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Forum Index : Windmills : visual effect of capacitors
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Just an information update. cap system is still working well on my F&P mill. I will be replacing the electronic boost DC-DC type converter with another capacitor doubler for the 12V cutin component of my 24V battery system. The lack of switching RFI noise is a huge plus with a cap doubler. At least until I find the RFI source in the DC-DC converter. I will be investigating the caps on my new AxFx mill when completed. This will have output frequency of approx 45Hz, max. This is approx 1/4 of the F&P, so cap sizing will not be too much of a problem. The cap sizing in a doubler for lower cutin seems to be a more critical aspect. The blade characteristics and efficiency impacts on the sizing. A torquey blade will require larger caps. In a homegrown system it would not be possible to calculate an individual system optimum capacitor sizing. In my system, the caps [135uF] that worked well on one set of blades [moderate torque] were too large for the new wooden blades I tested [low torque]. These required only half the capacitor size. More testing will be needed. Gordon. become more energy aware |
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| domwild Guru  Joined: 16/12/2005 Location: AustraliaPosts: 873 |
My two cents worth: Similar situation but three AC caps between phases and the author writes: "Capacitors are placed between input inductors and alternator terminals creating a low-impedance path for high-frequency currents, and only the fundamental component in same frequency and phase of voltage flows on alternator stator". Forget the inductor reference, he follows the caps with coils before the rectifiers. The article has been mentioned on Fieldlines before; it is called: "Maximum Power Point Tracker For Small Wind Turbines Including Harmonic Mitigation" and is (hopefully) given below: http://www.ewec2006proceedings.info/allfiles2/846_Ewec2006fu llpaper.pdf Enjoy! Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Dom, The SEPIC converter referenced has come up in MPPT discussions before. Oztules had some comments, as had I. I was intrigued at the response time of the MPPT algorithm. Wind gusts do not wait for electronics to catch up. In your first quote above, "Capacitors are placed between input inductors and alternator terminals creating a low-impedance path for high-frequency currents, and only the fundamental component in same frequency and phase of voltage flows on alternator stator". The caps are in star between the output phases. This is a parallel arrangement. These caps, in conjunction with the small series inductors, are to remove the high frequency switching voltage transients from radiating, back along the input wiring to the turbine. All of the power has to be passed by one series capacitor. Ripple rating has been raised as a problem with caps. This instance would not be any different. The natural way that the caps work with the varying frequency of the windmill with wind energy is a huge plus. The few readers I know who have successfully added cap doublers to their systems continue to be amazed with the additional power the windmill extracts from the wind when normally no output would be obtained. I still have reservations that a single cap system can give output that follows the wind energy across the full designed windspeed range. Phill has a dual stator overlapping system [effectively 4 systems], that works well. My system has a doubler and 2 series caps systems [three overlapping systems] and works well. Bolty has a doubler [effectively 2systems] and this improves the bottom end. Bryan has series caps and this improves the top end power. I think that any readers who have added caps to their windmills with success, or not should say something. Enough time has passed for individuals to have had a go, and give some feedback. I hope to see some responses. Gordon. become more energy aware |
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RevUpWind Regular Member  Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Gordon it seems that this capacitor discussion does not add up when you look at the wave forms seems to be a case of what you make on the hills you lose in the valleys. Only so much wind can be used by a particular or whatever set of blades. Or so it seems to one not so electronically minded. Where angels fear to tread 
Peter ....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. |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
