vawt geni theary

[electrondady1]

i have been thinking along these lines . in the case of a really slow moving savonius type direct drive alternator , if instead of a dual rotor with mags on each rotor . if all the mags were put on one larger rotor(same spaceing) with a plain steel rotor running in sinc.

the flux density would be half,(thats an asumpion) but the number of poles would be double and  the linear velosity /frequency would be double as well .

within the stator ,you could fit twice as meney coils, but i think they would need to be thinner,due to the loss of flux density.

i'm just wondering  wether there could be any advantage over a conventional design?

[Nando]

Why don't you think out of the box.

Instead of placing the magnets in the rotors, place the magnets in the coils center, then place two (2) disks rotors for the magnetic field modulation, which can be done by cutting slots in the metal to "open" the magnetic field loop circuit.

This process may do the same than placing 2 rotors with magnets, also if done properly the plates can be used as "fans" to help to cool the coils due to temperature increases.

Thinking out of the BOX, then one could place much larger thick magnets to be able to have higher magnetic field as well as thicker coils for either larger wire size or higher number of turns .

The magnetic effect is the same, and the plates can easily be cut with a water jet or plasma ( prefer water jet).

The slot between the magnetic shunts should be about one width of a Coil -- Not 2 coil widths.

Also the slot number one less( per phase) to obtain NO cogging action.

The slots can be increased for the equivalent of higher number of magnets.

Also the shunt can have ribs in the back for stiffening ( strengthening) if needed.

I give this idea to the world -- NO patent should be tried --

Idea good for Verticals or Horizontals wind mill generators.

Nando

[DanB]

Similar concept I suppose to a shaded pole generator - or a guitar pickup?

Be fun if someone plays with it, my guess is you'd get lots less for the copper/magnets involved in the machine though and I'd be surprised if you could really get away from cogging.

I expect unless you used really good steel then hysteresis losses would be signficant and it seems like eddy current losses might be a serious problem as well.

Are you serious Nando.. or joking on this one? ;-)

[electrondady1]

wow! that is out side the box.! i think i would need a sketch to understand your concept.
a magnet suspended inside  a coil will form a sphere of flux encompasing the coil.  i can't see how moving  segmented disk(spokes )past would expose the copper to alternating mag. flux polarity.
please, lets solve my riddle  before we solve yours. lol

[electrondady1]

 ok, i have lots guitar and bass pickups around here. but nothing i can put a meter on. what your saying is the rotating disks are acting like a vibrating string?

[vawtman]

Thanks for posting this Electrondaddy.

 Will follow along but have no experience with axial designs yet.We need good output at 120rpms and less with zero interferance at start.Gearing and slight cogging really complicates things.

[windstuffnow]

  Basically if you cut the flux in half and double the magnetic surface area the outcome is the same.  There is basically nothing gained by doing that.  The coils would naturally be thinner, each coil would need only half the turns but you still end up with the same amount of turns per phase to do the same job.  

  The really low rpm alternators definately present a challenge.   Most of the redrive components available are pretty efficient now a days ( 96-98% ) so using a smaller dual rotor and driving it at a higher speed will still give you an easy starting slow runner.   The losses through the redrive really arent that significant.   If you consider the turbine making say 300 watts with a 96% redrive your only loosing 12 watts through the process.  Some make it sound like it's a big NO NO and it should never be considered.. but.. for the cost of magnets, wire and heavy steel discs for a monster diameter machine you can do the same thing with a much less expensive alternator and a simple cog belt, flat belt or direct gear redrive.  

  I considered building a direct drive system for the large Lenz turbine but soon realized the size and cost would be rediculous.   After doing some calculations and considering the losses I found I could run an 8 inch alternator with a serpentine belt redrive and save myself a couple hundred bux... for that kind of savings I'll overlook the 12 watts.  

  Just depends on how you look at it...

.

[Nando]

DANB:

Before I answer your question think about it to see if it is possible or not.

why not or why yes.

Nando

[willib]

may i jump in here and ask Ed how many "turns per phase " are usually required for a 24V system using say 2"x1"x1/2" mags?

[DanB]

I think it would surely work - I just don't see advantage with it and it seems there would be some problems to solve.  Moving solid steel plates with cutouts past stationary magnets (if I understand you correctly)poses lots of problems with iron losses and cogging and Im not sure there is any benifit to doing things that way.  My intuition says you'd get less power from a heavier machine but I could be wrong there too.

[Flux]

Inductor alternators need laminated iron circuits and are invariably larger than their conventional counterpart. They do have advantages for high frequencies but otherwise they have little to offer.

