverters and the first question they ask is about the system size and module stringing, the second question they ask is concerning system grounding and the third question is what are the wire sizes on both AC and DC sides. I have asked them about why they want to know about the wire size and the techs will always refer to voltage drop and internal heat as a way to determine what caused the failure and eliminate the common mistakes concerning voltage drop. Ask them further to explain and they will always tell you that there is a voltage drop range and it will cause excessive heat. common sense tells anyone that electronic components fail quicker when exposed to a higher heat than they are designed for. So, again voltage drop will hurt an inverter and eventually kill it. I do not care if you believe this or not because it is true and I have had to change out DC wiring, under the manufacturer recommendation that met the NEC 2% ruling in order to permanently fix inverter failure. You need to understand the internal workings of the inverter to understand why this is so important for the life of the product. You will not see this in an installation manual because as a system designer or installer it is assumed that you already have this basic knowledge. Cheers.




    Comment


    • #33
      Originally posted by ncs55 View Post
      However, you need to understand that inverters are very sensitive to voltage drop and their algorithms sense the voltage drop and adjust the performance partly based on voltage drop.
      Inverters adjust to the max power point - they do not know the difference between resistance within the modules and resistance within the wiring between the inverter and the modules. They can see the voltage/current curve of the sytem and pick the best operating point - and while the wiring affects that point the inverter must be able to handle different panels and different conditions for the panels (ex. bypass diodes being used) which also affect that curve.

      Too much drop will cause the internal components to run hotter and the inverter will produce less. when the internals run hotter than optimal it is obvious that in a hotter environment internals will fail sooner and shorten the life of the equipment.

      There might be some truth to that - I can see some of the heat of the wire being dissipated into the inverter - so more heat in the wire would mean more heat being brought into the inverter. How much would be very very dependent on a lot of things - like wire dimensions, length, how the wire is thermally insulated and the environment it's exposed to (ex. wires in a conduit on a roof would probably gain heat from the sun, while wires in a buried conduit would dissipate e heat to the ground)


      I think most of what you've shared about inverter manuf. concerns about voltage drop is on the AC side though.
      And there they are concerned about getting out of range of the expected grid voltage. And since they will automatically turn off if/when the voltage is too high, that means when they're doing max generation they are more at risk of hitting that point and turning off - which the customer will be unhappy with.

      Comment


      • #34
        Originally posted by foo1bar View Post

        There might be some truth to that - I can see some of the heat of the wire being dissipated into the inverter - so more heat in the wire would mean more heat being brought into the inverter. How much would be very very dependent on a lot of things - like wire dimensions, length, how the wire is thermally insulated and the environment it's exposed to (ex. wires in a conduit on a roof would probably gain heat from the sun, while wires in a buried conduit would dissipate e heat to the ground)[/B]
        You have to admit though that wires conducting any signifcant amount of heat into an inverter is pretty far fetched. And if the heat were caused by the sun, bigger wires would conduct more heat in.

        I think most of what you've shared about inverter manuf. concerns about voltage drop is on the AC side though.
        And there they are concerned about getting out of range of the expected grid voltage. And since they will automatically turn off if/when the voltage is too high, that means when they're doing max generation they are more at risk of hitting that point and turning off - which the customer will be unhappy with.
        Agree. My SunnyBoy has output voltage range of 211v to 264v which is about 240v +/-10%, well above NEC voltage drop (3%) and expected line voltage variations. It will happily operate anywhere within that range, and it will operate at a voltage just high enough to overcome the voltage drop between it and the grid. In short, the inverter doesn't "know or care" if there is any voltage drop or whether its operating voltage is a result of higher wire resistance or the grid voltage itself. No extra heat is generated in the inverter if it has to operate at a slightly higher output voltage to overcome wire resistance. That heat is in the wire, usually a relatively long run buried and dissipated into the ground.

        If someone wants reduce heat in their inverter to prolong life, it's better to be concerned about where it's mounted. Inside of a well insulated cool garage might be a good choice.

