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jasonvanwyk

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  1. Like
    jasonvanwyk got a reaction from mmacleod in Solar power vs PV Power   
    thanks mmacleod - I was just wondering If I could make an estimate within a certain day temperature range. But You guys are right I think that there are so many other factors to consider as to the make the "estimate" unreliable" - still would be a good study/experiment.
  2. Haha
    jasonvanwyk got a reaction from ___ in Solar power vs PV Power   
    I thought i was...now I know I was🤣
  3. Like
    jasonvanwyk reacted to ___ in Transformer vs Transformerless Inverters   
    There are two more reasons for favouring LF:
    1. It is much easier to AC-couple PV to it.
    2. It is much easier to put units in parallel. You're essentially wiring identical transformers in parallel, a well known and easy to balance setup.
    These two might be the very reasons why the Goodwe cannot parallel or AC-couple with a PV inverter. It has a high frequency design.
    There is one other "trick" that is available with an HF design: You can inject your PV on the high voltage DC bus. So instead of bucking the PV voltage down to battery voltage, you instead buck/boost it to the 350VDC high voltage rail. The PV therefore skips the battery boost stage and you get an increase in efficiency for direct use, but a decrease in efficiency for charging batteries. Again, this is how the Goodwe does it, which is why it has a higher voltage PV input.
  4. Like
    jasonvanwyk reacted to Gerlach in Transformer vs Transformerless Inverters   
    The new MLT units. 



  5. Like
    jasonvanwyk reacted to Gerlach in Transformer vs Transformerless Inverters   
    Here is some images of mine. 
    Front tronsformer:

    And in the rear a monster of a Toroidal Transformer: 
     

  6. Thanks
    jasonvanwyk reacted to Youda in Transformer vs Transformerless Inverters   
    Hi @jasonvanwyk
    just to give you some more info on the differences between HF and LF inverter, this is how HF (aka transformer-less) inverter creates 50Hz sinewave:

    The IGBTs in a full-bridge configuration are producing ON/OFF PWM signal. Since there are just 2 states (ON or OFF), there's a very little resistance to the current flow on the semiconductors themselves. Therefore, even for several kilowatts of switched power, there's not much heat generated. The 50Hz sinewave peaks, valleys and edges are being reconstructed based on the variable width of pulses, as you can see in the picture. Since PWM operates at roughly 22kHz of frequency, the produced sinewave is very smooth. Each digital pulse is precisely generated by the CPU and there's a loopback too, so the CPU can adjust width of the pulses based on the actual AC load. For example, just compare this PWM approach with a conventional audio amplifier based on the transistors, producing analog 50Hz sinewave of 10kW: The transistors would be super-hot and smoking.
    Since there's not much heat wasted and you don't have to magnetize a huge LF transformer, the HF inverters are very energy efficient, have low self-consumption and some of them even have no fans at all, therefore are super-silent.
    Also, in the HF architecture, it's very easy to implement a low-consumption eco-mode:
    Basically, PWM will omit majority of pulses and will generate a waveform with narrow peaks, just to "probe" the connected circuit for any connected loads. Once the loads are connected and detected, the CPU will start to produce full PWM, which will turn into a pure sinewave.  
    On the other hand, since CPU is switching at the rapid frequency of 22kHz, if one of the IGBTs will fail, everything will blow-up in a second without a warning. Also, not every HF machine is really built for effeciency. For example, mine InfiniSolars are HF, but they have the self-consumption higher that a typical LF inverter.
    Anyway, HF inverters are more and more common and almost every modern 3-phase hybrid inverter is internally a HF machine.
    The next step in technology is the capacitor-less inverter. A machine that has no electrolytic capacitors inside, therefore is much more reliable in the long run.
  7. Like
    jasonvanwyk reacted to Richard Mackay in Transformer vs Transformerless Inverters   
    Transformers do have their place. The substations that transmit power to you are all regular 50Hz transformers. They have the edge with being able to handle power.
    Small laminated core transformers that we used to see have vanished having been replaced by switched mode PSUs.
    However every now and then you come across a beauty like this one: I salvaged it from a wrecked (having been 'repaired' ) old school battery charger. I'm sure these are destined to become a collectors prized item!

