18' Wincharger Hybrid update photos

[Dave B]

   It's moving along and here's the fun part of jacking down the front rotor. Although the coils are 15 turns less each than my previous I can actually increase the gap if I want and still have the same unloaded output per RPM as before.

  The legs of the coils are a little wider and now are basically all touching each other and the stator is slightly thinner at 5/8" and nicely flat on both sides. I squeezed coils slightly thicker than the mold to make my previous stator which was OK but this new one is much nicer and was easier to make with the coils resting just lower than the cover before the final cloth and pour.

  Time to tweak the gap and index everything so I can get it back together exactly the same back outside. Bought 100' of slightly heavier wire rope today for activating the brake. 200+ LB test for 3/32. The other worked fine but for as much as I ended up using it I wanted a little more security. If you think you have blades that may over power your alternator ... trust me that when the real winds come (and they will) you will never hold it back by shorting it out. Just something else I learned, I will never build a wind generator without a mechanical brake. What a joy it is to have that security besides the shorting technique.

  Blades are in the works soon, I can't wait to get this back flying with the new improvements. Updates as we go.  Dave B.  

[DanB]

Hi Dave - looking good.

'If you think you have blades that may over power your alternator ... trust me that when the real winds come (and they will) you will never hold it back by shorting it out. '

Yes...  the mechanical brake is a nice feature.  But ...  I would never build a machine with blades that will overpower the alternator in that way.  Every machines we've built for quite a while now will shut down quickly in about any wind if we just short even 1 phase (short 3 and it's very fast).  Perhaps Im too confident - but using the alternator to stop the machine is quite a nice way of doing things if the alternator is powerful enough - and if one phase will do the job then we basically have a redundant brake.  (any wire can fail and we can still shut down)

[Flux]

Interesting point. You certainly need a lot of magnet to guarantee the thing to stop on short circuit. For Dan the stalled operation is very peaceful and tame and has a lot going for it for battery charging, where the peak power in high winds is probably embarrassing.

Dave can get away with a lot less magnet as the voltage is rising with wind speed, thinner wire will still give an adequate rating up to the point where he needs to limit speed for noise and peace of mind. If he was to adopt Dan's size of alternator it would be even more efficient and probably if properly loaded with a cube law controller the 6 to 10kW figure would be realistic and it would still stop with a shorting switch.

Probably with no cube law controller the bigger alternator would make matching easier in high winds but it may worsen start up at the other end. It would allow short circuit braking.

Provided the alternator is powerful enough I think short circuit braking is ok. I have never done anything larger than 5ft without some alternative way of stopping it, but my things tend to be near civilisation and a run away machine would be a major embarrassment. I have always used the tail to stop it rather than a mechanical brake. As long as the connecting cables don't fail I think a brake switch should be ok with modern alternators, I started with wound field machines and in those days there were far too many failure modes to not have an alternative.

Flux

[Dave B]

Thanks guys for the comments. I may be a bit traumatized by the overspeed thing (once on purpose and the first by poor design) but now after using my mechanical brake (as well as shorting it out) I just plain sleep better. I would never have believed that my machine could  start up and then actually accelerate (briefly) to speeds that woried me with all 3 phases completely shorted. Albeit that this was in winds exceeding 50 MPH at times but still after experimenting with this in the basement before hand I could not believe how hard it is to turn.

 I will be shorting this now at the base of the tower (while pulling the brake on) as before this was done at my panel in the basement about 220' total run which added maybe an ohm or 2 of resistance. #8 down the tower and #6 to the house. I know this would have also contributed a little to easier turning while shorted but I have to give the main credit to the Wincharger Gottingen 222 blade profile. The concave front, no taper and constant pitch of 10 degrees for my 9' blades is creating a tremendous amount of torque and is just what I need for my resistive heating application.

I can't wait to get this back up flying, 30+ MPH winds and blizzard today would be testing the furling for sure. Dave B.

[jmk]

 I ran three phase #6 210' to my brake switch in my garage. With an 11/16 air gap on my 12' ( Hugh's ) machine it will start up in 40 plus mph winds and go into full furl. If I brake it at the tower it won't start up. It made a difference. I would like to have the manual brake too.

[Dave B]

JMK and others,

  Thank you for the information. I am quite certain that shorting at the tower base will help some instead of nearly another 140' or so away. I am also convinced my blades offer tremendous start up torque. It's not that shorting does not work for me and for the most part it has been satisfactory but I have seen the extreme like you have and with late furling besides it is a very helpless feeling indeed. (hence my mechanical brake back up even if the furling is properly set)

   I believe a flatter pitch, tapered blade (possibly higher TSR) would be less likely to start up in the high winds while shorted. My application is different in that I don't care to have a specific "cut in" speed such as the case with battery charging where the blades basically free wheel before the desired voltage level is reached. For the majority here who are charging batteries the flatter blades are not only easier to carve but perform very well. This because the higher low end torque is not really perceived as needed during this unloaded start up phase but rather the blades just need to get up to cut in speed and then beyond without extreme stall.

  All of us out here who have been doing this for a while now realize that based on the huge number of variables and for each application some things may work well for some but for other's it may not. Charging batteries and resistive heating are 2 very different applications for wind power. I hope posting my observations for my application can be helpful to other's who may want to heat exclusively with the wind. Comments are always welcome. Dave B.  

[Shadow]

And if youre dealing with a burned out stator?  Then what? Let it spin at sonic speeds until the blades seperate at the roots and land 5-600 feet away? Now instead of just repairing a burned out stator your also building a new set of blades.

         I'm with Dave on this one, all these machines should have a back up brake system on them. Not only for saving the machine itself, but perhaps saving a life or a lawsuit.I think now  that these machines have been perfected the way they have been, everyone should turn their attention to a good reliable brake system hopefully to just use as a last resort.

[TomW]

shadow;

Totally agree on the backup stopping system.

My half baked idea is an eddy current brake. They use these on roller coasters and no moving parts, gentle braking.

Just a nice, powerful magnet that can be moved in close to the rear stator or something? Possibly automated to trip on overspeed and requires a manual reset?

I haven't thought it out all the way. Just an idea.

TomW