What to choose - delta or star??

[michal]

Hi everyone.

After months of  on-off works on my VAWT I'm about to finish this project in the coming weeks.

The turbine is a 3 blade (lenz 2) design (app 2 m diameter with 2 meter tall blades).
So far the wind turbine was turning without the generator attached to it and was performing quite well.

It's turning slowly even when I can't notice the wind, and Is quite resistant to strong gales (it won't do more than 3 rev per second, no matter how strong is the wind).

I also finished generator (app 500mm diameter axial flux design with 16 "N 38" magnets (12x25x50mm) on each side.
The stator consist of 12 coils wired with 1.8mm2 wire - 215 turns.

So far I have it fixed in my workshop in vice and I'm doing some testing.
With 1 rev per second I'm getting app. 4 - 4.5 Volts.
When I connect all 4 (same phase) coils in series I'm getting app 15-18V with app.1 rev/s.

I want to use the generated power to help heat the water in my water tank (300ltr).
I wonder which configuration would be more suitable for me delta or star?

I understand roughly the cons and pros of both connections, but would like to hear the pratical advice on what to choose (the length of power cable  required from turbine to heater will be app.20-25m).



Additionaly I would appreciate clarification on connection of star and delta...
I found on the following page:

 http://autonopedia.org/renewable_energy/Generators/pmg.html

diagrams showing delta and star connections:
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I'm confused with the coils in invidual phases being connected (-) to (-) or (+) to (+)
Is it because of the magnet configuration?
 I have my connected as (-) to (+) and so on - forming an open loop.

I would appreciate all the replies, as I want to finish this project ASAP.

Bye

Michal

[electrondady1]

congratulations.
that's a nice size lenz2
star emits a higher voltage
a lot of guys here leave the star / delta option switchable.
what sort of heating element are you planing to use
what are it's requirements

[michal]

As far as the heating element  - I'm not sure yet what sort of load to put on it.
I didn't have a chance to test the complete set under load, so I'm not sure what to expect.

I'm leaning towards 24v (hence star), and using controller (cascade type??) that will plug in additional heating elements as the voltage goes up (once the turbine goes over 1 rev/sec).

It's still work in progress ... 

[bart]

   Would like to see pictures and details of your VAWT build. Am leaning this way and would like to see what you have done. Nice size!

[JW]

Were not seeing the images of the circuit diagrams, or images.

check out this thread on how to work with pictures-
http://www.fieldlines.com/index.php/topic,146470.0.html Remember the image has to be less than 100K to post. (this way)

You can also link to a picture you have uploaded to the internet it uses [img/] [img] tags

JW

[michal]

Ok
I'll try again to upload pictures.
The problem is not with the size of photos (I have them below 100kb) but my browser (chrome) keeps giving me problems with "fakepath" etc.
This time I try to do it from firefox...hope it works





and here is the question from my previous post :
____________________________________________________________________________________
"I'm confused with the coils in invidual phases being connected (-) to (-) or (+) to (+)

 I have my connected as (-) to (+) and so on - forming an open loop as in the typical connection in series"

Is it because of different magnet configuration?
__________________________________________________________________



Below is one photo I took with old mobile while testing turbine only

I'll send more pictures once I'll finish all works.

The generator will produce up to 75volts when connected in star (during the test in my workshop) at around 3-4 rpm, but due to the weight of it, I don't thing It will reach that rpm once fixed with turbine (it's quite heavy set)

[hiker]

in star hook the coils in series for each phase[end wire to start of next coil and so on]--then hook all the end wires of the phase"s togeather--leaving the start wires only --for power out...[those go to your rects]  star = more volts less amps
i jerry rig mine--all the phase"s go to a sperate rectifier--then the output wires from the rects are wired in parelle....makes for more amps less volts...
not sure what i would do with yours--if you  get a lot of volts at a slow rpm--than i would think delta would be the way to go -or jerry rigged.....not sure what your load is going to be-voltage that is...if your going for high volts than star would be the way to go.......hope this helped some what...............?

[tecker]

I'd go for the highr\er voltage in this case . One can also place the elements in series to a charging circuit  . Most wet cell batteries will take as much as you can through  put in the their voltage range . If heating is your only objective  a bank of batteries works will with heat lamps .
Looks like a nice location and build

[michal]

And what about the lifespan of batteries.

How do they usually cope with excessive charging voltage and deeper charge<->discharge cycles ?

I wonder also how the heating element will cope with varied voltage, say 12-40 Volts in the long term if I don't use any voltage controller/stabilizer (like bank of batteries or other controllers) ?

[gww]

No controllers?
Every time I hooked my turbine to a direct resistance load it would never take off faster then the speed to make 1.5 volts that were taken by the rectifiers.  Maby agressive blade might change that but watching mine makes me skeptical.
Good luck
gww

[michal]

I should have explained it in more detail...

