Axial Flux and Classic

[kitestrings]

Hi Folks,

We're working on a ~14' dual axial flux (more below) with load diversion on the AC side, or home-made 'clipper' (at least unitl the MS one is offered).  We're excited about the possibility of using the Classic.  I have a couple of questions regarding stator design and model choice and :

1)  If max Voc is key for protection, as I undertand it, and the unit can boost, why wouldn't it make sense to wind the stator for a lower voltage cut-in and let the unit boost in low winds?

2)  What model would you recommnend for our application?  Based on the spec's, I'm thinking that the 200 V unit is perhaps the best fit?

more details here:
http://fieldlines.com/board/index.php?PHPSESSID=736155546c17d02ed5a36edd7bcf4f04&topic=145104.0

Congratulations!  The hard work pays off (in statisfaction now, hopefully financially soon for you all).  And, thanks for any advice.

~kitestrings

[keyturbocars]

Hi kitestrings,

I'll let the real experts chime in here, but my understanding is that the Classic will not buck/boost at the same time.  It can be set up to do one or the other.  If possible, I'd say try to wind it to work with the Classic 150 if possible, since you will then get higher current handling capacity.
Ryan has some hands on experience with the Axial machines, so hopefully he'll be able to offer some better advice on winding the stator.  

I'm liking the way my Classic 150 is working with my turbine!  In addition to more power, I really like the ability to use the AC Clipper to keep turbine speeds under control.  I also like the fact that the Classic allows the turbine side voltages to go up (and current to go down).  This help reduce stator heating and further improve reliability.  More power and more reliable!  WIN-WIN!

Edward

[Halfcrazy]

Hi Folks,

We're working on a ~14' dual axial flux (more below) with load diversion on the AC side, or home-made 'clipper' (at least unitl the MS one is offered).  We're excited about the possibility of using the Classic.  I have a couple of questions regarding stator design and model choice and :

1)  If max Voc is key for protection, as I undertand it, and the unit can boost, why wouldn't it make sense to wind the stator for a lower voltage cut-in and let the unit boost in low winds?

2)  What model would you recommnend for our application?  Based on the spec's, I'm thinking that the 200 V unit is perhaps the best fit?

more details here:
http://fieldlines.com/board/index.php?PHPSESSID=736155546c17d02ed5a36edd7bcf4f04&topic=145104.0

Congratulations!  The hard work pays off (in statisfaction now, hopefully financially soon for you all).  And, thanks for any advice.

~kitestrings

The Classic Can not boost and buck in the same configuration. I would recommend would be to wind the stator for about 10 volts above nominal battery voltage so on a 48 volt system that would end up around 58-60volts cut in voltage. The decision on which Classic to purchase will depend on the highest voltage you want to run the turbine at. I can tell you the 17ft machine we built was very happy at 130-135 volts dc much more and it seemed to be spinning faster than I liked. So for this machine we could easily use a pair of 150 volt Classic's with the clipper set to 145vdc

The only time voltage comes into play when selecting a Classic for a wind turbine, (other than max operating voltage you want to run at) will be when you have a turbine designed to run free wheeling or that have there own clipper. The Bergey XL1 is an example of this they have designed a new stator to work with a Classic 250 and there turbine is designed to run unloaded so no clipper is needed.

[kitestrings]

Thanks this is very helpful.  i'm still thinking the 150 voltage range will be to low. especially given this slightly higher cut-in.

'imsmooth' posted an interesting shunt controller on the above OP post, but I have to look at it a bit closer.

Keep us informed on your collective systems.  We're poised...

~kitestrings

[kitestrings]

Ryan,

You wrote,

"The only time voltage comes into play when selecting a Classic for a wind turbine, (other than max operating voltage you want to run at) will be when you have a turbine designed to run free wheeling or that have there own clipper."

Being that the cut-in is at, or 10 volts over as you're recomending, battery input (48V nominal bank).   And, being that with mppt you will be tracking prop speed directly with wind speed - so one can expect something like 4 or 5 times cut in volts at full power at furling point - it would seem like voltage is the limiting parameter.

I understand staying under the max voltage is key, and that it won't happen without a clipper, homemade clipper, or dumpload (with redundancy), etc.  On the other hand, unless it is productive diverted load, it seems energy will be wasted.  Am I missing something?

We hope to place an order this week, so you're help is greatly appreciated.

~kitestrings

[Halfcrazy]

Well the VOC would be directly related to the rpm of the turbine. My experience here has been that my Other power style turbines are happy running 2-3 times the cut in voltage. If you truly want to spin at 5 times cut in speed than I would suggest a Classic 250 but that will come with a lesser ampacity. You may very well need to Classics anyhow a 14ft machine may be pushing the 6-7kw range pretty regularly? I guess my statement was more geard towards a balance of Classic capacity versus voltage limits etc. The Classic 250 is going to offer the greatest flexibility for a wide range of uses. I would be curious to see what the expected output of this turbine will be in watts? My experience with the 17 foot machine we built directly by the Otherpower plans has been great it will flat out peg 2 Classics when we are getting 60mph wind. I have seen over 9kw out of it a couple of times and it was doing 7kw with only 2 blades after we lost one

[Volvo Farmer]

it was doing 7kw with only 2 blades after we lost one

Does that mean you could see 3KW with only one blade? 

