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Forum Index : Windmills : F&P stator cut in Volts vs RPM table
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DaveP68 Senior Member  Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Hi All I've created 2 sets of tables for calculating what the RPM will be for the 3 common battery voltage systems described on this site. These tables are an additional reference to F&P stator rewiring page. F&P stator rewiring page The first table is for the 3 different 42 pole stators (60s, 80s & 100s).  This second table is for the 36 pole stator but with the 2 different rotor caps, white vs black.  *Please note where it states "Too Low" refers to RPM below 45 and "Too High" is above 165 RPM. Too low RPM is the possibility of stalling the wind turbine blades at start up. Too High the turbine will likely be free wheeling and produce little or no power in light winds. Hope this provides a rough guide to those new to here. There is always a chance of choosing the wrong rewiring system will likely render the stator useless! 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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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Nice work David. May I add a link on the F&P rewiring page to your graphs? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Hi Glenn Yes go ahead and do that as I wasn't expecting a rebuild of the stator rewiring page to fit these data tables in. I can also do some simpler tables for the staggered cut stator wiring page. 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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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
Good work Dave, Should help stop stators being mutilated by multiple cuttting trying to find right voltage etc. |
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fillm Guru  Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Yes good work and its is nice to have it all formatted like that. Sorry Dave but I will dispute the choice of what is regarded as too low and too high. Even the GOE which has incredible low Rpm power,but by low rpm I mean 90 ~ 180rpm range. I will guarantee 99.9% of blades and the GOE if loaded at 45rpm would stall ( load dependent ) to break free out from that rpm is difficult then requires more wind force and lost power. Most Blades have no problems spinning up to 180 rpm in under 3m/s if unloaded. My opinion for what its worth, the cut-in I aim for is 80 ~ 110 range and anything over 200 rpm regarded as too high. I could go into the benefits of te Cap Doubler and low resistance here but it gets more complicated than just a straight re-wired stator charging a battery. If you watch the GOE and (you will soon) it gets up to the 70rpm mark and then just accelerates from there in the lightest breeze even with iron core drag or slight cogging. Where I state previously for cutin ( I aim for ) is well clear of that lift point and would think as an example an aircraft would accelerate to past the actual lift speed before take off. I am sure you would know more about that than me. You have discounted what I consider the best configurations as being to high with the 80S & 100S for 48V and where a stock std 100S in delta goes very well. All the better Chinese generators that are marketed under different names Huaya , exmork, First Wind ...... 1~2.5kw all cutin around 200 rpm and the GOE blades or their Fiberglass blades have no problem in getting up to that speed in the sub 3.5m/s but its what happens after is different. Yes you can put more blades on but 3 has always been the the most efficient for power, balance and economics. I would say If it can be done with 3 then why put more. I would ask how you came to all the conclusions ? I assume you firstly worked out the volts per turn on each stator and with the knowledge of how many turns in each stator coil has and the calculated the rest ? Would it be better, Instead of having Too High or Too Low put the RPM value and allow whoever uses you table as a guide to decide What would also be handy and I assume you know , is the turns per pole for all the stator types to be included in your chart. PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Hi Phill Where it states "Too Low" I mean a Cut in RPM of 12, 18, 21, 24 or 36" I have included 42 RPM on the Delta side so should have said 42. It's there for all to see on the Delta table anyway. For "Too High" Cut in RPM I'm really referring to above 192 rather than the 165 (there is a 168 in the table). I just so happens 192 is the next highest RPM level above 168. So I chose not publish it and anything above that. Here are some Examples of "Too Low" RPM cut in levels; 60s Star 12V Cut in RPM's are: 1x14C is 12, 2x7c 24 That is way too Low. 80s Star 12V Cut in RPM's are: 1x14C is 18, 2x7c 36 still too low. Here are some Examples of "Too High" RPM cut in levels; 60s Star 48V Cut in RPM's are: 7x2C is 336 RPM That is way too High. 80s Star 24V Cut in RPM's are: 7x2C is 252 RPM That is too High. 100s Star 12V Cut in RPM's are: 7x2C 336 RPM That is way too High. 100s Star 24V Cut in RPM's are: 7x2C 672 RPM That is off the charts too High! 100s Star 24V Cut in RPM's are: 2x7C 192 RPM too close to your 200 RPM limit. As it turns out Calculations are derived from measuring the Volts at various RPM levels. Example a 42 pole 60s factory standard star is around 1 VDC per RPM out of a 3 phase rectifier. So 100 VDC out is around 100 RPM +- a volt or so (no load). 