[quote] Only so much wind can be used by a particular or whatever set of blades. [/quote] Truer words were never spoken. And it is not that difficult to optimally match the blades to the alternator..... to the windspeed... and to the battery state of charge either. The trouble begins the moment you change the wind speed from that which you have just set up for optimum.... It all gets very grubby, and becomes mired in compromise after compromise after compromise. The problem: 1. Wind speed goes up linearly. 2. The rpm of the prop would like to do the same thing. 3. The power in the linearly increasing wind speed is a cubed function. 4. It gets worse as we find that the alternators power (in a perfect world) goes up as a square function to the linear speed change. 5. If the loading is not correct then 2 starts to go out of whack. So we are left wondering how to make a straight line, a squared function curve and a cubed function curve, work together, to keep the TSR the same as the wind speed changes..... or at least keep it in the same post code. Now if this were not difficult enough, the alternator does not follow the square function like it is supposed to... due to armature reaction, resistance, and inductive reactance, temperature, state of charge, and what ever other excuse it can find at the time. As the optimal loading on the airfoils change (because of course the alternator is up the creek somewhere, trying to work out what to do to match the "lines"), then so too does the props linear rpm/windspeed line. It will change it's TSR in response to load drag and air drag... and air density, temperature etc.... so as the wind speed changes, don't hold your breath waiting for the TSR to hold good and the RPM to follow it. So what seems simple in static theory, becomes a mathematical nightmare when all the dynamics kick in. It is pure magic that anything comes out of the wires at all really. It had been envisaged by the computer literate crowd, that you could design an intelligent power converter that would take all these things into account, and provide a dynamic coupling to the batteries, so the alternator could pretend to be following a cubic function curve, and so present a constantly correct impedance to the blades. As it turns out, digging holes in a lake of quicksand is not all it's cracked up to be. In spite of the best minds in the business, this MPPT utopia has not been realised... at all. It turns out the best they have come up with is a simple power curve jump table based on RPM.... and thats it..... it's dressed up with some other powerful learning software apparently, but thats the guts of it. Gordon did some very impressive work on this, and I think concluded that jump tables work, fuzzy logic tracking does not. Next comes Capacitors... It was found by Dennis that capacitors on the output affected the alternator performance at the low end.... quite dramatically. Bryan found that series helped differently to Dennis's parallel arrangement, and boosted the top end. The previous 27 pages of information and (sometimes drivel from me too) has tried to quantify this, and Gordon has been instrumental in providing test beds, figures and results for us to play with. Now the tricky bit. Caps affect all parts of the system. Firstly for a stator like the F@P, they provide a leading power factor load, which directly influences the armature reaction positively (we get much better MMF and so EMF). Because of the high frequency involved with the F@P, we get some relief from inductive reactance as F increases (although this argument is appearing pretty thin I must say). The capacitors also act as a variable resistor which is rpm dependent.... this gives us a variable which can close the gap between the squared alt curve and the wind power cubed curve. (As the rpm increases, the winds cubed power curve has the alternators squared curve to deal with... plus the capacitor decreases XC in line with the RPM... and so it begins to look more cubic than before??) So this should help the wind loading on the blades track more closely as the power picks up. Now it seems you can't get it "all" to work for you simply, and Gordon has found that judicious use of caps to achieve different things at different speeds for different loads, can almost ideally extract the maximum that the wind and the blades can usefully expect... this to me is pretty flash really. So if it don't all add up..... don't feel badly. The waveforms are only a reflection of the voltage out. It does not tell you what is really happening with the MMF and the EMF as these are masked by the synchronous impedance of the electrical/magnetic circuits.... which influence the mechanical impedance of the blades to the air, and so can be misleading and difficult to unravel/interpret...... and so it goes round and around... 
Makes no sense to me either now I think about it
.............oztules Village idiot...or... just another hack out of his depth |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
I am not sure where you get this idea. Perhaps you can be more specific and show some measurements to back up your case. Gordon. PS edit, oztules has pretty well summed things up. The capacitor voltage doubler allows the alternator windings to be better matched to the upper power levels, where most of the resistance losses occur. As oztules has stated on many occasions, it really is about resistance when power is involved, especially lower resistance in the alternator. become more energy aware |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
I would not for a moment pretend that I understand the principles in which adding capacitors brings the advantages we have seen claimed but that does not mean the claims are false, mistaken or even exagerated, it just means I dont understand! 
