Burnt stattor

[shawn valpy]

I guess my pile of dead mill bits is still growing 
here is the worst coil
and the wires to the kill switch

[prasadbodas2000]

Can anyone see the images included in this above message? At least I could not see on Internet Explorer V6 and also not in Google Chrome 19.0.1084.56

With thanks and best regards,
Prasad

[joestue]

yeah i can see all of them.

what happened?

[Flux]

Without details of what happened it is not possible to help much. It seems fairly obvious that not all coils have suffered but the picture is not good enough to confirm that one phase is burnt.

Was this damage caused by trying to stop it in a decent wind or did it possibly get away from the braked position?

The wire in the good coil looks suspiciously red in colour, was it by any chance the polyurethane coated wire that you can solder without stripping the enamel. If so this dreadful stuff will disintegrate above a critical temperature and develop a short  failure is then more or less instantaneous as the shorted turn heats up and the damage spreads therough out the coil.

Flux

[shawn valpy]

I was home at the time and the wind picked up with a few high gusts nothing to serious but my bank was full so I shut it down, no point in running hard and just dumping the power!
about an hour later the wind went wild 140k gusts! this fried the wires into the off/on switch it was furling fine but the wind from this direction changes direction fast and furious constantly the yaw bering is free and turns easy but the hole thing cannot turn out off the wind fast enough causing big spikes.
each phase has some dead coils in it some worse than others though, and 3 seem fine, the wire was the correct type having to scrape and sand before soldering.
The wire size is 1.6 two in hand 42 turns per coil
24volt bank
4meter diameter chainsaw blades
17 deg tilt back on furl hinge
adjustable mast mill offset set at 200mm
there is room for more copper there though so I might try and fit 3 in hand in.
also lighten the tail, were it was at it furled around 45/50 amps and would be all folded up at 60 and droping back to 40 before unfolding again.

[Flux]

That was a bit of bad luck.

For it to have burnt the wires to the brake switch it will have got away from the braked state. You may well have done a lot of damage with it running against a short circuit .

Not really sure why each phase has some dead coils unless it is some effect of the cooling when running furled with more wind one side than the other, this does seem to happen, the wind flow past the stator is hard to predict.

Using all the available space makes good sense so thicker wire or more strands in hand as you propose makes good sense.

Short circuit braking is not without problems and unless you can absolutely guarantee that it will never break away it may be safer to let it run. It needs lots of copper and lots of magnet to be absolutely sure a short circuit will hold in in seriously high winds.

Flux

[jlt]

I believe That your machine blew a rectifier before you shut it down. and that 2 phase would not hold it back .

   jlt

[just-doug]

rectifiers are after the brake switch,so mostly irrelevent.but once it got away from the brake,rectifiers could influence what leg burnt first.ether way,they all appear burnt.in hind site,using the dump load may have been safer