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Forum Index : Windmills : visual effect of capacitors
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herbnz Senior Member  Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Hi The axe has fallen like last time I will fade away. Denis I have used caps to determine optimin performance in hydro's way before mentioned here I have Even have a Capacitor load bank as I have mentioned before. My hands are dirty. Herb |
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oztules Guru  Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Don't go fading away on me now Herb. We appear to be getting close to the truth. Dennis. I have no problems with being wrong. I have made more mistakes than anyone I know. I have also had more successes than anyone I know as well. Being wrong and learning from mistakes is the only way I know of finding out the truth. On this island I am the only person people can come to see with their fishfinders, dishwashers, ice machines, old Lister gensets, TV's video's DVD's washing machines tractor wiring faults hay-baling computers (yes agriculture is high tech now days), solar system problems inverter repair, windmill rebuilds (water and electric), excavator computers, car computers, rewiring armatures on grader starter motors, motor rewinding (single and three phase) and a host of other gadgetry. I don't just mix and match parts as you do on your F@P;s, but track down the individual components that have failed (pwm chips, caps, resistors... and yes the other day a F@P smartdrive controller board with 6 blown fets and assorted caps and diodes), I need to now how they work, we don't have spare machines here to pinch bits off. We have to work through from the basics. I suppose if I hadn't been able to fix the controller board, I could have gotten my first F@P motor.... In the last 2 years I have saved the people over here in excess of 250,000 dollars by doing this nonsense... and it's all free.... Some of the computer boards for these big excavators run into $6-7000 per board, one 30 ton machine sat on the island for 2 years with nearly 4000 spent on flown in mechanics... and still didn't work. The boards were unavailable for this model... I fixed it in 2 days ( including the problems that eluded the experts in the hydraulic system) and you still can't get them, but can fix them for pennies. It all adds up. Some where, some times you need to know whats going on, because the next problem that gets bought to me may have some obscure relationship with something you have learned from something else. This week it is/was a 21" tv, a $12000 fish finder from a trawler, build a huge shaft (60mmx900mm with steps and keyways) for a sheep dung vacuume machine out of an old Cambridge roller, design and build a solar controller with PWM output drive, injector pump on a diesel genset, chainsaw out some blades for the AWP up on the hill from a macracarpa log... and the week is not over... so I guess I saved these people in excess of 14000 dollars this week alone..... yes the fishfinder would have gone over the side, as the time it takes to get it sent off and back would amount to probably a month or more, and they can't afford a day let alone a month, and even then, being an older model, they probably could't fix it anyway.... (the usual can't get the boards now) Yesterday I built another dc motor/ ac induction driver to use some of the power from my mill to drive a few KWH back into the grid, just to see if a single phase unit would work as well as the three phase unit I had built previously...just to see it work, (and to use up some of the 2kw that was coming from the mill,)... I get my hands dirty too. I am supposed to be retired, but it seems the world still has a place for someone that can actually fix things, instead of replace boards. I retired at 48 because I was successful at doing things. I now am in a position with enough understanding to fix most things, I have never charged for labor... or parts... I am fortunate in that I don't need to. I am sorry that I have offended you by trying to further my understanding of the world and how it works, but it is how I do things, and over here an absolute necessity that some one is willing to at least try, fail and try again, and then get it right. And the islanders don't want me to change. With Herb's help (if he will be kind enough to continue with my education) I will get to the bottom of this... and then we will all be wiser for it. For me, ignorance is not bliss. ..........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 |
Hi oztules, I have to stop dragging you to the phone with so much else happening in your day. I have a bit more of a wait for a new rotor, so a trip to the city to check out a drill press will be delayed. I hope the theories are still being tested, even if not presented here yet. Hi Herb, I know you have been working with these F&P units for years. I went back through the older threads related to capacitors and I can see no reference to a series resonant wiring of capacitors. I guess that a capacitor could not be seen as capable of AC coupling all of the power to the load. I had only seen reference to caps to smooth diode switching spikes and providing voltage gain to lower cutin voltage, with an increase in power output within certain limits. The higher currents and extracting power at lower rpm was seen to need slightly more input power for the same output. I see the theory complimenting the seemingly random testing. I doubt that the series configuration that Bryan hooked up would have been considered suitable from theory alone, with a windmill. The testing by Dennis broadened the perspective and gave people like myself incentive to follow up and investigate further. This capacitor investigation has been tossed around for years now. I do hope you finish the testing you mentioned last year about this time. I have a lot of respect for individuals who get success with investigations without traditional scientific process or funding. The property of a forum that I find rewarding is the assistance that can be given to others and the general communication of ideas that can occur. This is a public place and sometimes care has to be used if IP conflicts may be involved. I have presented a