[Milsurplus] [ARC5] Question...

[David Olean]

Then there is the problem of hardware store generators (cheap gasoline 
powered) not supplying exactly 60 Hz. The RPMs slow under load and the 
frequency varies. This can negate benefits from constant voltage 
transformers abit. They want 60.0 Hz to work properly.  Old gensets with 
lots of "iron" tend to have better waveforms. I have seen some inverter 
types that are great. They do produce lots of RFI though.

Dave K1WHS

On 10/31/2020 11:48 PM, Dennis Monticelli wrote:
> Ken,
>
> You have a generator with a quasi sine wave switched mode inverter.  
> Yes, they're dirty.  My museum has run that type of inverter at street 
> faires before and the radios have issues.
>
> I don't think resonating a conventional power transformer is a good 
> idea because the circulating currents would be high and it would 
> probably overheat.  You have no doubt run across SOLA ferroresonant 
> line transformers; they are much oversized for their power rating.  I 
> recommend putting both differential and common mode filters on the output.
>
> Dennis AE6C
>
> On Sat, Oct 31, 2020 at 8:25 PM Kenneth G. Gordon 
> <kgordon2006 at frontier.com <mailto:kgordon2006 at frontier.com>> wrote:
>
>     At this point, I don't know where else to post this, so here goes:
>
>     I have a "small emergency generator", 7500 watts, brand new.
>
>     From my reading, I find that the output waveform is very "dirty"
>     as it is some sort of "stepped" square-wave. I have not yet looked
>     at the wave-form with an oscilloscope, but I am not expecting it
>     to be very pretty.
>
>     My old military generators output a nearly pure sine wave, but
>     these modern beasts don't.
>
>     SO....I have two heavy (about 70 lbs each) 115-115 volt isolation
>     transformers. good for at least 15 amps input/output each.
>
>     I propose to "tune" them to 60 Hz by connecting capacitors in such
>     a way as to make them into 60 Hz tuned circuits with the idea that
>     doing so should "round off" the waveforms and eliminate the harmonics.
>
>     What does the collective wisdom think of this idea? Has anyone
>     tried this? What was your result?
>
>     Ken W7EKB
>
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