Questions on Converting Induction motor

[thepaintingaccident]

I'm looking on building my first windmill and have decided to go the route of converting an induction motor into a pm magnet. So far I've decided on using a motor from an air conditioning unit and am installing neodymium 1" x 1/2" x 1/8" magnets. I know its on the smaller side. My question is how do i determine how many magnets to install into the armature and if any rewiring is necessary. I don't know all too much about the motor itself and the label didn't help. I'm also wondering if it would be more advisable to look for a larger induction motor say from a washing machine or any other machines people would suggest. I'm doing a 3 blade 8' diameter prop. Overkill? This is in a urban/mountain landscape. Was talking to my physics professor and he advised stepping up the rpm by gearing and a chain. I have bicycle gears and chain lying around.

Thanks for the help and

Mahalo

Zack

[Darren73]

Hi Zack,

You need to supply more information about the motor for anyone to give you useful advice, you may as well be asking how long is a piece of string at the moment.

Although you may not think the motor plate is of any use there is usually a lot of useful information on it, if you can post the details from it they may help provide some answers to your questions.

Darren

[ghurd]

Forget the gears. For about 100 reasons.

Mostly there are better ways to do the same thing without moving parts and their problems.

No idea about the A/C motor, except if you chose those magnets it isn't very big.

Guessing the fan motor?

Low power motor means lots of turns of small wire.

Lots of turns means lots of voltage output (no need for gears).

Small wire means high resistance and low amps output, and no way it should have a 8' blade.  Maybe 32"?

Guessing the fan motor is 3 speed?  All kinds of potential pitfalls with that.  Don't start a first project with anything but a single speed.

Bigger is a lot easier, but those are really little magnets.

Might make the first one, with those magnets, something like around a 1/10th HP 1750-ish RPM 110V motor.

Then 4 magnets placed N-S-N-S.

Thats what I did on one of my first ones that "worked".

Same magnets you have.  A 20" box fan blade was enough, both in speed and size.

http://www.otherpower.com/images/scimages/2050/ugly20.jpg

G-

[thepaintingaccident]

Hey thanks for the input. Would you have any more information on that first project you did. I'll keep any eye out for a single speed motor. What sort of results did you get from the box fan conversion?

Zack

[wooferhound]

Here is one of ghurds stories on a box fan conversion

http://www.fieldlines.com/story/2005/7/4/34446/17324

[spinningmagnets]

I think what you're talking about is called a "Zubbly conversion" here. Search that term for more details, but here's my favorite Zubbly links:

http://www.fieldlines.com/user/zubbly/diary

5 Zubbly diary stories

http://www.fieldlines.com/story/2008/4/18/14151/1216

Good pics of rotor, Coils are skewed, so mags are straight.

http://www.fieldlines.com/story/2008/4/4/23164/05034

Good pic of a PMM, 3-phase AC servo, 77lb, 12V @ 150 RPM's/48 @ 600

http://www.fieldlines.com/story/2007/8/5/233957/8576

1.5 hp, 230V/5.2A, 460V/2.6A, 1735 rpm, 3-ph

http://www.fieldlines.com/story/2007/7/21/22728/7603

7.5 hp single phase 1725rpm motor, 12-pole

http://www.fieldlines.com/story/2007/7/22/82515/9969

GOOD PICS, 7.5 Hp 230 volt single phase, 36 slots, 54V@ 250rpm

http://www.fieldlines.com/story/2006/12/17/22270/167

good pics, British 3HP 380V, now 260V @ 1500 rpm

http://www.fieldlines.com/story/2007/3/13/214531/690

good pics + magnet/coil drawings, 5hp Baldor

http://www.fieldlines.com/story/2007/7/15/143921/757

SEELY AirConditioning motor, 20 poles, 54V@120rpm

http://www.fieldlines.com/story/2006/6/23/185558/084

long discussion with CAD drawings on proper skew angle

[thepaintingaccident]

So its trash time of the month and i decided to scrap the small motor i had and look for a larger one to convert. I found an induction motor off of a old compressor. Here are the specs. Emerson motor. 115V, 7amp, Rpm 1725, Cyc 60, PH 1, Temp Rise 50C cont.

So again I'm trying to figure out how many poles to install into the armature. I'm still going to use my 1"x1/2"x1/8" neodymium magnets. I have 20 of them and can stack four down the side of the armature. There are 32 stator plates and 8 coils. Did some reading of the last post and have to say its alot of great information i need to go through. But few questions if you guys can help me out. Is this motor worthy of conversion? and any help with designing how to install the magnets into the armature. How many poles? ect. Tomorrow is my only day this week that i'll be able to access metal working tools.

Thanks again and Mahalo

Zack

[thepaintingaccident]

Oh and the armature has some sort of spring system installed similar to that of elevators. I'm not totally sure of what it does. But posssibly at too high rpms it disconnects from the power source. Anyone have info on this? and if i should disconnect leave alone.

[joestue]

Its a centrifugal switch that disconnects the starting capacitor.

[ghurd]

For 1725 to 1775 RPM (anything around there) it gets 4 magnets (or groups).

NSNS is important.

"Found" makes it sound like nothing to lose but a couple bucks on inexpensive magnets, and some time.

I use 24 hour cure epoxy to hold them on.  A lot of guys like JB Weld.

Best guess.

Find where the wires enter the coils.  I expect there are 3. One will join with 2 coil wires.  Snip one, and add an insulated extension.

http://www.otherpower.com/images/scimages/2050/forGuruji.jpg

This will make 2 sets of coils.  Add a bridge rectifier to each set.

Then see how it works.  That's what I do.

Don't expect much with those small magnets.

G-

[thepaintingaccident]

The three wires connect to one of the end plates of the motor which then brings them down to two, which is connected directly to the power cord. Any tips on this? and how to rewire the now 4 wires down to two after the snipping.

Mahalo

Zack

[thepaintingaccident]

Thanks didn't know that. Should it be removed and or modified? Or left alone.

[joestue]

eh.. if you could find something creative to do with it, like trigger a WYE-Delta switch leave it in, or take it out, your choice.

[ghurd]

Each pair goes to the AC inputs of that pairs bridge rectifier.

The bridge's outputs are paralleled.  + to +.  - to -.

That makes 2 wires.  The + from the bridges goes to the battery +. - goes to battery -.