Author Topic: stator question  (Read 12483 times)

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artv

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stator question
« on: April 27, 2010, 07:48:29 PM »
Hello again ....Flux,  BobG,  Ghurd,  Let me first say "I think you guys are the best" ........(hope I'm not leaving anybody out) I'm sure I did... sorry.. on the 10' 12mag  9coil.... do the coils see one pole on one side, opposite pole on other side because coils are wound in circular design ...left goes up ...right goes down.........left see's north ...right see's south.......when I say sides I mean legs...is this correct? if this is true is'nt this really direct current but alternated buy orientation of mags on rotors

Flux

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Re: stator question
« Reply #1 on: April 28, 2010, 01:59:19 AM »
I don't really follow the question.

Magnets are placed such that one disc has a N pole opposite the S pole of the other. Flux crosses the gap from N to S and returns from N to S on the next pair of poles.

Each coil of a phase has the same flux linkage at any instant. If one coil sees a flux passing from left to right, the other two coils will see the same so the three voltages add in series with coils joined start to finish.

There is no dc, there can't be. The instantaneous emf is proportional to the rate of change of flux linkage, if there is no change there is no emf. If the rotor is stationary there is no flux change and you get nothing. When it is rotating the instantaneous emf rises and falls and changes sign every time the other magnet polarity links the coils. The resultant waveform is some form of ac and the amplitude changes with rotational speed.

I think you are still thinking in terms of that original equation when you start worrying about coil legs and magnet position.

Think of it another way. When the magnets are over the centre of the coil maximum flux is linking but it is not changing so the instantaneous volts will be zero. When the opposite polarity magnet is in this position it ia again zero volts but you will be approaching from the opposite polarity.

The point of maximum flux change is when the magnets are mid way between the maximum linkage points, the rate of change is then the maximum so the instantaneous emf peaks. This happens when the magnets are over the coils legs in a conventional arrangement. Far better to think of it this way then your way of wires cutting flux lines at right angles.

You can't get dc as you can't maintain the situation, it is an interim stage in the flux linking process and the emf has to reverse when the next pole comes up.

Flux

artv

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Re: stator question
« Reply #2 on: April 29, 2010, 07:30:50 PM »
Flux....let me first thank-you for the reply...I've been reading every thing I can find ....I've read your answer a 100 times .....when rotor links flux while entering coil leg ....starts at zero and quickly rises then hits the hole drops to zero then rises again on the other leg. all  on one coil? This is AC because ....left side of coil is going up ......while right side is going down??To me thier just following the flow.So with the left hand rule the magnetic field is changing 180 degrees /coil leg..........thats to say the first180 degrees is positive(one leg)next 180 degrees negative second leg.Or is it  whole coil is pushing current one direction ... then reversing  with reversing polaritys on rotors.............just trying to understand               

dsmith1427

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Re: stator question
« Reply #3 on: May 04, 2010, 09:09:11 AM »
The following website does a good job of explaining three phase basics:

http://www.windstuffnow.com/main/3_phase_basics.htm

you may want to check this out.  If I find any other illustrations that might help, I will post them. 

artv

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Re: stator question
« Reply #4 on: May 07, 2010, 07:44:46 PM »
...Flux....when there is motion....the emf rises and falls in conjunction with magnetic polarity.....if the magnetic polarity doesn't change.......won't the emf just rise to infinity

luv2weld

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Re: stator question
« Reply #5 on: May 08, 2010, 08:36:47 AM »
artv,
Have you read this????

http://www3.telus.net/faheydumas/Wind_Turbine/Forum/AXIAL_FLUX_HowItWorks.pdf

It might help with understanding.

Ralph
The best way to "kill time" is to work it to death!

artv

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Re: stator question
« Reply #6 on: May 08, 2010, 10:28:53 AM »
thanks for the replies.........dsmith1427 I found windstuffnow before this site read everything on it ,actually how I found this (links)....so you can all thank Ed for sending me your way lol :)..Ralph I have had this for awhile now too read it several times both very good highly recommend to all newbies.The one real confusing thing about Eds' three phase turbine kit is how he winds the slotted stator, each slot shares reversing coils of same # of turns wouldn't this cause cancelation obviously not because it works but why?

