Author Topic: Active Pitchcontrol  (Read 225412 times)

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Ungrounded Lightning Rod

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Re: Active Pitchcontrol
« Reply #567 on: March 20, 2017, 03:07:00 PM »
posted this awhile back;;bike alt......coils mounted to a flat steel band...coils have stacked steel inserts in the coil holes....steel inserts made out of steel cutoffs from a length of flat steel..these were super glued together ..then glued down to the steel band... ...some drag thou..because the wheel has a slight drag to it

Is the "flat steel band" a solid piece of steel, or a stack of thin steel sheets, edge-on to the magnets, with the edges aligned along the motion of the wheel?
 
Are the punchings for the pole pieces inside the coil stacked so the face of each stack is presented to the magnets, or are the edges presented to them (preferably also arets are presented to the magnets and with the edges aligned along the motion of the wheel?

If either of them are the first case mentioned, a lot of your drag is eddy currents in the steel.

(Some of your drag is also hysteresis losses, unless the steel is transformer steel or other (magnetically) "soft iron".

joestue

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Re: Active Pitchcontrol
« Reply #568 on: March 20, 2017, 07:12:02 PM »
A small amount of the flux does pass through the copper according to the saturation of the core, the width of the slot opening, and the permiability of the core.

99% of the flux lines go through the core, not the conductor.

Answer me this: why do superconducting coils work in a transformer or motor if no flux can pass through the conductors

hiker

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Re: Active Pitchcontrol
« Reply #569 on: March 20, 2017, 09:25:38 PM »
Just worked with what I had...yes the flat bar is solid..and the coil steel inserts are laid flat..coils are laid wrong also...couldent have built it more wrong if I tried !...I new I would be fighting the steel as well as the coils..with all that metal..and extra windings...surprised it doesent really cogg that bad..thought it would with the metal in the coils...never thought it would work as good as it does or last as long as it has...being that the mags and coils plus inserts are glued down...was just going to be a quick project..its held up great..next one will be built right !  .......when ??
WILD in ALASKA

hiker

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Re: Active Pitchcontrol
« Reply #570 on: March 20, 2017, 09:35:02 PM »
Ps..I do ride it dang near daily..good way to start the day..mostly use the fan for a load..up to 10amps at 20v...little higher if I  try..or a couple of 12v 50watt headlights..give a good workout..fan is great to keep cool...works great to get a pre workout before I headout on my studded tired mountain bike..snow and ice here......
WILD in ALASKA

Ungrounded Lightning Rod

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Re: Active Pitchcontrol
« Reply #571 on: March 20, 2017, 11:10:56 PM »
Ps..I do ride it dang near daily..good way to start the day..mostly use the fan for a load..up to 10amps at 20v...little higher if I  try..or a couple of 12v 50watt headlights..give a good workout..fan is great to keep cool...works great to get a pre workout before I headout on my studded tired mountain bike..snow and ice here......

Ride it in shorts and point the fan at your upper legs to cool them.  That lets you do a LOT more work and burn a LOT more calories than if you didn't cool your muscles with forced air.

That's why moving bicycles are such good exercise - and why some stationary exercise bicycles have a little squirrel-cage centrifugal fan driven by the wheel and pointing at the upper legs, i.e. to let them be as good as a moving bike.

Ungrounded Lightning Rod

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Re: Active Pitchcontrol
« Reply #572 on: March 20, 2017, 11:48:12 PM »
A small amount of the flux does pass through the copper according to the saturation of the core, the width of the slot opening, and the permiability of the core.

99% of the flux lines go through the core, not the conductor.

At any given moment the bulk of the lines go through the core.   But when you move a magnet from one pole to the next the lines don't break at one pole and re-form at the next.  They move through the gap - and thus through the copper conductors.

Lines of force don't break.  They are loops that come into being at the atomic scale and expand, or contract to a point and disappear.

The closest they come to breaking is when they "reconnect", where fields going different ways in a plasma bump into each other and reconfigure into a lower energy configuration, dumping the energy difference from their relaxation into the plasma.  That is a very energetic process - the origin of solar flares, where they kick the plasma out to interplanetary distances at an appreciable fraction of the speed of light.  But even then, at no point does a field line disappear in one place and reappear in another.  They are ALWAYS continuous.

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Answer me this: why do superconducting coils work in a transformer or motor if no flux can pass through the conductors

Because flux CAN pass through superconductors - in two different ways (both of which involve losing superconductivity in one way or another).

In type I superconductors, a strong enough magnetic field makes the superconductor stop superconducting.  Then the field passes through the resistive region just fine.  But the overall wire (or other conducting structure) starts exhibiting resistance again.  (There are superconducting switches built on this principle.  They have been used both to close superconducting loops (after they've been pumped up to carry a ring current to create a magnetic field) and to make logic gates.