Flux

[Flux]

This one is awkward. If you put the magnets on one larger disc and keep the same air gap then you have half the flux per pole, but for the same coils you have twice as many. This cancels the drop in flux, but you have also doubled frequency.

Volts are proportional to flux density frequency and number of turns, so there is a gain in voltage but you will have double the resistance and that will reduce the power you can extract.

Ultimately it depends on how you load it as to the gain from this change.

Ed is right, low speed means high magnet and copper cost and it may be more cost effective to use a speed increase for the same overall efficiency.

[electrondady1]

well, the big guns have spoken!
i think i'll skip that set of experiments.
are these belt drives noisey?
the last two little genis i built could produce 14 volts at 60 rpm ,which was what i was looking for. but with huge resistance/minimal current.
if i can get some speed up with a belt drive system i may actually pull a few amps.
thanks fellows.

[Nando]

To all:

The Magnetic shunt "generator" may work BUT if has a basic problem, so it is best to clear the concept to STOP anyone trying to make such device.

IF A MAGNET is inside a coil and there is a Magnetic Shunt that may move in-out or slide across the coil, a VOLTAGE will be generated with the polarity of the magnet when the shunt closes in, and when the shunt moves away, the Voltage pulse goes to ZERO, the next shunt arrival will generate the next VOLTAGE PULSE of the SAME POLARITY..

This is a MONO-POLAR generator and the Voltage pulse will be 1/2 amplitude.

To generate a sine wave ( BI-POLAR pulse) the magnetizing field, in the coil, needs to change polarity if the coil winding connection is not varied .

PLEASE do not try to make such generator .

Nando

[windstuffnow]

  It would depend on all the variables, number of poles being one,  the rpm it needs to reach charging voltage, the gauss reading in a given airgap, and possibly the configuration.  I've never used those magnets myself but I could probably come fairly close given a set of circumstances...

.

[kitno455]

belt drives are quiet, at least if you keep the ratio sane. if they made lots of noise,  that would indicate lots of sliding contact, which would mean lots of heat, and the belts would burn up.

you've probably got a serpentine belt drive on any recent car you own, running half-a-dozen idlers and attachments all at once, and the electric radiator fan is much louder. the cheap sleeve bearing idler pulley tends to be the noisiest part of the system. if you can avoid idler, and use a spring-loaded or threaded assembly to move the gen, you will be ok.

take a trip to the salvage yard and look around. there are some great ideas, even if you then just go buy them new at the parts store.

allan

[electrondady1]

kitno, i think i'll google search the archives for 8-10"aternators and try to find a typical rpm for such a geni.

them i can decide on a ratio with the wind mill section. at it's present location it peaks out at about 120rpm.(maybe i can get a little more) but seems to cruise at 60rpm most of the time .

the system is modular so i can stack sections untill i get enough torque.

a visit to the wrecking yard is always a treat . it 's tough to go home empty handed most of the time . the most difficult part when improviseing like this is getting shaft dia. /pully ratios  to all live together  happily .

[electrondady1]

well, i did not have a lot of luck searching for rpm operating seed in relation to gen dia. some were between 200 and 300. so perhaps a 5 to 1 ratio.

[nack]

Yes, lot's of old organs used rotating toothy wheels as tone generators.

[electrondady1]

if the concept of direct drive is to be abandoned then it begs the question as to a suitable ratio to overdrive the alt. if the mill section were capable of perhaps 25ftlbs of torque would it not be possible to run a alt requireing 5ftlbs at a ratio of 5 to one ?.  it would follow then that an even smaller alt requireing only 1ftlbs of tourqe could be driven at 25 to one ?

[lohearth]

Have you considered using a variable speed pully system like the ones used in old combines? Just a thought I had a long time ago.

[electrondady1]

i'm not familiar with the devise you mention. would it give a constant speed on the geni?

[lohearth]

Most old grain combines use a variable speed pully system. The small pully is a fixed size while the larger pully is a double concave movable spit pully shaped like this )(. A lever controls the width of separation for the large pully giving it a variable speed for ground movement for the main ground drive rather than using gears. This could give you smooth speed ratios and with a servo attached to the lever, by means of a tac, could give you constant speed or a real speed boost at higher torque. In theory, it could give a vawt alot of flexability in control of output

[vawtman]

I love the idea of using a servo and tach to control a clutch.You may have solved my problem.Never gave electrical controls a thought.

 Thanks Lohearth

[electrondady1]

whats up with the margins of this post?