Author Topic: minor problem (Read 3684 times)

Nando · « **Reply #1 on:** November 21, 2006, 03:38:04 PM »

Minor problem

WHAT I SEE IS A MAJOR PROBLEM, INDEED !!!!!!!!!!!!!!

Nando

dinges · « **Reply #2 on:** November 21, 2006, 03:45:01 PM »

Nothing Ghurd couldn't fix with a bit of hotglue...

DanB · « **Reply #3 on:** November 21, 2006, 03:51:12 PM »

I was thinking duct tape and bondo.

harrie · « **Reply #4 on:** November 21, 2006, 03:54:46 PM »

Dan is that vinyl ester around the mags, or epoxy?

Phssthpok · « **Reply #5 on:** November 21, 2006, 04:18:09 PM »

That'll buff out!

richhagen · « **Reply #6 on:** November 21, 2006, 04:23:20 PM »

Uhm, about that warranty? If I drop the mill when the towers only halfway up, can I get it repaired for half price, or half my money back? It still has half of the magnets.

I'm guessing that was from a pretty good fall, I hope the steel rotors didn't get bent out of shape. At best I am guessing it will need a new stator, recast the magnet rotors and replace any missing magnets, at least one blade-provided you can balance a replacement with the other two, a new tail board, and probably a bit of straigtening and banging about. I hope the owner has redundant sources of power, that's basically a rebuild. Rich

bj · « **Reply #7 on:** November 21, 2006, 05:22:11 PM »

DanB-- always hate to a busted genny. Almost brings a tear.

Large fix, and good luck. But you have the technology.

bj

DanB · « **Reply #8 on:** November 21, 2006, 05:39:15 PM »

This didn't fall (parts of it did - but most of it stayed up there).

Parts that fell -

a few coils - bits of broken resin - half a blade, and the tail.

DanB · « **Reply #9 on:** November 21, 2006, 05:40:32 PM »

Oh... forgot, about 16 magnets also fell.

richhagen · « **Reply #10 on:** November 21, 2006, 05:57:33 PM »

Tail stop failure? It looks like there's a gouge on the one of the surviving blades about the same distance out as the broken blade, and of course the tail has damage. Rich

WXYZCIENCE · « **Reply #11 on:** November 21, 2006, 07:00:13 PM »

DanB, so what really happened? Tail looks like it got hit by the blade.
Joseph.

arrick · « **Reply #12 on:** November 21, 2006, 07:04:58 PM »

I'm kinda new at this but that looks like a bonding failure on the inside rotor.That rotor is clean.What looks like a gouge on that blade I think is a sliver of loose wood laying on it.My guess is the magnets came loose and locked up the machine.Possibly the tail came around and hit the broken blade.If thats minor I'd hate to see what you guys call major.

Arrick

DanB · « **Reply #13 on:** November 21, 2006, 07:28:56 PM »

Its always sort of exciting trying to guess what happened...

this was a 10' 48V machine. It was the most powerful alternator I've ever put on such a machine - we used larger wedge shaped magnets and wound the stator with 125 turns per coil of #16 gage wire. I expected this one would run more slowly and there would be less heat in the stator - and... I expected it might stall the blades a bit. We did all this because it's on a very windy site that gets high sustained winds frequently.

Here is my theory...

The owners had the three phase coming down to a sort of 3 phase 'cutout' - which, if it ever saw more than about 600 watts for more than a certain amount of time (not sure what that time was) it would disconnect from the rectfier and connect to a 3 phase heater - each phase of the 3 phase heater was a 1250 Watt 120V baseboard floor heater. I think possibly... it couldve switched over to these, oversped - made too much power and burned out. Thats one possibility.

Downstream from that was another diversion between the rectifier and the batteries. When the batteries were full, the wind turbines DC output was disconnected from the batteries and hooked to a 200 watt (200 watts @ 48VDC) heater - unless the temp in the battery room was below a certain point, in which case it became a 400 watt heater (400 watts@48V). Possibly - the batteries were full and it was running this heater, in which case I expect it ran quite fast and it's hard for me to guess how much current might have been flowing.

It burned out on Tuesday - Monday we clocked 81mph gusts up here - but this was about 90 miles away out on the plains so who knows. Tues was less violent up here - only 59mph was recorded.

Nobody was around to see it happen. Its interesting - the resin on the edges of the magnet rotors is black (it got very hot) - probably from rubbing on an overheated/warped stator. My guess is it ran that way for a while till the stator came apart which in turn tore off much of the magnets/resin on the magnet rotors. At least 2 of the magnets hit the blades (one blade survived it - but clearly got hit because you can see a 'bullet graze' thats exactly 1/2" wide - it fits a magnet perfectly. The other blade was destroyed from hitting one or more magnets. Then the machine ran with 2 blades for who knows how long and I expect the vibration caused more stuff to fall off... including the tail.

I've only had wooden blades fail under the following circumstances:

they hit the tower
they hit the tail
they hit magnets

(no birds yet and bugs dont seem to hurt them)

That's my theory anyhow - theres not doubt in my mind that the blades hit magnets and Im sure thats what made the tail fall off. (damage from the tail is due to the fall)

I think this is probably the result of being connected directly to heaters which did not keep the speed down enough - a fast running machine will also furl later (or not at all) so it had no way to protect itself.

I've run these up to 700 rpm with no glue or resin holding the magnets on at all and the magnets never moved.

Thats my guess - the other possibility is that it simply burned out, but I've not had that sort of problem before with 10' machines so I'm suspicious that they're system of diverting the power to resistors may be the problem. it could probably be solved if the resistors were lower in resistance in order to keep the speed down - or maybe even stall the blades severely.

