[aprssig] backup pwr systems

[Robert Bruninga]

> What you describe is exactly a grid-tie inverter, just not so 
> large as those used in all house or larger systems.  I have 
> never seen how they protect themselves and others from the 
> hazards of tying to the grid...

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.. ;-)
Bob, WB4APR

> 
> 
> ----- Original Message -----
> From: "Robert Bruninga" <bruninga at usna.edu>
> To: "'TAPR APRS Mailing List'" <aprssig at lists.tapr.org>
> Sent: Sunday, December 10, 2006 11:06 AM
> Subject: RE: [aprssig] backup pwr systems
> 
> 
> > What I want, and no-one makes,
> >
> > Is a 400 watt DC-to-Line synchronous inverter that can back
feed
> > into my house power to save me a few pennies on the electric
> > bill.  It is a whole lot of trouble to configure part of the
> > house load to run on DC because then you need a battery, and
> > then you have to charge it during the day, when no one is
home
> > and you don't need any DC, and they run it at night after
> > switching over to inverter.  All of this takes work, effort,
> > life style changes, and none of it is worth the trouble for
just
> > a few hundres Watts of excess green power.
> >
> > But if there was a synchronous 400W inverter with just a
line
> > cord that you could plug into any outlet in the house and if
you
> > had up to 400W of free DC power available (wind or solar),
then
> > just plug this thing in, and it would backfeed your existing
> > circuits.
> >
> > Of course it would be man-safe, and would only provide boost
> > current only if there was line voltage alreaady there.  If
there
> > was no 60 Hz AC, then it would do nothing.
> >
> > What it WOULD do is reduce my electric bill during the PEAK
> > summer rates (time of use metering charges almosst 17 cents
per
> > KWH duing the summer day).  And it would do this with
minimal
> > effort, because the total interface is just plugging it in.
And
> > I woiuldnt lose the battery charge/discharge inefficiencies
nor
> > would I be wearing out my batteries every day by cycling for
> > this minimal power.
> >
> > Think of it this way.  There are dozens of stupid little
> > "wall-warts" haniging throughout my house that provide a
> > constant drain on my electric meter.  The 5W of heat that
each
> > one is consuming is just not worth re-wiring the house for
DC,
> > but the total of them adds up to probably a few hundred
watts 24
> > hours a day.  By injecting my solar power during the midle
of
> > the day when I get the most, into my mains, it would be like
> > paying myself 17 cents for every KWH I put in.
> >
> > Again, do not confuse this with grid-tie inverters that are
> > desigend to run your meter backwards and which require
Electric
> > Company and all kinds of approvals and all kinds of safety
> > issues.  This is just a small device to help "reduce" my
> > electric demand.
> >
> > Anyway, it would be a dun design project for powering my
24/7
> > APRS system and any spare power I have.
> >
> > Bob, WB4APR
> >
> >
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> >
> 
> 
>