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Forum Index : Windmills : 1.5 kW @ 600 RPM with PF correction
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DaveP68 Senior Member  Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Have just tested a 36 pole copper stator with power factor correction capacitors wired 12x 1p Delta @ 600 RPM and got 1.5 kW output. The voltage was 57.1 VDC at 26.3 Amps. This was done on a lathe. This is a far greater output than I have ever achieved with a capacitor doubler. I'm no longer going to do any testing with capacitor doublers as they aren't as efficient in terms of power transfer. I think the gain in efficiency is greater than 10 %. There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :) |
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oztules Guru  Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
I think Herb in New Zealand did some work with this way back, and did strobe tests as well. From memory he noticed that the timing of the max peaks were shifted in space relative to the pole positions. This was apparently due to the MMF field positions changing some what. I never understood exactly why, or how, but this change was responsible for the increased EMF. I am guessing this MMF change modifies the way the MMF of the rotor reacted against the back MMF of the stator.... and somehow changed the relationship of the two fields, and where they cancel each other out to get the current limiting. Given that the synchronous reactions are now different, I can only assume we are using the phase shift attributable to the caps, to change the timing and relative reactive forces to our benefit. I wish I knew more about it, but your results speak for themselves in the real world... even if I can't understand the why or how. Your results are now making me more amenable to driving these units as a small back up genny arrangement, as the natural current limiting is useful in many ways. .......oztules Village idiot...or... just another hack out of his depth |
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| gpalterpower Senior Member Joined: 19/07/2009 Location: AustraliaPosts: 175 |
Hi Dave, Awesome work there, and all that from just one stator! You keep on sucking more and more power out of them!! Absolutely amazing! Do they perform just as well at a lower(say 100 to 300) RPM? Ive seen your pics of the blue PF correction caps in a recent thread and they look fairly small in size. Like to try one out on my mill. Are these an ebay item Dave? Marcus if it aint broke dont fix it!! |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
This could be some kind of resonance effect that peaks strongly at one particular rpm, but may also be disadvantageous at other rpm. Cheers, Tony. |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
There are a number of things going on in this set up and yes resonance is one. But in this case it works to your advantage, as wind is cube law. So low down the capacitors have very little effect if not no effect at cut in. No problem for high input voltage range inverters. This arrangement probably wont suit going direct into batteries. I had to do it at low voltage high current as didn't have very high voltage AC caps. The caps I used were 560 uf 250 DC back to back, so 280 uf AC which I had on had. If the stator was a Delta 1x 12p the DC output voltage would have been around 700 VDC way beyond rectifiers and capacitors. So the only capacitors I had on hand suited the 12x 1p configuration. I'm wanting to confirm the setup for Fred's new 40 - 540 VDC grid tie inverter. This will use a Delta 1x 12p stator. The Voltage for his setup will be limited to 400 - 450 peak. With the results from this test, I now know what AC capacitor to use on his system. There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :) |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
A 2.5 - 3 kw dual fnp windturbine is now possible, thanks Dave. awsom work. |
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| gpalterpower Senior Member Joined: 19/07/2009 Location: AustraliaPosts: 175 |
Well, I dare say that it's probably not going to work on my 24v setup. Just the same it's all very interesting and amazed how much power can be produced from one f n p. Your efforts into this subject Dave are greatly appreciated. Marcus if it aint broke dont fix it!! |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
yea Marcus, Daves test setup looks like it would suit a 36 or 48 volt battery system,with a mppt controller ,or a 22-60 volt input gridtie inverter. |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Hi Marcus A 24 VDC system might work with a Dual 36 pole copper staggered stator setup. The first stator (cut in) would be a 1x 6p Delta with 27-28 Volts at 80 RPM. Then the other half of this first stator is wired as 2x 3p Delta with cut in around 160 RPM. No power factor correction capacitors are required on this stator. The main drive stator is set up as a 12x 1p Delta with the power factor correction capacitor sized at about 300 uf AC in Delta mode as explained in my other topic. The total current could be as high as 45 Amps, so run some fat cables! Peak power of 1200+ W could be reached at 500 RPM or even before that. Think it's worth a try. Fred is correct in that the best output comes at 36 or 48 VDC battery systems or even better results can be achieved using 22-60 volt input grid tie inverter. David There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :) |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
A single 36pole fnp stator wind turbine with a 40-540 v input inverter and 3 of Phills blades at say 2.5 meters,about 1.5 kw peak output and would startup with a sparrows fart on a blade,lol would be simple to build for sombody, and have awsom watt hour performance. |
