Author Topic: First storm, great power, hard on the nerves ! (Read 4903 times)

youmanskids · « **on:** March 11, 2010, 06:26:28 PM »

We had our first spring storm system blow thru here yesterday evening. I thought about shutting it down but couldn't resist the power possibilities.

It started out great with 15-17 mph winds giving me 15-20 amps at 27 volts (540 watts). the wind picked up to 27mph gusting to 38mph...thats when it got exciting. It was putting out 32-35 amps (at 30v that's 1050 watts) and peaked out at 42 amps (1300 watts). It started furling at about 900 watts and full furl at 1200 watts. Due to the turbulent gusting it seemed to over-speed just before it got to full furl and would briefly hit 1500 watts. The pole tip was flexing about 30 degrees from vertical and guy wire were bouncing all over! the blades were a solid disk of howling wood! YIKES!! about that time I thought I'd better try to shut the thing down

... I waited for a lull, and after a looonnngg 2 minute wait, (it dropped to about 250 watts) I threw the short-out kill switch.... nothing happened, it kept spinning at full tilt and in and out of furling. Having visions of a smoking stator, I switched it back on. No apparent alternator damage or blade-tower strikes, and fortunately the wind died down and the the rain started. I breathed a sigh of relief and was very satisfied with the Dans design.

I did learn a few things... 1) It put out the power expected, 2) It furled when it was supposed to (and power dropped appropriately), 3) It was tough enough to take a 40 mph beating, and 4) the kill swithch does not work in high winds! strong winds seem to be able to break it out of stall even when shorted out. In retrospect I think it would be better to let it fly in the storm so at least it would furl for some protection.

After this experience I am left to wonder if there is anything else I should be doing to protect it in a thunderstorm... should it be lowered, or let her fly? what say you all? Im not sure my nerves can take another storm, but I know they are comming anyway! I'll be praying for now and looking for input from your experience. Roger

Dave B · « **Reply #1 on:** March 11, 2010, 10:41:46 PM »

Get it to furl earlier by possibly making the tail lighter. Otherwise, the next storm that brings you more consistant winds like you just had just might burn it up. Dave B.

bob golding · « **Reply #2 on:** March 12, 2010, 04:02:14 AM »

what i do is have a spare set of 8 foot blades for the really strong storms so far it has been fairly quiet here this winter. only one 80 mph storm in november but it looks like the westerlies are on their way. it will depend on how easy it is to lower your tower but that works for me. the advantage is you only have to set your furling once for the 10 foot blades and it will work for the smaller set as well.

bob

DanB · « **Reply #3 on:** March 12, 2010, 04:12:33 AM »

I'm really surprised it wouldn't stop for you. I would expect it to stop when shorted even at 1000 Watts output, but if it wouldn't stop at 250 Watts that's really very strange.

It should furl earlier... be nice if it would furl at 600-700 Watts. Part of the problem might be your tower, you said it was flexing quite a bit. If so - that effectively increases the angle of the tail pivot.

Perry1 · « **Reply #4 on:** March 12, 2010, 04:16:43 AM »

Hello,

Where is your kill switch located? Perhaps there is too much resistance in the line limiting the braking. I would imagine a switch mounted at the tower base would have better effect. If you are brave enough to get to it.

Congrats on your new turbine.

Perry

dlenox · « **Reply #5 on:** March 12, 2010, 04:43:27 AM »

Any idea on how fast the RPM's were?

Dan Lenox

Volvo farmer · « **Reply #6 on:** March 12, 2010, 05:23:30 AM »

I think you might make a valid point about the location of the kill switch. Mine is a good 60-70 feet from the tower and I experienced the same phenomenon when trying to shut down my DanB 10 footer last fall. I also have a tower base kill switch, but like you say, that one takes a little more bravery to approach in a storm than a shed-located one.

youmanskids · « **Reply #7 on:** March 12, 2010, 05:32:05 AM »

thanks guys, you have some good ideas, changing out the blades sound like too much work for a few hours of bad weather once or twice a month, but mounting an electric wench to rais and lower it more easily (instead of the car) may be the ticket.

