# Re: Voltage Multiplier Question

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Good choice.  It might be useful to see how such a motor is controlled
and used in the washing machinery.  See:
<http://www.freescale.com/files/microcontrollers/doc/app_note/AN3476.pdf>

Yep.  Power out is proportional to the cube of the wind speed (and the
square of the turbine diameter).  Are these measured or theoretical?
If measured, methinks 5kw is a bit high for a washing machine motor.

Watts = 14.3 PAV^3
where:
P = air density (2.3 x 10-3)
A = area swept by turbine blades (sq mtrs)
V = wind velocity (km/hr)

What did you use for a turbine blade (propeller)?  Getting reasonable
efficiency over a wide range of wind speeds usually requires a
variable pitch propeller.

What voltage battery pile are you using?  I'll assume you have
installed 6 diodes to form a 3 phase, full wave rectifier instead of 3
diodes to form a half wave.
The 6 diodes will produce about 30% LESS voltage than the 3 diode
array, but deliver twice the power.  In this case, power is what you
want, so live with the lower voltage.

Once you have some semblance of DC coming from the diodes, your
problem is basically a DC to DC converter.  There are numerous
complicated charge controllers available on the alternative energy
market that will do that.  The problem is that you will need to size
your controller for the expected output.  One of the reasons small
wind generators favor permanent magnet generators is that they work
well at low wind speeds.  Washing machine motors work well over a wide
range of rpm's (a good thing) but crap out at both low and high
output.  There's no ideal motor, that works over the entire range of
expected RPM's and loads, although complicated hybrid designs seem to
be improving.  (I haven't kept up to date).

6km/hr (about 3.7mph) is lower than even the smallest commercial wind
generator suggest as useful.  Most small DC PM generators start
producing power at about 5 mph.  I don't know where your 3 phase
washing machine motor starts, but I suspect 6 km/hr is too low.

Those are half wave voltage multipliers.  You need to use both halves
of the cycle.  If you insist, see full wave voltage multipliers as in:
<http://www.tpub.com/neets/book7/27m.htm
I'm not sure how to drive this with a 3 phase Y.

The problem with both of these is sizing the cazapitors.  At higher
power loads, the current through the caps is going to be rather high.
Each will need to store half the output power of the generator and
deliver it to the load at every half cycle.  It's possible, but
methinks this creates more problems than benefits.

At low RPM's, you're also driving the voltage multiplier at a fairly
low frequency.  That depends on your propeller and gearing, but it
could easily be a few Hz.  The required capacitance is going to be
rather large for that to work.

However, that doesn't stop anyone from using the idea:
<http://www.reuk.co.uk/Three-Phase-Voltage-Multiplier.htm
Note that this is for a small bicycle hub generator, not a much larger
washing machine motor.

Well, if you wanna use smarts, you could use a hybrid rectifier
design.  Use a full wave voltage doubler at low RPM's to get it to
produce useful voltages at low wind speeds.  When the wind speed gets
above a specific threshold, switch the rectifier configuration to a
more conventional full wave non-voltage doubler design.  Adding smarts
offers lots of other possibilities, such as pitch control on the prop,
smart feathering in high winds, non-violent yaw (direction) control,
turbulence and resonance mitigation, performance monitoring, lifetime
enhancement (mechanical wear detection), and maybe even a bird strike
alarm.

Half wave voltage doubles only use half the cycle and therefore
deliver only half the power.  That's one reason why you see voltage
multipliers mostly in low corrent applications.

Your biggest problems will probably be dealing with tower construction
and too much wind.  It's been perhaps 25 years, but I lost two wind
turbines that way.

The basics:
<http://www.homepower.com/basics/wind/
(Dig through the links in the article).

--
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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