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Forum Index : Windmills : new 36 pole stator

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brucedownunder2
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Joined: 14/09/2005
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Posted: 03:08am 18 Dec 2006
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Well,the new 36 pole stator has arrived by courier. a couple of surprises !!
1. it's wound with the .6 wire(fine wire), which has a coil resistance of 15 Ohms. Each 12 poles of the 3 phases would in series.
2. The pole "ends" are "domed' as the earlier diy attempts to reduce cogging. So maybe this is a further non-cogging refinement by F&P.

So, what do u think about re-configuring the wiring?..

I'll set it up stock standard with the new rotor and see what I get turning it by hand and then into a 12 V battery.

I sort of expect lower o/p than we have been getting in the past with the "cogging" type matched with a modified Neo magnet rotor.

Bruce

Bushboy
 
Gizmo

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Posted: 03:32am 18 Dec 2006
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Its all up to you Bruce. You need to set it up in a jig and crank it over so you can see how much cogging it has compared to a normal 3 phase 42 pole stator, and a 7 phase stator. And you would have to spin by hand to see what sort of volts you can get from it in standard trim, though I would expect close the the same figures we had from the old stators. Then try a few wiring combinations. All new ground here, your on your own bruce

Any chance of a photo?

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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brucedownunder2
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Posted: 04:46am 18 Dec 2006
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Well, just set it up on the bench --- get around 150v plus out of it just by spinning it by hand --absolutely no cogging at all.thing nearly free wheels at very low rpm

But.................. connect a battery to it -either 12v or 24v and whammo, can hardly turn it------soooo, it looks like I'm in for a re-configuration of the pole windings
Would like some assistance , as @ $112 I'd like to make the almost right re-config. lol.
Never had so much fun since our Tom left his balls on the barbwire
bruce














Bushboy
 
Gizmo

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Posted: 05:05am 18 Dec 2006
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You need to find out how many volts one coil makes at a certain rpm. Set up your lathe and spin the hub at whatever your windmill runs at, say for example 300 RPM. Then measure the output voltage from the star center to one phase connection. Be carefull, those volts could kill you. Then divide the result by 12 ( 12 poles per phase ). That will give you a voltage per pole, a good starting point.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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KiwiJohn
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Posted: 05:07am 18 Dec 2006
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Bruce, how about giving it a try with a transformer on one phase?

(Yeah yeah, I know no one on this site likes transformers! )
 
Gizmo

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Posted: 05:11am 18 Dec 2006
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Once you get the voltage per pole, multiply that by 1.73 to convert to 3 phase output levels. So if each coil made 10 volts, and you wanted to charge 24 volts, well 10 * 1.73 = 17.3 volts, not enough, so 2 coils in series = 20 volts * 1.73 = 34.6 volts, yipee! But you need the voltage per coil per RPM first.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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Gizmo

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Posted: 05:22am 18 Dec 2006
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The problems with transformers is they are usually designed for 50 Hz, where the F&P could run from say 43Hz at 100 RPM to 216Hz at 500 RPM. They will work but loose efficiency above 150RPM on a F&P.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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KiwiJohn
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Posted: 06:12am 18 Dec 2006
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Maybe so but a transformer provides an easy means of gauging what output might be practical at lower voltages. Safer too especially if you are going to drive the F&P on a lathe or somesuch.
 
kenputer

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Joined: 02/05/2006
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Posted: 12:09am 03 Jan 2007
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I recieved a new 36 pole stator today to go with the new rotor from late last year :-) Do I just divide up into six groups and rewire like the 42 pole for charging 12 volt?
Thanks
Ken
As good as you are and as bad as I am,I'm as good as you are as bad as I am!
 
Gizmo

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Posted: 03:10am 03 Jan 2007
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Hi Ken

Dont know, the new 36 pole stators and recofiguring them is all uncharted waters.

But yes the standard SP rewire should work fine for 12V.

Sorry cant give you a yes no answer on this one.

Glenn
The best time to plant a tree was twenty years ago, the second best time is right now.
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brucedownunder2
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Posted: 06:07am 03 Jan 2007
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Posted: 03 January 2007 at 7:29am | IP Logged    

------------------------------------------------------------ --------------------

Yes, Glenn,I've done the electrical test on the new 36 pole Stator.
Have to retake the pic's ,as my flash was turned off,and this Old Fella had to read 5 pages of instructions to get the bloody thing turned on again,lol.

1 Phase across the star point produces 244-250 v ac at 574-600 rpm.
calculating this ,I end up with 38v ac approx.before the rectifiers.

This makes me think I will re-configure the Stator into a 3phase 4 pole unit.

What do you think ?.