However I can imagine how it might work! There are a number of networks which combine rectification with capacitors to produce voltage multiplication and I can accept that what produces voltage doubling at one frequency would not be so effective at another frequency. So I have no difficulty accepting adding capacitors to the complex association of alternator, turbine and load might well produce a machine that produces high voltage per RPM at low wind speed and low(er) voltage per RPM at higher wind speed. So, considering that the power input from the turbine increases with RPM and if I accept that the voltage does not increase at the same rate I must then accept that the current must be increasing with RPM. Is that not exactly what is required? Current that increases faster than voltage as RPM increases? Whatever the real explanation and whatever the combination of solid theory and empirical effort those who have battled through with this are offered my congratulations. |
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| RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Oztules I agree both by the academic and by "the way you hold your mouth right" method to all you have answered up to "capacitors", as my own observations and calculations have born this out. I am intending to conduct some research into the high speed area of operation whereby a mill reaches a high speed an goes into "turbo boost or hyper drive" or some such without much increase in incident wind speed. I believe TSR's of 15 have been measured. I think that this is caused by the blades suddenly appearing to the wind as a solid disc with a general area of high pressure in front and low pressure at the back which may be causing a major wind flow to speed around the outer edge of the disc and "turbulate" back in behind the blades and thus reducing the drag normaly caused by upper surface turbulence. I have deigned blades with a particular bend an the last 10% of the tip which is of an angle and direction which doubles the lift to stall angle ratio to take advantage of the extra wind speed at the tip allowing a greater load to be applied to the mill before serious stall. Problem! my testing has shown that the mill must be allowed to go into "turbo boost" before drawing down power or it won't get there because of the dynamic stall which is occurring in all wind turbines under load. This would require computer control and may not result in an overall increase in power on a small say f&p mill but could have an application in large fixed speed turbines where Reynolds number has a more marked effect. Has anyone else noticed this turbo boost? It is terrifyingly wonderful to behold. Capacitors may be of use especially because of the effect of power factor change particularly for the high frequency of the F&P with its (low frequency optimised) laminated core. The effect of edy current ressance to current caused by MMF translating to lagging EMF if caps are large enough) may be lessend because of this very phase change causing the resulting out of phase eddy currents having a less reactive affect on the MMF. Could be as good as having a ferrite armature. Having said this I defer to your last paragraph. About the hills and valleys I assume theoretically will appear in the power versus frequency curve. It will really take evolutionary steps to select the right caps for the job. I take my cap off to you guys who are involved in this in the face of strong arguments against. HEY the proof of the pudding etc! People trying to get their heads around wind turbine blades have to forget about airfoils. Turbine blades are not propellers and behave quite differently even though lift and drag but not thrust play their aeronautical part. O my what can of worms have I now opened? Oh no not Pandoras box!! ....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. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
I'll leave it to Sparweb or someone else who has a better understanding of blades and their behavior to elucidate what happens at higher revs..... but I am unable to support your view on this. As for the "turbo" effect. The fact that you have witnessed this phenom... phenomi... behavior, means you are watching an iron cored turbine. Your unlikely to see this behavior with an axial flux, as the air gap is large and the magnets are very strong.... With a F@P style of machine, you have long spaced poles, weak magnets, and tight airgap. When you generate EMF in the stator and draw the current, you create an opposing MMF in the stator turns. This is called armature reaction. The MMF generated by the stator from the armature reactance will oppose the main field. This in turn will try to push the main field away from the pole faces towards the gaps between the poles. This makes the flux lines less likely to link all the coils and shows up as inductive reactance. In an axial, the magnets appear as airgap as does the airgap, and the magnets are necessarily very strong. A lot less turns for the same current will also mean less ampere turns for the same current.... less back mmf. So an axial should also exhibit more stable load characteristics. (mostly only R affected) Two things will happen as we increase speed, the impedance of the reactance component will increase with F, and the reactance itself will increase (more ampere turns in the stator as amps rise) but the main field remains static (perm magnets). This means the interference from the armature reactance plays a more and more prominent part in the MMF now available to link the coils. You can see where this is going... All the while the inductive reactance is climbimg (as less flux links the coils), as is the frequency so impedance climbs as well (XI), and the power curve will be showing serious signs of bending as the inductive impedance, XI=R (DC resistance of the stator). It will get to the point where all these things act to completely current limit the machine, and any more wind and it runs away.... or "goes turbo" as the load will no longer increase..... but the wind power does. It is possible to double your loaded TSR figure if you release the load, so TSR of 15 does not surprise me, as it will see little further load as the wind increases past the inductive reactance current limited point. Capacitors.... It would seem that the magnetising field being affected by the back MMF does different things with different loads. With a resistive load, one side of the main pole field is enhanced, and the other reduced. Nett MMF remains the same, EMF remains the same but due to impedance and R, terminal volts will plateau when XI and R get high due to increasing F and I. With an inductive load, the armature reaction demagnetises the main pole, with a drop in MMF and EMF, impedance goes up as does XI, and terminal volts go down quickly with load against EMF. With a capacitive load,the armature reaction is magnetising , and EMF rises, and if impedance is not too bad, then terminal volts may rise as well. So Capacitors should help this style of turbine deliver better currents before speed finally limits current again. Herb... I'm at your mercy....