  8. Thanks
    jasonvanwyk reacted to Richard Mackay in Transformer vs Transformerless Inverters   
    I doubt this. When a 50Hz transformer is used in a power supply (I presume a DC power supply) the bridge rectifier that rectifies the voltage on the secondary winding only produces a voltage pulse every every 10 ms. This is used to charge an electrolytic capacitor which has to be large enough to store the voltage until the next pulse.
    Switched mode PSUs rectify the mains voltage and this produces a  DC rail of 320V approx. This is the supply to the dc-dc converter that reduces this voltage way down to the DC voltage required. As stated this happens at a high frequency so the charge pulses are arriving every x micro seconds. Also due to this speed the voltage regulation is also operating at this speed which allows for better voltage regulation.
  9. Thanks
    jasonvanwyk reacted to ___ in Transformer vs Transformerless Inverters   
    People who sell low-frequency inverters will tell you they are much better at starting large loads. Though that is somewhat true, modern HF inverters are much better than they used to be, so it isn't as "obviously true" anymore. It will depend on the brand.
    Re clean signal, again it will depend on the brand, but the transformer definitely has a bit of a filtering effect and should get you a slightly cleaner sine wave. Neither inverter will get close to the signal of a good grid connection or a large Diesel generator though.
    HF inverters are typically more efficient, because the boost stage is much more efficient (93% to 95%). It's typically as good as the best switch mode power supplies (because it is a switch mode power supply). They are more complex though.
    HF inverters can be made cheaper (smaller transformer). LF inverters typically cost more.
    Here I might get a bit of flack though, but most of the top inverters (re warranty, support, track record) are LF designs. If you need robustness, go LF.
    And with all that said, many makers of LF designs are branching into HF too.
  10. Like
    jasonvanwyk got a reaction from ___ in Victron UPS for small office (8 PCs, server, network)   
    Just want to second the motion that 80’s rocks!😄
  11. Thanks
    jasonvanwyk reacted to Jaco De Jongh in PV Panels Creating A Current On My Roof   
    Okay , so the shock is real and the term we use for it is not. Maybe the real description will be "Induced Voltage" is this case mistaken for "Induced Current caused by a change in a magnetic field. Actually both are caused by the change in magnetic field. 
    At my previous work we had a 7 core cable between two substations almost 700 meters apart, used for monitoring different conditions and switching on one relay. because of the 220VAc over that distance in some of the cores created a "Ghost Voltage" in the Live and Neutral used for energizing the relay. It was enough to keep the relay energized after removing the live to its coil at the source. I had to put a nice resistor over its coil to ensure the relay de-energize when it should. I always said its caused by induced eddy currents in the cable, but now it seems like its actually two different concepts . If I could loop back the two end of that cable and connect the two ends of the "Neutral" core together, its a dead short and will that same Induced voltage now be seen as Eddy Currents? 
    So if something is shorted the induced "Power" is called Eddy currents, but if its induced into a Conductor, its called Induced Voltage because it can "Build UP" to a potential difference? 
    But both are caused by the Change in A Magnetic Field... 
  12. Haha
    jasonvanwyk reacted to PaulF007 in PV Panels Creating A Current On My Roof   
    As a rule , no it is not normal. Usually if you get a shock from a ladder it would be advisable to get a tester of sorts to avoid potential shock again. 🤣
  13. Thanks
    jasonvanwyk reacted to phil.g00 in PV Panels Creating A Current On My Roof   
    @Jaco de Jongh, Ah this is something different, still not eddy currents though.
    Eddy currents by their very nature are current flow internal in a metal and are effectively flowing in a short circuit so there is very little voltage. 
    This is induced current, but no real potential build up, think of a lump of metal as being made up of windings of a transformer but each winding being shorted out. Plenty internal current rushing about and plenty heat but no voltage build up to speak of. 
    I think your dealing with the capacitive effect of an electrostatic charge which does have plenty voltage, but normally not much current.
    Like the little shock you get when you touch the door handle from some carpets.
    You have all the components a large plate being the panels and the roof combination, the other plate being the ground, and high frequency MPPT switching.
    The higher the frequency the lower the capacitive reactance (it is inversely proportionate to frequency) so it could probably develop enough current to deliver a nice shock.
    Mmm, interesting.
     
