ART Turbine Peak V to 3ph RMS V??? Help

[oneirondreamer]

I understand that when 3 sets of coils are properly arranged and wired together in 3ph, the output is 1.7 x the output of a single coil , so

47.16 * 1.7  =  80.17 V 3ph RMS  if wired star.

Then if I wire that in delta, it's *1.7 again?

80.17 * 1.7 = 136v     

?   Does this sound right?   

I understand there are 2 ways to get 3phase, one the standard using the 12/9 coil to magnet ratio ala Hugh etc, and the other using interleaved coils ala Ed Lenz with a 3 coil /2 magnet arrangement.   Using the 12/9 means that from my 72 pole array I could less coils per phase and since I was looking to be able to get high v, I chose the more difficult  3/2 interleaved arrangement.  Other than the difficulty to construct, can anyone see a problem with this?   There are countless references to the Hugh P. arrangement, and yet almost none to the Lenz setup... 

One issue for me is the resistance.  My 25 turn coil of 18g wire ran .25 ohm  so I expect a resistance of 9 ohm   higher than I'd like

I'll post a photo of the turbine and mag array tonight, gotta run

[oneirondreamer]

OK, so I won't be making that ferry, and have time to post a pic or two right now

FYI this turbine is 5m tall, and 2m wide at the base.   The alt inner dia is about 1m, with the centre of the 1"x1"x4" mags at about 1.3 d.    The turbine turns about about TSR 1.3.    It started up at very low speeds (5km/hr)  before I added 300lbs of alternator (144 lbs of magnets alone).   Now it seems to start up at about 8-10km/hr. 

The bearing arrangement is a bit cobbled together ( I had to add an extra bearing arrangement at the bottom to support the alt, and to deal with some other stiffness issues).

[bart]

   Sorry, can no help with with your questions.
That is a pretty looking vawt. Seen pictures of that style. Did you build it?

[oneirondreamer]

I designed and built it, though I've had lots of help at different stages.   Some people would say it looks like a Windside, or GUS, however there's big differences to my eye.   If you search for ART Turbine on youtube you'll find a couple of video's, mostly of the older version.   You can dig up my patent application if you wish.

https://www.youtube.com/user/drewartturbine

[bart]

   Wow. Those exhibit darn fine craftsmanship. Best of luck.
Could never do anything like that and if I ever do wind it would have to be along the lines of an Ed Lenz design.
Keep us updated.
Song on third video. Have heard that on another vawt youtube video. Some guy in South America?
Used to have it bookmarked.

[electrondady1]

hey i wondered what happened to you!
 happy to see you still working on your vawt.
could you send a link to a description or diagram  of ed's method?
i have seen ed do a three single phase stator  overlapped
i think it was 12 poles 36 coils.
i've only built one three phase alt.
it didn't work very well for my vertical mills
i  build single and two phase stators.
 every thing i have read in regards to
three phase, between the the star/ delta methods gives the higher voltage output to star.
 your showing more voltage for delta . i don't think that's right.

[oneirondreamer]

http://www.windstuffnow.com/main/3_phase_basics is where Ed shows his arrangement for 3phase.   

I haven't seen this arrangement discussed elsewhere which makes me a bit nervous about it but my tests show it seems to produce 3ph just fine (I hooked up 3 test coils, overlapping as per Ed's directions, put voltage probes on all, and found 3 perfectly overlapping phases.
   
The  advantage  of Ed's arrangement is that for the same size and configuration magnet array, you should be able to get much higher output at the same velocity, because of 2 reasons.   1 a greater number of coils, 2 a more even distribution of copper in the stator  allows for much more copper per volume of stator.
 
In practice in for example a 12 pole magnet array with 9 coils, you get 3 coils in series per phase.   With Ed's  arrangement your number of coils per phase is 1/2 the number of magnets, so 6 coils per phase, twice as many coils.   In the standard 12/9 arrangement the spaces in the centre of the coils may make up around 20% to 50% of the total area the magnets are sweeping.  In my way of thinking I've always looked at the holes in the stators of the more conventional axial flux alts as being an opportunity to get more output out of the same magnet array, however at the cost of much higher difficulty to fabricate.   Since I like building tricky things, I don't mind that, and because I have so much space in the base of my turbine but need to try for high voltage, I decided to give the ceramic mag route a try with Ed's coil arrangement.   