        Comment


        • #35
          Originally posted by foo1bar View Post
          Inverters adjust to the max power point - they do not know the difference between resistance within the modules and resistance within the wiring between the inverter and the modules. They can see the voltage/current curve of the sytem and pick the best operating point - and while the wiring affects that point the inverter must be able to handle different panels and different conditions for the panels (ex. bypass diodes being used) which also affect that curve.


          There might be some truth to that - I can see some of the heat of the wire being dissipated into the inverter - so more heat in the wire would mean more heat being brought into the inverter. How much would be very very dependent on a lot of things - like wire dimensions, length, how the wire is thermally insulated and the environment it's exposed to (ex. wires in a conduit on a roof would probably gain heat from the sun, while wires in a buried conduit would dissipate e heat to the ground)[/B]

          I think most of what you've shared about inverter manuf. concerns about voltage drop is on the AC side though.
          And there they are concerned about getting out of range of the expected grid voltage. And since they will automatically turn off if/when the voltage is too high, that means when they're doing max generation they are more at risk of hitting that point and turning off - which the customer will be unhappy with.


          I see that you obviously know more about the algorithms than the manufacturer and what they instruct me on. I am only imparting my experiences and what I am taught. I will not argue this with you. And the manufacturers are concerned about the DC side voltage drop and the parameters in the software are not as broad range as you are speculating. I am not saying that heat is traveling through the wire to the inverter because it would dissipate in the DC disconnect and not make it to the internal components of the inverter. you need to understand exactly what is going on inside of the components, boards, power supplies etc. The internal heat generated is not an instant high heat, it is a constant higher than component tested value and that is where the boards fail. It is the same principal with computers and why some of them are liquid cooled. Long term higher heat exposure will kill circuit boards and or the components on those boards. Pay the price to get trained by the manufacturer to repair these inverters and you will be taught the same thing as I have been taught.

          #31.4

          foo1bar commented
          Today, 11:33 AM
          Editing a comment

          Ok - 50kW system producing 50kW most of the day because it's using trackers (not what you would actually see for someone's offgrid system or even any residential system - but sure let's use the numbers you supplied)

          0.56kW extra lost to voltage drop (comparing the two possible configurations.)

          Let's say a day is 8 hours and 365 days in the year - so 2920 hours per year

          50kW * 2920 = 146000kwh
          0.56kW * 2920 = 1635kwh

          In 25 years the total losses are 0.56kW * 2920 * 25 = 40880 kwh

          And 40880kwh is 28% of one year's production (146MWh)

          BTW you can use whatever number of hours per year you want - it cancels out and comes out that still only 28% of a year's worth of production is lost over that 25 year span.

          So in short - 1% of production loss is *AT MOST* ~25% of a year's production when looking at a 25 year span.
          2% of production lost is *AT MOST* 50% of a year's production when looking at a 25 year span.
          And most likely it will be significantly less because most people don't use trackers and most of their power generation is not at that max current condition. (Even with trackers, you're not going to be at that spot most of the year - but you will certainly be a lot closer to it for a much larger amount of time)

          Thank you for doing the math proving the production value and showing why the production losses are cheaper to address in the beginning. 28% is more than enough to pay for one wire size larger. I was not referencing off grid and I see plenty of residential trackers. That was an example used from an article I found on voltage drop as a reference not specific to what I initially said. i am just trying to show the value of a 1% drop in planning. By the way with trackers you are at that spot most of the day because the modules always run cooler and are always facing optimal direction all day long therefore optimizing and extending the solar window. Agreed about roof and fixed mount systems.
          Another thing I consider is that the modules do degrade with time and will harvest less as they get older. In that scenario where you came up with 28% of a years production gained by changing the voltage drop to a lesser value. The extra production gained by less voltage drop also helps to offset the degradation of the modules in the long run.
          Last edited by ncs55; 05-07-2016, 02:30 PM. Reason: added last comment

          Comment


          • #36
            Just gotta say that this is so far fetched, that looses in the DC wires cause inverter failure.
            These string inverters are designed to cover a range of DC inputs, using strings of 8 to 15 panels of various voltages. Panels vary voltage and wattage from summer to winter too, i just don't see how an additional 1% loss in a wire is going to cause an issue.
            But it's not my flaky design, I built solid stuff that can take hard rads, +-20% voltage variation and last 20+ years
            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