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| gpalterpower Senior Member Joined: 19/07/2009 Location: AustraliaPosts: 175 |
Well over the past few months I have managed to get my hands on some 36 pole copper stators. Best place I found to pick these up were at the tip, scrounging thru the white goods section. I definitely got some funny looks! As yet I only have one black rotor, but I'm always on the lookout for the second. Probably heaps in NZ! Once I have all the required bits Ill refit and reconfigure them to the mill. Ill definitely give it a go. Ill need to fit another rectifier and PF correction caps. Its gonna get tight in there for room. So where do I pick up the PFC caps from as mentioned in your other thread? They don't look that big! Just one question that my feeble brain is trying to understand.... What is the difference between a cap doubler setup and PF Correction caps? Is it the way they are configured? Marcus if it aint broke dont fix it!! |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Hi Marcus Yep once you get that other black rotor cap max power extraction can be achieved. Power factor correction capacitor at a "guess" at this stage should be 6x 680 uf 250 VDC wired back to back as pairs then in AC delta configuration. RS components 680 uf 250 VDC capacitors. Haven't done a test yet for 24 VDC system so not sure of results. Cheers David There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :) |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Just realise that those 680uF capacitors have a maximum ripple current rating of 1.9 amps. Cheers, Tony. |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
You have picked up on a good point if it was required for continuous operation in a power supply providing filtering for DC. The ripple current rating of 1.91 Amps is for 100 Hz. The F&P stators will output well above this frequency per phase exceeding 150 Hz at times as high as 240 Hz. That makes a big difference to the ripple current rating which is mostly calculated from the operating frequency for it's reactance value. Under most conditions on a wind turbine's not going to be above that current of 1.91 Amps @ 100 Hz (more like 3 to 4 Amps at 150 to 200 Hz range) all the time. Yes it might go 2 or 3 times that 1.91 Amps at "peak operation" for short periods but the reactance value will be lower anyway. They can operate up to +105 deg C! If the wind turbine is in an area where the wind is providing a more continuous high currant above 1.91 Amps @ 100 Hz per capacitor then use a different configuration. Like I said haven't tested it so use at your own risk... There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :) |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Another thing I noticed when looking at the wave forms on a scope of the current circulating in the capacitors is the number of 3rd, 4th, 5th etc order harmonics. These make the capacitors reactance drop even further thus increasing their ripple current carrying capacity. There are realities if you do not accept, will lead to frustration because you will be spending time on wrong assumptions and the results cannot follow! The Dunning Kruger Effect :) |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Maximum rated ripple current is determined only from permissible temperature rise, which also strongly effects its expected life. Its the rms current through the internal resistance of a very long length of some extremely thin wound aluminium foil that creates the heating, not specifically the waveform or the frequency. Electrolytics are basically designed to filter dc while having very small physical size for the large capacitance and energy storage. For very high ac current, solid film capacitors would be better. These are routinely used for power factor correction or for motor starting and running. Low esr electrolytics would be much better than crappy standard aluminium electrolytics because the method of construction greatly reduces the internal resistance and raises the ripple current rating. Electrolytics are fine for testing and experimentation, but if you want something that is going to be long term reliable (especially for a commercial product) thought probably needs to go into choosing a more suitable capacitor type. Cheers, Tony. |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
Most of what Dave is doing is testing ,its all about trail n error,I think he was only making a suggestion to Marcus as to what capacitor to use. what capacitor type would you suggest Tony? |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Electrolytics are fine for testing. For lower values up to about 50uF, those white power factor correction capacitors have suitable ratings. Something like these: https://www.ebay.com.au/sch/i.html?_odkw=capacitor+i0uf&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR2.TRC0.A0.H0.X run+capacitor.TRS0&_nkw=run+capacitor&_sacat=0 For something slightly larger, motor start/run capacitors might be worth a look: https://www.ebay.com.au/sch/i.html?_odkw=power+factor+correction+capacitor&_osacat=0&_from=R40&_trksid=p2045573.m570.l13 13.TR0.TRC0.H1.Xcapacitor+240v.TRS0&_nkw=capacitor+240v&_sacat=0 Cheers, Tony. |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
cool, thanks Tony |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Probably most convenient to stick with the electrolytics you have for now. But if you plan to build it up properly later on, in a metal box, then the larger and more expensive capacitors might be a good investment. Cheers, Tony. |
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