[ARC5] Question...

Sun Nov 1 15:17:30 EST 2020

The solid state inverters are indeed the future.  They cure all the major
ills, save space, weight, and maintain good efficiency over wide load
variations as people have noted.   And they don't have to generate RFI to
do their job, though unfortunately many do, leaving the mess for the user
to clean up.

Dennis AE6C

On Sun, Nov 1, 2020 at 10:27 AM Bill Cromwell <wrcromwell at gmail.com> wrote:

> Hi,
>
> We have mentioned the "flywheel effect" to help with sudden load
> changes. The prime mover (engine) needs a good surplus of power to
> quickly respond to sudden load increases. Training and experience
> generating electricity aboard Navy ships.
>
> 73,
>
> Bill  KU8H
>
> bark less - wag more
>
> On 11/1/20 1:18 PM, Scott Johnson wrote:
> > The biggest problem with toy generators is they have poor speed
> regulation,
> > and typically poor voltage regulation and droop compensation.  Inverters
> > cure some of these ills, but I doubt the SMPS in the computers cares all
> > that much about harmonic content, rather is is probably more sensitive to
> > voltage droop and variation.
> > Some very small gensets use a Lundall or "claw pole" generator, much
> like an
> > automotive alternator.  The machine intentionally produce a squared off
> > waveform, which , in the case of the alternator, is advantageous since
> it is
> > more efficient to rectify.
> > Most small gensets are two pole machines running at 3600 RPM (60 Hz),
> with
> > very little rotating mass to help short term speed variations, So as Ben
> > said they spend more time below 60 Hz than above.  The inverter addresses
> > most all of the problems, IF it is sophisticated enough to have a proper
> > high rate PWM output (many are not).  I recently had experience with a
> > Capstone 1 MW inverter derived turbine generation system, and the power
> it
> > produces has lower harmonic content that the grid to which it was
> connected.
> > I can see that very soon, most likely all small gensets will be inverter
> > sets, they are rapidly improving.  I look forward to replacing my 10 kVA
> MEP
> > generator when a decent one is available.
> >
> >
> > Scott V. Johnson W7SVJ
> > 5111 E. Sharon Dr.
> > Scottsdale, AZ 85254-3636
> > H (602) 953-5779
> > C (480) 550-2358
> > scottjohnson1 at cox.net
> > scott.johnson at ieee.org
> >
> > -----Original Message-----
> > From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On
> Behalf
> > Of Ben Hall
> > Sent: Sunday, November 1, 2020 8:57 AM
> > To: arc5 at mailman.qth.net
> > Subject: Re: [ARC5] Question...
> >
> > Hi Ken,
> >
> > First things first - put the genset on the scope and see if you've got a
> > problem.  There are a lot of people out there who like to scream "all
> > generators are dirty, they are going to screw up your computers" who
> have no
> > idea what they are talking about.  (and generally are in the business of
> > selling filters and whatnot)
> >
> > I've been inside a lot of gensets, fixed more than I can count, and have
> > learned a lot.
> >
> > It's likely that your genset, being 7500 watts, is NOT an inverter genset
> > known for being extremely dirty.  Most generators of that size have a
> > standard generator head where 3,600 RPM of mechanical rotation is
> converted
> > to 120 VAC 60 Hz AC without any trick circuitry.
> >
> > (when you run it, does it run at a stead speed regardless of the load?
> > Or does the speed change as you plug things into it?  The former is not
> > going to be an inverter unless it has some sort of "smart idle"
> > circuitry, and the later is definitely an inverter type)
> >
> > Theoretically, these non-inverter generators should generate a sine wave
> due
> > to the mechanical motion being converted directly into AC without any
> > inverter trickery.
> >
> > However, in practice, theory doesn't match reality.  Your generator is
> > likely single cylinder...and a four-stroke single cylinder at that...so
> for
> > three our of every four strokes, the rotational speed is slowing
> down...and
> > during the power stroke, it's speeding back up.
> >
> > So what you get, is not a pure sine wave...but it's not going to be
> horribly
> > dirty, either.  Those military gensets are likely multi-cylinder,
> powered by
> > a mil-spec engine like a 2A016, 4A032, or whatever multi-cylinder diesels
> > they are using these days...making the RPM much more steady...plus they
> are
> > going to have good output filters on them.
> >
> > I'd put the scope on it (carefully, of course) and see what you've got
> both
> > at no-load and whatever load you can put on it before doing anything...
> >
> > Now to the "screw up your computer" thing...modern computer power
> supplies
> > are multi-voltage, 100 (Japan) to 240 VAC (Europe) input, 50 to
> > 60 Hz input, and the first thing they do with the incoming AC is rectify
> it
> > to DC and filter it...  Very hard to kill these.
> >
> > Thanks much and 73,
> > ben
> >
> >> 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.
> >
> > ______________________________________________________________
> > ARC5 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/arc5
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:ARC5 at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: https://www.qsl.net/donate.html
> >
> > ______________________________________________________________
> > ARC5 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/arc5
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:ARC5 at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: https://www.qsl.net/donate.html
> >
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: https://www.qsl.net/donate.html
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20201101/82aeea76/attachment-0001.html>