            • ncs55
              ncs55 commented
              Editing a comment
              It is not far fetched if you understand how the software and the components on the boards react to voltage drop that is out of the optimal designed range. Please read what I originally said, that was, I am seeing this causing premature inverter failure. it has nothing to do with how many modules are in the string as long as the strings meet the design criteria of the inverter You do not see it because you are not trained in internal componentry and how to fix the failures or even what causes them. These designs are not mine either and I have no issues with my designs or production or how long they last. I do not understand why you guys cannot understand this simple principle. I'm tired of the closed minds in here. And I see in a lot of posts where others relate experiences and the self proclaimed experts shoot it down with basic 101 knowledge. Pay a few thousand dollars, and get some training on this subject and then come back and discuss this. You obviously do not know what you are even commenting on, so maybe you should not comment.
              Last edited by ncs55; 05-07-2016, 02:16 AM. Reason: sentence correction

          • #37
            To ncs55

            You have to understand that Mike has been living off grid for a long time and uses LiFe battery technology. He has first hand experience with the batteries and a number of charge controllers.

            You seem to have experience with repairing inverters and may have seen the same issue come up that was caused by overheating of the internal components. Certainly a high voltage drop will contribute to heat in the wires and electronics but I will tell you that if components are failing due to someone use a wire that causes 1 to 2% more voltage drop then I would say the manufacturer of that inverter is not building their equipment sturdy enough for the general public.

            I have had a number of head to head battles with some small companies like Allen Bradley, Siemens, Westinghouse, ABB, Fluke, etc where I found component issues that had nothing to do with the user but the manufacturer. While those companies did not immediately agree with me I got enough of their attention for them to review my comments and to make some software and hardware modifications to their equipment.

            Now I will get off my soap box and back to enjoying this forum and the knowledge I get from it.

            Comment


            • ncs55
              ncs55 commented
              Editing a comment
              Maybe the manufacturers components do have problems, but I do not think so. Most inverters are very rugged. 99.9% of the time inverter failure is due to improper design and or installation techniques, IE Improper voltages, voltage drops, improper grounding etc. I have not been able to go further with explaining the other contributing causes that we see in the field that lead to this failure due to the fact that I have to defend myself from these experts. I live off grid and for a long time also, but that makes me no expert on the subject. We have been able to keep Lead Acid batteries healthy and in the field longer than most others in this area who settle for a 5-7 year lifespan consistently. When we are asked how this is possible and how we can achieve this we are either flamed or called a liar and have to prove what we have already openly and willingly shared. I see the same type of closed minded thinking in this forum. As far as what I have shared on this subject, I have simply shared what I am seeing and how it gets fixed and what was determined as the cause of failure. Concerning this subject specifically, the people who do not understand what I am trying to say or think I am wrong obviously do not understand how an inverter processes the energy coming into it or how the internal circuits work and are affected for long term when the parameters are not at optimal conditions. Looking at the previous replies shows me that what I said was never even understood. I understand about manufacturers, and issues with products as I choose to share my field data to help them improve their products and in return I gain knowledge from them about their products that most people will never get. It is called collaboration. Head to head battles is a long and hard road. In the end, I see that when someone in here tries to share what is not common knowledge, or experiences in the field to this collective they had better be prepared to be called names and be flamed.

          • #38
            To ncs55

            And I do thank you for contributing your knowledge and experience concerning what you do for a living. It is always a welcome to get good feedback from those in the field. You are also correct that most failures are not due to manufacturers design or equipment but how the end users takes shortcuts to get them to work.

            But through my experience of determining root cause analysis I have found a number of equipment issues being caused by poor manufacturing and their lack of good quality control.

            Sometimes a manufacturer is under the gun to deliver equipment per the purchase order documentation. When a delay happens they might take shortcuts to make sure the delivery is on time and the equipment works as designed . But sometimes they miss the mark and a piece of crap has been let out of their control. Not a lot but it only takes a few times to get a black eye.