One other "turbo " possibility exists however. As the wind is cubed, and the alt squared, if the alt is not big enough (R is too high) in even an axial, the cubed will overwhelm the squared at some point. This will especially happen if driving a resistive (eg heating) load. Here we are not stall/load drag (call it what you will) limiting the blades. They will struggle to get going with a resistive load, but once allowed to get up to speed will quickly overpower the alternator and run away unless you can keep adding more load proportional to the power increases coming from the wind. (mine climbed up to 5kw and climbing when I shut it off doing this.interesting yarn Being an F@P owner, I don't think this is you. An interesting example of the armature reactance is this: We have an AWP up at Jamies place. It is 240v 3.6M radial flux ferrite magnets and 90 coils...iron core. If the wind is blowing say 20 mph, and you short the windings, the mill continues or speeds up, as it goes into current limited mode, It needs a lull in the wind to actually stop with the windings shorted.... If you use a 1kw dump load instead across the windings, it slows quickly to a stop. The ampere turns generated by the short at 20mph, is just enough to cause enough MMF interferance to current limit the mill, but the drain of the 1kw load, keeps the ampere turns below current limiting, and loads the mill fully and stops it, where a short wont...... interesting. It has only done that since we built the emergency macrocarpa chainsaw blades... I wonder if our blades have more torque than the fibreglass originals??? AWP Blade story] I'll re-read this and correct later must go. .........oztules Village idiot...or... just another hack out of his depth |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
All of the large windmills [MW sizes] around where I live. Starfish Hill, Hallett, Snowtown, Edithburg are grid synchronous. How do you envisage these type of machines be computer controlled in the mannner you suggest, that may be required with this "turbo boost". I did notice my F&P mill exhibit runaway in strong winds. This is the machine getting very fast just prior to fully furling. This did not provide any more power output though. This was prior to my experimenting with capacitors. This problem does not occur anymore with cap setup with multiple loadings. My AxFx has been recorded at 1200rpm unloaded. This is very fast and is not recommended. As soon as the load was replaced, the mill came back into control with normal outputs and not a boosted level. This may be a result of the maximizer between the mill and the battery. The blades you have made have low form drag. [very thin sheet metal] These may exhibit different characteristics to the usual wooden/composite blades on most windmills. There is a critical intermediate region with Reynolds numbers. This occurs between laminar flow and turbulent flow of a liquid over a surface. It is possible that your blades operate close to these critical Reynolds numbers. Removing the load allows the rotor to transition this region. Can this feature be objectively measured. You may need to record rpm and current output. If there is any benefit, this will be highlighted in the before and after transition power levels. Betts Law hopefully won't be broken. Gordon. PS edit: You may need to use a different editor. A hard carriage return is inserted and prevents the auto wrap in the forum software from formatting to a varying window size. become more energy aware |
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| Jarbar Senior Member Joined: 03/02/2008 Location: AustraliaPosts: 224 |
Oztules as usual I read every word and get about 1/3 of it but find this discussion stimulating.I have seen Demag motors used for braking crane loads.The Stator and armature I think are made with a taper that when energised pulls the shaft assembly away from a brake.When demagnitised it rengages.So if power failure occurs load will not fall. Hope this is coherent enough. What if the axial Flux was made with a taper or even if in its flat form the magnets can move away from the coils in low load low wind and be more deeply immersed in the field and would this be another way of better matching the cubed and squared power curves.The idea of the spinning blades simulating a solid disk to the wind which is used to facilitate furling,why couldn't the same forces be used to immerse magnets into coil field relative to wind strength.And a taperd winding and magnet set might be a more appropriate and progressive way to realise this.An appropriate sized spring would be used to disengage or push apart.The spring could be adjustable like a monoshock on a mountain bike.In a recent post a fishing reel was used for the hub/bearing assembly of a small windmill.Very creative but what if the same ossillating reciprocating action(like the old Fridgidaire washing machines) where a cam plate pushed the agitator up and down.A swash plate on a variable displacment hydraulic piston pump is another examlple I'm familiar with.This same action applied to the magnet/ coils could be used to potentaily modulate the squared with the cubed.More complex mechanically but if it can be show it would theoretically work,I would be more inclined to build one.Anyway I have distracted my thoughts from the fires at Kinglake which effected a family member. Thankfully they are OK. http://www.youtube.com/watch?v=6_41btVawMc Anthony "Creativity is detirmined by the way you hold your tounge".My Father "Your generation will have to correct the problems made by mine".My Grandfather. |
