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BarkyJ
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Posted: 04 May 2018 at 11:12am | IP Logged Quote BarkyJ

@DaveP68
The part number of the Black rotors, is that 438503P? or is it something else?
That is the number I got off the F&P website, however I do not see that marking on the Black rotor I have here.







Thanks


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flc1
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Posted: 04 May 2018 at 4:52pm | IP Logged Quote flc1

Thats the correct black cap
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DaveP68
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Posted: 05 May 2018 at 2:59pm | IP Logged Quote DaveP68

Hi BarkyJ

Yes as Fred stated, that's the correct black cap.
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yahoo2
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Posted: 06 May 2018 at 6:27pm | IP Logged Quote yahoo2

BarkyJ wrote:

Want to give this a go, and see what happens, and if it works then I can look at upgrading/changing as time goes on. I just want to prove the concept first without spending a lot of coin (which I don't have spare at the moment).


there are a few things that are complete dealbreakers with turbines. if you mess these things up it will wear you down mentally.

tower blades bearings

A tower that doesn't position the turbine above the turbulent air on a warm day is pretty powerless. A tower that cant be lowered easily for regular maintenance is a complete liability.

Blades that have high strength and high aerodynamic lift are a miracle in motion and worth every cent you pay or minute you spend building. and they are quiet! poor blades are either not turning at all or one full rotation away from exploding shrapnel.

Dont even think about running tapered roller bearings on a stub axle, they are not designed to be run without constant preload and will rapidly fail. Use tiny amounts of the best grease you can afford, I use Moreys waterproof grease.

everything else is fun, negotiable and tinker-worthy

__________________
I'm confused, no wait... maybe I'm not...
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BarkyJ
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Posted: 07 May 2018 at 8:18am | IP Logged Quote BarkyJ

Thanks Yahoo2

No issues with the Tower, have some ideas for that already.

Blades - while I would love to pay for the right blades right away, investing in something I dont even know if I will end up using long term, or if the property is suited - I will just continue down the path I am on now and make educated guesses based on knowledge from on here and other systems I have seen, and just see where I get. Yes I would love to just buy everything right, but thats not really in my nature. Failure is just a part of learning.

Regarding the bearings - what are the suggested bearings to be used? Just standard sealed 6005-2RS's or something else? This I have not got to yet, as I am not up to that stage. But good to know.

I am designing everything I do in CAD, even the blades I am doing in CAD based on the 18mm wall pipe I have, and adjusting the angle of cut on them to see the different profiles I get out of a blade. I have a good friend who was an aircraft mechanic for many years, and he is suggesting I am going on the right track, so I will persevere. If it doesnt work, then I will just try something else. End of the day, its just time wasted, materials for these things have so far been free or cheap.

I do appreciate all input though. I just don't want to go down the track of buying everything, I would prefer to give it a go myself and see how far I get.
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BarkyJ
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Posted: 10 May 2018 at 9:24pm | IP Logged Quote BarkyJ

Can anyone see any issues with this - a response would be appreciated.

If I have a dual stator windmill, set up to output 24V or 36V in currently unknown configurations yet. If I put that through a 3 phase rectifier (or multiple) and then join the DC lines together, through a suitably sized MOSFET which gets PWM'ed based on wind speed, directly into a immersed DC water element in a hot water cyclinder.

I have found a dual AC/DC element.
2x coils rated 36VDC 450W each, 3ohms.
1x coil rated 240VDC 2KW, 30 ohms.

If I take the DC coils, put them in parallel, I get 1.5ohms. For a 900W element, if generating say 30V, I should be able to push 20A into the 1.5ohm load, which would be about 600W. Adjusting the PWM to adjust the load, should then adjust the voltage, of which I could go up to 36V.
So its essentially a dump load of 900W capability into water.

Does anyone see a problem with this?

This is just to test out the windmill itself, before I take the next step and do batteries and electroncs and dummy loads and all that - which I am still not sure if I will need or not, as this element likely will be the main load.

Would love to hear from someone.

Found the Element for $70 locally...

Edited by BarkyJ on 10 May 2018 at 9:25pm
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BarkyJ
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Posted: 10 May 2018 at 10:17pm | IP Logged Quote BarkyJ

Another question I have is about the wiring of the stator, and how RPM translates into voltage/current etc. This I havent got my head around yet.

I have seen the table:


Unsure if 36V is an OK voltage to aim for or not, if if its a bit weird, and I should be aiming for 48V.
Looking at the table, it is not clear to me what 'Cut in Volt' actually means. Does it mean that if I had a 4x3C 36 pole single stator with black rotor configuration, that when the rotor is spinning at 81RPM, I should be getting about 24V out? Or does it mean something else.

Basically as per my last post, if I have a 900W element 1.5ohm rated to 36VDC, how exactly do you regulate the voltage that comes out of the windmill - is it purely by the load put on the stator from the controller?

I assume if it had no load connected, it would just spin faster and faster and the voltage would rise until the point it was free spinning and not doing anything other than tearing itself apart?
But if you then apply a load to it, the speed will drop. Its then a case of adjusting the load, to maintain the best voltage you want to see, and you basically get the current which matches that based on the voltage and the wind strength?
so if I was PWM'ing my FET which adjusted the average load that the stator sees, then this should vary the load, which should regulate the speed, right?
But how do you figure out a starting point, to know at this RPM I should expect to see this voltage? Is that where the table comes in, and was my assumption right about that? 81RPM on a 2x3C 36 pole stator with Black rotor, I should expect to see around 24V?
Where is the limit exactly, at what RPM do these stators stop working right? How do you determine the max potential the system has?