In type II superconductors there's also an easier way:  Flux impinging on the edge of the conductor creates a small resistive region and an eddy current resisting its further encroachment, just like with type I.  But in a type II superconductor the current is free to bend.  So (rather than just keeping the field out of more than a microscopic surface region) the eddy current curves and squeezes a bundle of flux down into a tight core.  The flux in the tight core is enough to make THAT part of the superconductor go resistive (though the average field before the squeeze-down is far too weak to do it), but the eddy current is in the still-superconducting part and doesn't decay.  The field penetrates into the superconductor and the eddy current closes into a loop around it, much like an amoeba surrounding a bit of food.  If the size of the loop is smaller than the width of the conductor (and it's microscopic - a quantum phenomenon - so it generally is), and the number of them is small enough that they don't fill the conductor from side to side, the flux bottled up in the eddy current tubes can cross the conductor just fine (carrying the tubes with them to the opposite edge, where they open up and eject the field), while the overall conductor still carries current (around the little whirlpools) with zero resistance.

Type II superconductors are useful because they can carry AC with zero resistance.

Again, because magnetic fields come into being as loops expanding from a point, when you go from a superconducting ring with no current to one with a current and a resulting (extra) magnetic field through its center, field lines MUST cross the superconductor.
« Last Edit: March 20, 2017, 11:58:04 PM by Ungrounded Lightning Rod »

joestue

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Re: Active Pitchcontrol
« Reply #573 on: March 21, 2017, 12:25:08 AM »
No, the flux lines do not have to pass through the conductor. Watch this animation here https://www.google.com/url?sa=t&source=web&rct=j&url=https://m.youtube.com/watch%3Fv%3D_uMuswyBw20&ved=0ahUKEwigmdLf-ubSAhUQyWMKHZwfAB4QtwIISTAM&usg=AFQjCNGeDACe5VaSXqOl7-R90yjvszaYR

The lines dont break, in the sense that they are imaginary, a better analogy is water flowing like a river. As the magnet passes by the teeth, the flow stops and starts flowing through another channel. But if the core had infinite permiability there would be no leakage flux through the conductor.
« Last Edit: March 21, 2017, 01:30:45 AM by joestue »

Ungrounded Lightning Rod

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Re: Active Pitchcontrol
« Reply #574 on: March 21, 2017, 01:49:04 AM »
Try watching it frame by frame.

The lines go through the coil very quickly in the animation.  So you usually don't see them in the coil space, because they're on one side in one frame and the other side in the next.  But occasionally you do see a frame where the line is in the coil space on its way from one pole to another.

Flux lines are "imaginary" only in the sense that each is an abstraction representing a given amount of flux.  The flux they represent doesn't "stop flowing" in one path and start in another.  The "path" propagates from one position to another at no more than the speed of light.

joestue

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Re: Active Pitchcontrol
« Reply #575 on: March 21, 2017, 03:28:11 AM »
If the flux lines have to pass through the conductor why does the presense of the core practically eliminate eddy current losses in the conductor?

From a certain perspective, yea the magnetic flux stops flowing through one path and starts flowing in another, instantly. Its like water flowing through multiple pipes each with its own valve. If one valve opens another shuts. If synchronzation isnt perfect u get cogging torque, not much different than water hammer. The lines of flux are just visualizations of the field strength or portion of flux in that area. They can indeed disappear and reappear somewhere else as quicky as conditions change. If the air gap was zero, and the permiability of the core infinite, no flux at all would travel through the area where the coils go, regardless if current was flowing in the coil or not.

Tl;dr yes lines of flux disappear and reappear instantly somewhere else as the magnet passes by the teeth. The total number of them doesnt even have to remain the same, but the rate at which they change is equal to the voltage potential generated. For neodymium magnets there is often considerable eddy currents induced inside the magnet by the varing air gap inductance which is what causes cogging torque.
« Last Edit: March 21, 2017, 04:23:56 AM by joestue »

mbouwer

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Re: Active Pitchcontrol
« Reply #576 on: March 21, 2017, 07:27:11 AM »
Interesting discussion. Today I have made the rotor.
My plan is to attach 64 neodymium magnets.

joestue

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Re: Active Pitchcontrol
« Reply #577 on: March 21, 2017, 01:14:10 PM »
So for what its worth there are actually a lot of people who refuse to believe that magnetic materials do in fact shield so to speak, a conductor from magnetic flux "lines" (whatever those lines are btw, the lines you see in a simulation are just representations of the flux's concentration, location, etc)

here's one such person.
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. The mathematics of induction are clear. It requires a changing magnetic flux - WITHIN THE AREA BOUNDED BY THE LOOP - and NOT ANYTHING AT THE LOCATION OF THE LOOP ITSELF OR THE ELECTRONS WITHIN IT. When it comes to understanding why electrons are forced around a secondary loop you must accept some "spooky interaction at a distance" without any local field at the electrons location to explain it. I have more than a bit of a problem with that.


