Author Topic: New post need some help 17 ft machine connected to 6 kw aurora inverter grid tie (Read 9252 times)

jlyons700 · « **on:** November 29, 2012, 04:12:08 AM »

Hello all,
New to this form so just learning how it works.

I have built a 17ft wind turbine based on otherpowers design; the stator is 3 strands of #15 wire with 53 turns per coil.
The magnets we use are N42 grade, 3 inch x 1.5 inch by 0.75 inch blocks 16 of them on each rotor.
I have grid tied this machine using an Aurora 6KW inverter but have encountered problems.

The turbine is 250meters from the inverter and I have used 6 squared 3 core SWA cable to bring the power from the turbine down to the inverter.

The turbine is not producing a high enough voltage which means the turbine is spinning at a scary RPM and only producing 100 to 130 volts therefore the inverter is unable to draw enough power to control the RPM.

I am now starting to wonder if the stator needs to be redesigned of if I am not entering the power curve correctly.

It is my understanding that the inverter is limited to what voltage/current ratio it can accept.

I was wondering if anyone out there has had a similar experience or if someone knows where I am going wrong here.

Will get pictures up soon it is a nice looking turbine but it would be better if it started to produce power

Any advice would be a massive help.
Thanks

Frank S · « **Reply #1 on:** November 29, 2012, 12:14:58 PM »

You didn't mention how you have your coils wired . You just mentioned that you used 3 in hand #25 and 53 turns. are they wired WYE or Delta all in the same direction or UP/DN 3 ph with the coils in series or parallel or wired as single ph
also how do you have your magnets positioned on the rotors. double check to be sure you don't have the N facing a S on the opposing rotor. are you sure you have the magnets arranged as NSNSNSetc or could you have them NNSNSNNSS or some such.
These will be the questions the guys who can actually help you are going to ask and Pictures.
OH yes they will be asking about your air gap as well

Flux · « **Reply #2 on:** November 29, 2012, 03:52:43 PM »

I would imagine your 53 turn coils were intended for 48v battery charging. I expect the inverter needs a machine designed to cut in at about 100v so that would imply you ought to have used about double the number of turns for your application.

That would explain the high speed and it is unlikely the blades will go fast enough without excessive drag. If you are seeing something about 100v input then I expect your inverter is programmed near enough at least near cut in. I don't know that inverter but that sort of voltage would tie up for the SMA low voltage inverter.

There are people here who know the requirements of the Aurora inverter and I am sure they will help when they find your post.

Flux

nekit · « **Reply #3 on:** November 29, 2012, 08:15:52 PM »

I have a very similar 17' turbine and the same inverter and they work great. The main difference is mine is wound 118 turns. I hardly ever get above 250V, but starts up at low rpm at 60 V. If I ever do it over I might go with more turns, maybe 150.

The Aurora can work with 90-580 V DC, but makes full MPPT 170-530VDC.

You can see all my specs here http://www.fieldlines.com/index.php/topic,144309.0.html in the "Users Diaries" section.

Would love to see pictures of you setup.

Rob

jlyons700 · « **Reply #4 on:** November 30, 2012, 04:33:49 AM »

Hello and thanks for taking the time for posting.
The inside dimensions (the hole in the center of the coils) are 1 inch at the bottom, 1.5 inches at the top, and 3 inches tall. Each coil is wound with 53 turns using two strands of #15 AWG wire in hand. It has 12 coils, each phase has 4 coils in series, and it's wired in star.
This stator is for 48v battery charging it is based on otherpowers design. My thinking behind it was if the Aurora can cut in at 50v this stator would achieve this and stay building up the voltage, it is here I think I went wrong with this.
The magnets are set correctly I am sure but will double check Saturday when I take it down again.
It has been working I have seen it to produce 1900W but I had to shut it down, the RPM was starting to scare the life out of me.
I think a new design on the stator may be necessary.
Nekit how has your turbine been performing and nice work with the slip rings. If it is possible you might show me what sort of a curve you have programmed into the inverter also if you know the weight of your tail off hand it would be great.
I was hoping to draw full power at 250-300V but unfortunately the turbine cannot achieve this as of yet. I an sure that there are limits to the Voltage / current ratio the Aurora inverter can handle.
I have had a feeling myself that a new stator would be required which is not the end of the world but would be so much better if this worked if not I may have a 48 volt stator for sale ha.
Again thanks for posting much appreciated
Joe

Rob Beckers · « **Reply #5 on:** November 30, 2012, 08:34:04 AM »

Hi Joe,

The 6kW Aurora wind inverter has an input limit of 36A DC, and it starts working at 50V DC. I suppose that a 17-footer (5.18m diameter) should produce around 4kW by the time you want it to furl (around 11 m/s wind speed), assuming reasonable efficiency. That means you'll need it to reach roughly 120V DC on the input for that to happen (the 36A limit is input current, the 4kW is output power, and there's some loss due to inverter efficiency).

