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MadRat Newbie Joined: 30/09/2008 Location: United StatesPosts: 21
Posted: 02:18am 30 Sep 2008
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Let's see, capacitors at 150,000 uF are available. Each one is about 50mm dia. x 100mm height. At 4,000,000 uF you'd only need 27 of them. At $65 a pop, that should set you back a little...
edit: Well, found some 1,200,000 uF capacitors that are 75mm dia. x 215mm height for $135 apiece. That's a little cheaper although they won't discharge as quickly as 27 of the smaller ones.Edited by MadRat 2008-10-01Go Huskers!
SparWeb Senior Member Joined: 17/04/2008 Location: CanadaPosts: 196
Posted: 06:01am 30 Sep 2008
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[quote]What happens to the AC voltage across the capacitor at resonance? [/quote]
Well, it gets kinda high, in fact. Multiply the impedance and current through any specific capacitor for the voltage drop across it. Since the impedance of the capacitor increases, but the current goes down, it's anybody's guess whether the voltage goes up, down, or stays the same once resonant frequency has been exceeded.
Steven T. Fahey
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 07:51am 30 Sep 2008
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Gordon,
To put some perspective on cap voltage at resonance.
reference circuit.
values at Fq.
text excerpt.
was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 09:09am 30 Sep 2008
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How to stick your neck out (and get it chopped off)....
Thanks for that Gill. It appears that there is no series gain to be had from the capacitor network in series configuration from the free energy folks,... so no surprise there.
It seems to me that this is what is occurring here with the F@P.
The F@P is a miserable alternator from the perspectives of power out versus power in, including getting the power you need at the rpm you need with a blade optimised to do it...... and if you folks were paying for the fuel to run these things, they would not have seen the light of day.
They have iron in the core, and large inductive reactance, high magnet count, which magnifies the problem because of high frequency, cogging, and less than steller harmonic generation (tooth rip etc) when coupled to the rectifier... further complicated by the high inductive impedance.
It is interesting that with the series capacitor, the high inductive quality of the F@P... in other words, all the evil things about the F@P , get minimised.
I'm sorry, but no amount of electronic trickery will solve over half of the F@P's MPPT problems... because at least over half the losses can't be solved that way with this machine.
Series resonance gives zero impedance to the cap and inductor, so all the reactive inductance gets reduced to nil, (cant do that with MPPT) and the capacitive reactance is shorted too. the harmonic distortion gets minimised by the tuned circuit, so diode can spend more time on in phase (yep you have cleaned up the power factor on the way through too) primary frequency, so system losses are less.
Suddenly, the only losses left are the resistive losses in the stator. All the inductive losses are negated, reactance limiting is pushed out of operating frequency, and basically the F@P becomes a darn good and well priced generator of power. Once the inductive reactances are nullified, then the usual problem of resistive losses are yet to be overcome...In the case of the 100 stator (standard), in delta that is only .4R, making this a very very cost effective unit... by any standard, and can only be made better by the good ole MPPT (that just doesn't exist yet), but the caps do the hardest and most rewarding (from an energy perspective) part of the job.
You do get something from the higher resistance stators as well, (sort of a B grade prize) ......a broader Q, with more rpm covered by improvement of some sort. We can lower the Q with the resistance, and it also has the inductive alternator looking into a PF positive environment before resonance, but an inductive environment above resonance.
I don't think this series arrangement will be useful at all in an axial flux, not because of the capacitance value, but because there is virtually no inductive reactance... for mine it works out to .001 ohms... if I used 4000000uf of caps (X3), I would have capacitive reactance at 30hz of only .0013 ohms, to get rid of only .001 ohms... can't see the use in this at all. It will effect the resistance of the mills current .4R by next to zero.
So it would appear that Dennis has stumbled upon the only thing that will turn the F@P into a good genny... caps. With the right caps, it should give an axial a run for it's money, even though it is ferrite full and neo challenged, and has iron drag as well,the the good old iron makes up for most of that.
Non-believers may turn away and put up with poor efficiency, but the rest will use a cap bank and double their output on those stators with high inductance (standard will notice the best improvement... by a wide margin, as it has the highest inductance before rewire). Induction conversions will benefit as well... but not duel axial flux machines.