Sorry for all the newbie type questions, having never touched one of these, and scouring posts and articles all over this site to pull together information, it is a little tricky to figure out.

Hopefully someone can help get some sense into my head.

Thanks


Edited by BarkyJ on 10 May 2018 at 10:19pm
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flc1
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Posted: 11 May 2018 at 9:07pm | IP Logged Quote flc1

Hi Barkyj
Cutin volts means the voltage that your inverter or charge controller starts to use the electricity(take current),, so if you have a controller or inverter that is set for a startup of 45 volts then when it sees 45 volts it will start useing that power and it will put a small load on your turbine ,as the voltage increases it will pull more current (amps) and put more load on and so on .
Yes ,,no load on your turbine means just that...no load, so its free wheeling its way to destruction lol.

I think from memory you will get(unloaded) 1 volt per rpm from a standered uncut 36pole copper stator with black cap, and if you cut the stator electriclaly in half (2x6 coils) then you will get about half a volt per rpm, and with a third cut stator (3x4Coils) you will get about one third of a volt per rpm.
I reckon if you aim for a cutin rpm of between about 75-95 rpm you should be ok,there is usualy a bit of useful inertia in the blades by then.

If you wire the stator in Delta you will get about 40% drop in voltage per rpm,but about the same % increase in current per rpm, and same with the previous stator cuts I mentioned you should get increase in amps relivant to what ever cut you have,,,,,so if you half the voltage ,,you double the amps, or current.
Once a load comes on you should see about 40% drop in voltage.
there are good charge controllers and solid state relays etc on aliexpress that are not too exspensive that you could use for what you want to do,

I know you want to do it all yourself, but spending a bit of money on the right things can save you alot of stress and sweat.
I think somebody will correct me if Im wrong ,in regards to your tower electricity travels more efficiently over distance if it is in AC form.
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BarkyJ
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Posted: 11 May 2018 at 11:13pm | IP Logged Quote BarkyJ

Thanks Fred

Good - So that all makes sense.

I have seen some charge controllers etc on Aliexpress yes, but I havent ventured too deep there yet. Because I dont want to use batteries to start with, and the Chinese explanations are not always too clear, its hard to know if they work direct with a load without batteries or not. Thats why I thought I would throw some bits I have together and make a controller myself, to start with at least.

Regarding stress and sweat, unsure if buying a Chinese controller will alleviate that or not, hah. But yes, I get what you mean, but I think I can do a pretty decent job at least to get something up and running.

Cable wise, AC or DC over a distance, is a good question. I know higher voltage (lower current) travels better than lower voltage (higher current), but unsure about AC vs DC. Tradeoff is then, 3 wires vs 2 wires, as the 3 wires of AC only save you maybe 1 or possible 2 AWG sizes, depending on length, so hmm.
10mm2 wire seems to be required to go 20m (40m round trip) - so there is $200 for the cable. If I need to go further, then its 16mm2 I guess.

How far did you have to travel with yours Fred?

Here is the same element as what I got coming.
https://www.trademe.co.nz/building-renovation/heating-cooling/heating-systems/auction-1626041473.htm
1x 60ohm 240V 2kW, and 2x 3ohm 36V 450W (Parallel for 900W 1.5ohm)

Cheers

Edited by BarkyJ on 11 May 2018 at 11:13pm
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flc1
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Posted: 12 May 2018 at 3:36pm | IP Logged Quote flc1

my cable run was only about 15 meters to the inverter, yep high voltage more efficient.
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DaveP68
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Posted: 12 May 2018 at 9:14pm | IP Logged Quote DaveP68

Hi BarkyJ

One extra point of note, the working output voltage of an F&P stator must rise in proportion to RPM and the current needs to increase at a rate of 2x RPM. This is also known as Maximum Power Point Tracking. This is the most efficient way to extract electrical energy out of any wind turbine.

Deviate from his rule on a wind turbine and you will drop the system efficiency dramatically. I.e. charging batteries directly from the output of the rectifier is an example of how to drop your system efficiency.

I have a working PWM circuit using MPPT, that can feed into a resistor of as low as a few ohms and happily operate up to 1 kW or more. The switching elements are IGBT's and it can start operating at a voltage of say 30 VDC cut in. Or be modified for high voltage application up to 500 VDC. My current unit has only been tested up to 7 Amps DC at 950 W. The MPPT part is a table programmed into memory that is pre-calculated.

Fred is correct in saying it's best to run a higher voltage system. The conductor size of the wire down the tower can be much smaller and system efficiency will be better overall. Also all the electronics including rectifiers can be located at a longer distance when using a higher voltage AC 3 phase.
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BarkyJ
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Posted: 14 May 2018 at 3:16pm | IP Logged Quote BarkyJ

Thanks Guys

Dave what IGBT's did you use?
I have some of these:
IRFB3006
and some of these:
HUF75339P3

If they cut in at the right time and never experience voltages over their limit, then they might be OK, but if voltage ramped up and got out of hand, then I would imagine they would pop.

So in my situation where I have a 36VDC Load capable of 900W, measuring 1.5ohm, what system voltage should I be aiming for? 48V? Higher?

Thanks
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