lot of data over the years. A lot of my research is just ideas and measurements. I try to look at one variable at a time with the if this then that approach. I prefer to see trends in relationships rather than a complete formulae. This may be over 50 syndrome setting in. At the end of the day another "Dr Chalko" may come and be paid to put all the pieces together and we all miss out on some of the credit. Gordon. become more energy aware |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi herb, flux, from otherpower.com has this to say and I quote, You are getting there, the shunt capacitors will give only slight improvement. Series capacitors are the answer and it comes down to cancelling the LEAKAGE reactance. This is not the winding inductance that you would measure from the machine terminals, a perfect alternator would have inductance measurable from this point of view but would not have LEAKAGE reactance. With most machines the leakage inductance is tiny but with the stupid construction of the F & P it will be large. It is a difficult thing to measure as you have to separate leakage reactance from synchronous reactance that includes the effects of armature reaction. I think your contributor Herbenz( or similar if I remembered it wrongly) has got to grips with this. end quote It appears we are still making some waves on the other side of the globe. I believe iron cored machines make better use of lower strength magnets, maybe not the best for a windmill application, but will always have a place in designs, even if a little more diffficult to model and slightly lower electrical/mechanical efficiency to ironless designs. Gordon. become more energy aware |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Hmmmm, if a series capacitance is required to cancel the leakage reactance and if it is difficult to get capacitors big enough for the job then what is the scope for using parallel inductance to do the same thing? |
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Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Gordon, Supporting comments from Flux I feel. Considering the influences causing the inductance, it is beyond my willingness to acquaint myself with all the required knowledge to attempt to plot the theoretical curves on the series 100 and the others in their various configurations. Just knowing what effects we are countering and why is a start. Sure some theoretical figures to kick off with would be good to leave only fine tuning the final values, But from an economical use of my time and energies I see the realistic way is by experimentation and not calculation. That is not to say this will suit all. I commend those with the skill to probe further though I suspect suitable equipment for measurement of the influences mentioned will cause some problem. I would like to see a test rig, a range of caps and a sample of each series F&P in the common configurations put together in a series of tests. The involvement of us less academically endowed will give some actual reference for those following the theory further at the same time provide values for immediate incorporation into numerous mills. With the coming wet season my hydro will fire up and then the wind gen will come down for cyclone season. I would like to try caps in both. They are both 80series, one star, one delta 2coil x 7parallel. The hydro I could test myself but don't fancy up and downing the tower changing caps. The test bench is best for that. Suggested values will suit many and will provide good feedback. Any supporters or problems with that idea?  was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Herb,: Here is some information from Flux regarding the XI=R =constant current mode. Coupled with his above quote via Gordon, it looks more to be the inductive reactance (XI) that is the problem #1 with current limiting. From Flux: "The leakage inductance is a consequence of flux not linking the coil completely. If flux linkage was complete there would be no leakage inductance. The actual windings would have inductance when measured on their own with a bridge or inductance meter, but there would be no inductive drop component in the load current. I think it may be easier to consider a transformer. A perfect transformer has a winding inductance and the normal to consider is the primary inductance and this determines the magnetising current. The primary and secondary should be completely coupled and any flux linking one winding will link the other. Any current in the secondary is reflected as a current in the primary in the ratio of the turns. The equivalent circuit would just be an inductor across the lines, simulating the magnetising current. Now if all the flux doesn't link the windings then you have the effect of a leakage inductance being placed in series with the load ( you still have the shunt primary inductance but we can forget about it for now as it doesn't affect the load current.) For a 1:1 transformer you can regard this leakage inductance as being in the primary or secondary side. If the ratio is not 1:1 then this is still valid but you need to multiply the value by the square of the turns ratio if you refer it to the primary side. In addition you have the winding resistance causing an internal drop. The alternator is less easy to follow but basically if all the rotor flux links the stator winding the output is determined by winding resistance as in the axial air gap machines. When part of the flux fails to link the stator winding you have the effect of an added series inductance which we know as the leakage inductance. The final load is determined by the vector impedance comprising the winding resistance and the leakage inductance. As the inductive bit rises with frequency there usually comes a time with Xl greater than R where the thing goes into constant current mode. This is very simplified and there are effects of the magnetic field in the stator due to load current reacting upon the flux in the rotor and distorting, reducing or increasing it due to something known as armature reaction. A capacitive component in the load will increase the effective rotor flux and an inductive load will lower it. Capacitive loads will to some extent compensate the drop due to leakage inductance and adding capacitors to an alternator terminals will reduce the effective volt drop. If you can use large enough series capacitors you can actually neutralise the leakage inductance at a fixed speed but it requires rather large capacitors and is not generally practical." ........................................................ So it looks as if XI is lowered by capacitive coupling. This lowering of XI stops the current limiting and reduces the XI losses, and at the same time seems to increase MMF in the stator..),So XI is the culprit, (and I was chasing the wrong "I"....  )