I've helped a few people get their battery-charging turbine grid-tied with Aurora inverters, it can work, but of course this depends a bit on how the turbine was designed. Ideally you want the MPPT curve in the inverter to load up the turbine so it's always running at the best TSR, for the entire range of wind speeds. If your turbine, when coupled to batteries, cuts in late and already runs at a high TSR by the time the wind reaches 11 m/s it will be difficult to get it to produce the higher voltage needed for grid-tie (at least not without grossly overspeeding, which will also make it inefficient). On the other hand, if your turbine is still going slow when on batteries at the higher wind speeds there's hope!

Do you have any means of measuring wind speed, preferably near the turbine on the tower? Any way to measure RPM, so you have some idea of what TSR it's running at? For a 17-footer at 11 m/s and a TSR of 7, it would be doing 280 RPM (or 4.7 revolutions per second). That is fast, probably noisy, likely scary, but for most turbines not a problem. It should be furling just about at that point anyway, to protect itself from higher wind speeds (and RPMs).

Without more information, making an MPPT curve for your turbine is an absolute crap shoot. If you want to try something, try this:

Code: [Select]

Wind (m/s)	RMP	DC Volt	Watt Out
4	       103	  50	 0
4.5	       116	  55	 280
5	       129	  60	 400
6	       155	  72	 700
7	       181	  82	 1100
8	       206	  93	 1600
9	       232	  103	 2300
10	       258	  113	 3100
11	       284	  123	 4000

This is based on just a single datapoint, which may be completely off for your turbine, of 123 Volt and 4kW out. The RPM is based on a TSR of 7, which may be wrong for your turbine as well, but if you have a way to measure it at least you'll have some idea if the turbine is over/underspeeding vs. wind speed.

In any event, if you post the design TSR of the turbine (where the blades run most efficiently), number of poles of the alternator, unloaded AC voltage (phase-to-phase) vs. RPM, and phase-to-phase resistance, I'll run the number and post an MPPT curve that should be a little more on target. The blade diameter is exactly 17'?

Now, this probably sounds funny since you're having trouble reaching higher voltages, but I see lots of Aurora inverters getting destroyed due to overvoltage. They are very robust inverters, and this is just about the only way to kill them. It's amazing how fast an unloaded turbine can spin up, and once it reaches 600V DC (about 440V phase-to-phase AC), that's the end of the inverter. You have to make absolutely sure that will never happen.

-RoB-

Flux · « **Reply #6 on:** November 30, 2012, 09:30:06 AM »

The only thing that I can add is that when tracking the wind speed at or near mppt the blades will be much faster than the stall operated battery charger and it may seem frightening.

For battery charging I would expect the blades to cut in at a tsr of about 7, run in lighter winds about tsr 6 and then head way into stall.

If you work at tsr7 in winds upwards of 25mph then it is going to seem really fast.

With the winding you have I would expect things to be rather fast and noisy if you get the input volts up to 150V.

Even if you doubled your stator volts you ought to stay within the rating of the inverter by a wide margin as long as you never let it run away. Furling will be of little use if you loose load and that is the time when you really need some form of clipper. It should never be needed in normal use but if the inverter comes off line there could be an issue.

With the present winding I don't think you would ever reach the voltage limit of the inverter and still stay near the thing if it run away.

Any chance you could reduce the air gap safely, that may give a useful increase in volts for the same speed.

Flux

jlyons700 · « **Reply #7 on:** November 30, 2012, 09:43:41 AM »

Thanks everyone,

I should have been more specific I am working off metric measurements so the blades are 16.4 feet (5 meters) diameter. I have two sets (windmax 16.4feet and a home made wood set).

The turbine has never been connected to batteries, I just constructed the stator from the design on the otherpower website and on the advice of Dan, a higher voltage would be easier I know now, but I am always learning.

Before full assembly I did some very rough testing with a hand held tachometer and seen 37-39 V at about 80RPM again this is just rough measurements carried out with a multi meter across two phases.

I have not purchased an anemometer as of yet they are quite expensive. But may have to as I know wind speeds are vital to the calculations.

This started out as cheap hobby now it has become an expensive hobby but all is worthwhile it looks good standing on the tower. I will post pictures later when I get home if anyone is interested.

I have a control unit that takes care of the incoming power before the inverter it has a overvoltage protection device connected to a large dump load therefore I am not too concerned about over voltage. It is not the aurora interface, it is a design specifically made for this and should work fine (I hope).

Do you think Rob if I stay adjusting the power curve that this stator may work. I am fearful of the turbine spinning out of control but maybe it is just me been over cautious.

