low rpm axle flux

[MAL]

I am trying to find information about the typical dual rotor 3 phase axle flux PMA.  I have about 50 RPM to start with.  So if i used a 4:1 gear ratio, could the axle flux be adapted to run eficiently at about 200 RPM?  It sounds like I could use larger wire and fewer winds, but I can not find any type of calculator...and I don't want to reinvent the wheel.  I am just looking for a proven generator that I don't have to make a lot/any modifications to.  I have read so much about these axle flux generators that I could almost build one in my sleep, but I can't find anything to tell me if it will work in with low RPM's.

Thanks to all who respond. I am open to suggestions   

[electrondady1]

the atlts. i build put out 14 volts @60 rpm
should be no problem to make a useful voltage at 200 rpm
just do a test coil

[MAL]

Do you have any sugestions on what guage of magnet wire that I should purchase and approximatly how many winds that I should start testing with?

[electrondady1]

make an accurate coil jig with the center section the same size as a magnet and the outer walls the same size as what your coils must be in order to fit  . use fine wire 25-28 gauge . put on 100 turns or as may as will fit and spin the rotors up to speed to see what the coil output is

you have to know what voltage you need from each coil in order to get the overall voltage output you need
  now you can take of turns to dial in the voltage.
now you know the number of turns you need to get the voltage you want at the speed you want
now you can adjust the gauge of the  wire  to completely fill  that  available space with that many turns.

[MAL]

Thanks electrondady1, that is the best explanation of the process that I have found so far. Do you have an opinion about using 3 phase verses single phase for a low RPM?

[electrondady1]

the vertical mills i build rotate slowly compared to a three bladed propeller kind.
i built single phase alternators with a coil for each magnet to get more amps.
now i build two phase alternators with overlapping coils.
two coils per magnet.
check out some of the posts from members "Jerry" and "wind stuff ed"

[Bruce S]

To the best of my knowledge ED is still building.
Below is a link to his site.

http://www.windstuffnow.com/main/vawt.htm
The LENZ turbine is attributed to him, ALL those on youtube are from his early days of building and testing. (Here one of many that actually acknowledge's him https://www.youtube.com/watch?v=4dO2pBcMdC4 )


ED was very much into "wave" winding coils. The kit I bought from him still works! lights up LEDs easily and will charge my NiCds during a windy weekend! (NiCds are Sub-C rated at 1.2V 1300ma

Hope this helps.
Bruce S

[MAL]

That was very interesting and informative.  I have a very different situation than a VAWT.  The VAWT has low RPM and low tork.  I have unlimited tork with low RPM, so I have the freedom to create any RPM that I need.  I am researching my options for powering my home from a slow moving river and connecting to the grid with a grid tie invertor.  My current usage is between 1000 and 1500 kwh.  I like the dual rotor design,  3 phase 48v seems to be the way to go.  The hard part is designing an alternator with out having any practical experiance.  I could use 9, 12, or 18 coils, any number of wire guages or twin wire coils and the number of windings is trial and error.  I am just trying to eliminate some of the guess work.  The simplest and most common alternator appears to be the 9 coil and 12 pairs of magnets, but I am not sure if it will deliver the wattage that I am looking for.

Thanks for your time...I did find usefull info on that site.

[electrondady1]

your situation sounds perfect for a geared alternator if you can build a mechanism to capture the energy in your river   i think the standard alternator that Danb makes produces 3000 watts.

[MAL]

Thanks, I was hoping to hear something like that. I have read a lot of Dan's posts, but I am not sure what is considerd to be his standard alternator.  Are the specs for his standard alternator public knolidge or are they a closely held secret?

[electrondady1]

not secret at all
 his book will give details. probably addresses any problems adapting it to a hydro electric application.
if not there are lots who have built such things

 

[MAL]

your situation sounds perfect for a geared alternator if you can build a mechanism to capture the energy in your river   i think the standard alternator that Danb makes produces 3000 watts.

electrondady1

What version Of Danb's generators are you considering his standard generotor?  I am in the process of reading all of Danb's posts, and I have been to his website and read it, but I have not yet found anything that could be considered his standard generator except maybe the one used on the 10' turbine.  But I am still reading Danb's posts...I'm only up to 2007 so maybe I haven't got there yet.

Trere are some amazing minds that have shared their wisdom and knolidge on these pages...and there are A LOT OF PAGES...and I have learned a lot so far.

Thanks

Dave

 

[electrondady1]

some thing like 12" dia  rotors with 1"x 2"x.5" mags
three phase, 9 coils 12 poles.
 12 or 24 volts
when he had his shop together he used to sell them complete

somewhere back there he switched to round mags.
 
check out what he  does on his seminars now.



 

[DanG]

http://www.forcefieldmagnets.com/catalog/product_info.php?cPath=22_30&products_id=228

[MAL]

Hi Dan,

That is a nice machine, but I would not consider 600 to 1000   a low RPM for my aplication.  I would have to gear it up roughly about 11:1

I think that I am looking more for plans for a  14" or 16" rotor design with the 2"round magnets.  Basically I am not sure  exactly what I am looking for, that's why spending so much reserching my options.

I appreciate that you took your the time to help me,  I look forward to any future conversations that we may have.

Dave

[electronbaby]

Hey MAL, I dont see any reason why you cant use a direct drive alternator (and skip the gearbox altogether). If you are running at roughly half the RPM that the turbine alternators we build run at, then an easy way to cut the cogging down would be to move towards a higher pole count (say maybe 32 pole stator) and increase the diameter of the alternator to get the magnet speed up. you would need to increase magnet rotor diameter from, say 15 inches to maybe 30 inches or so. You would need much smaller magnets, but more of them. I would definitely stick with 3-phase designs. Single phase will vibrate too much at any RPM or alternator size :/

RoyR