This coupled with Herbs: "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."........... No, but the leakage inductance is. It would seem that at resonance XI=0 so we can actually eliminate the losses from the load vector for XI, but not R and change the stator MMF positively at the same time (I'd still like to know exactly how). So it is all becoming clearer now... but I have yet to find the relationship between the coil inductance and how/if this is related to the leakage inductance and/or stator construction. Once that is established I think this "capacitors on the alternators effect" will be able to be to be described simply, and some ball park figures for different configurations..... It may be that we need to simply test for the fold over rpm where XI=R, so we can define XI at that speed, and so find best C..... That information should be available from F@P users who know when their current limit occurs and at what frequency perhaps. .........oztules Gill.... That seems practical and sensible to me. 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 hope I get this right. I see it that without capacitors, as the current in the coils increases, the flux has a harder time getting into the iron, so flux lines bypass the iron path. The caps increase the effective iron permeabilty, so the flux is not rejected as much, so more flux enters the iron and that creates a higher total current. A bit like pushing someone on a swing at the right time. I know that on my axial flux machine, the flux path in air is very short and the magnetic field so strong that any flux bypassing the coils would be a small fraction. The F&P has a relatively large gap between pole fingers and I have noticed build up of filings between magnets, so as the magnets straddle poles, a lot of the flux will bypass the iron. Is this the problem flux leakage? Gordon. PS edit. The current limit for F&P stators is well known and published. ecoinovation had graphs of power output v rpm for a range of stator combo's. If a reader could publish this graph again, now would be the time. become more energy aware |
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MadRat Newbie  Joined: 30/09/2008 Location: United StatesPosts: 21 |
Maybe it had nothing to do with flux - flux bypassing coils, etc. - and everything to do with the capacitors are the path of least resistance for the electrons... Go Huskers! |
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| 9c12m Newbie Joined: 04/09/2007 Location: AustraliaPosts: 28 |
Hi Folks, Have been watching this topic so decided to put a F&P 80 SP in the lathe and connect up some non polarised capacitors (created from 2 1000 electrolytic caps connected back to back "neg to neg")in series with each phase. See attached chart for results. One of the unfortunate results is that the motor on the lathe needs some more grunt as it suffers from rpm sag as the load goes up. 
9c12m |
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| FandPwithPVC Regular Member  Joined: 09/09/2006 Location: Posts: 64 |
HI 9c 12m. We have done all our testing using 24 volts and a large battery bank. Using 2 by 12 volt to give a 24 volt load creates a problem to a motor driving the F and P. This results in the load you talk about and it a bigger problem at 12 volts. Early on we tried 12 and 48 volts then settled for 24 volts. It is much better and most of us use it and it does not muddy the waters when comparing results.The max uf caps we use has been 400uf and it appears about 250 uf is the best match. In closing non polorised caps work the best. Regards Dennis L |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi 9c12m, Is this a std rewire, series80, 2S7P? I took the liberty of plotting your data. I do not know the input power, so cannot comment on how a windmill would see this change in output current v rpm. 
The better combination appears to be around 1500uF. As the capacitance is increased, eventually, the with cap and without will produce the same results. How the blades handle the additional loading and how this affects power output will be interesting. I would expect the 12V system is causing some stator overloading. Caps are providing a significant boost to output power, and this appears to be across the speed range as well. This is similar to my mill results. I extrapolated down to approx 0 amps, and the cutin does not appear to be changed with caps. Hopefully you can test with a parallel arrangement as well, to see if the cutin voltage can be reduced as well. I would start with a cap value of half the series cap size. ie 500uF at the 12V levels. Gordon. PS edit, unfortunately, the graphs still go the wrong way as the rpm increases. Ideally for a doubling of rpm, there should be 8x more current, so no maximising function here. If the blades can still drive the alternator to these rpm, then the extra current will become available though. become more energy aware |
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| 9c12m Newbie Joined: 04/09/2007 Location: AustraliaPosts: 28 |
Hi Gordon, It is a standard F&P 80 of 42 coils and 14 magnet blocks rewired as per the instructions of this website as 7 groups of 2 poles star configuration. As it happens I had already run a test with 200 uF non polarised caps in parallel between the series caps and the 3 phase bridge rectifier so I have attached that chart to provide some idea of where the results are heading. Might think of a higher value. Will look in the junk box. What I find interesting is that at 427 rpm with 2000uF series caps and 200uF parallel caps the no load voltage jumps to 64 vdc. I now think that my old lathe motor needs more get up and go to provide more meaningful data at the high current loads. A rough connection circuit is also below. 