I also will try to lighten the tail. its 1/2 birch ply and about 8 square feet.

the concept of the flexing tower changing the tail pivot angle makes perfect sense, this would severely inhibit furling and alow higher output in the strong gusts. I'll also try to stiffen up the top 20 ft of the tower with rebar diagonals.

my kill switch is at the bottom of the tower, the only other thing I can think of is the fact that I only waited about 10 seconds for it to slow down, and when it didn't, i bailed out and switched it back on. maybe it takes a little longer to slow down? how long can the stator take the dead short before burning up?

anyway, thanks for the comments guys, as usual, they are helpful (the more brains I get involved, the better the outcome!) Roger.

DanB · « **Reply #8 on:** March 12, 2010, 06:00:16 AM »

So your tail likely weighs a lot more than what we do being twice as thick. And again, if the tower is bending that much (you said 30 deg) - that's a problem, not only for the tower but also for furling.

I wonder what your blades are like...

I'm really surprised it's not stopping fairly fast. Could be the airgap is too wide and its running faster than it should (a wide airgap will make it stop more slowly, or maybe not at all).

bj · « **Reply #9 on:** March 12, 2010, 06:32:02 AM »

Hi-just a thought, it sounds like everything on your turbine works, except that it furls late, but are you sure that your short switch actually works? I had a brand new one not function a while back on a non-related project, and it threw me for a while.

bzrqmy · « **Reply #10 on:** March 12, 2010, 07:09:24 AM »

I use air-conditioner disconnects. They are made for outdoor use, can handle any current our turbines can put out, and are cheap. 8-10 bucks at Lowes or Menards.

DanB · « **Reply #11 on:** March 12, 2010, 07:09:51 AM »

Hi agian Roger - can you describe your tower some? What is it made from, and are the guy wires just right below the blades?

Jason Wilkinson · « **Reply #12 on:** March 12, 2010, 08:55:47 AM »

Hi I say take it down next time,you were fortunate to have winds at only 40 mph in that "storm" . Here in the caribbean we can get winds exceeding 100 mph yes 100 mph. You were lucky that time.

Jason

youmanskids · « **Reply #13 on:** March 12, 2010, 12:18:16 PM »

the air gap is a bit wide, I did this to give more mechanical clearance and to flatten the power curve a bit. maybe not a good idea, I can try to tighten it up a bit, that means I'll have to pull off the front plate...UGH!! we'll see. thanks for the great ideas. Roger

youmanskids · « **Reply #14 on:** March 12, 2010, 12:19:55 PM »

the short switch works fine when its not spinning fast, it dosen't cog so i'm fairly sure all three are getting shorted.

youmanskids · « **Reply #15 on:** March 12, 2010, 12:30:25 PM »

hey dan, the tower is of sch 40 steel pipe. bottom 20 ft is 3 1/2inch, middle is 3 inch, and top 20 ft is 2 1/2inch with a 3 foot stub on top of 2 inch to fit inside the yaw bearing. My guys are 3/8 surplus utility cable, the top set is 8 inches below the blade arc at 56 feet, the mid set is at 38 feet. when the turbine is pushed back it bows back above the top guy attachments and bows forward below, then back to the midline at the middle guy attatchment... like an "S" shape. I think the top 2 1/2 inch pipe section is too flexable and needs to be stiffened up. this would keep the tail pivot angle correct and help with furling.

back to the air gap issue, I dont have a tachometer, but it seems to cut in at 8-9 MPH wind (less than 1 amp but is generating). that seemed right to me. should I take it down and hand spin it with a tach?

youmanskids · « **Reply #16 on:** March 12, 2010, 12:31:55 PM »

ouch, for now i think i will lower it. glad i dont live in hurricane country.

Ungrounded Lightning Rod · « **Reply #17 on:** March 12, 2010, 01:41:34 PM »

I'd be tempted to install a kill contactor, as well as a kill switch, at the base of the tower to remote-control it. Shut it down in a storm from the house. Then, if I decide to keep it shut down for a while, walk out and throw the manual switch at the next break in the weather and then cut off the contactor (to save power).

Ungrounded Lightning Rod · « **Reply #18 on:** March 12, 2010, 01:45:08 PM »

You can check that easily some light-wind day: Hang a voltmeter across one side of the switch and see if it goes to zero when you turn the switch on with the mill spinning. Repeat for the other side.

