I'm looking to design a UPS/transfer switch/inverter circuit that can supply ~1kW 115 VAC for around 5-10 seconds. Such a thing does not exist commercially, unfortunately (and not surprisingly, really, pretty niche here) The use case is this: I live in an RV and my whole place is battery-backed. If external power is shutoff via a breaker, my inverter transfers to battery power quickly enough that nothing has any problems. However, if I'm running my generator (Generally, I'm solar-powered, but trees and rain do happen), and I shut it off... the power goes 'bad' (as the generator spins down, frequency drops) and while eventually (and 'eventually' is like 100ms) the inverter takes over, it doesn't happen quick enough. Almost everything I have either A> is fine to lose power for a quarter second (laptops, screen, etc), or B> is running directly off battery anyway. However, my main workstation is AC-powered, and it inevitably reboots when I turn the genny off if I don't go through a whole sequence of tripping the breaker first, which is annoying. An off the shelf (lead acid) UPS fixed this problem, but it takes up too much space and weight in my rack (as you can imagine, every U is precious in an RV rack 
) and I'd like to get it gone.
So I've got a basic idea in my head on how to design a UPS/transfer switch, and there's some example schematics and such out there. I'm hoping to fit this little project into my existing PDC (A 1U Pyle PDBC70), but we'll see I guess. I'm debating a few issues and I'd be happy to have anybody weigh in with any thoughts/ideas before I really start digging in. I've not seen anybody doing what I'm trying to do, but if you know of anyone who has, please let me know.
A> I don't even really need 5-10 seconds. A 1 second "capacity" would probably do me just fine. But I may be running a lot of power at the time.
B> I have access to power from my house batteries (albeit, 10ga cable and about 15 feet of run away) in and near the PDC I want to fit this into. I was originally thinking capacitors, but now I'm thinking skipping having a 'charging' circuit or energy storage at all, and simply drawing on the house battery. I would not want to run 1000W through this cable for very long, but a couple seconds should be fine.... If I go this route, I'll want to accept 12-26VDC or so -- I'm on a 12V nominal bank now but I'm debating moving to 24).
C> I could probably get by with 8 or 900W, but it's always best to build in some headroom. Likely in most cases my graphics cards won't be fired up and really, 150W is fine, but I'd rather do this right and make sure it works even if I'm sucking power full-tilt.
D> I suspect somebody's gonna say something like "you need enough capacity to shut down cleanly -- a minute or two" -- like most UPSes -- I say no, I don't. I'm absolutely fine with my workstation just losing power if it takes more than a couple seconds for things to stabilize -- that's gonna be really rare.
tldr: I need a UPS that can provide 1000W of 115VAC for a _very_ short time (<1s) while a generator spins down.
) and I'd like to get it gone. So I've got a basic idea in my head on how to design a UPS/transfer switch, and there's some example schematics and such out there. I'm hoping to fit this little project into my existing PDC (A 1U Pyle PDBC70), but we'll see I guess. I'm debating a few issues and I'd be happy to have anybody weigh in with any thoughts/ideas before I really start digging in. I've not seen anybody doing what I'm trying to do, but if you know of anyone who has, please let me know.
A> I don't even really need 5-10 seconds. A 1 second "capacity" would probably do me just fine. But I may be running a lot of power at the time.
B> I have access to power from my house batteries (albeit, 10ga cable and about 15 feet of run away) in and near the PDC I want to fit this into. I was originally thinking capacitors, but now I'm thinking skipping having a 'charging' circuit or energy storage at all, and simply drawing on the house battery. I would not want to run 1000W through this cable for very long, but a couple seconds should be fine.... If I go this route, I'll want to accept 12-26VDC or so -- I'm on a 12V nominal bank now but I'm debating moving to 24).
C> I could probably get by with 8 or 900W, but it's always best to build in some headroom. Likely in most cases my graphics cards won't be fired up and really, 150W is fine, but I'd rather do this right and make sure it works even if I'm sucking power full-tilt.
D> I suspect somebody's gonna say something like "you need enough capacity to shut down cleanly -- a minute or two" -- like most UPSes -- I say no, I don't. I'm absolutely fine with my workstation just losing power if it takes more than a couple seconds for things to stabilize -- that's gonna be really rare.
tldr: I need a UPS that can provide 1000W of 115VAC for a _very_ short time (<1s) while a generator spins down.
