Ceiling fan PM alternator conversion

[gotwind2]

I thought I would give the ceiling fan alternator conversion a go, as I have seen it done before with reasonable results, not this time, unless i have done something wrong??

Total coil resistance of the outer coils is 450 ohms

Total coil resistance of the inner coils is 300 ohms

I used 14 3/4" round Neo magnets (that's all I had to hand) in a N-S-N-S configuration, the air gap is massive 1/4"

Even so,

I got plenty of volts, 100v AC for the outer coils, 60vAC for the inner coils with a hand spin of the outer casing.

I bridge rectified both coil outputs, and was seeing around 80v DC, again with a hand spin - Not very scientific, but it gave me some idea.

But very little current, <100 mA. It would easily light a LED, but not a 6v, 3w bulb.

There was some mild cogging even with such an air gap.

So I am guessing, that with our 240v mains power the coil resistance is just too high to get any decent power out as an alternator. I could be wrong, but that's what I think.

Thoughts welcomed.

Ben.

[tanner0441]

Hi

I played with one of those and the magnet numbers seemed critical. I had more output with four magnets than twenty.  Gave up in the end and put the magnets back in their tube until the blade on my tile cutter is dead then I can use that with the dead one I also have and make a 7in dual rotor, I have a number of test coils to play with.

Brian.

[gotwind2]

Interesting Brian.

I simply matched the number of magnets to the number of poles (14) as it is a single phase motor.

This could be totally wrong, but I got loads of volts, but minimal current.

Maybe the U.S. 110v ceiling fan motors have thicker gauge windings than our U.K 240v versions, the wire in mine is a tiny 0.18mm in diameter.

[RP]

I wonder if the the issue is related to the number of poles / magnets but just for grins have you considered trying a transformer?

Even a transformer pulled from a wallwart might be able to exchange some of that voltage for current.  You'll have to use a seperate transformer and rectifier for each coil set of course.

BTW:  I forget, do these fans have a shaded pole on them?  That's where you find a fairly heavy loop of copper or aluminum wire in a shorted turn on each pole.  If so, you'll want to cut those loops and/or remove them.

[taylorp035]

.18mm according to my chart says about 1/2 an amp, so looking into a 110v system maybe help you out, or charge at 120 volts or something.  Or you could use it as an ultra low rpm generator for mini a vawt that produces power in 2-3 m/s wind.  

[tanner0441]

Hi

I am in the UK Denbigh North Wales.

Brian

[Fused]

Wow, you have your own RE site?

With a motor running at 240v with that wire diameter and that kind of resistance you may want to try to just salvage those magnets.

Im new to RE, but ohms law was a good starting point.

Lol, good luck

Fused

[Flux]

You look to be very short of magnet but things are not as bad as you think.

It will be a high voltage machine and short of rewinding it there is not much you can do.

"But very little current, <100 mA. It would easily light a LED, but not a 6v, 3w bulb.

There was some mild cogging even with such an air gap."

Probably it would have lit a 110v 3 W bulb if you could get one. The 6v bulb is too badly matched to do any good.

Try a 240v 15W pygmy bulb and see if it will make any attempt at that.

These things always become reactance limited and with your small magnets 100mA may be your lot. Cog is mostly a factor of physical dimensions of magnets and poles, moving a few of the magnets a bit one way or the other would almost certainly get rid of all of it.

Flux

[hiker]

they make nice little alts if you rewire..

toss the stator on your grill and burn off the old windings[or hacksaw]..

then rewire with like #17-19 wire..

it would be a single phase alt--havent tried 3 phase yet..

 just did one awhile back-still have to test it out on my pedgen...

made a gas powered ceiling fan conversion-put out 20 amps-old ironhorse

engine for power..heres one powered by a little 2hp briggs..

    http://www.fieldlines.com/images/scimages/1236/enginepowered_boxfan_conversion

[electrondady1]

if there are 14 coils per phase (speed )why not run run 7 and 7 in paralell

half the voltage twice the amps

or jerry gig the thing

[tecker]

As you probably a know the stator is wound single phase the coils are wound clockwise then counter clockwise progressively.The outside stator and the inside electrically separated and there are usually taps on the inner stator .The blade set has to be heavy enough to start and over come cog . You can find a center tap opposite the wiring starts to get the outer stator to configure to 2 amps and use your taps on the inner stator for same .Keep the wire size fairly small down the pole to limit the total current and place your battery load to pulse by installing a pickup coil on the inner core and a magnet on the face of the chassis .Try to match the impedance of each tap with in 20 to 30 ohms It really doesn't matter because the voltage is over cut.I 'll post a linl to the pulse circuit that is simular to a pwm with the wind speed as a reference.It's a simple circuit withn 2n3055 .

