Author Topic: motor conversion help  (Read 12668 times)

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Basil

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motor conversion help
« on: August 09, 2011, 07:14:13 PM »
I started the motor conversion I have been wanting to do. I picked a 480 volt 1.5 hp, 1740 rpm.
I went in and cut the star connection and ran 3 more wires out. This gave me a total of 12 wires.
I counted the wire raps and it was 36. So 6x6 is 36. Good so for. I took a battery charger and found all six set of coils.
The problem is the coils ( 6 ) are wider than the magnets I have.
The magnets are 1 inch wide by 1/2 inch by 2 inch. I would be leaving 2 stators ( I think you call it. )of the 6 will not be covered.
I need to off set the magnets around 10 % to lower the cogging from what I read in Zubblys files. Doing this will cover the last two some but not much.
The questions are.
Will this be ok?
And how many magnets to use. ( 8 )? 6 coils 8 magents?
I have milled the rotor down for the magents and gave it room to offset the magents 10%.
Two inch magents would fit perfect to cover from end to end.
Any advice will help at this point.

SparWeb

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Re: motor conversion help
« Reply #1 on: August 10, 2011, 12:28:40 AM »
Would it have a stator that looks like this?



That's a shot from my 3HP, it has 36 "teeth" in the stator (and 36 "gaps" of course).  In a lot of these motors, there would be 36 coils inside it, too.
That would mean that each coil shares a gap with another coil.  Is that the situation in your stator?
Smaller motors might have 30 or 24 teeth.  If you're counting four poles, with 6 teeth each, then maybe that's what you've got: 24 teeth in the stator.

The speed of 1740 RPM says 4 poles to me.  That breaks down into 3 phases x 4 poles x 2 coils per phase per pole = 24 coils.
I think I know what you mean by the 6 sets of coils, but confirm that you have 24 stator teeth before we talk more about it.

You don't really have to count the stator teeth to size up the rotor's poles.  It's rather obvious if there are 4 wire poles then the rotor has 4 poles too, so each will cover 90 degrees of the rotor's circumference.
The magnets must do the same.  Just cover each quarter of the rotor with magnets and you're good.  Until you measure the diameter of the rotor, I can't tell how many magnets will fit.
1x2x1/2...   bricks with holes or without?  Nickel-plated or black epoxy?

Just taking a step back from the questions...  don't get the axial-flux 4:3 ratio for magnets:coils involved in this.  Not yet at least.  There's no changing the 4-pole nature of the motor unless you re-wind it.
But if you do want to re-wind then you have a lot more options, so don't let me stop you!  There's a helpful way to draw out the stator's teeth when laying out new windings.  I can dig up some Zubbly diagrams if you want to consider that.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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oztules

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Re: motor conversion help
« Reply #2 on: August 10, 2011, 02:09:13 AM »
Gee Sparweb, I'm not so sure about that explanation.

He claims 6 sets of coils. This tells me that this unit is indeed 4 pole.... but half of them are phantom poles.... ie don't exist in copper terms, but do exist in magnetic terms. I think they call them consequent poles. Each set of coils will probably have 3 concentrically smaller coils making up the bigger ( effectively) wound (12 span) coil ..... to make a single pole....... so by definition I think he has 18 physical coils of wire in this thing.

Each coil group is three concentric coils of 12 slots, 10 slots and 8 slots width.... one wound inside the other...... and inside the other.

For the first 2 poles ......the first coil group takes up  12 slots like this:

Slots   1 and 12 first coil, 2 and 11 is the second and the smaller coil,   3 and 10  are used up....... leaving the 4,5,6,7,8,9 slots empty (6 inner slots of this group). There is no opposite wound pole for this pole..... we wind one pole group and get 2 poles.?????.... yep.

We get the  next 2 poles of this first phase, by wiring a set of coils of the same 1-12, 2-11, 3-10 geometrically  exactly opposite the first pole group, and wire it up so it is of like polarity to our first pole group.....ie.  if we energise this phase group ( now 6 coils) with DC, we would see 2 N poles at the coils themselves, and 2 S poles halfway between these coil groups..... the aforementioned phantom poles

Thats how we get the 4 poles with effectively 2 coils (centric wound groups of three each).