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| RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Thanks guys for the amazing thoughts I will try to investigate some of these things to join ya'all in advancing wind turbine technology and hopefully someone might stumble upon watershed discoveries and make these little fellas reach the power generation that theory promises. With the turbo boost thing I admit that I have been unable to generate extra power and still maintain RPM at turbo levels, which is why I am playing around with tip modifications... May come to nothing but nothing ventured nothing gained. I haven't noticed this effect under load or dump conditions. I do however reach sustained wind load stall at 22odd amps on the mill without gurney flaps. I have another related item. I have noticed that some experienced and knowledgeable people have arrived at turbine blade construction dimensions which they present as the theoretical gold standard. In this case I would respectfully suggest that theory does not cut it because of the simple reason that the end game of maxing power has not yet been fully realised. Taking into account the fact that the factor of wind volume to power is a cube related function and wind speed versus root to tip speed is a linear function and TSR is a squared function and that actual power out versus wind speed is variable and affected by many factors including the number of blades used, let’s take these variable factors out of the equation as they can and are being perfected mechanically and electrically. I have calculated that the theoretical proverbial blade would begin at 90 degrees to the incident wind at the pivotal centre with a tip at an infinite distance from the centre at an angle of zero degrees. The chord dimension would be infinitely wide at the pivot vanishing to a point at the infinitely distant tip. This chord width would follow an exponential curve (debatable perhaps). This is obviously a ridiculous device to engineer so empirical evolution must have been responsible for arriving at the blade dimensions that are out there. I would like to add my own two cents worth to this tweaking. NASA wind tunnel experiments have shown that lift is maximised between wind incident angles of 0 degrees to maximum lift at 12 degrees, after which dynamic stall begins. Negative stall can only occur in decreasing winds due to the inertia of the mill but would be pretty savage with this blade angle. Taking the stall angle of 12 degrees into account we arrive at the optimum tip angle of approximately twelve degrees which is permutated all along the length of the blade following as best as possible the exponential curve which gives a reducing angle twist to the blade with a linear angle change. In doing this we find that empirical measurements in the most part bear out the theoretical in a real world blade of finite length. However we now have the action of load put upon the blade by the drawdown power from in our case a generator pulling down the blade speed and hence causing the incident wind angle to steepen into the dynamic stall area in which incidentally all power generating mills operate and for maximum efficiency of lift we need to keep the IWA as close a possible back towards 12 degrees along as much blade length as practical. I feel that the optimum blade angle for maximum power generation is therefore not 90 degrees at the pivot but 78 degrees and 12 degrees at the tip which are somewhat arbitrary numbers generally determined by holding my mouth right and judicious thumb licking and up to wind holding. Other determinants on blade angle are such things as expected draw down load and desired TSR to achieve blade speed at the optimum generation RPM for a particular mill based on generator characteristics and local wind conditions. One can therefore note that evolutionary and empirical results a well as theoretical design are crucial to creating the optimum wind turbine blade design for a particular mill. So all you boffins out there don’t think that the published blade designs are the be all to end all so experiment away and may it always blow a gale at your place. P.S. Edit Note: Oztules, cannot see how to unlock word wrap. Using my MS Word and pasting it in does same thing. Have copied it to Word, justified it etc. and no go. What's up?
