> [Original Message]
> From: Ken James <[EMAIL PROTECTED]>
> To: <[email protected]>
> Date: 2/5/2008 9:24:49 PM
> Subject: Re: [Liveaboard] repair old wind gennys
>
>
>
> Norm of Bandersnatch wrote:
> > I don't know anything about a "dump" load, there was nothing in the
manual
> > about that. The lit says there are protective devices in the generator,
but no details about how they actually function, that protect the unit in
high winds. I imagine they disconnect the load when the unit heats up.
> >
> I really doubt they simply disconnect the load!
> A 'dump' load is what is used to keep the batteries from being
> overcharged, otherwise when they are full you would need to disconnect
> them from the generator, thereby 'unloading' it. It is a design problem
> with perm mag alternators such as these wind gennys use that since the
> magnets are always rotating when the blades are spinning, making flux
> lines pass through coils, there is no good way to 'shut off' such a
> device electrically (as with electro magnets in a car alternators field
> windings that can be shut down or reduced to effectively lower output
> current through a given load and also voltage as a function of that),
> because if the PM alternator is simply electrically disconnected from
> the load, then there is no current flow through the coil windings and
> the output load, and so no back EMF is produced (Electro Motive Force,
> the magnetic force that causes a voltage to flow in an inductor or coil
> when exposed to a changing magnetic field flux) in the coil windings to
> counter the voltage across the output, which will then rise to very
> great levels possibly blowing rectifier diodes and maybe even 'punching
> through' the coil windings.
>
There is no mention of a dump load in the printed matter that comes with
the KISS wind generator. There is no provision in the supplied equipment
to use a dump load.
If, as they claim, there are protective devices in the generator, I imagine
they either open the load or short the output. Since shorting the output
would increase the heating of the coils I doubt that's what they do. I can
only imagine they open the output to stop overheating the coils. If this
is the case, as it appears to be, then the increased no-load voltage does
not damage the units since they are still working after a 82 mph squall.
Ditto the overspeeding of the blades. And since the output is open, the
(external) diodes are not exposed to high voltages, at least when the
switches open. When the coils cool off and the switches close when the
unit is still overspeeding I imagine high voltage is then applied to the
diodes, however, from practical experience this has no effect on them since
my two units are still working properly after ten years of full-time
operation including occasional high winds.
> Also, since no electrical load means no back EMF there is no counter
> torque. This is bad because without that to keep it from going too
> fast it will run away like a truck going down a mountain with no brakes.
> If you are not using a 'dump' load than it means you have enough
> batteries/load connected so that you have not needed it, otherwise you
> would have severely overcharged them by now. Not a problem for you,
> perhaps, but with my boats 330AH capacity, it would be a big problem.
>
KISS dismisses the use of regulators with their wind generators by saying
that occasional overcharging of the battery bank is a good thing
(equalizing charge) so no regulator is needed in most cases (with a large
enough battery bank).
Of course, I don't see why a shunt type regulator could not be added if
desired.
> My Air Marine can take the batteries from 50% to fully charged in just
> an afternoons worth of summer thunder squalls in a good location. After
> that, if it was not regulated, the bank would be in trouble. I don't use
> more than 15 AH most days, and I can get that in 1/2 hour with my wind
> genny!
>
We use at least 200 AH/day when on the boat, sometimes more depending on TV
and/or computer time.
> BTW, there is another type of solar panel regulator just in the market
> now, it doesn't just regulate or limit max power to the batteries from
> solar panels, it also boosts the solar panels voltage when needed via a
> switch mode controller and keeps the voltage high enough to keep
> charging in low angle sun, when the output of the panels by itself would
> not be high enough to charge effectively. It can add as much as 20% in
> total AH per day, but it is not yet cost effective for most applications
> as it is still cheaper to just add 20% more solar panels.
>
Maximum Power Point Tracker PV panel regulators have been around for a
while, I have one. They work best in cold climates. They work by
adjusting the load on the panels so as to produce the most power into the
batteries, much like a controllable pitch airplane propeller does to allow
the engine to run at peak performance rpm while varying the power produced.
> In any case, the KISS may now have an internal 'dump' load similar to
> the way a motorcycle PM alt. regulator works by shorting out the load to
> ground through the regulator casing when the battery is fully charged.
> This would of course also act to limit blade speed.
>
They very well may. My units are ca. 2001 and there may be improvements.
I hope so, they could easily be greatly improved.
> But since this type of design makes the genny run as hard as it can when
> wind speed is above a certain level, the output either all going to
> power in the house bank or some in another load, it can make the magnets
> overheat. When that happens all control is lost and unless it is
> 'furled' it may run-away. However it would take more than a short lived
> event for that to happen.-Ken
> >
>
Yes, I agree, that's why I think the "protective devices" open the output.
Of course they may have another technique so as to apply a small load to
both lower the load but still have a load enough to keep the voltage from
rising too high.
Norm
S/V Bandersnatch
Lying Julington Creek FL
30 07.72N 081 38.4W
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