Replaced with star....... Cheers 9c12m 
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Thanks 9c12m, That's the simple report I am hoping to see for the full range of F&P series and configurations. It'll give us a good start point to boosting power on all the variety in use. Still a lot of blanks to fill in though. Unfortunately you don't state if this is Star or Delta or if the 80SP is 3 phase, 2 in series times 7 in parallel or 7 in series times 2 in parallel? Unfortunately there are these short-cut codes around that instead of making it clear and convenient only leave us confused from their ambiguity. That 80SP code introduced by Ecoinnovation is a case in point. Please clarify so we can tick that one as done?   was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Seems we were both writing at the same time. I'm thinking your battery may be overcharged as per the 18 volt readings. Maybe dump some power from the battery and see if the readings are same? Also in the text you say Star but the circuit shows Delta, hate to be a pain but these contradictions confuse me. was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| 9c12m Newbie Joined: 04/09/2007 Location: AustraliaPosts: 28 |
Hi Gill, Thanks for that Star/Delta check. Not enough coffee and have updated cct. Just to be on the safe side re the type of F&P stator I am using I have provided an image and hopefully with enough clarity for it to be correctly identified. So please let me know when you get a chance to have a look at it. The windings are .75mm - .78mm dia which I understand to be the 80 series. I hooked up an old aux motor from an aircraft to the 12 volt battery and let it run for a few minutes until the battery voltage dropped down to 10 volts and then powered up the lathe. The motor increased its rpm (high pitched scream) and the F&P with 2000 uF caps in series with the 200uF caps in parallel provided a reading of 15 volts and 25 amps at 305 RPM. This rpm is down some 153 rpms hence my thinking that the lathe motor can not provide enough power for the F&P to reach what ever its potential is. 
Cheers, 9c12m |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi 9c12m, The picture you present is very clear, your wiring is a star connection for the stator. The stator is the standard rewire, series80, 2S7P. The 2S means, 2 coils in series, and the 7P means, 7 of these groups in parallel. There are of course 3 groups of all this for the 3phase configuration. I have made a stator with this same configuration. cutin for my 27.6V battery was 300rpm. The capacitors are a series configuration and then there is a parallel configuration as well across the phases[Delta]. It does not seem to matter which side of the series caps, the parallel caps are, on the simulator. The unloaded voltage gain at the higher rpm with caps is complimented by an unloaded attenuation at the lower rpm with the parallel caps it seems. I intend to take measurements at discrete input power levels. I intend to record rpm, AC output voltage and current and DC voltage and current and voltage across the series caps when tested, for a range of power levels, up to 700W or so, with a battery load, and also with a boost maximiser. I have the opportunity to recycle the power with my battery inverter setup. The voltage may drop slowly, but this will be minimal with a 2-3kWhr battery reserve. I will only waste the system losses, and my other windmill should keeep the battery topped up. This is still looking to be a major exercise. Gordon. become more energy aware |
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| Gill Senior Member Joined: 11/11/2006 Location: AustraliaPosts: 669 |
Gordon, I don't see what you are hoping to achieve with the caps in parallel whilst the series caps are still fitted. As I understand it, you have the same effect as slightly less series capacitance. Having quired that, I am by no means a master of the Smith chart. Parallel caps may give a lower cut-in and series caps a greater power at higher Fq., but adding the two produces a combined effect of less series cap reactance? If as you indicate an intention to take 'current and voltage across the series caps' then I think it will vary these readings as to where parallel caps are placed. However I don't see where these particular readings fit in other than a distracting curiosity? was working fine... til the smoke got out. Cheers Gill _Cairns, FNQ |
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| herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Hi 9c12M These tests are the best I have seen here. One simple addition that I seem to have trouble getting across here is to measure the input power. When testing in my lathe I clamp the shaft in the chuck. I do not support the unit but to stop the stator turning I attach an arm and a spring balance so that it is acting a tangent to the arc the arm would scribe. Now in every test you do measure the force. Watts in = 2 * 3.142*rpm*force*arm length/60 force in newtons. 9.81newtons =1kg arm length = distance balance attachment to shaft centre in metres. My results have shown that caps effectivly increase the excitation and allow the FP to produce at a lower rpm all good but there is no power gain. the fact you are dropping rpm with load also confirms this. I believe that for those not wanting to delve into the reasons its enough to say that adding caps is like increasing the field strength. output volts increase or if tied to batteries the current increases BUT we must supply the increase in power to the input +little extra for excitation. Yes there is a point were it will not work but if we get the characteristics that suit the driving force before that alls good. There is no free lunch here its its a means lowering the generating speed by increasing magnetic field. Herb Ps for the 80sp measured here what is the current limit most have seen . I think 20 odd amps measured here is about it . |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
Herb, I agree, those De Prony brake tests are invaluable. I did one recently myself, based on the setup as shown by the Dans on their website. http://www.thebackshed.com/Windmill/forum1/forum_posts.asp?T ID=1246&PN=3 |
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