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KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 08:27am 11 Feb 2009
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I see an enormous lot of effort, both muscle and brain, has been expended on the subject of capacitors and the advantages to be had from using them.
Ummm, you will see I have not been paying attention when I ask is there a concise post that sums the subject up?
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 06:28pm 11 Feb 2009
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Well, at least, is there any agreement on how they work to get the benefits?
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 11:02pm 11 Feb 2009
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Hi kiwijohn,
how capacitors work is very complex. There are a lot of factors that interact. The rotor rpm [output AC frequency] and the influences on loading impedance do it for me. Capacitor Voltage doubler,[tripler,quadrupler] etc, arrangement gives a lower cutin so a lower winding resistance can be used, without mechanical winding switching or DC-DC conversions. This is not MPPT, but the loading can be closely matched to the wind energy curve over a wide range of wind energy. Capacitor sizing is determined by the impedance required to give the correct windmill loading across a particular rpm range.
Capacitor sizes have been provided that work in particular systems, but I cannot provide any sizing equations.
Gordon.
PS edit: I will have to go through the process of determining the windmill loading curve for my new AxFx alternator, so this can benefit with capacitors as well with a lower cutin, to make use of the very low winding resistance I am hoping to use.Edited by GWatPE 2009-02-13become more energy aware
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 12:01am 12 Feb 2009
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Gordon, my theory ( ) is that the capacitor circuits as being used create frequency sensitive voltage multiplication, as the RPM and hence frequency increases the voltage multiplication effect reduces so I propose that as a minimum we can at least say the larger the capacitor the higher RPM the voltage multiplacation will be effective.
Now if voltage multiplication is really the effect we are using then we dont need bi-polar caps? (The online circuits for voltage doublers etc show polarised caps.)
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 08:28am 12 Feb 2009
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Hi kiwijohn,
A charge pump voltage multiplier is much different to a full wave AC to DC voltage multiplier.
In my testing of the voltage doubling cct, this only produces double the normal mill rectified AC voltage, up until battery loading cutin voltage.
[quote=kiwijohn]I propose that as a minimum we can at least say the larger the capacitor the higher RPM the voltage multiplacation will be effective.[/quote]
I would not look at things this way.
I use the Zc to set the loading of the alternator just enough at a particular rpm[Hz] and wind energy level. This is not an exact science, as blades TSR changes as well with loading. I record how my mill performs without, and then check performance with caps in similar wind conditions. The production of battery amps at lower windspeeds and the lower cutin give good indications of performance.
If the caps are too large, then the windmill will be overloaded and performance will probably be lower than without caps. {There is also a danger the caps will be required to perform beyond their ability}. If the caps are too small, then performance will only be marginally better than without caps.
I hope this helps your understanding.
Gordon.become more energy aware
woodchips Newbie Joined: 05/01/2009 Location: United KingdomPosts: 27
Posted: 05:47pm 12 Feb 2009
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Hello all.
I have been working on a summary of capacitors as used with the alternators.
Minor snag is that I have just had an operation on my hand and typing is very slow and error prone at the moment, also can't do any practical work.
Bob
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 08:01pm 13 Feb 2009
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Hi
I am at complete loss to savy charge pump multiplier. I understand What must be refered to as Ac to DC mutiliers and switched technics to charge caps then series them and hence obtain doubling etc. Gordons circuit tho has AC charging and discharging. Can any one explain or point me to a referance that explains this different approach.
To my simple Ac approach I see Two parallel ccts one with series caps feeding the batteries via rectifiers, second a parallel cct with the other caps being charged via diodes then discharged via another set of diodes on the alternative half cycles ie same as being connrcted in parallel with the windings. (this ofcourse will give a increased output due to the leading current in the windings but not due to doubling action )
Herb
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 12:04am 14 Feb 2009
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Hi herb,
charge pump multipliers are normally used to make high voltage at low current. These are normally a chopped DC source coupled to a multiple capacitor-diode ccts. Do a Google search on charge pumps. I have made numerous, jacobs ladder power supply, ozone maker for an aquarium filter. These I made with basically high voltage diodes and greencaps. Not a big deal, but useful for demonstrations.
