Using an LC circuit to brake the turbine

[warpsta]

I had a thought to simlify the design of a wind turbine and (maybe) do away with the furling mechanism.

My thought is this: use an LC circuit, which is tuned to the frequency of the ac output of the turbine at normal furling.

Since there is already an inductor in the stator, all that would be required are 3 capacitors of the appropriate value connected in series with the coils and all connected to the neutral of the star wound stator. Alternatively another inductor (of the approriate inductance) could be connected in series with the capacitors.

Since the LC circuit only turns on (resistance reduces to next to zero) at around the tuned frequency this would have the same effect as shorting out the 3 phases at this frequency and thus stopping the turbine.

The main advantage, as I see it, is that the LC circuit has bandwidth, so that the stopping action is not instantaneous, it would gradually stop the turbine as the frequency of the ac increases.

If this is possible it could mean that the furling mechanism could be removed, therefor simlifying the design of the turbine, I don't know if this would work in practice but I would be interested to hear your views....

Jim

[Flux]

If you hit series resonance you will indeed see a barking torque ( capacitor dynamic braking is s standard practice) but as soon as you come below resonant frequency the braking torque will go away . You will end up with the thing running stalled somewhere below resonance where the prop has sufficient power to equal the braking.

As Far as I can see you could possibly match this to a prop designed for stall regulation and keep the speed under control. If the prop doesn't stall out hard enough you will have a nice means of burning out the alternator.

Also it will only be effective with iron cored alternators which are reactance dominated.

Axial air gap machines are resistance dominated under working conditions and the change in resistance will be tiny.

Flux

[warpsta]

Thanks for the reply Flux.

So theoretically it is possible, however the biggest problem would be burning out the stator? Do you think that the addition of a series resistor after the series LC circuit would help to solve this problem?

I think that the stator coils are going to exhibit inductance although, being air core, that inductance will be relatively small. So perhaps an additional inductor would help to solve that problem too?

Jim