[aprssig] [OT] RE: APRS Solar Power (I was wrong)

Steve Noskowicz noskosteve at yahoo.com
Sat Oct 3 22:23:05 EDT 2009

--- Dave Baxter wrote:
> I don't know about US refrigerators, ...an almighty
> kick to get the compressor motor started.  
> ...once the compressor is running, the genny run's it just fine ...

  That's the normal characteristic of "ordinary" motors (over 'here' as well). When the rotor is not turning (yet) this is referred to as "locked rotor" and it draws current only limited by the motor's resistance. As the rotor speeds up, it acts like a generator and generates "Back EMF" (voltage) that opposes the applied voltage and therefore reduces the current drain to a lower steady-state value.  It is very source-hostile.  For fridges, starting current can easily be 10x run current.
Resistive loads, of course, don't have this characteristic.

I have a couple 400 W inverters with the "modified sine wave" (60& duty cycle square wave).  When I did some mobile noise hunting for the local 2M repeater, I discovered that I couldn't turn on my HP 141T analyzer.  I tried turning the analyzer on first, _then_ switching on the inverter and it then ran.  It also took a dozen or so clamp-on beads to quell the RF riot so the analyzer was useful.

>... some warning that it's all about to go dark so as to
> "prepare" for it, ...

  Unfortunately, the compressor may not be running when the power fails.  In addition, if the compressor is running when the power fails, the system is charged with pressure and trying to re-start the compressor immediately  (after the rotor stops turning) leads to an even worse start-up because of the increased load on the compressor due to the internal pressure.  A compressor, ingeneral, shoudn't be restarted without a few minutes rest to allow the pressure to drain off.

> CFL lamps though, ...

Some time ago, I got some GE CFLs and looked very closely with the Spec analyzer to see what frequency they were running at. I just brought a probe close to it.  I saw NOTHING!  These were very quiet.  I even called GE and was told it was a company secret.  Certainly opening one up would show the filtering.  I had one blow a few weeks ago with a hissing noise and a smoke filled ceiling. Didn't smell bad though.  Litics all bulged out and a very black resistor or two.

> Lead Acid batteries are also not that efficient, ...
> that is, and the higher the discharge, the worse they get.  

  All batteries are like this.

73, Steve, K9DCI APRS user (see, On Topic)


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