Hugh Piggotts Axial Flux Design

[(unknown)]

Hughs manual gives his axial flux turbine a design output of 500W, or 20A at 24V, but it also states that the alternator is capable of producing up to a kilowatt, or 40A, for short periods... I would like to control Hughs machine with a plasmatronics PL60 controller, but the rated continuous capacity for the shunt load switching circuit is only 30A... Does anyone here have any experience of actual outputs from Hughs design? If the output can spike at 40A, how long for? presumably just the moment before the yaw mechanism kicks in?

I suspect that it'll be ok - but any experience would go a long way towards my peace of mind. Alternatives would include a switching circuit that would dump the output to a secondary circuit should 25A be exceeded... But to be honest that seems like too much work for my limited electronics ability! Using a relay to control the shunt load circuit is not ideal as a mechanical relay would be too slow to make use of the PWM facility of the PL60, and a solid state relay would be ridiculously expensive - and I'd lose all the nice metering the PL60 gives me... If anyone has any horror stories of hughs yaw mechanism getting stuck in the open position, or ideas of how to protect the controller in that event, then please let me know.

My second question concerns the PL60 - has anyone ever seen a PLX expansion board for this range? The controller has a lot of useful functions like remote low battery alarm and cut-off, back-up generator on and off, secondary battery bank switching and 'event control' for preset things like outside lights... But you can only use one of these (the second output is needed for the wind turbine dump load) at a time without the expansion board. However despite several mentions in the manual I haven't seen one for sale yet and there are no details given on the website... Any ideas?

Many thanks if you can help, same again even if you can't!

[antw]

What are you using as a dump load?  Do you realise that your wind generator has to have a load on it at all times, either the battery bank or some other dump load, otherwise if it is disconnected it may overspeed (spin too fast) and nasty things happen then.

Is there a problem turning off the pwm control and using a mechanical relay?  That would seem to be the simple solution.  I thought pwm control was more for solar panels.

I will be interested in your final solution as I have a PL40 with solar panels and will be adding a wind generator to it in the future.  I have not seen a PLX either.

Regards

Antony

[PaulJ]

   I use a PL60 to shunt regulate a mill that peaks at just over 1kW @ 48V, at 20 - odd amps its well within its max rating though.

   My mill uses pretty much the same furling method as Hugh's design; from my observations, I'd agree with your presumption that max output occurs just before furling. Typically, a sudden increase in wind speed (or change in direction when the mill's partly furled) will result in a spike lasting maybe a couple of seconds, I would rarely see more than 750W sustained.

   Having said that, a resistive shunt load will draw more current as the battery voltage increases. If your battery voltage starts to run away because you can't dump the extra 10A, then you could find the shunt load pulling more than 30A, possibly resulting in a fried controller. Not worth the risk in my opinion.

   I've never seen the expansion board but I've seen the specs for it somewhere. If you end up using it please let us know how it goes, when I add a bigger mill to my system I'll probably need one!

   If in doubt, give Plasmatronics a phone call, they're pretty helpful in my experience.

   Paul.

   Off grid 5 months and still married.