Each conversion will have differing inductance and reactive component, and so different cap values.
Those rewinds with less coils in each series string will notice less of an improvement, as the impedance and so reactive component has already been lessoned.
Well thats my view of whats going on so far.. Feel free to shoot it down.
So that's it, I've stuck me neck out
............oztules
Ps Gordon, I calculate your axial flux machine has an impedance of only 1.77uH..... you won't be resonating that any time soon, and will get no improvement if you do.
Axials will only benefit if you need a soft start for resistive driving without stalling the blades (me... about 10000uf) eg hot water heating etc, without those pesky relays.Edited by oztules 2008-10-01Village idiot...or... just another hack out of his depth
Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1215
Posted: 11:14am 30 Sep 2008
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Well Oz that post above proves the credit good ol' Dennis has done and yes it was silly ol' me who went against Dennis's advice in parrallel caps and went serial caps as I'm a lazy bugger. Now you blokes have sorted all the maths out just to proves the fact.
Man the Aussie Way is just do it and see how it works Now since I started the serial flavour on these caps maybe when Dinges does this I can get some royalties off him Mind you anything less than aussie greenback wont be accepted.
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 12:14pm 30 Sep 2008
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Bryan,
You'll be a 2 centair overnight, although you may have to split it with Dennis... I think he blew up some caps testing out the series stuff too.... he may want material costs for those caps from Jaycar.
I may not have it completely correct, but I think it is close. Further testing from you F@P'ers, will prove me wrong or right I guess.
It is worth a try to use some modest size caps in parallel as well. Gordon may shed some light on what happens in this instance.
Don't run the tests without a battery load, as the voltages generated near resonance with series caps will probably exceed the cap voltage rating and smoke em up a bit... or a lot.
.............oztules
Edited by oztules 2008-10-01Village idiot...or... just another hack out of his depth
Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669
Posted: 12:18pm 30 Sep 2008
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miserable..... MISERABLE !!!
I'm thinking more of an elusive alluring temptress where patients and understanding slowly seduces and secrets finally reveal. And in the new found harmony of the union.. You pounce sink your fangs in and suck it's life blood out before the wind dies.
As for well I just happen to have a new supa-dupa design in mind that gloves with these caps so we're not at the ultimate yet just a lot bloody closer.
Bruce,
With your test unit and all those red F&P's you have there, Is it possible to do some simple runs using an 80series to sus out an approx cap value? was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ
MadRat Newbie Joined: 30/09/2008 Location: United StatesPosts: 21
Posted: 12:46pm 30 Sep 2008
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Is the high number of low-turn count coils in the F&P the reason the capacitors help?
Where I live the wind is pretty well non-existent for the summer months but from mid-August to late-May there is wind to capture. If there is a way to use a high blade count then it would make the lower average wind speeds around here all that more useful. Could the use of high coil counts and blade counts coupled to capacitors be an avenue towards that goal?Go Huskers!
SparWeb Senior Member Joined: 17/04/2008 Location: CanadaPosts: 196
Posted: 04:53pm 30 Sep 2008
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[quote]So that's it, I've stuck me neck out ...[/quote]
Don't worry, I did that a few posts ago and nobody swung the axe on me either.
There are bound to be many members seeing this thread who are a bit bewildered by the terminology. It's really not obviouse what's going on without taking some time to read up on AC circuits. Most people aren't keen on "going back to school", so either they figure it out with some other mnemonic, or they give up.
It's a hobby, after all, and not many of us keep electrical engineering textbooks at home...
...well, I do. But my wife calls me a geek. To my face.
Once more of us get a handle on what works and what doesn't, and the info gets around to people who are good at 'splainin' stuff like this, more builders will be able to try it, too.
If you get a mental picture of what power factor is: the sine wave of current leading or lagging the voltage sine wave, then you can picture things that move them farther out of phase with each other, or closer into phase with each other. Here we have a motor, that we're using as a generator, and one of the features that is necessary as a motor, makes it a problem as a generator. The inductance in the induction motors basically gets in the way. It moves the current sinewave out of sync with the voltage sinewave. We're working on a way to reduce the effect of the inductance, and the tool we have to do it is the capacitor.
The inductor also creates a "resistance" to the current, but once people start insisting on using the correct terminilogy, which is "impedance", then more folks tune out because that's RF-speak.