[tecker]

Here's the link make sure that each line tap is over cut with hand spin and one bridge for each tap will be best you can mix the taps on the ac side if they are phase matched

Bridges can be make with 1 amp diodes in a pinch without any real power loss.

http://www.fieldlines.com/images/scimages/1431/snapshot3.jfif

[Turfdr]

I have a 110v Hunter with 16 coils.

I just happen to have 16 1"x 1/2"x 1/4" neos and tried placing them around the stator but could only get 7 to stay before they started to stick to the stator but with some good voltage and it also has 1/4" air gap.

I'm not sure how the round neos affect it but seems to be getting good voltage, I would try a step down transformer as RP suggested.

I plan on maching the rotor down if I can figure out how to mount it to a lathe and if I can find small enough roll pins or screws to hole the lams together once all the aluminum is gone.

I think the transformer thing is the best idea without having to rewind.

My only concern is burning out the stator and or transformer , but can always rewind then.

The thing I like most about these motors is the bearings look decent, I happen to have an odd lot of 5 Hornet style blades that should match pretty good and can be mounted right to the rotor with  minimal mods, and the mount should bolt right to my turbine plate.

And the cooling slots will even turn the right way.

[tecker]

The only problem with a transformer is the primary is a low resistance  load that puts the stator in a bind .

[dnix71]

I did one of those. It doesn't work unless you rewire. The wire guage is too thin. The magnet config matters a lot, too. One magnet for each outside coil and alternate poles gave the best voltage. I got almost 100 volts spinning by hand, but less than 3 watts.

If the magnets are too close together, their fields overlap and the output drops way off. I used ceramic magnets, not neos.

I connected the inner wire loop to the outer wire loop in series to get the highest voltage. That makes a big difference, too.

[ghurd]

I do not see them as worth the effort.

(metric to US, 0.18mm is about #34!)

"Fixing" the problems is more difficult than starting with a better motor.

Problems- Thin stator, huge resistance, no decent flux path 'behind' the magnets, not possible to configure in 3-ph (meaning it will cog with correctly placed magnets) , cheap bearings (usually), wire hardly large enough to see let alone work with, nearly impossible to reassemble correctly after the modifications...

And a 220V is worse than 110V in the resistance area.

Easier to start with an old box fan type motor, the kind with 6 coils.  

The old furnace blower motors just like them, but 3~4X thicker, are a lot better.

Then just add 4 magnets and suitably separate the coils.

Tools required- hack saw, file, pliers, soldering iron.

Problems?- all I ever found had bushings.

Not perfect, but a LOT better.

G-

[gotwind2]

Great answers as always, that's why I posted it here.

As it is, it would be a great/simple directly driven VAWT Led decorative thing - at minimal windspeed.

But no power whatsoever.

I guess it is a case of volume/demand.

If a ceiling fan can be made and sold for £13 ($21), and still make a profit, all be it small.

Surely if demand was high enough, China could add a few neo magnets and provide something similar for that price.

A PMA for $21, maybe a complete turbine for $50..

Ben.

[tecker]

I have them to sell to folks that need a dock light or a back yard shed combo .

 Wood blades around around 200 watts in a 10to 15 mph wind you can keep a 200 ah set in good order for winter boat storage and a winch.    

[ghurd]

By the time they fix all the problems, the item becomes an AC servo motor,

which China already makes.

Fixing the problems is not cheap.

G-

[Ungrounded Lightning Rod]

The core is set up for two-phase so I'd try that.  Just rewind the coils with fewer turns of heavy wire, alternate CW and CCW as you go from coil to coil around the stator for a phase, and leave the magnets as is (N,x,S,x,... or N,N,S,S,... where each letter represents a pole piece from the stator.)

[Ungrounded Lightning Rod]

Try putting seven magnets on the rotor, all facing N (or S) pole inward, at every other pole location.  That way they'll repel each other, stay in place, be pretty well balanced, and you'll get "consequent" (i.e. virtual) S (or N) poles on the missing-magnet locations.

Lower field due to the added gap at the vacancies and half the magnetic material.  But the stator core is pretty thin anyhow so you might still saturate it with those big neos, which is as good as it gets.