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[aprssig] backup pwr systems

Alex Carver agcme2002 at yahoo.com
Mon Dec 11 23:34:28 UTC 2006

> Message: 12
> Date: Mon, 11 Dec 2006 08:50:13 -0500
> From: "Robert Bruninga" <bruninga at usna.edu>
> Subject: RE: [aprssig] backup pwr systems
> My thought is just a sensing circuit that only fires
> the
> inverter MOSFET's on the rising side of the 60 cycle
> waveform.
> And then fires them for 50ms or so on each cycle. 
> If there is
> no waveform, then the inverter transistors don't
> fire.  Should
> be very simple.
> And would let me keep all my APRS stuff running 24/7
> and take
> advantage of the sun at midday.... Without having to
> re-wire
> anything.. ;-)

You would have the power company beating down your
door that way.  Switching the MOSFETs on only a half
cycle would introduce even more harmonics into the
output power and get fed back into the grid.  Best to
just stick with a standard UPS for each item (or group
of items) you want to keep powered or go with a
grid-tie inverter system.  Having something that plugs
into the wall as you describe is a sure-fire way to
electrocute a line worker when the power goes out
(because you don't have an anti-islanding relay
installed as would normally come with a grid-tie inverter).

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