From there on, it's an engineering problem. I'm an engineer myself, so I don't run away when that happens, but I don't know a lot of people whose eyes don't glaze over once I get going....
I almost stopped listening, too, but sat down, did the math one evening, and realized that this isn't rocket science.
My rooting around in the garage has turned up some 270uF non-polarized caps, 24,000uF caps (only 2, though!), and a handful of 2200uF polarized caps, which are only rated for 50V. I'm not quite there yet: I need non-polarized 4-5000uF per phase and it would be nice to have 65V or higher.
I'm going to rig things up on a relay so I can throw the power into the caps briefly, monitor for any signs of improvement or speed correction, then switch back before they blow up.
Steven T. Fahey
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 07:07pm 30 Sep 2008
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Hi All
For those people out there having problems following this thread,I would like to say that as a person who has trained in electrical engineering (power) and worked in the field for 40 + years. I find the discusions beyond me.
These little generaters in actual practice behave very much like their big brothers. The point being forgottern here is when generating the inductance of the coils is not a factor it cannot produce flux only magnetising force the rotor flux must predominate. The result of this is a generater delivers a current and voltage that has a phase relationship as demanded by the load. The lead and lag is adjusted in the generater by the rotor advancing or laging back as required. On my test rig I am experimenting with Caps and this movement is easily observed with a timming strobe. The reason the voltage increases with Caps is the rotor is advanced to give the rotor mmf ability to produce more flux in the stator. The reasons for this are various but include the crowding of the flux (what flux on otherpower calls armature reaction )reactance or inductance of the stator coils is not a reason.
I not that the theory site that Sparweb pointed to while being a good source neglects to mention Ac generaters sycronise condensers is as close as it gets what is needed here is a good simple text on the basic theory I cannot promise as I dont have the time but will try to put together a sequence of what goes on in a generater its fasinating the balencing act as load is applied be it resistive or other wise.
Herb
ps Most of my old textbooks have over the years disappeared but I have found one that goes into AC machines a little mathmatically for those not trained in theory but covers the facts. Electrical Machines for technicians and technical engineers by Stefan F. Jurek
Another thing the use of Capacitors for those that dont want to understand can be thought of as a means of increasing the rotor flux no gain in power is achieved but the unit will generate a higher voltage at a lower rpm my tests show a slight drop in efficiency but if you can make say a windmill generate at lower rpm why not.
One scary thing tho is the situation that can happen when it stops generating the true inductance of the stator coils reappears and series resonance can occur particaly in parallel connections can and has on my testing caused drive breakages or component breakdown.
Edited by herbnz 2008-10-02
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 09:04pm 30 Sep 2008
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Herb,
Flux seems to think that "At best capacitors in parallel will only give a modest improvement, permanent magnets behave as air gaps and the effect of armature reaction is not great."..., which is why I have mentioned to Gordon that he may get a little more improvement if he added some small caps in parallel as well...., but if we lower XI, then they may be only useful away from resonance to clean up the PF.
He also seems to be of the opinion that "those alternators become reactance limited and no matter how fast you run them the current will eventually become constant. The thing starts to curve over when R becomes equal to Xl. as Xl dominates the reactance rises with frequency and it goes into constant current mode like a bike dynamo."
This seems to correlate well with Gordons testing, so I think Inductive reactance is the main thing to overcome. The armature reaction will fall as the XI falls anyway, but the limiting thing appears to be the XI as F increases.
.........oztulesEdited by oztules 2008-10-02Village idiot...or... just another hack out of his depth
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 09:20pm 30 Sep 2008
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Oztules
I respect Flux's Views.
But as he says he does not have these units to trial .
This Xl is not the inductance of the stator coils they cannot produce flux or else no generation.
the current limiting occurs in FP when the stator mmf approachs the rotor mmf.
All the testing I see on here fails to show me any thing mainly cause no input power is mentioned all test rigs need to measure input torque.
Herb
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 12:36am 01 Oct 2008
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Hi herb,
I am in the process of setting up a 1.5kW 3phase motor on a drill press with 3:1 mechanical reduction. I intend controlling the rotor rpm from 0-500 with a VFD[VSD].
