Generator/Blade mismatch

[imsmooth]

I have a F&P motor that I modified with neo magnets.  There is a graph of its performance at http://www.mindchallenger.com/wind/wgpage5b.html

I am carving 10' blades.  With an overall efficiency of 0.15, I won't have enough wind wattage to drive the generator properly until I hit 25+ mph winds.  I will stall out before this.

I am waiting to get a PowerOne inverter.  According to the manufacturer, I should be able to program 7 or 11 (I can't remember the exact number) points of how much power to extract at a give voltage or rpm.  If I can tell the inverter to apply only "so much" load to the generator this should solve the problem, right?

Looking at my graph at 300rpm the generator puts out 600watts.  It will need more wattage to drive it there.  A 10' rotor will only deliver 200-240 watts at this rpm.  If I tell the inverter to only draw 200 watts will this work?

As another solution, could I fill down the iron cores and increase the air gap between the magnets?

[Flux]

You have been asking a lot of questions for a while and I guessed you were only telling us half the story.

At least you seem to have chosen to keep your blades wide and with a lot of twist at the root, something that is pointless and wasteful of timber for an axial air gap machine but which may be necessary for you to get a decent start up with an iron cored machine with lots of flux.

Your power curve is into a resistive load so I have no idea of how it will load into a battery ( which I assume you are using at that low voltage).

Unless you do a run into a battery then I have no idea if you are too powerful or not.

Similarly I have no idea if this resistive load is single or 3 phase but as you only mention one resistor I assume it is single phase unless you used a 3 phase bridge with the resistor on the dc side ( so little information as usual)

If the alternator is too powerful then some sort of loading device that matches the load to what the prop can produce will work if it does the load match at good efficiency. I have no idea what your inverter thing is or what it does, if it works something like the grid tie inverters then yes it should be fine. I am not aware of anything commercially available for battery charging that does this job and if it was feeding a battery then it would not be called an inverter.

If you want any more help you will have to give all the information in future, asking bits of questions in isolation is very risky and may not get you an answer useful to your requirement.

You seem to be going the mppt route while asking about blades and other things as though you were building an axial, the loading conditions have no similarity.

If your internal resistance of that alternator is 25 ohms as you suggest then I seriously doubt that it will be too powerful for the blades and for mppt working the maximum power transfer theorem is a snare and delusion and you want very high alternator efficiency not 50%.

Just imagine a 500MW power station running at 50% and dumping 500MW from the alternator as heat just to extract maximum power ( no I don't think so).

Flux

[imsmooth]

Sorry Flux for not giving all the info.  The generator is a three phase going into a 3 phase rectifier block with capacitative smoothing.  The resistive load is a combination of 100ohm/100w resistors to give me a net resisitance. I am not charging any batteries.  I plan to buy an Aurora Wind inverter with MPPT and programmable power extraction and various rpm/voltages.

[Flux]

I assume the Aurora is grid tie if you don't intend to use batteries.

As long as your voltage comes within the inverter range then it should be ok.

Your voltage seems low for a typical 120v grid tie inverter but may be ok especially as you will never be loading it to half volts to suit the maximum power transfer thing.

There will be a minimum voltage for the inverter and ideally that needs to match your cut in wind speed. From there upwards you should be able to programme the inverter to track the load. What do you do before synchronising in a high wind or if you loose load in a high wind, these inverters have a maximum voltage input and it is absolute.

Have you dealt with that issue.

Flux

[imsmooth]

I spoke with Power One today.  There are 16 programmable points.  It is grid tie.  The range is 50v-550v which is what is why I wound the generator myself.  I had the generator up to 500rpm and I still was not close to the 550v maximum.  However, there is a diverter circuit that will feed the extra amperate to a load that I have built in case so I don't fry the inverter.