hugh piggot 4 foot turbine

[jonny]

hi can anyone advise me how big the gap between the magnet rotor and stater should be for a 4 foot hugh piggot turbine  thanks jonny

[Ungrounded Lightning Rod]

The gap between the magnet rotor and stator is not significant (of itself) for the power generation characteristics.  It's only significant for mechanical clearance.

What matters is the gap between the magnets on one rotor and the magnets on the other.

This is because there is no magnetic core in the stator, so "the gap" is just the spacing between the opposing poles on the rotors.

(Sorry, I don't know what the actual gap should be.)

Note that you may need to adjust it to match the blades and your local winds.  For instance:  If the cutin is very low and the mill stalls out in moderate winds and turns slowly, rather than spinning up and giving you decent current, you can fix that by increasing the gap.  Conversely, if it whirls away madly but produces little current you can improve things by reducing the gap - up to the point that the mechanical clearance is low enough that you risk rubbing during gusts, yaw, and furling.

[Flux]

Being a single rotor with no direct return path the air gap is not clearly defined and doesn't mean much when compared with a dual rotor.

In this case the gap between magnets and stator doesn't behave as for a dual rotor.

The leakage flux increases rapidly away from the magnet surface so for good results you need to keep the stator fairly close to the rotor. Gaps beyond 3mm will start to affect the performance quite significantly.

Use enough gap to give sound mechanical clearance but try not to make it excessive. The cut in speed and high wind performance are both affected by this clearance. For good low wind results try to keep the gap small. In high winds a larger gap will do no harm but don't exceed 5mm or things will suffer badly.

Flux

[Ungrounded Lightning Rod]

Thanks, Flux.  I missed that this was a single-rotor.