Regarding how this doubler works:
Gill has attempted to explain on another thread. Not sure if successful. The arrangement would be described somewhere, but I just cap couple the normal inputs to the rectifier bridges. The cap coupling allows only AC to pass, the rectifiers give the necessary DC separation, and hence the same single AC unloaded source voltage can be multiplied. The minute loading is applied, then the impedance of the capacitors [Zc], at the AC frequency, and the driving voltage differential will determine the current available. This in not really voltage gain from Inductive/Capacitive resonance.
[quote=herbnz](this ofcourse will give a increased output due to the leading current in the windings but not due to doubling action ) [/quote]
this discussion is difficult enough. Increased output, I assume you mean power. The voltage doubler is not actually a power doubler. The alternator windings play no real part in the voltage doubling, apart from being an AC voltage source. This is purely a convenient way of achieving a lower cutin voltage from the same winding and battery load. With a windmill, the frequency [rpm] normally should increases proportional to windspeed. The changing impedance of a capacitor with this changing frequency and AC voltage gives a non linear power transfer to a battery loading. It is important to have normal windmill AC battery rectifiers in place to limit the AC voltage, as at upper rpm, as harmonic resonance between the alternator winding and the capacitors will occur, with severe loading. This voltage doubler is a parallel arrangement to the normal rectifiers.
I will explain more:
As the windmill AC output voltage increases towards the point when the normal battery rectifiers can conduct, the voltage doubler arrangement has changed function to only provide a gain of 1. The capacitor doubler had started out at cutin with a gain of 2, and by the time the AC had risen to normal rectifier conduction, the effective gain has reduced to 1. The capacitor sizing and effective impedance [Zc], is selected to allow the alternator loading to best match the wind energy curve.
The larger the capacitor, the more loading the voltage doubler provides. With infinitely large capacitors, this would be the same effect as an alternator rewire with twice the turns at half the wire section. With zero caps, this is obvious, the same as just normal rectifiers. It is possible to select a cap size that allows thw windmill to provide additional current to the battery load when normally less power would be harvested from the wind energy.
Additional testing on my setup is on hold for the moment. I am reluctant to change my setup until my new AxFx alternator is flying.
Gordon.
Edited by GWatPE 2009-02-15become more energy aware
RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60
Posted: 07:51am 15 Feb 2009
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Hi Guys and gals (mebbe): Whats an AXFX alternator? ....River Heads - Australia
The wind blows wherever it wishes; you hear the sound it makes, but you do not know where it comes from or where it is going.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 01:04pm 15 Feb 2009
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AX= axial
FX= flux
I think Klaus
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 02:36pm 15 Feb 2009
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I do believe Tinker, you have hit the nail on the head.
Gordon.Edited by GWatPE 2009-02-17become more energy aware
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 06:24pm 15 Feb 2009
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Gordon I have Googled the net all the charge pump ccts traditionally use series stages and differ from yours in using series feeds with the problem of increased XC at higher stages. To me your parallel feed is unique, as you say you have tested & it works. I believe it would be worth slapping a patent on it
Herb
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 11:07pm 15 Feb 2009
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Hi herb,
The cct I presented may be novel, but like many other ideas I have had, but not exploited, others have patented at a later date. I had decided not to sit on this idea, but to just publish it. I doubt that a patent can be granted now anyway. I have reached a point where I am doing what I feel is right, rather than for any future potential personal economic benefit. I still think this must have been done before. There is not much novel in electrical fields these days.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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) is that the capacitor circuits as being used create frequency sensitive voltage multiplication, as the RPM and hence frequency increases the voltage multiplication effect reduces so I propose that as a minimum we can at least say the larger the capacitor the higher RPM the voltage multiplacation will be effective.
