big axial flux

[fanman]

hello all

fanman here, ive been trying to finish up my 120volt axial flux machine, and im just about there, i have to cast the magnets yet and some other some things like that. well my specs are these;

24 poles

magnet plates are 29.5" across

stator disk is wound with #14 2 in hand

star connected with 1.9 ohms resistance, beteewn any two phases

cut in is 55 rpms at 85 volts ac

20 foot 4 inch blades, 17" at the root, 9" at the tip

i hope thats all the specs, anyway what i want to do is hook mthis machine up to my tractor and load test it for maximum output, and here is my guestion to you, can i hook up a very large dump load say 8 to 10 kw directly to the machine, and then spin the gen up to speed until i get the amps i want, i have a sensing bulb inserted into the stator disk, that im going to watch the output and the heat rise of the stator untul i find my best output, does that make good sense? ive done alot of research here on the board and found a formula that says it should be 50% efficient at 63 amps, i am keeping all these figures and cross checking them as the testing goes on, just to see how close they come out,

when im all done withn this i will be hooking it up to a programmable logic controller to heat directly air or water

is there any other formulas to figure out say output at different speeds, and maximum output?

i will post some pictures of the testing soon

thanks fanman dave

Typo Fixed. TW

[fcfcfc]

Hi Fanman:

Do you really mean you wound 23 wires in hand..??.. 23 #14's in parallel..??..

.....Bill

[Tritium]

fanman,

How thick are the plates and what are the magnets (size and grade)?

Also how thick is your stator?

Thurmond

[Flux]

What are you trying to do, this information is so confusing I don't know where to start.

You say 120v, this makes sense for 85v ac cut in for 120v dc. Are you charging batteries? if so fine but you then go on to say you intend to use for heating with a PLC controller. If so are using that controller as a dump for a battery or are you trying to load directly to a heater.

If you are aiming for direct heating then you have missed the point of direct heating and if you can manage to load it at constant 85v ac you will be restricted to that low 50% efficiency that is a compromise between aerodynamic and electrical efficiency for stall operation into constant volts.

You should be looking at a full load voltage of over 300 with that winding correctly loaded to the cube law for heating.

No point in saying more until I know what you intend to do.

Flux

[fanman]

sorry that was a little misprint its #14 2 in hand

[fanman]

mornin thurmond, my plates are 1/2" thick, and the mags are 3x1.5x.75" n42, and my stator is .75"

[fanman]

hello flux, i do have batteries that will be charged also, but mostly i want to heat water with it and that where the plc comes into play, i want to sequence a bunch of different resistive heaters on and off throuout the output of the generator, doesnt that make sense? and yes it will be a direct connection no batteries involved, thats the goal anyway.

thanks dave

[Flux]

Yes at least I know that you want to charge batteries.

When you are battery charging you will be effectively clamped to battery voltage so your rating will be similar to Dan's.

I am not sure how much luck you are going to have with direct heating without batteries. Do you wish to continue to charge the batteries or is it to be diverted to a completely different heating scheme. If you keep things at 120v and use the controller to keep banging more load on to maintain the 120v limit you will be in stall mode just as for the battery charging.

It will work but you will be restricted by the stator heating problems just as in battery charge mode.

Not sure if you intend to run the heaters on dc or balanced 3 phase ac. Either way your stator is more suited to higher voltage and 240v heaters would make far more sense.

You would presumably start with a base load heater that allowed start up and produced a match to lower winds ( probably little heat to be worth catching below 10 mph) you would then use the controller to add load as the wind picks up in such a way as to let volts rise with wind speed. This would get you to about 240v at just over 20 mph. If you are stuck with 240v heaters you would then have to increase load more rapidly in higher winds to clamp the voltage to your heater limit of 240. This would bring yopu towards stall and make things more controllable. You would need to furl when you reached the stator temperature limit when loaded into 240v.

At 240v load you would have potentially 4 times the heating power compared wioth clamping at 120v for the same stator temperature limits.

Don't know how you intend to use the controller to do this, ideally a pwm IGBT controller would be the ideal but crash bang control with solid state relays may be good enough.

I think I would be tempted to go at this another way, it would require odd value heaters but would give a simpler solution.

If you kept to battery charging with a diversion controller you would get all the diverted heat when batteries are full. You would be working stalled and limited by stator loss. Now if you added a series heater between the rectifier and the battery it would bring you out of stall, battery charging results would improve and you would have more heat from the dump load. You would also be able to use the heat in the series resistor when battery charging or dumping. If you proportion this resistor right it would improve your blade match and the heat dissipated in the resistor would not be heating your stator. Better battery charging and a heating scheme that does not involve any experimental technology.

Flux

[fcfcfc]

Hi: Thank goodness, I was trying to visualize that...LOL...