I do intend testing a limited range of cap sizes and a rewired 7phase unit. I see the limitation of std configs being the hum produced. I am happy with the power levels produced and twisting poles has reduced startup cog, without noticable output power reduction. A programmable boost cct I employ brings the output power closer to the wind energy curve at the lower power levels, and reduces cutin speed.
I have some rewiring of an 80series stator and I await delivery of a new rotor. I hope to start some testing next week.
Gordon.
become more energy aware
oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686
Posted: 12:41am 01 Oct 2008
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Herb,
MMF is ampere turns..... but if you have iron in the coils this will effectively increase the useful gap flux available, so cant be used in this instance to calculate the apparent Fm in the gap....grrrr.
The permeability of the magnets is low, and this effectively increases the thickness of the air-gap. This will lower the effects of the back MMF compared to traditional machines... (magnets appear as air gaps, and the field distortion is lowered.)
However, if you have found the inter-reaction through actual testing... then this must take precedence.
One thing is certain, if we can decrease the effective resistance of the coil (R + XI), to the AC EMF, then we do better... Watts out =EI. We get more power with less loss in the coils. This effectively lowers the back MMF for the same power. (reduces the generator impedance).
It is beginning to look as if we can current limit by MMF=back MMF or XI=R or a combination of both... egad.
I would welcome more input from you regarding your testing results and explanations of them...... more real results are only going to further the depth of understanding on this.... it seems damn complicated to me.
............oztulesEdited by oztules 2008-10-02Village idiot...or... just another hack out of his depth
KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691
Posted: 01:33am 01 Oct 2008
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I dont have a big enough drill press or other rig that I can test and experiment with but I do have a F&P stator which I reduced to about 1/3 size for a pedal generator. I could reduce it even more, down to maybe only three coils! Would this give me a true representation of a full stator? (With greatly reduced turning effort and voltages of course)
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 02:59am 01 Oct 2008
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Oztules
I have initially given test results and shown the setup I used in the Lathe.
re mmf yes usually measured in ampere turns for the simple reason more than often produced by amps in a coil. so magnets also produce AT .
mmf is like emf in a electric cct, flux is like current, permability is conductance, reluctance is resistance. Magnetic ccts are like electric ccts. we have mmf and a cct then flux will flow, the value of flux depends on the permability.
in the case of a generator the rotor mmf causes flux flow into the stator inducing an emf this emf will cause a current in the coil if connected to a cct this current will produce another mmf that will try to create a flux flow but cannot as by Lenz's law is created in such a direction to be opposed by the rotor emf.hence no flux can flow from the stator mmf hence my comments that there can be no self inductance at this point.The fact of air gaps steel or no steel does not affect this basic fact. These things affect the permability that only affect the value of the flux at this stage produced by the greater mmf from the rotor. If the stator mmf = the rotor mmf no flux no generation.
Yes the subject is complex I have simplfied here back to basics. In our case there is leakage flux, armature reaction, even the flux produced by the other phases create a phase shift.
I note most textbooks avoid the subject.
The thing you can watch is the rotor moving back in forward in relation to the pole as loads are changed its this way that a generator adjusts itself. Capacitors make it advance itself giving a stronger flux at a critical time.
In big units attached to the grid we increase the excitation to make a unit take up more reactive power.
here basicly we cannot increase the excitation but the clever little buggers do it any way.
Gordon
When you mount the FP allow the stator to swing and stop the tendancy to turn with a spring balence this value is the torque input power can now be calculated. Reselts like i have seen on here mean nothing without power in.
John
If you ever feel like a break come across the ditch and I will set up my rig so you can test. This retirement to remote areas means no time to research topics like this.
We live in the French Pass area. Or in that case anyone else.
Herb
Edited by herbnz 2008-10-02
SparWeb Senior Member Joined: 17/04/2008 Location: CanadaPosts: 196
Posted: 05:19am 01 Oct 2008
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Welcome to the discussion Herb, I see you brought your axe,
Completely testing anything is a laborious process, so the fact that anyone is actually testing this is unusual. My experience with internet forum discussions is that when all is said and done, more was said than done!
Testing the input and output power simultaneously are ideal goals, but hard to do on a working mill. Some experiments can be done, and a lot can be learned from them. Especially when you're just trying to get in the ballpark and try out different connection arrangements. Using a lathe or drill press as a test bench requires having a suitable generator at hand; one that isn't about to be hoisted up the tower.