Only time will tell!

ghurd · « **Reply #14 on:** November 21, 2006, 08:31:15 PM »

It needs 'a drop of solder'.

Then hot glue.

What's salvageable?

G-

asheets · « **Reply #15 on:** November 21, 2006, 08:33:37 PM »

POST OF THE DAY!!!!!

kitno455 · « **Reply #16 on:** November 21, 2006, 08:37:36 PM »

do the magnets you have seem to have reduced strength? got hot enough by friction to reach the currie temp and started throwing them?

allan

Nando · « **Reply #17 on:** November 21, 2006, 10:43:56 PM »

DanB:

At such high Wind velocity with the resistive loads the generator over heated and melted the material holding the coils, also the magnets may have got very hot.

Even with lower resistive value loads the problem would have been GREATER because the stalling may have not occurred due to the high wind velocity.

This is exactly the reason we used a pitch controlled 10 KW wind mill, in an area that has periodic high winds, at least twice a year for several days.

What type of furling this wind mill, if any and the setting ?.

Over power generation without proper stalling, I think this is the problem

10' machine, what about a Pitch controller Hub for the new one ?.

Nando

Dave B · « **Reply #18 on:** November 21, 2006, 11:20:18 PM »

Looks like on this one both rotors were supported by all thread behind the wheel hub mounting plate ? Probably didn't contribute to the failure but seems like a much less stable design from a gyroscopic / balance standpoint than to stradle the hub plate and mount one rotor directly flat to it. My 16" rotors will be mounted this way with one bolted directly to the backside of the plate first and then the front rotor spaced with possibly a machined spacer sliding over all 6 bolts with the back holes of the spacer countersunk to slide over the existing nuts holding the back rotor on. 2 very rigid rotors with neither "hanging" or relying on just the all thread for support. It's just my opinion but I think on some of the failures we are seeing flexing of both the stator "mounts" and or rotor all thread causing the air gap to go by by when under load at speed and then a quick yaw and CRASH. There is an incredible amount of torque on that stator while under load and switching a load on and off at speed will jolt it like hitting it with a hammer. It's possible in this case the braking forces of switching the loads flexed things just enough to start the snowball effect. Maybe, Dave B.

DanB · « **Reply #19 on:** November 22, 2006, 07:23:51 AM »

Hi Dave - no, it may appear differently in the picture, but this machine has the back rotor mounted flat to the machined surface on the back of the hub - and the front rotor is on the front - so there is actually one bearing behind the assembly, and one in front. It's a very rigid arrangement and there's not threaded rod supporting anything here.

DanB · « **Reply #20 on:** November 22, 2006, 07:28:39 AM »

Hi Nando -

"At such high Wind velocity with the resistive loads the generator over heated and melted the material holding the coils, also the magnets may have got very hot.

Even with lower resistive value loads the problem would have been GREATER because the stalling may have not occurred due to the high wind velocity."

Right - so the blades run faster and even more current flows. I think that was a possibility.

"This is exactly the reason we used a pitch controlled 10 KW wind mill, in an area that has periodic high winds, at least twice a year for several days."

Yes, I expect pitch control might have prevented this... complicated though.

"What type of furling this wind mill, if any and the setting ?."

It was setup to furl early - due to the site it was on. But if it was running very fast that would change the nature of the furling system. Proper furling depends on a proper load.

"Over power generation without proper stalling, I think this is the problem"

Yes - me too.

"10' machine, what about a Pitch controller Hub for the new one ?."

No- keeping the load under control is much easier here and I believe that if we do that it can be reliable. We've made plenty of these without this sort of problem. A pitch controlled hub would be great, but a bit expensive and I expect very time consuming before we get it right. Something I'd like to mess with down the road - but not for this machine.

Gary D · « **Reply #21 on:** November 22, 2006, 08:39:51 AM »

Hi Dan B, Perhaps an approach that Zubbly is using might be what is needed. He has 2 sets of load kick on at different voltage values. If they would have had 2 sets of heaters of the same value as their first set up in that way, the blades most likely would have gone into stall(and allow furling)? I'm not sure where or what Zubbly scrounged those relays off of, but that might be just the ticket? Also Hugh posted something about needing time for the stator to cool off before switching from heating mode to charging mode (back in a different thread)... Take ALL of this with many grains of salt, just a few thoughts from the most electronically challenged person on the planet (probably)! Hope you can repair their machine, looks like it will take a bit of work! Gary D.

badmoonryzn · « **Reply #22 on:** November 22, 2006, 10:10:33 AM »

Those blades still look better than mine. Maybe you covertly shot a picture of mine! Kind off sneaky.

Badmoon

wayne · « **Reply #23 on:** November 22, 2006, 10:40:45 AM »

Sorry to see bad news Dan, I went through a big storm last week and wind score 3 and me 1. It really takes the wind out of a guy seeing everything broken. You do great stuff.

Wayne

DanB · « **Reply #24 on:** November 22, 2006, 10:50:32 AM »

It's more frustrating for the owners than me. Every time this sort of thing happens we try to make one or more things a bit stronger and I enjoy building them so it's not a big deal. Usually - a catastrophic failure is worth the price of admission and everyone learns something.

ibeweagle · « **Reply #25 on:** November 22, 2006, 04:17:23 PM »

would an electronic switch from star to delta work? Like RobD's design? turn on to delta when rpms get to high.just my two cent good luck ibeweagle

Kevin L · « **Reply #26 on:** November 25, 2006, 11:40:20 AM »

Seems like a better method of holding down these magnets is needed. Has any attempted thin aluminum strapping over the magnets that is then bolted down. Seems like there has to be be a better way, relying on epoxy does not seem to be all that reliable. Possibly epoxy and aluminum or SS strapping would provide better holding strength.

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Author Topic: minor problem (Read 3684 times)