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Forum Index : Windmills : visual effect of capacitors

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fillm

Guru

Joined: 10/02/2007
Location: Australia
Posts: 729
Posted: 02:50am 12 May 2011
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Noel,

The voltage is a bit on the low side , if your wind generator somehow becomes unloaded and the voltage increases above the cap limit then you would start to hear some loud bangs .

You can also find at this uF that it might over load to early and stall the mill , with DC caps around 680uF you can series/paralell to find the best loading for your generator/blade to voltage combination.

The use of the Cap/Dblr is more suited to low resistance windings which give high cutin RPMs , if your generator is making power around 80-100RPM then they are most likley not needed .
PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits
 
Xmaswiz
Regular Member

Joined: 14/04/2011
Location: United States
Posts: 69
Posted: 05:12pm 12 May 2011
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thanks for the feedback. Will go the DC caps route. Right now I am planning on a higher voltage low rpm gen to drive in to a grid tie with built in load dump/switch.
Santa Maria, CA.
Noel
 
Electric519

Newbie

Joined: 29/07/2011
Location: Canada
Posts: 3
Posted: 05:42pm 28 Jul 2011
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Hello Everyone,

I am having trouble following the diagram to make the voltage multiplier.
I have 12 caps and 6 35 amp rectifiers.
The caps are rated at 560 uF. So I take 2 caps and wire them back to back ( negative to negative, to make 1 AC cap) Then do I wire another set back to back and use positive terminals and then wire the two sets in series with one another?

Thanks for the help and great work.
Cam
10 Foot Axial Flux 24 Volt
 
fillm

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Joined: 10/02/2007
Location: Australia
Posts: 729
Posted: 10:23pm 28 Jul 2011
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Cam,

I usually join them neg to neg but it wouldn't matter either way as long as they are all the same, and the uF and Volt are also of same value.
12xDC caps will make one doubler, and they are coupling and dividing each of the AC phases before the rectifiers.
The rectifiers are then connected in series on the DC to double the voltage.
PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits
 
VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 02:14am 29 Jul 2011
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Hi Phil

Just a quick one on the doubler on the LG it is doing over 7 amps into the battery at around 200 HZ

Bob
Foolin Around
 
Electric519

Newbie

Joined: 29/07/2011
Location: Canada
Posts: 3
Posted: 09:55am 29 Jul 2011
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Fillm,

Thanks for the info. Cheers all the way from Canada.
Another question would be is their a need for a diode between the alternator and the caps so the mill dont start up? or can you wire a different set of rectifiers in parallel before caps?

Thanks again
Cam
10 Foot Axial Flux 24 Volt
 
fillm

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Joined: 10/02/2007
Location: Australia
Posts: 729
Posted: 11:05am 30 Jul 2011
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Cam

You dont need the diode the caps won't start the mill , and you need to have your main rectifier in paralell with the cap dblr for the high current/normal cut-in , so then they both work together.

What is the normal cut-in that you mill is running at now?

I think there is a pic on the previous page .
PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits
 
Electric519

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Joined: 29/07/2011
Location: Canada
Posts: 3
Posted: 02:05pm 30 Jul 2011
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Phil,

Thanks for the info.
That makes sense because the caps are non polarised now. So the main rectifier would be in parallel with the DC side of the doubler?

Cut in is around 120 rpm. About 2 revolutions a second. Its the same mill from otherpower, the 10 foot axial flux. Not much wind here in the summer months, more sun.

Cam
10 Foot Axial Flux 24 Volt
 
Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206
Posted: 12:40pm 23 Aug 2011
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Hi all
I have spent a bit of time reading through all this and most of it is way above my head.
Having a Vawt that is running at a lot slower RPM than your average Hawt, I am wondering if running a cap doubler would be any advantage. I have been getting alot of light winds lately where the mill will spin at around 60rpm which is under the cut in speed at 12volt even with a standard 80s stator in star.
I know that there is not much power to be gained at these low rpms, but a little bit is better than nothing.
I have thought about trying a standard 60s in delta to try to get something out of these light winds, but this will very much limit the out put when the wind does start to blow.
I am thinking that by lowering the cut by using a cap doubler it may allow me to run the 80s in delta or even the 100s I have in star which should increase my top end output.
I havnt had any desent wind since i put this mill up so the top end performance of this mill is still unknown.
I can see that there has been a lot testing and work done on 24 v systems that run at higher rpms but not much on slow reving 12v set ups.
If this is worth giving a go at, im wondering what size caps I should start with, im thinking that at low rpms in light winds the mill would stall very easly.

Any coments on this would be much appreciated.

All the best Dean.
 
Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904
Posted: 01:56pm 23 Aug 2011
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Dean, I too have a VAWT that tops out at 60RPM. I have the cap doubler arrangement installed and separately metered but the Amp meter *never* shows charge from that, though my battery bank is at 24V not 12 like yours.
What *does* help is the small DC to DC step up converter that VK4AYQ first mentioned, the Amp meter from that does show battery charging when the RPM's are up.

Problem is the marginal cut in at 24V - its not a F&P alternator - and the what appears too small wings of my modified Lenz II. Fixing both of these should give me wind power charging, just need time to do it.
Klaus
 
Air Bender
Senior Member

Joined: 25/01/2011
Location: Australia
Posts: 206
Posted: 06:47am 25 Aug 2011
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Hi Klaus i will look into the DC - DC step up converter.
One day when i get a bit of time I think I will have a go at building a small axial flux as I think it would be a lot better suited to the mill. When i take the magnet rotor of the F/P it easly spins up to twice the rpms and it becomes a light wind flyer, in the F/P there is a lot of iron core resistance in the stator even with the battery disconected. I think a small axil flux would allow the mill to run up to a lot higher cut in speed espcialy in light winds. But the F/P will have to do for now.

All the best Dean.
 
artv
Newbie

Joined: 02/09/2011
Location: Canada
Posts: 1
Posted: 11:57pm 01 Sep 2011
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Hi All,..

I'm new here ,been reading postes here on the odd occasion( directed here from Fieldlines)...Excellent site.
I got into this stuff awhile back...seems like an endless trail...
I'm currrently testing caps in different arrangements myself...
I've read many pages of this post..
Was wondering if page 15's schematic has been improved yet???
Alot of smart people here( and there)....I appreciate the effort everybody puts forward...
On both sites....Thanks for your time....artv
 
wotavidone
Newbie

Joined: 28/12/2011
Location: Australia
Posts: 4
Posted: 08:11am 02 Jan 2012
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This has been a truly fascinating thread. All 41 pages!!!

A few observations:

1)Gordon is a genius. (And can it be he is a fellow Croweater? Good onya Gordon - keep showing the convicts how us free settlers do it.)
2)How the circuit on page 15 works is a mystery to me.
3)If the circuit works, and actually doubles the voltage, understanding it isn't really necessary.
4)Most people seem to get too cerebral about these things.

I find it easier to consider the concepts like this:

The supply voltage needs to be higher than the battery voltage if you want current to flow into the battery.

At a certain windspeed, the windymill is going round, i.e. a tiny bit of power is being put into the mill from the wind, but it's rotating slow enough that the output voltage is not higher than the battery voltage, and no current flows, so we can't convert the small amount of windpower available to charge in the battery.

Stick a voltage doubler on the end, and now you have a voltage higher than battery voltage, so current flows in.
Only a little bit of current since the generator is going very slowly - i.e. even though you've doubled the volts, you still only have that teeny bit of power that you had before, but now you can store some of it...

Of course, you now have current flowing, so you now have load. The mill slows down. I can't see how the mill would actually stop going round, because at some stage, the reducing rpm's would mean that output voltage drops below that required to cause current to flow into the battery, thus reducing electrical load to nothing.

More likely, in my humble opinion, that the load on the generator, the power input from the wind, the output voltage and current etc would reach a balance.

What Gordon would call matching the load to the generator.

And not an equation in sight. You don't really have to understand reactance, inductance, etc., to use this brilliant idea. Gordon has already done the thinking for us.

It helps knowing that frequency and current dictate the values of the capacitors, but even here, Gordon has suggested values for common sorts of generators.
In anycase, the idea of running the circuit in parallel with the standard rectifiers means that when the generator reaches a decent voltage above battery voltage, current is generally going to bypass the capacitor network. This makes the choice of capacitor values less critical, since they will have to work over a lesser range of frequencies.

It also means your current will be going through less components, resulting in less losses as the generator gets into the higher rev ranges.

I think it all very elegant.
Cheers,
Mick

P.S. I once used back to back electrolytic capacitors to link the windings of a three phase three horsepower motor that I was using as a 240 volt generator. Nothing exploded. :)
 
jean
Newbie

Joined: 09/06/2013
Location: France
Posts: 2
Posted: 09:28pm 09 Jun 2013
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Hi there.
Did everybody die ?
I recently intalled a chinese 12' wind mill.Not very happy with the original controler, I built a PIC controled stepping system using mosfet (boost type). I am now trying Gordons way with back to back caps (page 15) fed up with blowing mosfets... Though its working good on Proteus ISIS. My power station is made of the chinese 48V WM feeding a 500A 48V battery (800 kg !) in turn feeding a 6 KW inverter feeding the house.
Usual problem : not enough wind (I need a storm to fully charge that battery) If anyone is interested, I desing & test with ISIS then do th PCB with ARES and use Microchip PicKit3 to prog a PIC18F45k20 with MPLAB X.
I hope gordon is still with us, I need his light.
 
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