The other two phases are the same thing but offset 120 degrees. This takes up the whole 36 slots for 18 coils. The coils are 6 groups of concentrically wound 3 coils.


In theory, if we reverse the polarity of each opposing coil group, we could have a 2 pole machine, as now we would have a N and S opposite each other and no phantom poles present so 180 degrees apart.............rather than a N opposite a N and making the phantom poles between.... making 90 degrees apart..... downside is that each pole will not cover 180 degrees of stator like a properly wound 24 slot 2 pole would.



clear as mud I suppose..... but I tried.

so I expect a 4 pole 36 slot stator with only 18 coils.




..................oztules

Edit... yes it is messy.... I'm not very good at this words to pics business
« Last Edit: August 10, 2011, 02:25:22 AM by oztules »
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SparWeb

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Re: motor conversion help
« Reply #3 on: August 10, 2011, 02:55:09 PM »
I assumed it looks like the stators I already know.  Stuff I've seen has over-laying coils that each fill 1/2 slot.  I've seen concentric and offset coil overlaps, too.  If it's got phantom poles then I'll just stop here.  I can picuture what you describe, but it didn't cross my mind as I was writing, sorry.  I can get out an old motor re-winding book at home and see what it says.

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SparWeb

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Re: motor conversion help
« Reply #4 on: August 10, 2011, 03:39:18 PM »
Yes, of course...   Zubbly described it well.

http://www.greenbits.com/User+Pages/zubbly/Induction+conversion+1st+edition




Is this what you've got Basil?

Sorry 'bout the mixup
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
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Basil

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Re: motor conversion help
« Reply #5 on: August 10, 2011, 05:57:52 PM »
Thanks for the reply Sparweb and oztules.
Would it have a stator that looks like this?
Here it is.
Lots of infomatio. Thanks I think. My head is hurting now.

That's a shot from my 3HP, it has 36 "teeth" in the stator (and 36 "gaps" of course).  In a lot of these motors, there would be 36 coils inside it, too.
That would mean that each coil shares a gap with another coil.  Is that the situation in your stator?
I think it is.

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Re: motor conversion help
« Reply #6 on: August 10, 2011, 06:46:27 PM »
I'm afraid the re-wiring you've done hides the answer to Oztule's question: if it's a consequent pole motor then the each coil will wrap almost all the way around to the other side of the stator, whereas if it's wired the way I was expecting, then the coils go around the stator 1/4 of the way.

Here's a bunch of guys who really know what's what inside a motor (countrymen of yours Oz, presumably you keep them out of trouble, too):

http://forums.aeva.asn.au/forums/forum_posts.asp?TID=1237&PN=1

Though they're setting them up to run from a VFD...

Anyway, until someone tells me differently, the 4 poles on the rotor should be just 4 poles - don't try to make 2 poles out of it if you do have one of those consequent pole setups.

How big around is the stator ID?
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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Basil

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Re: motor conversion help
« Reply #7 on: August 10, 2011, 07:25:46 PM »
The stator ID was 3 inchs.

Basil

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Re: motor conversion help
« Reply #8 on: August 10, 2011, 07:32:17 PM »

It is turned down to fit the 1/2 magnets. Best a flat magent will fit a round hole.

oztules

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Re: motor conversion help
« Reply #9 on: August 10, 2011, 08:31:00 PM »
Yes, Sparweb,

That Zubbly pic is what I was endeavoring to describe in words. If he has this, then the coil wrap will be 1/3 the teeth for the big wrap. (12 slots)

Provided he does not change the phase groups themselves ( ie keep them N-N not N-S), it will remain a candidate for a 4 segment rotor. N-S-N-S.

Your the mans for the next bit... how big (as much as you can for me), and any skewing information he may find useful. I think he needs near 90 degrees of magnet for each pole, but I bet it works just fine with less.




....................oztules
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SparWeb

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Re: motor conversion help
« Reply #10 on: August 11, 2011, 12:48:47 AM »
Then it's a simple matter of drawing to scale.



