Thank you, Richard,
I failed to explain it in the terms neccessary to
cover all of the fine points,...... the engineering
degree not working tonight.
Strange as it may seem the military gensets have self
excitation schemes, so they can be run without the
batteries installed, or a failed control system.
The voltage regulator is complicated and of a high
quality. More than a home owner would need but then
they were running sensitive electronics with these.
The 5 Kw set has three diodes in the rotor and the 10
has 6, just to do the same job better.
Either one will put out single phase of three phase by
turning the big drum switch in the control panel.
The 10 Kw will put out 120/240 at once but the 5 Kw
will only put out 120 OR 240.
Joe
> > > Also, with one of these generators you have to
> watch the load as it
> changes
> > > the engine speed which changes
> > > the output frequency, then you have to adjust
> the governor to match.
> This may
> > > be a problem for radio
> > > equipment or computer stuff.
> >
> > Most equipment, including radio and computer gear,
> does not care much
> about
> > line frequency (50 to 70 HZ is usually OK), but
> can be damaged by wide
> voltage
> > swings. I assume, but do not know, if these
> puppies have voltage
> regulators. Are
> > you sure the voltage regs are working, BTW?
> >
> You do have to be careful about several things.
>
> Expect a shift in frequency, even a good engine
> governor will necessarily
> have some hysterisis and probably a shift in output
> frequency by a few hertz
> from no load to full load.
>
> Domestic generators, even of reasonable size, more
> than likely have a simple
> self-excitation method, this produces acceptable
> voltage stabilisation
> although not what you'd expect from a commercial
> supply, worse, the output
> is usually a quite poor sine wave that becomes worse
> with load and any
> reactance like transformers or power factor
> corrected items. (fluorescent
> lights).
>
> Things with switch mode power supplies, like
> computers, don't worry as they
> will take anything AC from typically 90V - 300V and
> 40Hz - 600Hz. Things
> designed for true sine-wave mains input will
> possibly not work, or have
> severely reduced output, including battery chargers.
>
> I expect all of us with AC voltmeters have mean
> reading devices since the
> true RMS meters are delicate things for lab use
> only, only on a pure sine
> wave does mean = RMS so you can fully expect your
> meter to lie measuring a
> typical generator.
>
> The lower end generators are made this way for cost
> and low maintenance as
> this novel self-excitation method doesn't need slip
> rings and a stable DC
> supply for excitation, slightly flickering lights
> are a symptom of this
> method but they're fine for resistive loads and
> commutated power tools as
> intended.
>
> The mil generators may well have proper excitation
> methods and are
> continuously rated at full loads, the necessary
> maintenance to slip rings is
> not a factor to the mil and nor is high
> manufacturing costs to good
> standards. The Onans we see here are very large
> devices for just 6kW but
> will likely run for ever, both Onan and Powerlite
> have a UK agent who is
> immensely helpful to the private owner.
>
> Apart from the larger, high-end domestic generators,
> the only smaller
> devices with controlled and pure sine wave outputs
> are the smaller Honda's
> (something with i in its title) with electronic AC
> generation using UPS
> technology where the engine/generator just supplies
> rough "watts" to the
> electronics package, there is not only no governing
> per se but the engine is
> actually revved up with a stepper motor controlled
> throttle above about 1/3
> power to make more "watts" as demanded by the
> electronics. These are very
> quiet and very frugal at lower powers as the engine
> is just running at a
> fast idle. They will stagger though with sudden
> huge loads since there has
> to be a short delay whilst the engine revs to meet
> the demand, auto-switched
> AC motors are a perennial problem.
>
> Richard
> Southampton - England
>
>
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This archive was generated by hypermail 2b29 : Fri Dec 07 2001 - 00:36:30 PST