Ungrounded Lightning Rod · « **Reply #19 on:** March 12, 2010, 01:47:43 PM »

Sounds like you need a third set of guys.

youmanskids · « **Reply #20 on:** March 12, 2010, 07:41:12 PM »

yea, that was another option, to put a third set between the top and middle set. that seems more expensive than just stiffenig up the top section, I'll have to do the math and figure which is cheaper. it would take 80 feet of 3/8 inch rebar -or- 200 feet of cable/4 turbuckles/and 16 cable clamps. I'll have to think on that..thanks

ChrisOlson · « **Reply #21 on:** March 12, 2010, 08:55:32 PM »

I waited for a lull, and after a looonnngg 2 minute wait, (it dropped to about 250 watts) I threw the short-out kill switch.... nothing happened, it kept spinning at full tilt and in and out of furling.

Sounds to me like you got either too much air gap letting it "slip" when it's shorted - or you have a bad shutdown switch. At only 250 watts output, shorting it out should've stopped it dead in its tracks (in fact, at that output shorting just two phases should stall it).

--

Chris

Volvo farmer · « **Reply #22 on:** March 13, 2010, 05:56:43 AM »

I have no idea of the engineering differences between rebar and guy wires in your case, but I will say this: Every single tilt-up 60 foot tower design I have seen on the 'net has more than two sets of guy wires.

TomW · « **Reply #23 on:** March 13, 2010, 06:21:02 AM »

VF;

I concur, adding a set of guys is relatively cheap compared to the whole system and certainly cheaper than a failure due to flexing. Somehow hoisting more iron [beefed up tower] into the air seems a step backwards.

Just an opinion.

Tom

DanB · « **Reply #24 on:** March 13, 2010, 07:15:57 AM »

I would check it with a tachometer if you can. If it's too wide that will make the stop switch less effective. It will also delay furling if the blades are overspeeding.

I would also fit a lighter weight tail...

and shore up the tower.

All three of these things could affect furling.

freejuice · « **Reply #25 on:** March 13, 2010, 07:29:36 AM »

This might help,

I buy my wire from these folks...shipping is free....well at least in the "48"

I have bought several things from these folks and the shipping is fast, usually under a week....usually with a few days to spare

)

http://cgi.ebay.com/Wire-Rope-Aircraft-Cable-1-4-7x19-250-ft-Reel_W0QQitemZ150423023855QQcmdZViewIte
mQQptZLH_DefaultDomain_0?hash=item2305e930ef

youmanskids · « **Reply #26 on:** March 13, 2010, 08:51:14 AM »

you both make valid points, I've not seen any other 60 footers first hand before. If I can get cheaper cable (local is 69 cents/foot) then another set of guys would be better.

youmanskids · « **Reply #27 on:** March 13, 2010, 08:54:19 AM »

well in low winds it does stop dead-fast, but this time the wind was gusting up to 35+ mph, the lull I refer to lasted about 1/2 second. but I will try to tighten up the air gap some as one of the many changes/upgrades to do. thanks

youmanskids · « **Reply #28 on:** March 13, 2010, 08:56:03 AM »

thanks for the tip, that is alot cheaper than local.

imsmooth · « **Reply #29 on:** March 13, 2010, 11:45:13 PM »

I just had a big storm here with 30-40mph winds. The grid went out so I decided to throught he magnetic brake (shorting) switch. I waited for a lull and threw it. THe blades stopped instantly, and even howling winds could barely get them to crawl around.

youmanskids · « **Reply #30 on:** March 14, 2010, 07:02:34 AM »

yah, it sounds like my brake failure must be due to the wide air gap. Ill try it again after the fix. thanks again to all you guys for the input and great ideas! Roger

youmanskids · « **Reply #31 on:** March 14, 2010, 08:56:46 PM »

in retrospect i think i should have used 3 1/2 inch pipe for all three sections (all 60 feet) this would have solved the flexing problem with only 2 layers of guy wires...maybe..

.

Ronnn · « **Reply #32 on:** March 16, 2010, 12:15:40 PM »

Freejuice or anyone, is this size, 1/4" 7x19, what every one uses? Does the 7x19 describe the structure of the cable? Does this mean there are seven mini cables with 19 strands of wire wound into a 1/4" cable? I am planning a 60' 4 inch tower with a homebrew 10' turbine.

Ron

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Author Topic: First storm, great power, hard on the nerves ! (Read 4903 times)