80s is 66.6% (2/3) of 60s and 100s is about 25% of a 60s (1/4). It's just simple math to create the tables. All very predictable when the stators are not under load which is exactly where cut in happens. Remember these RPM numbers are "cut in" values and don't represent the higher RPM operating range (above cut in) that power is "going" to be extracted from. I'm going to leave the data table as it is. Not wanting to cause any confusion to those who are new to here and that is exactly why I published in that format. 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 |
The stall speed of a turbine is dependant on several diffrent things such as blade pitch ,number of blades and diameter etc , you could have a rpm of 50 for example,with a load, and the turbine won't stall if it has a large enough diameter ,but a turbine with the same load,but a smaller diameter would stall,and same with numbers of blades,,, more blades, less likely to stall than a turbine with fewer blades.More blades for low wind performance, the most being about 8 or 9, 3 blades work well in mid to high winds,my turbine blades start lifting at about 65-70 rpm, with a cutin at about 75-77 rpm, from what I have seen with it, I could reduce the cutin to about 70 without stalling it. Haveing a high cut in rpm well above your lift rpm of your blades is wasteing the energy in the inertia ,which could be converted to electricity to charge batterys or gridtie etc. So too high of too low cut in speed is only relevant to what turbine setup you have. |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Hi Fred Thanks for your input. Without actually stating it above, the table is ONLY a rough guide and indicative of what to expect on a battery operated system. Another factor to take into account, is that the F&P stator (Not for other types of PMA's) only takes a small amount of current at cut in. It doesn't grab the shaft and want 80W at say an 80 RPM cut in speed. I't will be around 0.4 Amps @ 12 VDC vs 0.1 Amps at 48 VDC and that is ONLY about 5W at cut in (not much of a load). Increasing the RPM by only 15% the current will jump up by a factor of 10x, so will now be 4 Amps and 1 Amp respectively (12V vs 48V system) with power output now 50W in both cases (more wind to drive blades too). A 15% increase in wind speed translates to 50% more shaft power to drive the stator. Also when the batteries get to full charge that is another 15% increase in the cut in speed as the voltage climes from 12V to 13.8V or higher on that type of system. My graph of the difference between MPPT and battery systems shows this in the battery part of the graph (it's not a vertical line). 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 |
I hope that this graph IS added to the sites f n p page , so it does not dissapear off the site and hard to find in old forum posts, no use to the newbies if they can't find it. |
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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
Hi Phill Be great if you publish some results of what you regard as your "best configurations" of the 80S & 100S for 48V. The 100S in delta at 48V by my calculation would cut in at 333 RPM and yes if it gets to 500 plus RPM would make upto 450W. Try using a 36 pole stator Delta cut 4x3C using a black rotor cap, 48V cut in will be 281 RPM. Power output could reach 650W above 500 RPM. 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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| DaveP68 Senior Member Joined: 25/11/2014 Location: New ZealandPosts: 292 |
A word of caution re using the above tables. They are NOT to be used with the "The capacitor voltage multipliers" described on this site. That is why I put the "Too Low" and "Too High" entries in as to not cause any confusion. They where ONLY ever meant to be used for calculating cut in RPM for direct feed into rectifiers that are charging batteries or an MPPT inverter. Here are 2 new tables for use when using "The capacitor voltage multipliers" (2x & 2x + 4x) which by the way will give a significant increase in power output to charge batteries.   The "Too Low" and "Too High" entries still exist to simplify the use of these dedicated tables. Also cut in RPM will very much depend on floating battery voltage. I.e. a 42 pole 100s stock standard wired Delta mode will cut in approx 83 RPM using the 2x + 4x Cap Multipliers into battery at 48V. With a good charged of 53.2 V on battery would shift the cut in approx 92 RPM same setup. "The capacitor voltage multipliers" can be a bit tricky to build as the correct choice of component values is required for each different voltage operation i.e. 12 or 24 or 48V. More tables for 36 pole etc, to follow soon. You can find the details here Gordons Cap Mod. 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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