Windmill alternator questions, can I pick your brains?

[wind4Reg]

I have been scouring the internet trying to find a decent PM Alternator for my wind project and I can't find anything suitable for sale out there. So it has come to this, I will make my own. I did happen to have a new (10 years ago) 1 HP motor that has been laying in my basement and then garage for the combined last 10 years. I bought this motor for $1 from a company I worked for because they were throwing it out and couldn't just give it to me. Since I already had this I decided to take it apart to see what the internal workings were like to see if I might be able to convert it to a PM Alternator. Turns out it looks like it just might work! Here are the specs:

Brushless Aschyronconous wound AC induction motor, 1725 RPM, 115/230 V, C-Face mount, 1 Phase, 4 Pole, 1 HP.

I measured the rotor and it is 3.5" in diameter. I found a site that sells sectional arc neos that will form a circle of 3.5". So I have to get the rotor turned down to fit the magnets. Here is where the questions come in... magnet arrangement, since this is a 4 pole motor I have seen it posted on here that you have to match that with 4 magnetic poles. Is this the case or can I go with 8 or 12 magnetic poles and why or why not?

Below is a sample picture of how I have envisioned the magnet arrangement based on 4 poles. Can you guys take a look and let me know if you see any obvious problems with this arrangement? Imagine the dark background rectangle as being the cylinder of the rotor if it was laid out flat.

Any guesses at to how much power this would make at say 600RPM?

Reg

[ghurd]

Zubbly is the man.

Read part #1 + #3.

Not sure where #2 went. TomW had a link for all 3.

By the time you get through reading #1, you'll need a break anyway!

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

[TomW]

G;

Here is a link to the whole series in one PDF:

LINK

It is quite large at 4 megabytes but thats smaller than some of the photos we see posted. ;=]

Enjoy!

TomW

[ghurd]

(my wife yelled at me for posting 3x5" 8K photos because thats not right somehow)

[wind4Reg]

I have read Zubbly's info, thanks for the link. I still have the same questions about my proposed magnet placement. If your reading this Zubbly or someone who has knowledge of magnet placement on a rotor perhaps you can respond? I had the rotor turned down at a machine shop this morning, $27 Canadian, you can't beat that price. Now I have to bite the bullet and buy the magnets.

Reg

[ghurd]

Your image is how I do it. 4 magnet poles for a 1725 RPM motor.

I think about it like 2 series coils, 4 coil legs, 1 magnet pole per leg.

For 6 magnet poles it takes a 1050 RPM motor.

Thats 3 series coils, 6 coil legs, 1 magnet pole per leg.

That is for using the stock windings.

Rewinding is something better left to people who are not me.

My limited experience, all with smaller motors, shows about no difference between slapping on a bunch of good magnets so it won't cog, and 6 months of planning to slap on a bunch of good magnets so it won't cog.

The performance with stock windings seems more related to the number of turns and resistance.

G-

[zubbly]

hello wind4Reg!

if your motor is a 4 pole, you make 4 poles on the rotor, alternating the polarity,

n-s-n-s.

if it is a 6 pole motor, make 6 poles on the rotor.

do not put more poles on the rotor than the motor is designed for.

zubbly

[dinges]

Zubbly,

Do you know an easy way to tell the number of poles on a motor? I'm new to motor conversions, but have built a few axial-flux generators. Still trying to read up on the theory behind motors & conversions. Like the pdf-file on motor conversions (part 1-2-3), BTW!

Peter,

The Netherlands.

[zubbly]

hi peter!

usually the name plate will specify the speed.

3450. rpm-2 pole
      
1725. rpm-4 pole
      
1140. rpm-6 pole
      
850. rpm-8 pole
     
     

these speeds are what is refered to as slip speed, or full load rpm. synchronous rpm in order would be 3600, 1800, 1200, 900.  and all for 60hz

if no name plate exists, you can inspect a single or 3 phase motor in this manner to determine number of poles.

dismantle motor and look at the winding. you will see a pattern of coils, and most times the coils form a group of from 1 to 6 coils. look to see how may groups you see in the 360 degree circumference.  you should see 2 for a 2 pole, 4 for a 4 pole, and 6 for a 6 pole motor.

if a single phase (for a 4 pole) you should see 8 poles total. 4 for the run winding and 4 for the start winding. for a 3 phase, you should see 12 poles, 4 for each phase.

this is what is called a lap winding and is what is refered to as an adjacent pole connection. an adjacent pole connection forms one pole per group of coils. the coil groups should span approx 1/4 the way around the stator.

a 4 pole "consequent" pole connection forms 2 poles per coil group. the coil group should span 1/3 the way around the stator. there is only 2 coil groups per phase to form 4 poles. there would be a total of 6 coil groups for the entire winding.

single phase windings usually only use adjacent pole connections.  3 phase windings commonly use both types of windings.

hope this helps  

zubbly

[ghurd]

(I always put a letter before a number on a new line so that won't happen)

A 3450 RPM is 2 pole.

