 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. |
Forum Index : Electronics : NEED A LITTLE ADVICE ON CAPS
| Author | Message | ||||
AMACK Senior Member  Joined: 31/05/2009 Location: AustraliaPosts: 184 |
I have used the disign that Gordon posted some time back and need a little feed back. I have used 6 220uf caps back to back ( 110uf real) 180 volt caps and they feed into 3 bridge recs then ito the batterys. It works well on High voltage gens but only shows amps at high gen speeds at low voltage( 12volt ) It is connected to 7 groups of 6 polls STAR. 
*Note to self 1. Make it thick 2.Make it heavy. 3.Make it stronger than it should be. 4. Don't rush the first job as the second job will cost more and take mor |
||||
GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi AMACK, The pictures you have posted are not of a capacitor voltage multiplier, but just a series cap connection. This is used to unload a windmill that would be normally stalled by the load, and needs reduced loading to get going. The outputs you quote are expected in this arrangement, but this is not the optimum arrangement. You have heatsinks on the caps????? Is this just to make mounting easier?? I use hot melt glue, and glue the caps into a block, and then wire them up. If the caps get hot, then the voltage rating is not high enough, or the power required to be passed is too high for the cap size. I have series caps as the main power passing component on my 48V AxFx mill, but these are 200V and 2300uF. These are in addition to cap voltage multipliers. the scenario you describe above is not the way to best use caps. Rewire the coils, so that the battery cutin voltage occurs at approx half the expected maximum rpm. What is the expected maximum power output of the alternator, and what is the maximum rpm, and pole count of the alternator and system voltage??? The uF and cap voltage rating required can then be estimated. The best matching occurs with an alternator wired for the top end performance, that has poor low winds performance. Normal rectifiers are used for the bulk of the power handling. A capacitor voltage doubler, and possibly a capacitor voltage tripler can be added to extract more power in low winds, when the rotor would not be spinning fast enough to achieve normal battery system voltage cutin. It seems as though you have some more work to do. Gordon. PS: I recently purchased 450V, 270uF caps for $2.50ea. Rockby electronics was the supplier. Sometimes you get lucky. become more energy aware |
||||
fillm Guru  Joined: 10/02/2007 Location: AustraliaPosts: 730 |
That doesn't look any thing like a voltage doubler if that is what you are trying to make , the set up you have there appears to be a series cap connection and I would think the uF is mabe a bit on the low side , I am only guessing that this is the problem as not much was done with testing caps at 12v , but I think Glenn is looking at that PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
||||
KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
do you need to match the ratings too? I notice one of the caps has 180V on it and another 250V. These are the type used un PC power supplies right? Gordon would you use this size in the tripler (ie the 110uF at 180+V as shown) on an F&P (48V 2p7s)? .....if so i can get these caps in hard rubbish readliy for free! I'm still at a loss as to how it works with lower cap sizes suitable for triplers and quadrouplers..... Is the tripler a replica of the doubler circuit with just lower voltage / lower size caps? ie normal recs + doubler say (340uf 450V)= 6 bridge recs normal rec + doubler + tripler (135uF 450V) =10 bridge recs. and if this is the case then we should always be wiring in delta and the caps will solve the low end problem right..... Karl Luck favours the well prepared |
||||
| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Karl, I doubt you will find suitable caps in the rubbish. Why would you bother to try. I purchased caps suitable for a doubler, all new for about $30. These were 450V rated. The arrangement for a F&P mill 48V system is described I think on the Cap testing thread. This is on one stator of Phill's mill. Re rectifiers. I use 2 bridges for 3phase direct connection. A cap doubler uses an additional 4 bridges. A cap tripler uses an additional 6 bridges. the minimum caps for a 3phase cap doubler using DC caps is 12, and a cap tripler is 18. The optimum configuration ultimately comes down to blade alternator load matching. If you have poor blade performance, rpm will probably be lower, so a star config may be required. With better blades, higher rpm is usually achievable, so delta may be a better match. If a windmill is set up with blades for torque then this affects all the calculations. Dumpster diving is a good place to find caps for testing before spending crinkly. I tested my setup with a single phase initially. I have given an outline in the cap article of what I have working on my mill. A F&P uses smaller uF but requires higher voltage caps. The operating Hz of a F&P controls these aspects. My AxFx has 50Hz at 500rpm, while a F&P would have 233Hz. For the same power handling capacity, the F&P would have approx cap size 1/5 the uF, but 5 times the voltage rating of my AxFx on the same system voltage. You are not alone with how the caps work. Rest assured, better loading will be achieved with the caps. Gordon. become more energy aware |
||||
Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Ok, Im still yet to get my head around this cap system to. But a quick look at the schematic on the front pages on Caps. Would indicate your bridges are wired wrong? and need 4 of them not 3. The cap's you require another 6 configured the same as you already have to make up the multiplier. Have a look at the schematic on the front pages and look at the one with the bridge rectifiers in it. HERE Labelled. [ The circuit below uses the common 35Amp bridge rectifier instead of individual diodes ] Im not sure if you understand the setup of a bridge rectifier. (if im telling you what you already know please forgive me) A bridge has 2 AC terminals often marked with a squiggly line. Each AC input has 2 diodes connected in reverse to each other, one goes to the positive output terminal and the other to negative output terminial. The diodes gate the AC input into +/-. The other AC input is the same as the first, and is also connected to the + & - outputs. This enables us to rectifie 2 AC phases. You have both of your AC terminals connected together. All this will do is double the amp capacity the bridge can handle. In other words you use 4 diodes to do the job of 2. Solution:- Add another bank of cap's. Add another bridge. Rewire the bridges correctly. You should get some results then. Pete. Sometimes it just works |
||||
herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Hi Pete Need to be diplomatic here. Yes both circuits are different. Notice in one of Gordons posts he uses deticated 3 phase rectifiers, yet another cct I suspect. I have been bench testing caps and have tried both ccts, but only with capacitors I have around. I need to lash out and buy a heap to truly test Gordons doublers. To date tho I have seen no evidence of doubling only increases are due to the increased excitation on the Gen ie when tested on a three phase supply no increase. Gordon notice you say you tested initially on single phase can you show cct used so I can evaluate here without buying in heaps of caps? Also Gordon can you explain how you see the double working in a 1/2 cycle by 1/2 cycle sequence? I very much get the feeling you see caps as isolating the AC and then adding the DC outputs of the rectifiers in series. This could be achieved with transformers but not IMHO with caps. If the cct? works as a doubler you would not need non polarised caps. but I notice no DC charging only AC. In cct using the bridges it does as Gill observed have for one 1/2 have one cap in series with batteries returning via the other cap in another phase. this second cap in the +ve phase is meantime in parallel so could in theory charge to a different level than its discharge but the values I have here show no evidence of this. Better shut up until I have results that can be publised Herb |
||||
| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Herb, you need to visualize a synchronous adding of the AC voltage at any moment on each phase with the cap voltage multipliers, with DC isolation by the rectifiers. The caps are not used to increase the output emf of the windings The capacitor voltage multiliers are power matching components. The voltage gain is not fixed. The cap uF, the voltage across the cap, and the frequency controls the power. The system best matches the essentially constant voltage low impedance battery load, to the wind energy curve. We all know that the wind energy is a cubic power relationship to windspeed. A HAWT turbine blade is most efficient when the TSR is at an optimum particular value. The rotor rpm then should linearly follow the windspeed. The alternator produces output voltage proportional to rpm. So to get a cubic power relationship, the loading has to produce a squared current output. The power transfered by a capacitor in an AC arrangement is proportional to frequency and the voltage across it and the capacity.. These are the principles working here. On the second part. This is what does happen with caps. I might suggest that the capacitor wiring is incorrect in your test setup, or you are looking for AC resonance. The arrangement is essentially 2 series cap coupled alternators feeding a battery through rectifiers, with the 2 battery loadings stacked to be in series. If you can wire a series cap arrangement, then this should be no problem. The caps provide DC isolation, so the outputs can AC add. I suspect that loosely coupled transformers could be used in a similar way. You would need to make the transformers, wheras caps are mass produced. Gordon. become more energy aware |
||||
Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Amack. I'm not sure what you mean by I think you mean 2 coils/poles ( or 6 poles if you count the 3 phases ) in series, times 7. Have a look at this page and see if its a 7X2C? Also need to know what wire thickness the stator is wound with. This page will tell you. Let us know what you find out. If it is a 7X2C and your using a 100 or 80 series stator then that would explain why it only works at high rpm. A 60 series may work, but you would need more capacitance. If its a 80 series, you would probable need more coils, 4 or 5. This would mean a few coils left unused. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
||||
| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Amack, BTW do you have many lost tourists around your area???? Those metal things on sticks by the side of the road are not normally council rubbish. Ok guess we call it recycling? the new in craze. Im curious what the sign said.??? Pete. Sometimes it just works |
||||
| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Round street signs are not common. Not much wind today, so windmill only just at 24.6V battery cutin. Tests on the cap voltage doubler connected to 24V nom battery. Volts across each DC output of bridge rectifier was 12.25VDC & 0.1VAC on the top rectifier, and 12.35VDC & 0.1VAC on the bottom set of rectifiers. The input voltage to the AC input to the bridge rectifiers was 9.6VAC between phases on the top rectifiers, and 9.7VAC on the bottom set of rectifiers. If there was any problem with the arrangement, then high AC ripple would appear on the centre DC connections between the 4 bridge rectifiers. There is no filter capacitance or battery across this connections, even though there could be. Any problems with the arrangement would result in loading problems, either at the upper power levels, or the lower power levels. The single phase arrangement reduces the cap component count to 2/3 of a 3phase setup. Probably not really worth it. In my case, the theory of summing separate cap coupled AC ccts correlates to measured results. My battery was a slightly lower voltage, and the mill a slightly higher AC output voltage, and there was approx 5-10W power. My mill would not normally charge the 24V battery with only 9VAC output, but does with the voltage doubler. Hard to tell what the wind energy was at the time. Windspeed was 2-3m/sec. windmill output was at approx 10-15Hz. As the rpm increases up to cutin, the battery loading holds the rectifier output voltage quite constant at the battery voltage. As the windmill rpm continues to increase, the output AC emf rises. The voltage across the caps increases, as the battery will hold the rectified outputs at a quite constant DC voltage. This results in a non linear current increase to the load with increasing rpm, as the current is proportional to the frequency as well as the voltage across the caps. At an rpm where the mill output emf is sufficient, the normal rectifiers start to conduct as well. At this point the voltage doubler AC input voltage is clamped by the main rectifiers, and power through the caps increases proportional to frequency only. The total output power at this point is the sum of the power through the normal rectifiers plus the power passed by the cap voltage doubler. A similar effect happens with a trippler etc, but with smaller caps, and lower power levels. Hi Herb, You may wish to show the output you would expect, and this can be compared with the experimental result. In this case, galvanic isolation is not required, only AC coupling. Gordon. become more energy aware |
||||
| herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Hi Gordon I will at the moment disagree with your way of thinking, but would'nt the world be a boring place if we all agreed all the time. Being in the back of beyound I can only use componets at the moment from my considerable junk box, but will continue to test. Will use try single phase versions to simplify your theory. My approach to analysing the going on's in rectifier ccts is to follow 1/2 cycles paths tho their paths as Gill was doing. Better not hijack this thread further sorry amack. |
||||
| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Herb, The AC current in the caps goes a round about way to give the outcome. It is not a simple double. I will be testing the single diodes cct of a cap doubler presented in the article. I have not used this arrangement before. It looked OK, but I will check it just to be sure it works as well. I don't think this discussion is any worse than where the bits you make something from, come from. I will be looking at a possible simulation of what happens, to help the why aspect. There are really 12 areas of interest, namely the rising and falling of each cycle for positive and negative relative voltage transitions, and there are 3 phases. The instantaneous voltages and current flows in each time slice interact with the caps and diodes. A bit like a chess game. Have to heat the soldering iron first and then wait for some windmill output. Gordon. Gordon. become more energy aware |
||||
| AMACK Senior Member Joined: 31/05/2009 Location: AustraliaPosts: 184 |
Man Sorry I spoke.. GIZMO.. The winding I am useing is 7X2C 80 series into a 12 volt battery bank. I do have a 7X2C Delt ready to go also. DOWNWIND the sign was the other half of the failed tain from my first wind gen..why let godd free aly go to the tip. Herb.. It is a learning curve from reading others idears. I like to try thing then just talk about them. Feel free to discuss this topic further, Its not a hijack it's a talking point. I will by the end ot the week have the set up and wiring complete that was put forward. The caps were not put in heat sinks for the heat it was just to hold them in place. The cap holders were the heat sink out of the F&P washing machine control board. GORDON.. Can I use polarised caps and non polarised in the same set up is the are the same value and voltage? Eg. 2 x 200 uf back to back or 1 x 100 in the same wind gen?? Final thought... Is stagged wiring or caps the way to go to get the best out of a wind gen?  AGAIN.
*Note to self 1. Make it thick 2.Make it heavy. 3.Make it stronger than it should be. 4. Don't rush the first job as the second job will cost more and take mor |
||||
| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Herb, You may have noticed a change to the pics on the cap article. I have had the opportunity to test the discrete diode cct that was shown in the article. I did not measure voltage doubling on the simplified diode arrangement, so Gizmo has worked his magic. I have now made both arrangements, one with discrete diodes[pic has been removed from the article], and the other with full bridge rectifiers, wired as cap voltage doublers. Hopefully there will be enough wind soon to show photos of some measurements of the input AC voltage, and the output DC voltages of each system in real time on a windmill. I am still working on a way to show what is happening on paper. Hi AMACK, You could in theory mix the caps with the same value, as long as the DC caps are still paired. Gordon. become more energy aware |
||||
| herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258 |
|
||||
| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Herb, I will continue this discussion on this page. Gordon become more energy aware |
||||
 Print this page |
