DC-AC inverters and wall outlets


by Sedmic
Tags: dcac, inverters, outlets, wall
Sedmic
Sedmic is offline
#1
May9-07, 04:43 PM
P: 1
I was wondering if anyone could provide me with more information regarding DC-to-AC inverters. Specifically, I'm wondering what stops me from hooking up a power source (i.e. lead acid battery, small solar panel, etc) to an inverter and discharging it into the wall. I know that grid-tie systems exist for applications such as solar power. If the inverter can reliably convert to 120 VAC at 50-60 Hz with a modified sine wave output, is there any danger to simply plug this into the wall? Would a pure sine wave inverter be better for this purpose? Alternatively, if you know of some good websites or other sources that can explain this concept to me, I'd love to know.
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berkeman
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May9-07, 04:49 PM
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Well, if you are disconnected from the power grid (you've shut off the main breaker for power entry into your house), and your power source and inverter have enough power to power whatever is turned on at the moment in your house, then yes, you could just plug the inverter output into the wall. That's how you power your home with a generator when the power fails, for example (after carefully shutting off the main breaker and preferably locking it out).

But you can't do that without shutting off the main power entry breaker to your home. The phase angle of your inverter will not match the phase of the AC mains source power from the street, and the inverter will pop.

You may be interested in the concept of "cogeneration", where you have some power source at your home (like a running stream, or solar panels, or a big windmill), and want to sell power to the grid. Here's some intro reading on that subject:

http://en.wikipedia.org/wiki/Cogeneration
chroot
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#3
May9-07, 04:52 PM
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Berkeman's got it. If you want to feed power back onto the grid, you need equipment that will match the phase of your sine wave with the phase of the sine wave on the grid. Also, you'll need a meter that's capable of measuing your output current (I'm not sure if standard meters can do this or not, actually).

- Warren


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