I've been trying to pin down as much of the theory as I can while getting my next motor conversion finished, since I can't get to the testing stage until then.
Trying to follow what you're writing, above, and I'm not sure about something: is a motor conversion, or one of these Fisher & Paykel conversions, operating synchronously or with a slip? I've always assumed that is is synchronous.
If it is synchronous, could you just say if either the voltage or the current are in phase with the rotor?
I'd also like to see if you can help me with the list of required input power components that can be identified in these generators. The list I come up with goes:
1: Output power through the load (V * I) whether it's a battery or resistors,
2: Stator winding resistance, (I^2 * R)
3: Reactive impedance, (I^2 * Z)
4: Iron resistance (Q * f) from magnets dragging their field lines through the stator teeth,
5: Bearing friction (negligible)
The reactive power components must be calculated in VARs, then do the vector math on the non-reactive components for the total apparent power.
Adding capacitors to the input power equation makes a sixth component to the input power. This one is also reactive, but opposite to the inductive component - and at some frequencies #3 and #6 cancel out. Simultaneously, by cancelling out reactive components, the total impedance is reduced so more current can flow.
I might have something wrong, here, because when I do calculations on this basis, the efficiency of the system doesn't change. I don't understand that.
Steven T. Fahey
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258
Posted: 06:46am 01 Oct 2008
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Hi Steven
The units are synchronous slip only occurs in induction motors we are not driving a mechanical load. Motors that have magnetic poles such as these are used and called synchronous motors these have no slip I was once commisioning a 1400hp unit that did slip the noise was unbelievable.
The answers to your input power will take some time as some need us to go deeper into generator theory. At this point time I do not have the time also I think we need another topic as I would like to get the basics cleared up before delving into Caps.
herb
FandPwithPVC Regular Member Joined: 09/09/2006 Location: Posts: 64
Posted: 12:27pm 01 Oct 2008
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HI ALL
IT HAS TO BE SAID
Perhaps we should have a page for those people who have not tried caps at all.They appear to go into a know all phase and cannot accept that other people may know more than themselves and are actually getting there hands dirty by doing it.
Congratulations to those who are achieving something practical. This caps thing seems impossible in theory and it is not important to understand as to WHY IS IT SO
JUST BUILD THEM Regards Dennis L
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127
Posted: 01:55pm 01 Oct 2008
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I will add a small point.
Today we had relentless winds, and this gave my series cap setup quite a test. We had 20-30knot winds for over 6 hours, and yes, I did see a rise in temp on the caps. The caps temp rose to over 60C. I flicked the cap shorting switch, a bit of a crackle, the current dropped to a max 9A. The temp dropped to 30C in under 5mins. My caps are wrapped up in electrical tape. There is some energy lost in the caps. If they were properly spaced on a pcb, then temp rise could be minimal. A higher voltage cap in the non polarised variety may run cold. The principle of series caps is sound and now proven. I set up this thread to back up Dennis's work and then Bryans observations. I was looking at more testing. I have no intention of trying to model or fully understand what is going on. My testing has confirmed a F&P alternator will benefit from caps and the capacitance will primarily be determined by the upper mill rpm and the type of stator and rewiring and system voltage[preferably 12-24V only].
I think the engineering and physics has a place but is complicated for many readers.
The 7phase conversion will be a particular challenge. I will need to rectify with 2 sets of rectifiers and caps on the mill head and inside the yaw box. I will bring 2 positives and the negative down through the slip rings. This way I will still be able to shut the mill down. I expect to still use 230uF. I will look for 250VAC caps.
I hope others can present some experimental data. Configurations for successful and unsuccessful trials with stator type and rewire etc will help the engineers with a desire to know what is going on.
My F&P mill has today, made almost 2x the expected power that would have been made if it was unmodified. My surplus is not wasted in dump resistors, so I want it to make as much as possible to satisfy the base load of my house.
I still maintain that it is most important that the furling and shutdown have to still function if the caps fail.
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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Now since I started the serial flavour on these caps maybe when Dinges does this I can get some royalties off him 
Mind you anything less than aussie greenback wont be accepted. 