     
  14. Thanks
    jasonvanwyk reacted to phil.g00 in PV Panels Creating A Current On My Roof   
    @jasonvanwyk,  while I am fully aware of eddy currents, they don't explain your shock. They just run around in circles and make heat. Induction pots would be lethal if they were dangerous.
    It is possible that it was a capacitive static charge, but that takes time to build up and you said it happened a few times in succession, so I'll rule that out too.
    I assume this was a aluminium ladder with insulated feet? And a normal non-metallic hosepipe?
    Your shock was because your roof is live relative to earth where you were standing. Your ladder was just the equivalent of a wire connected to your metal roof.
    The DC side of solar is often unearthed, is your DC side or are your batteries earthed?
    This isn't necessarily a solar issue, if your DC side isn't earthed elsewhere. You represented one earth but there has to be another earth elsewhere to make a circuit.
    This is why I asked you to measure the voltage and see if its AC or DC.
    We know there will be an earth on the AC.... and if I was a betting man.
    See if it goes away if you trip your AC.
  15. Thanks
    jasonvanwyk reacted to Jaco De Jongh in PV Panels Creating A Current On My Roof   
    Hi Phil, this would be the first time i will disagree with you to an extend. I had the same issue on more than one installation, including my own home. I was seriously surprised when I was shocked and pulled everything apart, even replaced all my PV wires as i thought that the insulation might have broken down and allowed a leakage. My metal gutters were well earthed and if I touched the metal gutters and any of my panels I received a nice shock. Even measured  50-80 volts between earth and the frames. It was during a period of moving my panels from a ground mounted frame to my roof and they were not yet earthed. One String were operational while I was busy installing the rest, it became so unbearable that i had to solve it before i could continue.
    I also suspected it was an AC leakage that might cause it, but even with the AC switched off at the Boundary box and the inverter output breaker switched off, the voltage remained. I wanted to test if it was "Ghost voltage" or real power and connected different 24 & 48 Volt coils and globes between the panel frames and earth and the moment i did that the voltage disappeared. 
    In my case the eddy currents were induced in the unistrut frames. The only way I could make it stop was to break the string, Earthing everything solved it on more than one installation. 
    EDIT: 6 of my panels were lying flat on wire mesh supported 2.2meters from the ground, they were part of a string of 12 panels. the other 6 were on the roof, so only a + and - wire were running from the combiner box, through the air to the panels. No earth were installed. At midday, you could not stand on the ground barefoot and touch the wire mesh at the same time. Nice serious shock. There is no other power within 10 meters from that mesh. My wife came and called me after she got shocked, i laughed at her and told her it is impossible, there was nothing that could shock her....... until I touched the mesh myself... guess who were the one laughing then? 
    I thought its static and tried to discharge it by touching it first and then hold on, I could not hold on much longer than a second and had to let go. Earthed the mesh, and no more shock. 
  16. Thanks
    jasonvanwyk reacted to Jaco De Jongh in PV Panels Creating A Current On My Roof   
    Thanks Plonk. I was able to explain exactly this to Jason over a phone, but trying to put it in writing will take forever. Thanks for taking the time....
  17. Like
    jasonvanwyk reacted to Coulomb in PV Panels Creating A Current On My Roof   
    This will also have another, related benefit. When lightning strikes nearby, a voltage is induced into the cables roughly proportional to the area between the conductors. Keeping the conductors together minimises this area, thus minimising damage from the induced voltage.
  18. Haha
    jasonvanwyk reacted to Krokkedil in PV Panels Creating A Current On My Roof   
    When I started off about a year ago i also had the roof bite me  
    I Earthed the frames panels and roof using a copper spike of about 3m into the ground and 6mm2 earth cable. Never had a shock again.
    I cant remember where i read it but someone said that i must actually drive spikes in every 5 meters and install a 16mm2 cable to them. I looked at the cost of the cables and decided i will do that when i win the lottery.
     
     
  19. Thanks
    jasonvanwyk reacted to ___ in PV Panels Creating A Current On My Roof   
    Physics 101. If you put an electrical conductor into an alternating magnetic field, a current is induced in that conductor. Such currents are usually referred to as "eddy currents". It's the reason why grid codes mandate that the life and neutral for all circuits must pass in the same conduit, especially when the conduit is metallic. The 50Hz alternating current in house conductors induce currents in any metal in the vicinity, but if you put both wires in the same conduit they cancel each other.
    These eddy currents can of course generate a fairly unpleasant shock. It's rarely dangerous, but that is no excuse really.
    Now you may wonder where the alternating field comes from given that PV modules are DC, and the answer is that it comes from the MPPT. The MPPT switches the power on and off in a square wave, usually in the 40Khz to 100kHz range, and this causes enough of a ripple to induce current in nearby conductors.
    The fix is to earth the frame, and to try and keep your cables together as much as possible, ie try to avoid a situation where the positive cable runs alone along "this" side of the frame while the negative runs somewhere else.
    I would expect the effect to be worse as the batteries get full. While the MPPT is tracking the maximum point there will be less of a ripple. The ripple is worse when it's limiting power.
  20. Haha
    jasonvanwyk reacted to Jaco De Jongh in PV Panels Creating A Current On My Roof   
    Welcome to the experience. @plonkster  has a very nice way of explanation why this happens. Its got to do with the internal frequency of the MPPT. (Cant remember, 40KHZ or something crazy like that). 
    The best solution is earthing your frames properly. Bring the Panel frames, Mounting rails Roof and ground to the same potential and that should be the end of it. 
    Do a little test, connect a wire to a water steel water pipe or something that is earthed well, then touch the other end on the roof, you should see quite a nice spark. 
  21. Thanks
    jasonvanwyk reacted to seant in Fibreglassing   
    I'd look at dropping probably 2/3 of the height of the tank below the ground it will make it easier for the return of the water from your grow beds.
     
  22. Thanks
    jasonvanwyk reacted to Thunderdolt in Fibreglassing   
    The below link has containers from R700 and complete aquaponic system from R2950 that might suit your needs.
    http://www.flowbins.co.za/
    Happy New Year
  23. Thanks
    jasonvanwyk reacted to Jaco De Jongh in Fibreglassing   
    Maybe THIS  or THIS can help. 
    What I found with fiberglass is that a "mold" is needed.
  24. Like
    jasonvanwyk got a reaction from Ewald in Newbie from Benoni - Grid to Solar   
    Welcome Ewald - you are at the right place, Happy "solar-ing"!
  25. Thanks
    jasonvanwyk reacted to MIT Z. Power in Hail Damage   
    I've been through this and I've been paid by the insurance company
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