Rich's 7' Wind Turbine alternator

[DanB]

This is a brief posting about Rich's 7' wind turbine that we built last year.  We've yet to get this machine installed, so yesterday we tested the alternator on the tractors PTO.

This is a single rotor alternator - the magnet rotor is behind the stator and contains 12 N35 grade disk magnets, 2" diameter x 1/2" thick.  The stator is wound with 53 turns of #13 gage wire.  The cutin speed is around 170 rpm right now - we should probably open the airgap a bit and get it a touch faster I think.  As it is now the mechanical airgap is about 3/32".

Thats what we came up with.  I was surprised that this ran for a while at 500 watts output and got a little bit warm -I expect it to get hot quickly.  I think it will be a pretty decent little 300 watt 7' machine  - not terribly efficient in high winds but probably pretty good in lower winds.

[Nando]

DAN:

Your graphs drive me nuts, since You have watts / RPM and no indication of the generated voltage, at all.

Generated voltage / RPM @ no load is a better indication of the mill power if the winding resistance is known and the GAP Voltage stator - rotor ( at peak RPM) is defined ( which is done by lightly loading the generator - around 10 % of peak power -).

Then a power curve with clamped output voltage as You show them now.

Even if battery clamped, the output voltage should be taken, as well, because the voltage is not "fixed", it may vary several %'s

Maybe if you get a MPPT ballast controller for testing the mill, generating all the parameters including the efficiency.

I have a good design but not the man hours to build it, at the present time.

I understand that You want to reduce the electronics since it is an unknown for You, with electronics, the generator can have a very close AIR-GAP and the winding can be made to produce higher voltage for much better power harvesting with MPPT.

A 1 KW wind mill used with a battery bank "clamp" producing 50 % efficiency, with a MPPT charge controller, the same wind mill will be able to produce around 1700 watts and possible more if windings are optimized for MPPT harvesting.

Regards

Nando

[DanB]

Hi Nando -

12V cutin here is stated to be around 170 rpm - and open volts/rpm is a linear relationship.  If we one data point then we know open volts at any speed as I see it, so posting further data doesn't seem necessary unless I misunderstand something here.  Double the rpm you can double the open voltage etc...

Unless I don't understand what you're asking for it seems like all the info is there.

[Flux]

Agreed Dan.

Actually the missing bit was 12v , I guessed from the number of turns.

The air gap machines all behave the same. 10% load or full load all lie on the same curve. There is no leakage reactance to worry about.

Your input and output curves for the 17ft machine are typical of all the air gap machines.  Cut in speed and stator resistance tell you all you need.

This gap voltage is a term I don't understand, probably something lost in translation. I think Nando is familiar with slotted core machines with leakage reactance.

The slope with 10% load will be a lot higher than at full load where some machines may be approaching reactance limit.

[force9BOAT]

Is the stator wired for Delta?

[force9BOAT]

Two more questions,  What TSR are the blades and what minimum wind speed do you expect will reach 170rpm cut-in?

[badmoonryzn]

I would love to see the plans for:

a MPPT ballast controller for testing the mill, generating all the parameters including the efficiency.

I have a good design but not the man hours to build it, at the present time.

Let me know please as I would like to build an MPPT (Maximum Power Point Tracking controller) And save some bucks.

Badmoon