Voltage doubler questions

[stag]

A friend is just is just completing his first small mill. We are concerned that it may not make 12 volts judging by hand cranking tests. If this proves to be the case, would a voltage doubler solve the problem,say,bringing it up to 20v open, maybe?? This also got me thinking about my own mill which charges a 12v battery nicely between 12 & 15v. I have a 40yd cable run, so I was wondering if a voltage doubler would enable me to change to 24 volts and thereby reduce cable loss?? Pete.

[DamonHD]

I have successfully used a voltage doubler, but for a *tiny* mill (~1W)!

Getting caps beg enough for any significant power may be tricky/expensive.

http://www.earth.org.uk/wind-power-pilot-autumn-2007.html

Rgds

Damon

[Flux]

I agree with Damon that you will need monster capacitors to make a voltage doubler handle significant power at the low frequencies envolved. Making it 3 phase adds even more of a challenge.

Where the Australian folks have done it with the F & P motor they have used it to boost the low end and let the thing run normally in higher wind, that way the boost circuit only handles the small power near cut in. I have done the same thing with a small boost converter.

If you are a bit fast on cut in  you may be able to do this as long as the thing runs well in higher winds. I think it a bit unrealistic to try to use a capacitor doubler to run a 12v machine at 24v where you are expecting it to handle the high wind power.

So much depends on how much too fast the cut in is and also the frequency of the alternator, the F & P does have a lot of poles and works at a more realistic frequency than the normal axial machines. Far better to wind a stator with the correct number of turns if the machine is expected to produce more than a few Watts.

Flux

[tecker]

Rectifying with a doubler is worth a try . Here's a circuit  with the classic delta or wye rectifier pairs  They will punch down  if you bring out all wire from the head .
 Doublers will probably throw a c luge in the delta Wye connection output
 

[OperaHouse]

Maybe you want to look at that picture again..........

[OperaHouse]

"This circuit can produce interesting voltages across capacitor C2. "

So says the web page you pulled this from.   Interesting indeed!

[stag]

Thanks for all of the above guys. I did not realise that the concept had problems at higher voltages. The examples I had seen on line were for low power devices like small, single phase, bicycle.generators. Further tests of my friends mill look a bit more promising and it will soon be up and flying, so we will wait and see what happens. I will stick with 12v on mine. It was just an afterthought which I thought might be worth exploring. Pete.

[tecker]

 The caps act on the stator simular to rectifier block and release the voltage charge .

[tecker]

The voltage is not really going to double on a battery charge circuit but it will probably pulse until you reach cutin .

[OperaHouse]

So, no one can find the error in that circuit?

[Larsmartinxt]

So, no one can find the error in that circuit?

Well yes. And it does not make sense since nothing is charging C2.

[boB]

That is a portion of the  Walton-Cockcroft  voltage multiplier.  It requires
AC to work.  Not really good for high current applications but small to
medium is useful.  I've used it lots of times in the past...

http://en.wikipedia.org/wiki/Cockcroft%E2%80%93Walton_generator

[Larsmartinxt]

Well ok. But the schamatic indicates a dc current

[tecker]

It's pretty vague here's a couple of links that will push forward the concept of rectifying with a voltage doubler .
this is the one I posted .here the double charge is a the combination charge of combining both half cycles this is a little weird and is part of a classroom activity .
http://www.facstaff.bucknell.edu/mastascu/elessonsHTML/UsefulCircuits/VoltageDoubler.htm
 here's one that shows the combination of the serial Caps and has a good explanation
http://www.youtube.com/watch?v=byCtTlUlHXo

 The beauty of this  method is that The bank is isolated from the stator and the charger is self regulating .   As the bank increases in resistance the caps don't discharge .So if the state of charge in up ( as in a saturated electrolyte )the caps average slightly over the bank voltage .

[OperaHouse]

Look again at that link you posted
http://www.facstaff.bucknell.edu/mastascu/elessonsHTML/UsefulCircuits/VoltageDoubler.htm
C2 polarity is backwards.  That intreagued me a couple days ago so I did a google search and found it on my fifth click.  Surprised it was an edu source.  No wonder Johny can't read......schematics.

[tecker]

I'll checkit out

[boB]

The diodes would discharge the top capacitor to 2 diode drops as it is drawn.

That schematic is not right.

boB

[tecker]

Ok nix the class room drawing for now and use doubler both
6 wire . and wye  both work. The 6 wire is self regulating .
And with the star node out and down connected to the serial connection between caps holds the star around battery voltage