A 1725 RPM is 4 pole.

A 1140 RPM is 6 pole.

A 850 RPM is 8 pole.

for 60Hz.

[dinges]

Thanks for the info; have read your message twice and still don't completely grasp it :-) I consider this a good sign: there's still something left for me to learn ;-)

Esp. the difference/relation between poles and phases. I'll study a bit more, make some drawings and it should come. If not, there's always this board.

One detail: here in Europe, we have 50Hz; so this also means that instead of 3600RPM, we have 3000RPM; instead of your 1800RPM, we have 1500, etc. Just a detail, like I said. Though with generators, this detail might have influence on the lifespan of the powersource: the difference between 3600 and 3000RPM is pretty high, in engine terms.

Peter,

The Netherlands.

[ghurd]

It came together for me when it was drawn out flat and straight and single phase.

For 1725RPM at 60Hz.

Draw 2 square series coils. Draw a magnet over each leg, that is 4 magnets.

like  O  O (coils)

annd ll ll (magnets laid N-S-N-S)

For 1150

RPM at 60Hz.

Draw 3 coils and 6 magnets.

like  O  O  O

annd ll  ll ll

North magnet cuttent goes up, South current goes down.

Rotating magnets make AC. Up down up down...

With a single phase motor, it ends up being a 2 different single phase alternators in one box.

Think about it like 2 alternators.

Seperate the start from the run winding. In your head, and in the motor.

With 3 wires, the 'center tap' is connected to 2 wires, Cut one of these, and add another output wire. Now it is 2 sets of coils and they are different (wire size and turns) from each other, so it is 2 single phase alternators in one box.

Each 'alternator' gets rectified seperatly, and the outputs are parelleled to the battery.

If the V and resistance is too high with a 4 pole, seperate and parellel the 2 coils in phase. Up side with up, down side with down. Like half the volts, double the amps.

Up until here is easy. NOW it can get confusing!

For a 3 phase rewind, lay the common coil and magnet drawings in a straight line.

Like a 12/9 or 8/6 configuration.

Maybe draw 2 papers 48cm long, 8/6, one with magnets, one with coils, each phase a different color, one paper moving past the other?

Instead of N-S-N-S, I draw up arrow ^- down arrow v- up arrow ^- down  arrow v.

First look at 1 phase at a time. Then everything comes together.

-

-

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Hi Zubbly!

Sorry if I totally butchered your superb explanations.

This is how I, personally, figured it out before I understood what anything meant.

G-

[dinges]

Thanks for your attempts to educate me. Still will need to do some proper studying to get it, though... The extra explanation should help. Thanks.

So, even in a single-phase motor you have basically two 'phases': one for normal operation, and one that is only active during starting; suppose that phase is connected to the starting capacitor? Wonder how the 2 phases are connected together; will check this out, some motors I've seen had a label on it with wiring diagram.

As you see, this is new stuff to me. Am pretty good with electronics, but this is new to me. Have some motors lying around and will check them out; with your explanations and some pieces to actually hold in my hand, I should get it.

BTW, any online resources that give good explanations on the subject are appreciated, if you happen to know of any. If not, will do some googling myself.

Thanks,

Peter,

The Netherlands.

[ghurd]

Don't wast time googling. This is it. IMHO.

The cap limits the starting current to what the cap can "hold".

With 2 sets of coils, one set (starts) is small wire, high turns, and high ohms, and one set is large wire, low turns, low ohms.

The starts are a low cut-in rpm PMA.

The runs are a higher cut-in rpm PMA.

The center tap is where the cap was, and has both (2) coil sets connected to it.

One set needs seperated, and a wire added, to complete the second pair of output wires.

Change 3 wires IN to 4 wires OUT.

Add neos.

Thats it!

It can not get easier!

LOOK AT THIS MESS!!!

Added 4 neos, 1 wire, 2 bridges.

It works!

G-

[ghurd]

Jerry explains the seperation of starts and runs better.

That is part of how I learned it.

And the magic smoke might stay in the translation software longer reading his posts than mine.

[wind4Reg]

Hi Zubbly, I was looking at your pictures again and I was wondering, is there a preferred space distance between the group of north pole magnets and the group of south pole magnets? The reason I ask is because if you look at my pic above I have them pretty close together, where as in your designs there is significant space between the poles, was this intentional for some reason or just worked out that way because of the number of magnets you had? I do realize that the N S N S poles have to be spaced equally, just curious about that amount of equal space. One more thing, did you coat your turned down rotor with any kind of finish (varnish etc) before adding the magnets?

I got the impression you were in Canada as well from reading something you had written, if so which province are you in?

Thanks,

wind4Reg