            Case in point were some of the early version of micro inverters (manufacturer name held to protect the guilty) that quickly failed due to heat issues.
            Last edited by SunEagle; 05-07-2016, 09:34 PM. Reason: added last sentence

            Comment


            • #39
              It is not far fetched if you understand how the software and the components on the boards react to voltage drop that is out of the optimal designed range. Please read what I originally said, that was, I am seeing this causing premature inverter failure. it has nothing to do with how many modules are in the string as long as the strings meet the design criteria of the inverter You do not see it because you are not trained in internal componentry and how to fix the failures or even what causes them. These designs are not mine either and I have no issues with my designs or production or how long they last. I do not understand why you guys cannot understand this simple principle. I'm tired of the closed minds in here. And I see in a lot of posts where others relate experiences and the self proclaimed experts shoot it down with basic 101 knowledge. Pay a few thousand dollars, and get some training on this subject and then come back and discuss this. You obviously do not know what you are even commenting on, so maybe you should not comment.
              I am afraid it's you who doesn't appear to understand this enough.

              An inverter can not know what the voltage drop is within wire that connects it to the modules.
              It knows what the voltage-current curve characteristics are.
              And adjusts to the max power-point.
              All it can measure is at the terminals connecting to the modules - there is no way for it to know how much power is being disipated in the wire between the modules and the inverter.
              And because that's the only place it can measure, it will not know if there is voltage drop on the DC side that is outside the "optimal range". There's simply no way for it to know that the curve it is able to observe is because of 2% vs 3% voltage drop within the wires or because the system is using Mitsubishi modules instead of LG modules.

              So if a 1% vs. 3% voltage drop on the DC side impacts an inverter's longevity, please explain what mechanism is it that impacts the inverter's components. Claiming it's too complex for us to understand isn't going to carry much weight with people who have electrical engineering degrees and work in related fields.


              Decreasing the voltage drop to provide higher production MAY be worthwhile economically.
              However whoever is footing the bill should do the actual calculations. Because someone may try to claim that it's more benefit than it really is. (ex. claim it's a years worth of production over 25 year lifetime when really it is 1/4 of a year's production)

              Comment


              • Mike90250
                Mike90250 commented
                Editing a comment
                Exactly my earlier point. A string inverter has valid input from 300Vdc - 500Vdc (generally) it's such a wide range, the difference of 1 or 2% wire loss is meaningless. Lost in the noise. heck my old inverter accepted 280V - 540V and the MPPT was valid from 320- 480Vdc, which was a much tighter band to dial the array configuration into.
                And circuits are circuits, either in space or on the ground, the components follow the same basic rules. They are either designed to survive reasonable conditions, or not.

            • #40
              Originally posted by foo1bar View Post

              I am afraid it's you who doesn't appear to understand this enough.

              An inverter can not know what the voltage drop is within wire that connects it to the modules.
              It knows what the voltage-current curve characteristics are.
              And adjusts to the max power-point.
              All it can measure is at the terminals connecting to the modules - there is no way for it to know how much power is being disipated in the wire between the modules and the inverter.
              And because that's the only place it can measure, it will not know if there is voltage drop on the DC side that is outside the "optimal range". There's simply no way for it to know that the curve it is able to observe is because of 2% vs 3% voltage drop within the wires or because the system is using Mitsubishi modules instead of LG modules.

              So if a 1% vs. 3% voltage drop on the DC side impacts an inverter's longevity, please explain what mechanism is it that impacts the inverter's components. Claiming it's too complex for us to understand isn't going to carry much weight with people who have electrical engineering degrees and work in related fields.