Hi flux thanks for your input, the air gap is as small as it can be any closer may be dangerous. I was aiming towards a TSR of 7

It may be a wise option to take it down and carry out some more detailed testing
Again I will get some pictures up and a video to see what ye think.

Again thanks everyone all help, advice is welcome.

Frank S · « **Reply #8 on:** November 30, 2012, 10:38:21 AM »

[This started out as cheap hobby now it has become an expensive hobby but all is worthwhile it looks good standing on the tower. I will post pictures later when I get home if anyone is interested.]

Never heard of a cheap hobby remaining cheap or a hobby for very long

Rob Beckers · « **Reply #9 on:** November 30, 2012, 02:31:33 PM »

Joe, if you're afraid of overspeeding, set up the control unit to kick in at, say, 140V DC. So the turbine will have a (dump)load on it at that point. With grid-tie inverters the turbine will always have times that it runs unloaded: Every time the wind picks up from nothing it will take time for the inverter to start up and connect to the grid, and during that time the turbine runs unloaded. What I'm saying is that you should count on the rotor being unloaded, and have a mechanism in place to protect it.

So, do you have a multi-meter that can measure frequency? If you tell me the number of poles/magnets on the rotor, I can tell you what frequency the AC waveform will have vs. RPM. With that, and a light wind, you could measure the unloaded phase-to-phase voltage vs. RPM.

You mentioned the diameter so we have that one. I would also need to know the phase-to-phase resistance (you can measure it at the end of the line, before it goes in to the rectifier, that is fine), wait for the turbine to stand still before measuring! You mentioned it's wired up in wye-configuration, and we will assume it's meant to run at TSR=7. If you could get me those missing numbers I'll be able to tell you with a lot more accuracy if the current stator will work for grid-tie.

-RoB-

oztules · « **Reply #10 on:** December 01, 2012, 02:04:37 AM »

If you can get a half dozen microwave transformers of the same physical size, you could tear them apart and rewind them into a 3 phase 1:2 step up transformer.
If you place it at the tower it will also lower your transmission losses.

I use microwave transformers extensively for their lams, as they are usually free to get hold of, and make good toys to modify into whatever you please.

If your lucky, and they have all got the same E and I lams, you can make bigger or smaller trannies to suit whatever your doing.

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

nekit · « **Reply #11 on:** December 01, 2012, 11:05:30 AM »

Joe,
Looks like your getting some good advice. I can't say enough good things about Rob Becker. He has helped be get my MPPT curve tuned in. You can see it on page 4 of my dairy post. Flux is a great help to everyone here.

If you try and measure your frequency for RPM you will probably need to filter the signal. Here's what Flux helped me with and worked

"I have not found many multimeters that will measure frequency directly from wind turbines. Nearly always I have had to include a filter to remove the offending higher frequency mess. Something as crude as a series 47k resistor and shunt 0.1uf capacitor is often good enough. Some of the more up market meters seem capable of reading frequency to the mHz and are very difficult indeed to filter.

Even if you get stable readings you need to satisfy yourself they are correct.

Flux"

Until I figured out the RPM at various wind speeds I really wasn't able to tune the power curve.

When you turbine gets spinning at 250rpm it can be a little scary, but you get used to it after awhile. Just make sure you have well balanced blades.

Hope this helps. Would love to see some pictures of your setup.

Thanks,
Nekit

FYI My turbine seems to run in the 140VDC-250VDC, about 120-240rpm, in 10-25mph winds with my curve

jlyons700 · « **Reply #12 on:** December 03, 2012, 04:55:18 AM »

Hi all,
Thanks so much for your help so far, I spent the weekend looking at the wind turbine and sure enough there was no wind, Murphy's Law was out in force.

The control unit can be set to cut in the Dump load at whatever is the desired voltage so this should help prevent the over speed issue when the turbine is unloaded, this was my thinking from the start.

I do have a multi-meter that can measure frequency but unfortunately the wind let me down. And will not be back to the turbine site for a few days (Travelling with work).

What method is best to use when measuring the frequency with a multi meter??.

The wind turbine is a 16 pole machine.
The magnets we use are N42 grade, 3 inch x 1.5 inch by 0.75 inch blocks 16 of them on each rotor.

I believe I am missing numbers for what is mentioned below,
â€“   phase-to-phase resistance.
â€“   frequency.
â€“   unloaded phase-to-phase voltage. in a light wind (My neighbour has a hand held anemometer but it looks a little dodgy and would not be 100% on the accuracy of it)

Hopefully I will get these soon but I am away for a bit with work at the minute.

I also tried to upload pictures and was unable is there a technique to this or am I missing something silly.

Again thank for all the help.
Joe

nekit · « **Reply #13 on:** December 03, 2012, 07:10:33 PM »

Joe,
To post pictures you need to click on "Attachments and other options" under the area that you type in your reply. The pictures can only be 100K in size.