[kitestrings]

Volvo Farmer,

I like the logic.

Ryan,

Thanks for the response.  The Classic changes alot of the assumptions, and perhaps we need to scale it down a bit (rotor dia), but on paper, our goal had been:

1) to leverage the a bit more power in lighter winds afforded the slightly larger wind-swept area

2) furl reliably and early - under 300 rpm in the 14' configuration

3) load divert and/or clip to stay with the Voc max

4) design within a safe operating range of the (single) Classic

I'm not expecting the rpms to be anywhere near the 5x cut-in.  I don't think I could stand the noise for one thing.  Rather, I was trying to make the (albeit overstated) point that if we're starting at 58-60 volts, and the voltage rise is linear with repect to rpm, that it would likely be the limiting factor.

My preliminary estimates are that we'll be in the 3,500-4,000 watt range at Pmax.

That is some crazy output from your 17'-er!  Very much appreciate the real-world experience and feedback.  Just trying to make the best informed choices we can.

~kitestrings

[keyturbocars]

kitestrings,

Since you are building this wind turbine from the ground up, then it seems that it would make sense to try to design around a Classic 150 if possible.  It has the most power handling capability of any of the Classics.  Would give you the best bang for your buck.

You are more ambitious than me in building your wind turbine!  That's great!

Edward

[kitestrings]

Edward,

First off, congrat's on getting your system going.  I've been following your experience with it.  What is the rotor diameter of your mill?

Regarding our system, I understand the 150 has the highest overall power capability, but we will undoubtly exceed it's voltage limit (or continually be clipping to protect it).  That's okay if it is doing something useful, but otherwise inefficient.

I'm still leaning toward the 200 as a happy medium between voltage and current capability.

~kitestrings

[keyturbocars]

Hi kitestrings,

My HY-2000 wind turbine has a rotor diameter of 10 feet.  I continue to be surprised how much power it can output under high winds.  To give HY Energy credit, they did a good job designing the HY-2000 wind turbine.

Your wind turbine might need the Classic 200.  I'm just basing my comments based on my limited experience with my own wind turbine.  Even when I've programmed my Classic to limit turbine voltage to 110V max, I've still seen over 4000W.  At least in the case of how my turbine stator has been wound, it doesn't require high voltages to make good power in high winds.  So, the Classic 150 is a good match for the HY-2000.

Edward
   

[kitestrings]

Well, I'm seriously starting to rethink my stance here.  I'vwe been following Ryan, yours and others experiences.  Not the least of which is a Bergey 1.2 putting out some 2.3 kW on you-t!  I also hadn't previously seen his post on 'stacking units' as he's done with the 17' unit.  Seems like a solid approach.

We don't want to be penny wise and pound foolish.  And, I'd rather this not dictate the design.  Perhaps two 250's would make the most sense?  It would afford the higher power capability (5-6 kW), and have the highest buffer on voltage, perhaps allowing the 'clip' setting to be a tad higher?

~kitestrings

[keyturbocars]

That makes sense, kitestrings.  I was also thinking I'd go with a pair of 250's if I went with dual Classics.  I did my homework and studied the power curves on my HY-2000 turbine and chewed it over in my mind for a while, and I really believed a single Classic 150 would be a good match.  I concluded that it would be very close (and it is close to the capacity limit).  Thankfully, it turned out to be a good match.  I really don't want to spin my turbine any higher than 125V anyway, because I want to keep turbine speeds under around 750 RPM.  So, the Classic 150 worked out well in my case.

Edward

[Menelos]

HI There,

I am as well currently building an axial flux design turbine with 4.5 to 5 meters diameter.

From what I read, the maximum voltage handled by the classic 150 would be 150 Volts plus battery voltage, right?
So on a 48V Battery Bank, this would be about 200 Volts. So should I set the clipper to a maximum voltage of lets say 190 Volts then or is it 150 volts that should not be exceeded?

Anyway I will set my turbine that on light winds I will have TSR higher than design TSR to reach voltage early without it beeing too high in high winds when power curves are exactly matched.

Basically I feel that it would be verry nice seeing lets say 6 or 7 KW from that turbine...but thinking practicaly we only have those wind conditions a coupple times a year and also the battry bank must be able to deal with this. If the batteries are full, power is wasted anyway so I would be quite happy aiming a nominal power of lets say 4 KW at 190 V input Voltage into the classic (if that works and is not limited to 150 as asked above).

So I hope I can handle that with only one unit.

My most important question to the developers would be:

What happens if the clipper gets active...?
Will it completely cut off power from the classic or will it (via dumploads) only reduce voltage so that the classic can still continue working on "maximum" power output or will it just deliver everything to the dump load then?


Max

[niel]

the guys can correct me here if i don't get any of this right, but the 150 will only operate to 150v. the battery voltage addition is basically a cushion against cc damages. if it goes above 150v then a classic 200 or 250 may be in order depending on how high the voltage goes to. if it gets clipped, by say the clipper, then this just caps the voltage and some of the generated power is lost.

now as to the max power on one classic 150 for a 48v turbine would be 48v x 96a = 4608w.