[ARC5] Question...
Bill Cromwell
wrcromwell at gmail.com
Sun Nov 1 15:30:46 EST 2020
I was able to convert a sinful PC power supply so maybe it is not too
difficult to clean up a messy 'genset'. If the cost difference is
worthwhile. In the case of the PC power supply I had all the parts in my
junk box so it was worthwhile. That power supply still lives in the PC -
now retired.
73,
Bill KU8H
bark less - wag more
On 11/1/20 3:17 PM, Dennis Monticelli wrote:
> 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
> <mailto: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 <mailto:scottjohnson1 at cox.net>
> > scott.johnson at ieee.org <mailto:scott.johnson at ieee.org>
> >
> > -----Original Message-----
> > From: arc5-bounces at mailman.qth.net
> <mailto:arc5-bounces at mailman.qth.net> <arc5-bounces at mailman.qth.net
> <mailto: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 <mailto: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.
> >
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