              Decreasing the voltage drop to provide higher production MAY be worthwhile economically.
              However whoever is footing the bill should do the actual calculations. Because someone may try to claim that it's more benefit than it really is. (ex. claim it's a years worth of production over 25 year lifetime when really it is 1/4 of a year's production)
              I am sorry you feel that way. I never claimed that it was to complex for you or anyone to understand firstly, in fact before I had a chance to explain anything, I had to defend myself from the flaming. From what I understand all inverters work with a proprietary software or programming that uses complex algorithms to sense and control the power input and the power output, mppt tracking etc. These algorithms do not just affect the components on the board, they govern the components in their functions to create optimal performance and are constantly changing. There are narrow parameters for each function of each component to operate as tested and designed for on each board for it to perform its function. Yes you can run an inverter with whatever voltage drop you want and it will work, but it will not last a long life. No the inverter does not know what type of module it is connected to and I never even came close to saying that. The software which governs each component and adjusts to the input changes, actually does know what the voltage drop is, in order to keep the components in a state of maximum output. It does not know per say what we know voltage drop is, as say 1-3% or what is in the wire. The software senses voltage drop through the data it receives from the components on the board as I am told, and this has something to do with the mppt. I did not design the boards or write the software, this is what I have been told by every manufacturer that I have repaired their inverter. From the limited amount that I have been told about this, (as it gets into their proprietary software and they are a little tight lipped), their programming can detect voltage drop on both sides via the algorithms and the data they receive every few seconds or milliseconds or each time it scans the components and adjusts them for maximum output. If it senses lower voltage drop then certain components on the board will run hotter than what they would normally, ( with a lower voltage drop) in order to keep the output at maximum. Sometimes and mostly the hotter temperatures last for milliseconds and sometimes and on partially cloudy days it can last longer. As I have seen some weird things burn up on these boards, I also see the patterns of the components that fail on the boards and the boards are mostly on the DC side and have obvious heat damage at certain components and not the whole board. Most of the time, when these burned boards are discovered on the DC input side of the inverter, the techs start asking me about the wire size, array current and array voltage that is directly upstream. 99.9% of the time they relate the bad board to, and I quote, out of range voltage drop. Although sometimes it is a grounding or lack of grounding issue. So when I ask them what is the optimal voltage drop to keep this from happening they always tell me 1% or less for the longest life of their product. I started practicing this in my designs, installs and repairs and have not had any DC board failures. They work great and I have older Sunny Boys in the field now well past their ten year warranty with only normal degradation. Most repairs have lasted longer than it took for the initial failure. This is what I have been instructed on and what the results are after applying the 1% or less rule.
              The production claim, I only claimed that to get someone to do the math and actually show the percentage. It was an exercise to show the value of planning for this in the beginning and that the benefits outweigh the costs. You were the only one smart enough to take the calc and do the math. My customers already know the benefits as they are mostly referrals from other satisfied customers.
              Last edited by ncs55; 05-08-2016, 05:01 AM. Reason: added verbage

              Comment


              • #41
                Originally posted by ncs55 View Post
                Most of the time, when these burned boards are discovered on the DC input side of the inverter, the techs start asking me about the wire size, array current and array voltage that is directly upstream. 99.9% of the time they relate the bad board to, and I quote, out of range voltage drop. Although sometimes it is a grounding or lack of grounding issue. So when I ask them what is the optimal voltage drop to keep this from happening they always tell me 1% or less for the longest life of their product.
                I'd probably say the same thing if I were them - easier to blame the wires outside the box than explain that my company had used some components that had a chance of failing.

                Originally posted by ncs55 View Post
                The production claim, I only claimed that to get someone to do the math and actually show the percentage.
                That's the explanation you're going with for why you were wildly optimistic about the benefits?

                Comment


                • ncs55
                  ncs55 commented
                  Editing a comment
                  OK and yes.

              • #42
                Sadly, NCS55, the mfg's have been BS'ing you. To measure resistance in an active wire, you need a 4 lead tester or a dedicated circuit which is not likely present in any MPPT controller. As has been said before, if an inverter is rated at x Watts and the input range is 300 - 500VDC, and you feed it 302v, it supposed to perform as well as at 500V. Or they are fudging on the specs, to capture more market share.
                Now it's true that a 302Vdc 4Kw circuit will have more amps flowing, than a 495Vdc 4kw circuit, and the internal components are SUPPOSED to be sized to handle this, as to if they actually are, is a whole different story, it's often the case mfg's will overspec stuff, and deal with the 1% warranty claims for their failures, but they still make more money than if they lost market share.
                And solar MPPT gear works no different than any other electronic circuits at the same voltages / wattages. Nothing magic about it other than it will light your house on fire if designed wrong. UL lab testing is supposed to weed out the fire hazards, but not poor design failures.