....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. |
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| RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Gordon, Perhaps you mean Betz theory. The jury is still out. See www.ilr.tu-berlin.de for interesting reading re high power and wind conditions. ....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. |
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| RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Oztules, The F&P is a toy but a usable one at that. I am a new chum t this but I can see an advantage in replacing F&P magnets with neos that span three coils at once giving greater flux density and reduced frequency and the consequent benefits. ....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. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
RevUpWind, [quote]P.S. Edit Note: Oztules, cannot see how to unlock word wrap. Using my MS Word and pasting it in does same thing. Have copied it to Word, justified it etc. and no go. What's up?[/quote] Just suffer like the rest of us perhaps, and use the post reply page window. I don't use windows, but perhaps try notepad?? I think thats in windows. If it is stuffing up in the post reply window, then your in Glens territory, and he may explain the problem. It does make it difficult to concentrate on your story when it stuffs it into a huge skinny block. I struggle to understand these things at the best of times. ..........oztules Edit, we posted at the same time, you obviously have it sorted 
Edit#2... looking below we'll say half sorted. Village idiot...or... just another hack out of his depth |
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| RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Edit, Of course adding caps changes the impedance of the electrical circuit which will of course reflect back to the magnetic circuit. But by adding capacitors you also have created a tank circuit with obvious resonance and harmonic peaks. My question is that accepting that capacitors radiate loss in the form of heat as well as leakage loss. has there been an overall power gain through the whole RPM range or is there a need to optimize the circuit to give the greatest gain specifically to an individual mill with regard to it's design and geographical location? ....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. |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Jarbar, It looks a fiendishly  complicated way to turn a watt out.
However opting for a high cut-in speed and using a low speed booster until cut in will match the curves of the square and cubed lines reasonably well, and solve most problems without a mechanical minefield. If you draw your two graphs (x^2 and x^3), you will see that there is a fair portion (away from the origin) of the line that have not too dissimilar gradients. If you design to use this as your generating range, you will get a good match. The TSR will forgive the change in rates for the most part. It will require a booster, other wise you will get nothing below about 15mph. I don't have the guts to try and put complicated gear up in the elements facing 100mph winds.... just a sook I guess. ..........oztules Village idiot...or... just another hack out of his depth |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
I would use notepad, with word wrap ON. Maybe you use a Mac. If you compose a reply and use enter key, this keystroke will be recorded in a posting. I have just tried Word and notepad and these work. Must be something different you are doing. Re blades: Any decent blade will have a tapered twist with a blended series of airfoils to allow for the changing local airflows over the surface. The problems occur with designs that operate over very wide windspeed ranges. The design of a blade is a complex process. My own design is really a modification of a good existing design. I doubt you will get much better than 30% blade efficiency from the wind at the shaft, with a machine of <4m rotor dia. The 100m size windmills already get > 50% blade efficiency. My own windmill blades are just < 30% efficient. Betts Law still applies. Gordon. PS edit: A lot happens in the short time you think about a reply. become more energy aware |
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| RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60 |
Thanks Gordon, am still sorting this out and am using Windows. The tech stuff is my son and he will reply. I am just typing and letting it put in returns so do not know whats up. Only enter at a paragraph change. Typed this earlier trying to explain: Am only using Post Reply and only tried Word to see if would make a difference. Have taken normal text from Word and pasted into Post Reply and still comes out wrapped? At moment it seems to be unwrapped sometimes. Word wrap is turned on it seems? Even when you select text in the preview it highlights the blank space to the left and also in the form. And when you select just a quote from a reply it copies the whole thing in a different blank Post Reply and not the one you are working on? You say you use notepad, but then you still have to past it into Post Reply,where else can you post into this form?
Or is this only me? 
....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. |
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| RevUpWind Regular Member Joined: 03/05/2008 Location: AustraliaPosts: 60 |
....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. |
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