Pvusers Archive for July 2002

I've never had the experience of listening to either a Trace or Statpower 
sine machine, but I certainly would before buying one. I'm in a small 
house far from city racket. I had to rearrange things so that the Trace 
was better isolated acoustically, or I would have gone mental.

Cheers,
-=s

On 19 Jul 2002 at 17:16, Michael Welch wrote:

> Scott Willing wrote at 07:10 PM 07/19/2002 -0500:
> 
> >Oops, another quick question gig,
> >
> >What kind of acoustic noise do they make? Right off the unit, I mean
> >- hmm, buzz, sizzle? Silence plus fan noise?
> 
> There's been a recent discussion among RE installers about this very
> issue. The consensus is that high quality electronic appliances have
> not had a problem.
> 
> However, lower quality ones have. Here is a a recent post from an
> Exeltech technician on this very issue:
> 
> >Greetings Wrenches:
> >
> >I've been nudged out of lurk mode to reply to the recent series of
> >interference-related postings.
> >
> >Rather than turn this into a complex dissertation on EMI
> >(electro-magnetic interference) and RFI (radio frequency
> >interference) .. I'll do my best to cover the specifics in a summary
> >form, beginning with Interference 101.
> >
> >One of many sources of electronic interference occurs when
> >electricity is turned on or off very rapidly.  To achieve the
> >inverter efficiencies we all desire, some of the circuits spend their
> >time either full on, or full off, with as little time as possible
> >spent in the middle.  It's the transitional region between those two
> >states that represents one of the larger causes of loss in the
> >circuits.  Thus, in switching rapidly between on and off, we create
> >unwanted interference in the process, which must then be reduced to
> >FCC mandated levels if we are to attain specific certifications on
> >the equipment.
> >
> >Interference escapes from the equipment in two ways - conducted
> >(where power leads act as "pipes" between the inverter and other
> >electronic equipment) and radiated, where the unit and connecting
> >wires act as antennas.  Interference also encompasses frequencies
> >from very low (low audio range to a few hundred kilohertz) to very
> >high - well into the television frequencies and beyond.
> >
> >Solutions differ greatly for interference types and frequency ranges.
> > Conducted interference filters may not do well on radiated signals. 
> >Filters for low-frequency interference are generally ineffective for
> >high frequencies, and so forth.  Subsequently, combinations of
> >filters must be utilized.  To further aggravate the situation,
> >filters for the DC side must deal with very high currents while
> >posing minimal voltage drop.  This requires very large conductors,
> >which in turn make for some very unwieldy inductors (coils).
> >
> >That having been said .. it's a given that no two situations are
> >identical.  Solutions aren't either.
> >
> >
> >In summary:
> >
> >Keep all DC leads as short and heavy as possible.
> >
> >Twisting DC leads together helps on some forms of interference, but
> >not all,  It won't hurt to try, but don't expect miracles.  Tighter
> >twists work better than loose ones, but use care not to damage
> >insulation.
> >
> >RF (radio frequency) filtering of the AC output leads directly at the
> >inverter AC output may be helpful in some cases.  There are countless
> >sources listed on the Internet.  I found over 25,000 using "RFI" and
> >"filter" as search words.
> >
> >TV reception in remote areas with a regular (non-satellite) TV
> >antenna MAY be helped in some instances by the use of an
> >antenna-mounted signal amplifier; the use of coaxial cable for a feed
> >line (though it loses more signal than quality twin-lead); locating
> >the inverter and TV antenna as far from each other as possible;
> >separation of AC and antenna leads (don't run the antenna lead
> >alongside the extension cord feeding the TV); use of better quality
> >power strips that have self-contained RF filtering; and keeping in
> >mind that some receivers (TV, AM/FM, or otherwise) are more
> >susceptible to interference than others.
> >
> >And finally .. keep in mind that no electronic power device is
> >interference free.  Even with filtering, some junk still gets out. 
> >If you or your customer are in a very marginal signal level area, all
> >the filtering you can install may not be enough. Remember, the
> >interference must be reduced below certain levels to attain
> >certification - not eliminated.
> >
> >One big secret to all this is to keep the receiving antennas as far
> >as possible from the interference source.
> >
> >This is a synopsis.  I have a much more detailed reply I'll be happy
> >to send to you if you contact me offline.
> >
> >Regards to all from Fort Worth...
> >
> >Dan Lepinski
> >Sr. Engineer
> >Exeltech
> 
> 
> Michael Welch
> 
> ------------------------
> "In a nation of sheep, one brave man forms a majority."
>    Edward Abbey
> 
> Michael Welch, michael.welch@homepower.com
>      Home Power magazine
>      www.homepower.com
>      To reach me: 707-822-7884
>      To reach Home Power: 800-707-6585
> 
> 
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