If you need to I can give you my email address and you can send them to me, then I'll post them.

Rob L.

jlyons700 · « **Reply #14 on:** December 05, 2012, 09:51:56 AM »

Hi nekit
I have tried uploading the pictures again and it still is saying they are too big not sure if there is a way to reduce the memory used by a picture. If you send me your e-mail i would be more than happy to send them on to you
Thanks
Joe

nekit · « **Reply #15 on:** December 06, 2012, 07:47:50 AM »

Joe
I sent you a private message

Nekit

jlyons700 · « **Reply #16 on:** December 11, 2012, 02:09:48 PM »

Hi Nekit,
I have sent you a PM containing pictures and also tried include a video,
If possible you might post them for me.
Thanks
Joe

nekit · « **Reply #17 on:** December 12, 2012, 08:26:37 AM »

Joe,
Here's the link to the video you sent me.
https://skydrive.live.com/redir.aspx?cid=9209a3086e7a4507&page=self&resid=9209A3086E7A4507%21179&parid=9209A3086E7A4507%21123&authkey=%21AHrbbFL_iNC-0n0&Bpub=SDX.SkyDrive&Bsrc=SkyMail

Hopefully other can open it too.

You didn't send me any pictures. If you send me some I'll post them here.

gww · « **Reply #18 on:** December 12, 2012, 01:51:10 PM »

I thought it was a skystream when I first opened it. I too would be interested in some more pictures. The vidio did not play well for me. How tall is your tower? Hope you get your mppt curve worked out with what you have now.
Cheers
gww

jlyons700 · « **Reply #19 on:** December 13, 2012, 05:30:07 PM »

Have tried again with the pictures hopefully this time they work.

nekit · « **Reply #20 on:** December 13, 2012, 07:46:19 PM »

Here you go

nekit · « **Reply #21 on:** December 13, 2012, 07:48:57 PM »

And more.

Nice work

nekit · « **Reply #22 on:** December 13, 2012, 08:03:36 PM »

Found these too. Hotmail put them in my "Junk" Folder

jlyons700 · « **Reply #23 on:** December 14, 2012, 04:26:33 AM »

Thanks Nekit,
Not sure what ye think of the pictures, now i need to get some time and wind to get the readings for ye and hopefully see some power been produced. Hopefully it wont be too long.
Joe

gww · « **Reply #24 on:** December 14, 2012, 02:04:54 PM »

Looks great
gww

nekit · « **Reply #25 on:** December 14, 2012, 09:07:58 PM »

Looks very nice. Hope you get some wind soon.

jlyons700 · « **Reply #26 on:** January 26, 2013, 03:37:16 PM »

Hi all,
Sorry for the delay on my part i have been out of the country with work for the past while but got some light wind yesterday and took some rough measurements.
Phase to phase resistance = 158.8 K ohms,
Frequency = 30KHz,
Phase to phase voltage = 40 - 43 volts
Number of poles = 16 per rotor

fabricator · « **Reply #27 on:** January 26, 2013, 06:24:44 PM »

Where did you get the tower, looks nice.

jlyons700 · « **Reply #28 on:** January 29, 2013, 01:27:07 PM »

Still at a loss with my suiation I need of help and advice if anyone has info

Rob Beckers · « **Reply #29 on:** January 31, 2013, 08:45:15 AM »

Hi Joe,

Sorry, wasn't following this thread for a while...

So we have:

Diameter = 16.4 ft
TSR = 7
16-pole alternator

You mentioned phase-to-phase resistance is 158 kOhm (158,000 Ohm); that can't be right. This should be a few Ohms, typically less than 10. It shouldn't be hard to measure this, just hold an Ohm meter between two of the three AC wires coming from the turbine (make sure it's not spinning and there's nothing connected besides the turbine).

Also missing is the voltage-per-RPM (unloaded voltage). I need to know what the AC phase-to-phase voltage is with no load on the turbine, and what the RPM is at that voltage. If you have a multi-meter that can measure frequency, just let it spin freely when you have light winds (and I mean light, without a load the turbine will run away in a heartbeat if the wind picks up), measure both voltage and frequency at some instant. I can calculate RPM from the frequency now that I know the number of poles.

It doesn't matter what RPM you measure this at, I just need one datapoint. Unloaded voltage is linear with RPM; twice the RPM will produce twice the voltage.

Last question: Is the stator connected in wye or delta? Most common (for grid-tie) is wye.

If all of this makes no sense whatsoever, find a friendly electrician or someone with a bit of electrical knowledge to help you out. With these answers I can calculate a fairly accurate MPPT curve.

-RoB-

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Author Topic: New post need some help 17 ft machine connected to 6 kw aurora inverter grid tie (Read 9252 times)