I must admit that my main reason for looking at this in the first place is my lack of confidence in the controller I'm using - a very (maybe too) simple one at present but the next version will be tracking current in and out of the battery bank as well as monitoring the voltage of all the individual batteries in it (shame I can't monitor each cell really) and using some predictive algorithms to make the most efficient use of the power available to keep my pool clean and warm. Complex enough to be sure to go wrong.
Roll on summer (the 10" of rain over the last 10 days - half our annual rainfall here - have had me checking the guy anchors!) when I can get some real use out of the system.
Until the new batteries arrive the mill is parked (i.e. shorted manually) anyway - its a toss-up on whether the batteries or the new mast happen first. Robin - Down Under (or are you Up Over)
People seem very reluctant to copy someone's alternator design that works, they all want to invent the wheel but other factors such as control seem to be set in stone and few ever challenge it.
If you suspect your controller then a back up will do no harm. Whether stopping the machine is better than using a backup voltage limiter is another matter.
A fail safe once only shutdown is reasonable thing even if it needs a slow down resistor and a final short. You know what your machine behaves like. For a normal brake switch you would choose to stop it at an easy moment with a lull in the wind. An automatic device may choose the worst possible moment so you have to bear this in mind.
Flux[ Parent ]
One idea as far as braking and not burning up windings that comes to mind is to first wait for that "lull in the wind", (Flux, you might have a new song title there!), and then short it, while monitoring the AC current during the short. If the auto-short current sense finds the RPMs either not slowing down quickly, or speeding up after the short has been applied, it could then open the short letting the turbine fly freely.
You could also add some variable electrical loading to try and get the RPMs to be within a certain range I suppose.
This all of course depends on the turbine design.
boB [ Parent ]
(Interestingly, variable load trying to hold an RPM is what a battery charging load approximates - and what it would achieve if the coils and drop wire were superconductors. We already have trouble with burnout from that in the nontrivial-resistance non-ideal case. If the non-ideal case puts burnout-level heating into the stator, adding a controller to INCREASE the current - and thus the heating - in the stator {while letting the mill spin fast enough that the blades aren't stalled} will make the problem worse, not better.)
You might want to consider, instead of trying to hold an RPM, trying to hold some maximum CURRENT and let the mill speed up - but only somewhat, since it's still under load. This would mean an adjustable series dump load - that could take a lot of power and a lot of overvoltage.
You'd still be risking a tear-apart from the somewhat reduced overspeed. But there's be less risk than if you let it burn out, maybe catch fire, go unloaded, spin up to some hysterical RPM and either tear apart or strike the mast as it yaws with hysterical gyroscopic effect from high RPM and THEN tear itself apart. [ Parent ]
