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Axial flux?

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hjl4

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I understand most of this technology, but what happens to the energy from the coils, if you touch both wires together, shorting it out? Does the electrons, not just simply loop back and force in the coil.? Does or would it create unbearable heat in the coil?
Also if the energy produced during a windy day is not used, does it mean the alternator wil cook itself?
Does a waste load have to be included with such a windmill system?
Just wondering, or does it work the same as a dc generator?
Thanks.
 
hjl4 said:
I understand most of this technology, but what happens to the energy from the coils, if you touch both wires together, shorting it out? Does the electrons, not just simply loop back and force in the coil.? Does or would it create unbearable heat in the coil?

This shorts the output, it will try to pass unacceptably high amounts of current, and the generator will overheat and die (assuming no safety precautions - such as fuses). This will also produce excessive mechanical load on the driving mechanism (windmill etc.), and will cause it to slow and possibly stop - this technique is also used for braking a motor. Just try it with a small DC motor - spin it with your fingers, then put a short across the terminals and try and spin it again.

Also if the energy produced during a windy day is not used, does it mean the alternator wil cook itself?
Does a waste load have to be included with such a windmill system?
Just wondering, or does it work the same as a dc generator?

AC and DC generators are really no different, they both produce AC, just that a DC one includes a rectifier to convert from AC to DC (which may be a simple mechanical rectifier with brushes and a commutator).

If there's no load been taken from the generator it won't get excessively hot, but it's voltage output may become excessive, and could cause insulation breakdown problems?.
 
Hi hjl4 ,
for a three phase machine ;
the axial flux alternator (alt) is when multiples of four magnet poles are placed on a steel disk and rotated against a fixed set of coils.the coils are in multiples of three .
so the smallest three phase alt is one with three coils and four poles
the poles alternate N-S-N-S around the Rotor disk. they are mostly constructed with two rotors whose poles attract each other.

a favorite of mine is an eighteen coil 24 pole machine , but nine coils & 12 poles is common ,as are 12 coils and 16 poles..
 
Nigel Goodwin said:
AC and DC generators are really no different, they both produce AC, just that a DC one includes a rectifier to convert from AC to DC (which may be a simple mechanical rectifier with brushes and a commutator).

But DC generators actually produce pulsed DC which I know you think doesn't exist, therefore (following your logic that pulsed DC is AC) there are no such thing as DC generators, they are all AC.
 
Hey WilliB.
Yes my gen is a 12pole 9 coil monster that measures 14" dia.
The stator still not complete, but 40 turns of #10 awg in each coil, fills the space nicely.
Just needed to confirm a few things, and thanks to Nigel.
Thanks WilliB asyou seem to know your stuff.(I've read many of your posts).
For this kind of project, there is no room to second guess, especially when others have done this stuff.
Why reinvent the wheel.
Winter is at my door step, and needed answers today. I feel much more prepared now, and will begin with microcontrolled voltage supervisor.
The unit for now will only be used for hot water and baseboard heaters.
The big wire gauge in the coils, is to ensure that a steady draw of 30 amps will not affect or overheat the stator too much.
And Yes, here it is always a windy day, especially winter months.
A calm day is 7mph wind.
I guess living on the east shore of a huge lake makes it a prime location.
My tower is 50' tall.
Also what do you think, of 6' long fiberglassed wings x 3(total of 12' rotor dia).
It dips down to -48C some days here.
Will that be strong enough or too brittle?
Sorry if off topic.
Thanks everyone.
 
hjl4 i like your choice of wire "especially for heating"
how many feet is in one coil?
have you got a furling system yet, that is what usually protects the stator from overheating , and the blades from over speeding.
 
I never thought of measuring how long 40 turns on the coil is(I think it's 30').
As for furling, The blade pitch changes automatically at a preset speed via a governor using a spring and cams.
So that way the wings can stay facing the wind, but no chance of overspeed.
And yes, there is one more overspeed protection, via 16f84,a tach, which If the turbine should overspeed, the power gets dumped in a large load, like two 1500w baseboard heaters mounted on the tower.
With the help of a microcontroller, the heaters in the house also get controlled, and also water heater.
By using the mill this way, no fancy battery storage ect... is needed. The power goes thru a homemade transformer,(which still needs to be done), to up the volts, and directly to heating element.
If volts vary 20-40%, who cares, the energy is not wasted, as a load like a heater(with no fan), will either run slowly or heat up quickly as the voltage changes.
In a 220v baseboard heater, put in 120v and you will get heat out of it, just not as hot or quick as if it were 220v.
Anyways hope this clarifies a bit of my project.
BTW, you never gave me your opinion on fiberglassed wings?

Thanks
 
since i have been working on my own fiberglass over foam blades i have a lot of opinions on them.
figure about 98 rpm in a 7mph wind for your blades
are they still on paper or have you built them cuz that is a lot of work in itself, a lot of work.
recently i've been working on a way to test them , and for that i need instantaneous wind speed and torque measurements
without seeing your blades i cant form an opinion other than what the rpm may be at a certain wind speed.


the first photo is a completed epoxy-glass over foam blade , they are 3.5feet in dia.
the second photo is a shot of the 3.5 foot blades - no glass
 

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Stator and Coils

Im about ready to build my stator. Im building a 3 blade VAWT. I plan on useing 12 1x2x 1/2 magnets and 9 coils the disk will be 12 inches.Will be charging 12 dc bataries and then running through an inverter.Seeing that a VAWT is LOW RPM would it be better to use 16 magnets and 12 coils and a 14 inch disk.Im thinking that both the Rotor and stator will be larger and more coils to make more electricty from the same RPM.
Next what would the best size of wire and number of windings to use for each way for gereral use.Ive read of many different sizes and windings.Sounds like number 20 wire was the best.
TKS guys
Johnny
 
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