The forum software re-sized my drawing just enough to make the numbers hard to read.  Click on the image link at the bottom and what opens will be the original size and much clearer.
Assuming that the stator is EXACTLY 3.0 inches ID.  Gotta be pick about this, otherwise it will have too much clearance, or worse, won't fit in at all!!

The 2x1x0.5 magnets don't do so well because you can only get 4 around.  Trying to put 8 around just won't work.
On the other hand, having magnets 3/4" wide and 1/2" deep will work - though just barely.  Using 3/4" wide magnets that are 3/8" thick will fit comfortably, and still be plenty to fill the stator with imaginary lines of force!

I won't guess about the lengthwise direction - how long is the rotor?  If you have to skew by turning the magnets then you have to watch out for the clearance.
« Last Edit: August 11, 2011, 12:53:08 AM by SparWeb »
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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Basil

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Re: motor conversion help
« Reply #11 on: August 11, 2011, 05:26:24 PM »
I may have messed up But I turned it down to where the 1''x 1/2''x2'' would fit.
Here I just stuck the magnets in. Looks that I will have about 1/8 or a little more space between the sets.

I turned the whole stator down so don't let looks fool you. You said 8 would not do so good. Why?
Going by the photo you did I can do the top left but It will have gaps between the sets.
Boy I must have messed up bad. But I messured and it should just fit when done.
You answerd my question. I need 4 N-S-N-S.

SparWeb

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Re: motor conversion help
« Reply #12 on: August 11, 2011, 08:22:38 PM »
Not such a big mess-up.  You have to work within the rotor size you have.
How about getting some 1/2" wide magnets that you can fit between the empty spaces?
See that dimsension off at a 45 degree angle "0.49" ?
What if it's actually a bit more, and you can fit a 1/2" magnet between the bigger bricks?
Then you'd have 4 poles that go like this:

N-n-S-s-N-n-S-s

Where each pole is made up of one big and one small magnet, each having the same pole outward.

I did something similar to that with my Baldor - too much empty space with 2 magnets per pole, not enough room for 3 magnets per pole, but I did fit in "2.5" magnets per pole, in a manner of speaking.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
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oztules

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Re: motor conversion help
« Reply #13 on: August 11, 2011, 10:16:10 PM »
It just dont add up....
"The stator ID was 3 inchs." you said Basil..... but your picture shows 8 mags already on the turned down rotor...... Sparweb's scale pics say that is not possible.

I can only assume you meant to say that you had turned the rotor down to 3" OD,  which would then fit your 8 magnets with about 1/8th inch separation at the steel .... which matches your comments later on.

I suspect Sparweb is laboring under the impression the stator id was 3"..... in which case 8 magnets cannot fit around the turned down rotor which would have to be close to only a few inches in diameter diameter.... not 3".


Is that correct?

..... Sparweb, that rotor you did with the weird placements....  I was pretty darn impressed.... ( still not sure how it stopped the cogging... but it did apparently.



..............oztules
« Last Edit: August 11, 2011, 10:22:53 PM by oztules »
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Basil

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Re: motor conversion help
« Reply #14 on: August 12, 2011, 07:59:40 AM »
sparweb and oztules
Sorry for the confusion. I did say it was 3''.
The stator is right at 3 and 1/4 now that it's cut down. ( The out side ( OD )
So it all makes sense now. Again sorry.
I'm trying to do this and 100 other things at the same time.
Ok, I can go with NN-SS-NN-SS. Right?
« Last Edit: August 12, 2011, 08:02:22 AM by Basil »

oztules

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Re: motor conversion help
« Reply #15 on: August 12, 2011, 08:25:20 AM »
Answer ... yes.

Now Basil .... the thing with the wire coils  is the stator, and the thing you turned down is the rotor..... thats why we were confused.


Have fun



.............oztules


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SparWeb

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Re: motor conversion help
« Reply #16 on: August 12, 2011, 04:28:53 PM »
Goodness, I don't know what's been measured any more.
Suddenly I realize that there already ARE 8 magnets on your rotor Basil.

NN-SS-NN-SS    4 poles, 8 magnets, done...  right?
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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Basil

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Re: motor conversion help
« Reply #17 on: August 12, 2011, 05:10:19 PM »
Sparweb
Sorry for confuseing you. I told you wrong.
I had the stator and rotor mixed up.
I gave you the wrong messurment of the rotor. Well all of it.
Sorry and thanks for the help.
I will post how it comes out. Good or bad.