                You have been allowed lots of space to spin your tale as you know it, but I'm (as an electronics engineer and moderator) saying it's going to stop;
                A full 1/3 of my design was high voltage spacecraft DC bus stability electronics, and there is nothing as you describe, that is feasible, even with an 8 hour re-education.
                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


                • #43
                  Most of the time, when these burned boards are discovered on the DC input side of the inverter, the techs start asking me about the wire size, array current and array voltage that is directly upstream. 99.9% of the time they relate the bad board to, and I quote, out of range voltage drop. Although sometimes it is a grounding or lack of grounding issue. So when I ask them what is the optimal voltage drop to keep this from happening they always tell me 1% or less for the longest life of their product.
                  What you are describing is a failed LVD circuit that failed to sense undervoltage (and overcurrent) conditions and the gear ran till it burned up.
                  In a 4Kw inverter, running 400VDC input (10A), an extra 1% voltage drop (4V) [ 2% V drop total ] in the lead in wire would cause a whopping extra 0.1 amp. If 0.1 amp can burn an inverter up, it's a failed design.
                  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


                  • ncs55
                    ncs55 commented
                    Editing a comment
                    I am not spinning a tale. I do not claim to know exactly how the software works with the boards. I am simply relating what I have seen and been told.

                • #44
                  Originally posted by Mike90250 View Post
                  Sadly, NCS55, the mfg's have been BS'ing you. To measure resistance in an active wire, you need a 4 lead tester or a dedicated circuit which is not likely present in any MPPT controller. As has been said before, if an inverter is rated at x Watts and the input range is 300 - 500VDC, and you feed it 302v, it supposed to perform as well as at 500V. Or they are fudging on the specs, to capture more market share.
                  Now it's true that a 302Vdc 4Kw circuit will have more amps flowing, than a 495Vdc 4kw circuit, and the internal components are SUPPOSED to be sized to handle this, as to if they actually are, is a whole different story, it's often the case mfg's will overspec stuff, and deal with the 1% warranty claims for their failures, but they still make more money than if they lost market share.
                  And solar MPPT gear works no different than any other electronic circuits at the same voltages / wattages. Nothing magic about it other than it will light your house on fire if designed wrong. UL lab testing is supposed to weed out the fire hazards, but not poor design failures.

                  You have been allowed lots of space to spin your tale as you know it, but I'm (as an electronics engineer and moderator) saying it's going to stop;
                  A full 1/3 of my design was high voltage spacecraft DC bus stability electronics, and there is nothing as you describe, that is feasible, even with an 8 hour re-education.
                  Mike, While I am sure you are competent in what you have achieved on spacecraft, That does not make you an expert in the internals or software design of inverters. I think it is easier for you to say the manufacturers are wrong and put yourself up on the white horse. I doubt very much that you or anyone in this forum including myself have enough knowledge to second guess a team of engineers who actually make a good product. If you know so much why are you not making a better product? I put the exact boards back in the inverter and I look at them for changes in componentry, usually they are exact. I don't think the manufacturers are in a conspiracy to BS me or anyone else. I fix many different types of inverters and I am only relating my experiences, I learn something new each time and in no way understand everything that goes on within the boards. It seems that you want to appear smarter than the manufacturer, you are not.

                  Comment


                  • #45
                    Can we cut the BS here? As Mike said, this needs to stop.

                    ncs55, I respect your vast field experience (and I'm sure there's a lot I can learn from you there), but understand you are dealing with some full-on electrical engineers who know their shi!t. Quit pawning off your reasons because we don't know the "internals of software design of inverters", etc. Most of this is basic electronics 101, V=IR, etc. I believe you sincerely want to help and are not a snake-oil salesman but it is also You that needs to have an open mind and learn.

                    If that's not enough, I'll take you up on your rhetoric, please gives names of your contacts who tell you other-wise and we'll conact them and plow forward.

                    Comment


                    • ncs55
                      ncs55 commented
                      Editing a comment
                      Im not trying to pawn any reasons. I do have an open mind. None of you have tried to explain the 101 electronics, only flaming me for what I have shared. And The mod asked to stop, so I stopped. Maybe you should do as the mod asked as well.
                      Last edited by ncs55; 05-08-2016, 07:52 PM. Reason: added verbage
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