TomW

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Re: stator question
« Reply #7 on: May 08, 2010, 03:00:05 PM »

 he winds the slotted stator, each slot shares reversing coils of same # of turns wouldn't this cause cancelation obviously not because it works but why?


Simply put, it is about how you connect the ends of each coil or coil group.

Basically it doesn't matter what way the coil is wound by swapping the end connections you can change its polarity.

Might look for coil posts mentioning starts and ends

Tom
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artv

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Re: stator question
« Reply #8 on: May 08, 2010, 09:57:47 PM »
Hello TomW ...yes I realize you can reverse flow by reversing leads ....but Ed uses a coil of wire with one start one end ,then criss crosses them in the stator(his three phase turbine kit)...in each slot half the conductors are going one direction ,the other half going the other way....dosen't this contradict the left hand rule??.............artv

Flux

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Re: stator question
« Reply #9 on: May 10, 2010, 01:08:37 AM »
You only need to consider the coils of one phase. They will be just as in any other single phase machine except that it is a wave winding done with a skein of wire rather than individual coils, the end result is the same.

The other coil side in the slot that you are worrying about is in another phase and the current in it will be displaced in time, that's how 3 phase works. In fact the vector sum of the phase volts at any instant is zero but that doesn't mean that things cancel out in normal operation.  The rectifier swaps the leads round at the appropriate times to keep the load current flowing in the same direction.

Get to understand single phase before worrying about 3 phase.

Flux

artv

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Re: stator question
« Reply #10 on: May 12, 2010, 05:08:07 AM »
Hi Flux ...single phase with (9 coil, 12mag)...is it all the coils are hooked in series one right after the other?Three phase every third coil hooked in series? So single phase is basically one coil, Three phase basically three coils.This way the three phase would be better because it creates less heat being its' only producing 1/3 of the time,compared to single which produces all the time?When things get hot effiecency goes down.......don't know if I'm reading things right...........artv

wooferhound

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Re: stator question
« Reply #11 on: May 18, 2010, 02:33:47 PM »
in a single phase machine
the Starts & Ends are reversed on half the coils
to match the fact that half the magnets are reversed

Each coil set in a 3 phase machine is producing just as much of the time as the coils in a single phase machine, but the peaks of the 3 phase AC waves are only slightly offset from each other and better able to make a steady DC output after rectification. A single phase machine will produce AC peaks that are much farther apart and creates a Pulsating DC after rectification to DC voltage. Because of this a Single phase machine will Hum or Vibrate much more and at a lower frequency than a 3 phase machine.
« Last Edit: May 18, 2010, 02:43:20 PM by wooferhound »

artv

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Re: stator question
« Reply #12 on: June 08, 2010, 05:45:37 PM »
Hi all ,you guys are the greatest been doing some reading ......from what I understand ,elecron flow is instantaneous,,if you send electrons one direction ,next to a conductor in the opposite direction .............this creates cancillation.......induction??......probably not reading things right ...........artv

DanB

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Re: stator question
« Reply #13 on: July 12, 2010, 10:07:14 PM »
Hi Flux ...single phase with (9 coil, 12mag)...is it all the coils are hooked in series one right after the other?Three phase every third coil hooked in series? So single phase is basically one coil, Three phase basically three coils.This way the three phase would be better because it creates less heat being its' only producing 1/3 of the time,compared to single which produces all the time?When things get hot effiecency goes down.......don't know if I'm reading things right...........artv

Hi Art.
you cannot have single phase with 9 coils and 12 magnets.  In order for 2 coils to be in phase, they must be seeing an 'identical magnetic situation' (not sure how else to say that) - which is impossible with 9 coils spaced evenly around 12 poles.  But -  with 9 coils around 12 poles, then 3 of those coils are seeing an identical situation and they are therefor 'in phase' with one another.
If I ever figure out what's in the box then maybe I can think outside of it.

artv

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Re: stator question
« Reply #14 on: August 03, 2010, 08:27:34 PM »
DanB....when the three coils ,seperated by 120deg.(one phase) ............the leading leg (of all three coils)see the same magnetic polarity............producing electron flow all in the same direction added together (in series) ...but hit trailing leg electron flow induced is opposite direction....but because when field collapses in leading leg............this addes to the trailing leg............when mag leaves the leading leg, the induced flow reverses..............this is back emf...............n/s hit leading leg,inducing flow ,exit leg,flow reverses ,s/n hit leading leg as n/s hits trailing leg adding to the original reverse flow caused by the n/s leaving the leading leg....................artv

Flux

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Re: stator question
« Reply #15 on: August 04, 2010, 03:29:13 AM »
You would find life very much simpler if coils had no legs, arms,feet or anything else.

