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InPhase Senior Member Joined: 15/12/2020 Location: United StatesPosts: 178
Posted: 02:11pm 05 Jan 2021
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I've decided to take a stab at one of the inverters the group here has developed. A nano type of about 3 kW @ 24 VDC, I figure. But before I commit, I'll beg the group's opinion and advice. For this project, the battery bank will be 210 AH @ 24 V.
Spec:
24 VDC Input 120/240 VAC Output 2-3 kW Continuous 18 degree C Ambient over the year. Never more than 40.
What I have on-hand and plan to use, until better can be procured, is a battery bank, and a totally potted and enclosed 3 kVA 240/120 V : 32/16 V transformer, what an electrician would typically connect as an autotransformer to slightly raise of lower the line voltage into spec. "Buck/boost". I know it will be less efficient than a toroid, but it will do for now(?). Assorted basic electronic parts in not-too-shabby quantity, including various flavors of analog ICs and digital logic. Tools, o-scope, skills.
I have read for many weeks through the various threads and watched the evolution and iterative updates of some of these builds. For fear of finding a flawed or old design using search, I will ask: what is the up-to-date cutting edge of the Nanoverter software and power board design?
Any other insight and suggestions (besides "Spend more money..") also appreciated.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 08:30pm 05 Jan 2021
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If you have a 32v transformer that is potted, and you cannot change the turns, the minimum dc voltage that can be used will be 32v x 1.414 or 45 volts.
If only half the primary is used, it will work down to 23.6v but at only half rated power or 1.5 Kva.Cheers, Tony.
InPhase Senior Member Joined: 15/12/2020 Location: United StatesPosts: 178
Posted: 10:42pm 05 Jan 2021
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There are really two primaries and two secondaries. They can be wired in series or parallel. It's like having two 120:16 transformers. I figured putting 24 volts on the two 16 volt coils wired in parallel would work, even if the output voltage drops as the battery drains. 120/240 is nominal but I don't have a single piece of equipment that would mind 110 or 108.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 12:13am 06 Jan 2021
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Ah ! Then you are definitely in luck. Parallel up the two 16v primaries and it should work down to about 22.6v dc which is just about right for a 24v lead acid battery.Cheers, Tony.
InPhase Senior Member Joined: 15/12/2020 Location: United StatesPosts: 178
Posted: 01:22am 06 Jan 2021
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How big of a difference can I expect between this transformer and a toroidal? Besides a lower efficiency, will this transformer behave differently from a MOSFET driving point of view?
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 01:59am 06 Jan 2021
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Highly likely that the no load idling power will be a fair bit higher than with a toroid.
You can check that by connecting one of the higher voltage windings of the transformer to a power outlet, and measure the current. That should be a pretty good indicator.
The mosfets could not care less, to them its just a load.Cheers, Tony.
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