[electrondady1]

eds a clever man

[oneirondreamer]

I think so too.   Just to be clear, what I said was "you should be able to get much higher output at the same velocity", what I meant is that an alternator having more copper, in the right places, should give more watts, and a larger number of coils in series should be able to output more volts.   So Ed's design should give more watts, and a higher voltage at the same speed.   The tradeoff as far as I can is that the stator is much more difficult to fabricate.

[electrondady1]

overlapping stators are difficult but the time invested pays off with better output.

[oztules]

"I understand that when 3 sets of coils are properly arranged and wired together in 3ph, the output is 1.7 x the output of a single coil , so

47.16 * 1.7  =  80.17 V 3ph RMS  if wired star.

Then if I wire that in delta, it's *1.7 again?

80.17 * 1.7 = 136v     

?   Does this sound right?   
"

No It does not sound right. The delta will be your 1 phase voltage, and star will be delta X 1.7

So if a single phase put out say 10vac, then Delta will be the same. If you look at delta, it has three phases all delivering different potential at the same time.... but the Max V will still only be the voltage of a single phase group. ( current will be more in delta then single phase obviously )

If you look at star, you will notice your EMF is gotten from two single phase windings in series...... but mechanically/electrically out of phase by 120 degrees. The vector addition will be 1.7 X the EMF of a single phase..... ie 10v X 1.7= 17vac

The DC voltage will be your AC voltage X 1.414. This is because you get to have the peaks as your V max. .... so 17vac X 1.414 or 24vdc. for star or 10X1.414 for delta or 14vdc.  These peak volts will be where you start to charge the battery....... but this is the peaks only.

If you look at your countries three phase to single phase voltages you will see the same thing. Here we are 240vac 50hz for single phase. Our three phase is 415v If we divide the 415v/240v we get 1.7..... so from phase to phase we get 415vac from phase to neutral we get 240vac.

A practical example is... if we have a star wired motor for 415v, if we wire it delta, it will be nominally a 240v three phase motor........ so we can now use a VFD single to three phase converter and drive what was a 415vac three phase induction motor as a 240v three phase variable frequency motor.... or as I do, make a phase converter from single to three phase 240vac using caps and a three phase motor as a rotatory converter, and drive 415v star motors as 240v delta motors ( in my milling machine and brake press)... so it does work in the real world too.


As for the "hugh V's Lenze".....

For any given RPM and flux density, it is only the number of turns being cut by the changing field that vectorially add up to the output voltage. It does not matter which system you use. The interleave will allow for slightly better stacking of your after sheer power density, but for the room you seem to have, maybe that is not so important.

If you want higher voltage, simply use more turns per coil number. When space is at a premium, this will mean smaller wire to get the same mass of copper into the same space..... our resistance will increase with each extra turn, and with each smaller wire diameter we go to.... nothing is for nothing.

So the only advantage the interleave may have is that you may get the resistance down for the SAME number of turns.... but that is all you can achieve with it. The difference has been found to be not worth the extra effort, and crowding the magnets, and squeezing the coils a bit seems to make them on a bit of a par for my money.

Hopefully Flux will intervene and set us both straight. Chris Olsen has done some fine work with both serpentine, interleaved and standard. As I understand it, he runs standard 3:4 for the best results, with the least effort. He is a perfectionist, and no doubt will have done a very careful analysis of all systems before committing to only one of them..... and may have more to add..

In short ......the total turns per phase = voltage.... ( for the same number of RPM and flux density.)  Current is regulated by the resistance and your threshold for pain with heat.

Providing you have the forcing voltage to achieve it, any wire will support any current for a finite time. 1000A through wire the thickness of a human hair will  have a voltage drop of V=IxR..... and that drop X current will be the watts lost in that circuit.... survival will be measured  in nano seconds before the circuit breaks (vaporises), but a 3" busbar will support it indefinitely as the voltage drop will be very small.

Now we can see why we try to keep the R down in the stator....... but we do need R in the stator to allow for not stalling the rotor. If we could wind with no resistance, the prop will never go past cut in, as the zero loss stator will stall it at that point...... so we need a bit of everything, some voltage and some resistance ( unless using an MPPT converter) to make the system work properly.

All a bit of a symphony really


.................oztules