Basil

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Re: motor conversion help
« Reply #18 on: September 04, 2011, 06:20:14 PM »
I have it put back together.
I had to turn the magnets down a little for it to fit. With no wires hooked up it turns easy with nearly no cogging. Very surprised.
As I hooked the wires up there would be a little more cogging. When fully wired the cogging is worse. This is with all the wires tied together with nothing hooked to it.
It is wired
White 1,  Brown 2,  Yellow 3,  White 4,  Brown 5,  Yellow 6,  Black 7, Red 8,  Blue 9,  I cut the star connection so there is wire 10 form 7, Wire 11 from 8, Wire 12 from 9.
U1            V1           W1            V2           W2           U2             U3         V3        W3
I tied wires 1,6,7,12 together then 2,4,8,10 then 3,5,9,11.
I gave the wires there numbers. The wires did not have numbers on them. Just color.
With it wired this way. It cogs a lot more than when none of the wires are together.
It seem that each time I tied in coils it cogged a little more. Don't take it wrong I can turn it by hand easy but not as easy as before.
Is this normal? 

SparWeb

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Re: motor conversion help
« Reply #19 on: September 04, 2011, 08:21:44 PM »
It could be normal to have a bit more cogging when the phases are hooked up.
Are you trying to connect in parallel-Delta?  The first list: 1,6,7,12 would suit that...  so do the other connections.
Any small imbalance in the position of the magnets will be an imbalance in the field in each coil.  Not only that, but a small current can circulate in Delta that you will feel when free-turning the shaft.

So yes, probably just normal.

If you were to wrap a string around the shaft, how much force would you need to pull to get it to turn and keep turning at a constant speed?
If it's say 10 pounds, then it's no big deal.  If it's much more, then this could be an indication of a problem.  In that case you should connect in star, and compare.  Then double-check the wires for something that isn't labelled right.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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Basil

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Re: motor conversion help
« Reply #20 on: September 04, 2011, 11:45:03 PM »
Thanks SparWeb
I will test it as suggested.

Basil

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Re: motor conversion help
« Reply #21 on: September 05, 2011, 06:34:22 PM »
SparWeb
I did some rewiring test and the cogging nearly went away and voltage went up. Best I can tell by hand.
I tried. LOW voltage WYE 1,7  2,8  3,9  4,5,6  10,11,12. It did better. Less cogging and seem to be around the same voltage turning by hand.
Next I tried HIGH voltage Delta 1,12  2,10  3,11 4,7 5,8 6,9. The voltage went up with slower speed. Even less cogging.
I do not have a scale to do a string test. Yet.
I think I have a good conversion for a wind mill. I was hoping to use it on my hydro.
I have no way to compare rpm to voltage / current here at home. I will take it to work one day when I get it ready for testing.

Thank for the help.

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Re: motor conversion help
« Reply #22 on: September 06, 2011, 04:11:39 PM »
Yes it does sound like everything's working well.
You don't need to study it to death either. 
Keep building cool stuff and leave the geek stuff to me  ;)
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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Rover

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Re: motor conversion help
« Reply #23 on: September 06, 2011, 04:46:41 PM »
SparWeb

You really didn't mean this ...

"You don't need to study it to death either"  What? now what am I'm I going to do with my time?. Might as well chuck the variable speed DC motor, the laser tach, the current sensors, the voltmeters, the RF transmitters, heat sensors .. etc...

I may have to watch professional sports or something ... no....... no .....

I do so enjoy watching a graph grow...

:)

Rover
<Where did I bury that microcontroller?>

SparWeb

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Re: motor conversion help
« Reply #24 on: September 07, 2011, 03:52:23 PM »
Sit in the corner and watch while I have all the fun!   


SparWeb

You really didn't mean this ...

:)

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
System spec: 135w BP multicrystalline panels, Xantrex C40, DIY 10ft (3m) diameter wind turbine, Tri-Star TS60, 800AH x 24V AGM Battery, Xantrex SW4024
www.sparweb.ca