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Forum Index : Electronics : Inverter building using Wiseguys Power board and the Nano drive board
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KeepIS Guru  Joined: 13/10/2014 Location: AustraliaPosts: 2268 |
Something I did for fun. No VFB 20V DC supply. A: Test Inverter, Power board with 34,000uF. B: DC voltage DOES NOT CHANGE, monitored with A DSO. C: No AC Feedback connected, besides it's below VFB activation in any case. D: Inverter powered by regulated 20Vdc supply with a max current of 21 Amperes. Pink: Primary Current. Blue: LT AC output. Capture 1: Idle.  Capture 2: 180w Restive Load. A: 11.5A Primary current via Clamp meter. B: 12A vPrimary current via TLS76L1.  Capture 3: Heat Gun. A: 34A Primary current via AC clamp meter. B: 35A Primary current via TLS76L1. C: DC current switches between 11A and 20A every few seconds. D: Buzz in Toroid does not change with that swing.  . NANO:Inverter V 8.4ks - Linux AvrDude GUI script V4.1 |
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wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1317 |
Great image shots and good idea to remove feedback as Nicks also recently did. The yellow drive waveform appears to be phase reversed compared to the output - it just made it a bit harder to interpret at first. Maybe my analysis below is wrong or questionable, I am not trying to speak with authority, its just a theoretical comment and I invite comments for or against. The peak voltage for the positive unloaded 180 degrees is ~ 2 divisions, The peak for the loaded negative 1/2 wave is ~ 1.5 divisions. The result of the asymmetrical waveform results in the positive unloaded current but with saturation peaks. This is why I described our toroids as "puny" compared to the mains. With a distorted waveform such as this applying feedback might make it even worse as it tries to drive harder for the lower average output? My suggestion of 180 degree measurements and applying them to the second 180 degree waveform - not the next immediate period should try to prevent or at least partially mitigate the issue of the low negative toroid drive voltage. I am unsure but suspect that changing the phasing of the feedback might only make a small difference on the idle hum. I am not telling you or anyone to write the code but I can see an issue that we can either accept or have a further play with the code to see if we can get a better result. I am happy to offer up my inverter as a sacrificial unit for testing if it makes any difference. Edited 2026-09-21 18:07 by wiseguy If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2268 |
I'm currently laying a partial false floor to finish the Workshop extension, so still no time to do much on the Bench. I intend to capture the Heatgun on the Main Inverter in a real world off-grid situation, I'm sure that 1kW or more of normal running loads when the Heatgun is connected, will considerably dampen the effect on the Inverter. Years ago I remember reading many posts on various forums bemoaning the destruction of Inverters when a stupid load like this was connected. Again, it has never caused a problem for my Inverters. I do understand the desire to see if the effect can be reduced as a technical exercise, I'm just not sure I want to start changing 100% stable Inverter code to accommodate a piece of crap that has no right to be sold or used with Inverter power, or Mains for that matter. If you want to play with that and no one else comes forward, we can certainly do that in the future. Unfortunately, as soon as I'm finished the Shed extension, I will be heading down to inspect the Toroids that have finally arrived, and winding two for a second complete Dual Inverter backup, I then have 6 solar panels to add, cabling to run, an MPPT controller to build, and I still haven't got around to cleaning up my part of the workshop  On another note, and the main reason for a second Dual backup Inverter, I see the cost to just have Mains power connected as a backup is expected to be around $1200 a year or more!! And I can see more control laws coming to prohibit us from saying NO and disconnecting from the grid.   : Edited 2026-09-22 13:39 by KeepIS NANO:Inverter V 8.4ks - Linux AvrDude GUI script V4.1 |
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| wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1317 |
Hope your flooring punishment is almost done by now. After a few days of thought I am coming around to your way of thinking. Whilst I will remain curious about whether it could behave better with poor loads, when it is presented with typical daily loads including welding etc it behaves just fine. I think I was falling into a trap of trying to fix a perceived problem rather than a proven problem. I guess I wanted the inverter to behave really well no matter what crap was plugged into it which is probably overthinking a solution for someone elses poor choice. After replacing 16 FETs maybe better choices will be made  .If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike |
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| mab1 Senior Member  Joined: 10/02/2015 Location: United KingdomPosts: 287 |
I've been following this mostly in the hope of understanding the come-&-go hum at idle (i will try swapping the v feedback polarity, but haven't yet), but i am fascinated by the torroids reaction to a recified load: it's as if having passed current (or more like coulombs - is the area under the curve equal i wonder?) on one half cycle, it needs to pass an equal number of coulombs in the other half cycle, but, being unable to pass them through the load on the secondary, the 'pressure' builds on the primary until the H-bridge voltage drops towards zero, letting them all through on the end of the cycle. And yet the secondary voltage doesn't show this 'pressure'. And then having reset to 'no load' current for the zero crossing, it has to build the load current up again on the new cycle, indicated by the 'sag' on both voltage and current in the rise from zero. Not really planning on experimenting with asymmetric loads myself, but i sometimes think i should scope the waveforms when charging the EV as i get some quite loud transformer noise from that - but then it is a quite powerful ac-dc convertor (up to 22kW) being modulated down to just 2kW. Edited 2026-09-25 01:49 by mab1 |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1308 |
This is also present in an old 700w 24v Selectronic inverter, still works, who knows how many others do the same thing.  Cheers Aaron Off The Grid |
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