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Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 08:05am 08 Nov 2024
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Thanks wiseguy, your post did the trick and my inverter AC is now rock steady
Engineering inputs are priceless to us mere mortals who are blissfully ignorant to what's very obvious to you . I did not believe at first that this voltage sensing circuit could be so sensitive to external noise but you proved me wrong .
Fortunately, this inverter lives in a rather large enclosure, so it was relatively easy to incorporate these modifications. The control board (on a grounded shield plate) is now located at the very top, about as far as possible from the power components.
And here is a view of the output, AC voltage is the same from zero to this load:
I also changed the AC volt sensing point to upstream from the C/B, thank you for pointing out why this is important.
wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156
Posted: 11:21am 08 Nov 2024
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Just a lucky guess, glad it is now working fine. I must say that when you stick your neck out it can be a bit of a tense time waiting to hear hopefully a positive result. Because otherwise your credibilty can get shot to pieces in a very public manner, just by trying to be helpful. I find it much less stressful & risky fault finding my own creations and board layouts. Edited 2024-11-08 21:54 by wiseguyIf at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 09:53pm 08 Nov 2024
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Glad you got it sorted, the need for a metal ground plane and care with controller location were covered in detail in two other threads.
Some of us should have read your reply more thoroughly when you mentioned the ground plane you were using Luckily wiseguy picked that up and saved you more needless fault finding
It's all too hard. Mike.
analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 108
Posted: 06:10pm 09 Nov 2024
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Glad it's working. However, I would suggest you also follow wiseguy's recommendation about grounding all unused opamp inputs. You have moved the controller further away from the main noise source but it's still vulnerable to noise.
wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156
Posted: 10:11pm 09 Nov 2024
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The bead is still there - I assume that screw also grounds the metal plate? If any HF noise comes down the negative feed wire it is now connected to the shield which can still radiate noise into the PCB traces due to the decoupling effect of the bead to the PCB ground plane & traces.
Yes it may sound slightly pedantic but a lot of my career has involved solving these types of issues. If you remove the bead and leave just the link there and place a bead on the positive feed wire it would have a much better noise rejection. The effect is turning differential noise into common mode noise. If the ground plane and metal plate are joined together solidly then the same noise present on both has essentially no effect on sensitive nodes. Ok I confess maybe it was not a lucky guess. Edited 2024-11-10 08:12 by wiseguyIf at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike
Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 10:29am 10 Nov 2024
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OK, I can do these mods. Yes, that screw connects the negative to the metal plate under the PCB. The PCB itself has a ground area on the component side.
But I'm very impressed by the AC voltage regulation now, it changes about by only about 1 V from no load to >5KW. This is much better than any of the previous Vfb arrangements that were posted here (and I tried most of them), it is also a lot better than my warpverter (when I still had it) managed - sorry Tony .
After doing the suggested mods I shall see how that AC regulation performs when I do back charging through a GTI. Doing that always boosted the AC with previous Vfb methods.
As an aside, I also made another control PCB that uses the EG8010 chip, all else being identical to the Nano control board. I could not detect any difference with AC regulation or trace shape between these boards. So, either will do the job for me now.
I might even do a small PCB with just that little 1:1 transformer and the two OP Amp chips on it so I can retro fit it in my other inverters. This could be fitted into a metal jiffy box for complete shielding and a shielded wire to the Vfb input at the control board.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 10:45pm 12 Nov 2024
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I'm glad you went to the trouble of making your own PCB versions and the comparison between the Nano and 8010 controllers versions.
It confirms the observations of better line regulation that I had noticed, more importantly, you found the reason for that improvement It's all too hard. Mike.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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. I did not believe at first that this voltage sensing circuit could be so sensitive to external noise but you proved me wrong 
.