A coil is a loop of wire and emf is induced in it when flux links it. The emf depends on the magnitude of the flux linkage and the rate of change. This is all you need to understand.

Thinking in terms of legs goes back to that stupid equation for the emf induced in a conductor moving through a uniform magnetic field, it is correct but doesn't apply in the real world of electrical machines. It becomes complicated to adapt it to real life and you have got yourself in a right muddle trying to come to terms with it.

Don't get back emf mixed up with all this, it applies to morors and electromagnets and is the base of Lenz's law but you needn't worry about it here.

Flux

artv

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Re: stator question
« Reply #16 on: September 17, 2010, 06:32:33 PM »
Flux ....as the rotor (magnets) approach the coil(s) flow is induced ,......when mags exit,.... field collapses.............this is back emf..........trying to get a clear understanding...........thanks.........artv

artv

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Re: stator question
« Reply #17 on: October 28, 2011, 06:47:19 PM »
This may be old to you ,but it's new to me,....
As electrons flow from one end to the other (regardless of direction) in the coil ,....each wire in that coil produces ,..an EM field around it (around its' outer circumfrence of each turn).......kinda link a spiarel..........
When you spin dual rotors.....you create a spinning magnetic field, on two sides...............
Introduce a conductor into ,that field , it causes electron flow.....inside the conductor.................
When the wire starts conducting it produces the same EM field...
Any time you use a wire to work your wasting the EM field...........Unless you can catch it some how ???

ghurd

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Re: stator question
« Reply #18 on: October 28, 2011, 07:21:25 PM »
It is not 'wasted'.  It just happens.
If you light a candle to make light, it gets hot.  Same idea.
If you light a candle to make heat, it makes light.  Same idea.

You might want to look up "super conductor",
G-
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seilertechco

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Re: stator question
« Reply #19 on: April 12, 2012, 06:47:54 PM »
ARTV,  As the north pole of the magnet approaches the coil the wave form will go up on the positive side.  When the coil is directly above the north pole, the wave will peak out.  As it moves away from the north pole, the wave form will go down (that's half of a cycle).  Then at exactly half way between the north pole and the approaching south pole the wave form will be at the zero or starting point.  Then as the south pole approaches the wave will go negative.  When the coil is directly over the south pole it will reach the bottom of the wave form and turn upward.  Once again at the midpoint between the south pole that just passed and the next north pole approaching, it will be at the zero position.  That's one complete cycle, passing both north and then south poles.  And do it all over again for every set of poles per revolution.

Bridge rectifiers use diodes to take the bottom half of the wave form and mirror it to the opposite side of the neutral line, so instead of electrons going backward, they flow only in one direction.  A diode is like a check valve in a water system, permitting flow in only one direction.  Google bridge rectifiers.  In single phase, the wave form returns to the neutral line as it passes each magnet and reaches the midpoint to the next and opposite pole.  This gives a rough but workable flow of electrons in only one direction (dc).  The wave looks like a series of bumps, but all in the positive direction. 

Three phase has that same series of bumps but they are offset 120 degree.  That gives a top of the waveform that has three bumps, but never returns to the zero line.  It eliminates the pulsing of going from peak to neutral or from full speed to a full stop in flow terms. 

I want to point out that when the direction of flow changes as in alternating current, one needs laminations to control heat from the change in direction of electron flow, but with DC, the electrons always flow in one direction and do not re-orient polarity (180 degree), thus laminations are not a necessity.  In my case, combining electromagnets and permanent magnets, the flow is dc so laminations are not a requirement and I'm using regular old cold rolled steel.  Google electro-permanent magnets for more info.  Of course the power coils will be seeing ac so that does require laminations to limit hysteresis derived heat.

Perhaps this explanation makes some sense to you. 

Best regards, Toby
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