Also ,I'm heading towards a dual set-up with ,like you say, different wired Stators, 1 of the 3 phase and 1 of the 7 phase ,seperate rectifiers up at the platform ,then 2 wire dc feed to the workshop control panel.
Anybody that wants to do this should consider Trev's extended s/s shaft (extended milled spline for the dual rotor) , and his cast extended bearing holder .
The only thing I'm worried about is the strength of the s/s shaft being directly connected to any 3 bladed mill of more than ,say, 11 feet diameter.
Mine is up now and is spinning slowly even in no apparent wind.
So, direct drive looks like the only way ,unless you are going over ,say,12 feet ,then the belt drive may be successful.
Sorry to be so long winded,haha.





Bruce

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Edited by brucedownunder2 2007-01-05
Bushboy
 
KiwiJohn
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Posted: 07:52am 03 Jan 2007
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Bruce, I suggest to get a useful voltage reading you would need to connect some load, did you do that or did you measure open circuit voltage?
 
brucedownunder2
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Posted: 08:20pm 03 Jan 2007
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hi Kiwijohn, Thanks for that ,I didn't have a load connected ,but maybe I could install another stator and rotor on the other side of the shaft and see what happens . I could short out 1 phase ,this should give it a load.
(I just edited a previous post to show the testbed,smallish drive motor ,but does the trick for evaluation ).

I don't think Glenn has suggested in the past to apply a load,this was with the old re-configured stators and they seem to have come out fairly well.

BruceEdited by brucedownunder2 2007-01-05
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KiwiJohn
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Posted: 05:29am 04 Jan 2007
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Hi Bruce, I feel shorting out is a bit severe.   If I recall the lessons of long ago the maximum power transfer will occur when the source and the load have the same impedance.**

If we ignore the niceities of 'impedance' versus 'resistance' I think a suitable test load would be a resistance about the same, maybe a bit less than the resistance of the phase you are testing (15 Ohms?). If you have another stator you could just lie that on the bench and connect as a 'load', I think that would be an ideal load having the same resistance and even impedance as the one being tested. Measure amps and volts at various revs. Would someone please correct this if I am wrong!


** It may be convenient to think of this load matching as being similar to loading a mechanical power source. Put too much load on an engine, for example, and it will not be able to turn fast enough to develope any useful power but put too little load on and the engine just revvs and still does nothing useful. A short circuit is like too much load, a high resistance or open circuit is like having no load on the engine.Edited by KiwiJohn 2007-01-05
 
Megawatt Man

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Posted: 07:54am 04 Jan 2007
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G'day KiwiJohn, no you are right on both counts.
Megawatt Man
 
KiwiJohn
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Posted: 08:10am 04 Jan 2007
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Thanks.

I have some 0.5mm resistance wire from an old clothes dryer. 1 metre has a resistance of about 4 Ohms, originally coiled in the familiar shape I stretched it out straight to do the measurement.Edited by KiwiJohn 2007-01-05
 
Megawatt Man

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Posted: 12:03am 06 Jan 2007
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  brucedownunder2 said   Posted: 03 January 2007 at 7:29am | IP Logged    

------------------------------------------------------------ --------------------

G'day Bruce, You probably have received an off-forum message from me by now. Can you give me some details about your calc after measuring no load voltage output too? Does "across the star point" mean from star point to end of one phase winding or perhaps from one phase to another?
Megawatt Man
 
Megawatt Man

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Posted: 05:59am 12 Jan 2007
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G'day KiwiJohn, a slight amanedmant to a compliment I paid you the other day. The maximum power transfer froman alternator occurs when the magnitude of total resistive load equals the magnitude of the machine's inductive reactance. THat's another rerason why I want to know more about the fundamentals of these machines, such as the saturation flux, the reactance etc. If you have a set of maths equations to start with, you can predict and recommemnd and hopefully save a lot of blokes a lot of time!
Megawatt Man
 
Megawatt Man

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Posted: 06:00am 12 Jan 2007
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I wish I could type!
Megawatt Man
 
KiwiJohn
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Posted: 06:45am 12 Jan 2007
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[quote]G'day KiwiJohn, a slight amanedmant to a compliment I paid you the other day. The maximum power transfer froman alternator occurs when the magnitude of total resistive load equals the magnitude of the machine's inductive reactance. [/quote] OK, I think I understand. So if there is an inductive load capacitance should be added to bring the load's inductive reactance into phase with the source? But a battery under charge is pretty much resistive.

I am a bit suprised though if the resistance of the machine's coils is not part of the picture.

I agree entirely, a few calculations could save an awful lot of cut and try, I gave it a bit of a go but its really beyond me!
 
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