I saw on some website a controller that was adjusting number of heating elements , based on the input voltage.
The input was three phase, output was DC.
One could set it to turn on first heater at (for example) 12 volts and set additional increments of voltage that initiated additional heaters.
So if the wind was strong and turbine could oppose the resistance of connected load, additional load was added until speed/voltage stabilized.

But as far as I know, it does nothing to control the voltage (apart from plugging in more load), so if the wind is really strong, I would imagine that the voltage could go past the 12 v range...

Would that damage typical heating elements?

Do they work in wider voltage spectrum or will they be affected by increased volts (say from designed 12v to 30v) ??

[gww]

I don't know how a vawt works.  I know on my turbine the blade has a tsr speed for maxamim thrust or tourqe.  Being below this tsr due to drag makes the blades almost worthless where by the wind just goes through them.  If the voltage gets a load on them that slows the blades prior to reaching speed it loses everything.  I don't know if a vawt has a simular tsr requirement. 

I think that if you have a 48 volt or 120 volt heating eliment, that it will take lower voltage but not higher.  I don't know what the result will be ie: "half voltage making only a quarter of the heat?"

If vawt blades have to run at a tsr to be effitiant then you need to run unloaded to that point before putting a load on it and you have to have a regulated load so that it doesn't slam to a stop due to overload.

If I am saying this wrong or don't understand,  I hope someone smarter corrects me.

Hope this helps
gww

ps  twelve vote will element will start drawing at one volt and put load no the altinator.  you need to stop this by not reaching any load till you reach speed.   

your  - to = and + to + is paralel connection = higher amps and your - to + is series connection for higher volts.

[JW]

WYE, DELTA
 http://www.fieldlines.com/index.php?topic=145795.0



JW

 

[tecker]

The elements respond to a lesser wattage the way you would imagine . Just kinda low heat but if the charger is able to constantly push to the battery bank through that resistance they work good as space heat or heating some heat storage . When the batteries top off you can invert to get power to match the elements . It does look like your location is good for a constant wind . Get a good look at what the
regular power for yourself . ED setup those blades to continuous  low amp production that are quiet enough to be co built. with a structure
Ie build a house or out building add a turbine and batteries .
If you search you"lll find a post with Turbine mounted on his house .

[michal]

Thank you for all your comments.

I'll make the connection switchable ...star <-> delta
I'll keep an eye on the performance in star (preferred for higher voltage), and change if needed.


I'll keep you posted with the results, once it's tested (however it's still winter here....)

thx

[SparWeb]

I may be too late; I hope you see this...

I think I see mistakes in the diagrams you posted.  Is that exactly how you wired your alternator?  I can see some reversed connections.  It's not really "delta" though I think the artist was trying to accomplish that.  No wonder you're having trouble.

Do you have the same arrangement of coils in your alternator?  If you marked the wires in a similar way, then you need to do this:

PHASE 1:   A1+ _ A1- _ A2+ _ A2- _ A3+ _ A3- _ A4+ _ A4- *
PHASE 2:   B1+ _ B1- _ B2+ _ B2- _ B3+ _ B3- _ B4+ _ B4- *
PHASE 3:   C1+ _ C1- _ C2+ _ C2- _ C3+ _ C3- _ C4+ _ C4- *

- and all of the phases are tied together at the * point "Star point" and that connection must be isolated from the rest.  The result is a shape ( if you drew it) like the letter "Y", and the point where all three come together is the common connection.

I reccommend you start with Star wiring for your VAWT (knowing not enough information about your machine to make any more reasoned decision other than a coin-toss).  As you observe the turbine working with the alternator in Star, you can decide later if Delta will work better.

Generally (I mean very generally) when you change from Star to Delta, you change the turbine behaviour is a way that (a) allows it to turn faster before starting to charge the battery, (b) restricts further speed increases once the cut-in speed has been reached, (c) prevents the turbine from starting to turn, when wind increases from calm to strong enough to cut-in speed, (d) adds vibration if the phases are not identical enough to be balanced.

There is a third option, if you try Star, but find that it's not optimal, and Delta also doesn't work - but I'll go into that later and let's see if we can diagnose the wiring first.

[Flux]

I tried to keep out of this one. Normally an alternator with 12 coils and 8 poles will be overlapped coil. If you short pitch the winding to the point that it will fit on to a single layer I doubt that it is going to make much use of the magnets.

There are so many bits of information on the web that it is a gamble which you believe. I personally would look for another source of information on building alternators and leave that site well alone .

Flux

[SparWeb]

Oh my, I didn't even think of counting the magnets!  Now it makes no sense at all.

I hope this will not be too discouraging, Michal.  How far are you with the construction of your alternator?  Perhaps a new rotor can be made, or maybe it is not too late to remove the magnets and re-arrange them properly. 
Try reading this:    http://www.sparweb.ca/Forum/AXIAL_FLUX_HowItWorks.pdf     With any luck you'll get back on track.