you can find the discussion here, i believe its worth reading. http://www.practicalmachinist.com/vb/transformers-phase-converters-and-vfd/true-3-phase-transformer-how-does-really-work-how-can-i-test-310120/
« Last Edit: March 21, 2017, 01:18:42 PM by joestue »

mbouwer

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Re: Active Pitchcontrol
« Reply #578 on: March 22, 2017, 03:42:31 AM »
After mounting the axle and rotor.


 

Ungrounded Lightning Rod

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Re: Active Pitchcontrol
« Reply #579 on: March 22, 2017, 04:55:11 AM »
If the flux lines have to pass through the conductor why does the presense of the core practically eliminate eddy current losses in the conductor?

It doesn't.  (But unless the conductors are quite broad the eddy current losses there are swamped by the added ones in the core.)

Quote
From a certain perspective, yea the magnetic flux stops flowing through one path and starts flowing in another, instantly.

No, it doesn't.

It snaps across the gap between the pole pieces of a generator, or the core paths of a transformer (as "leakage flux") at nearly the speed of light.  (If it weren't slowed by the eddy currents from its passage through the conductors of the coils, or the refractive index of the air, insulators, and other non-conductors in the gap, it would be at the speed of light.)  In the core it only needs to penetrate half the width in a quarter-cycle, which is glacial by comparison.

Because the field density in flux in the core is something about 1500 times that of the gap, and the animation you referenced shows only four lines per pole piece plus gap, the poles about three times the gap, and five gaps, you have about a one-in-300 chance of seeing a line in a gap in any given frame.  The lines appear to disappear on one side and reappear on the other.

Nevertheless, there's one frame (in second :33) that clearly shows a simulated field line nearly centered in the second gap and "cutting" the coils.

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Tl;dr

THAT post was too long for you to read it?  Then you certainly won't want to bother studying http://web.archive.org/web/20031002111405/http://www.itee.uq.edu.au/~aupec/aupec00/edwards00.pdf until you understand poynting vectors.  But take a look at 1.4 (a)-(b).

It's about transformers.  But you can view a generator as the secondary half of a transformer where the field is varied by splitting off and moving a DC excited primary half (or other magnet), rather than changing its magnetization by supplying it with AC.

joestue

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Re: Active Pitchcontrol
« Reply #580 on: March 22, 2017, 10:11:04 AM »
Did you read section 2.2.2 in that paper you just linked to?

Yes i understand generators are like transformers with a rotating airgap.

Take a generator and fill the teeth with solid bars of copper. Measure the drag with and without them. Now remove the core and replace it with plastic. Rinse and repeat and you can measure the effect. Btw you will need to keep the airgap flux the same for both with and without the core for this to work as a demonstration of why electric motors have cores.

Place for example a one turn loop within the conductor fill of a motor, make the loop as wide as you can and move it around, rotate it 90 degrees.. Let me know how much voltage you get. Now remove the core and place the coil in the same place, let us know what you get. Best to do this with a concentrated pole motor so you can ignore harmonics. I think youll be forces to realize that the magnetic flux lines can indeed be confined to the core and push the electrons around without passing through or even nearby them.


Imagine the Magnetic field lines are like photons, imagine the rotor is a light source, and the core a series of optical fibers that send the light back to the rotor. This analogy isnt a good one but it should help you understand that ideally if the slot opening were zero, the light wiuld never cross through the conductor. Of course the slot opening is finite and the magnetic core is similar to a piece of stained glass, so some of the flux goes through the path of highest resistance.


But try maiking an axial flux generator with half inch solid copper. It would be practical with a core, and the same airgap flux density.
« Last Edit: March 22, 2017, 11:19:01 AM by joestue »

joestue

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Re: Active Pitchcontrol
« Reply #581 on: March 22, 2017, 11:42:49 AM »
You must be able to understand that if you slide a neodymium magnet into a bar of steel, the flux in the magnet is now about 1.3t instead of one. Pull it out and its back to one. You just created and destroyed a whole bunch of magnetic flux lines. Simulate it yourself and ask where did they go?

mbouwer

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Re: Active Pitchcontrol
« Reply #582 on: March 22, 2017, 04:22:17 PM »
Your knowledge is very wellcome specially now that I try to make this radial generator.
64 magnets. 48 coils?
And what configuration will I apply? Is it better to lay the coils on each other like roof tiles?
« Last Edit: March 22, 2017, 04:27:38 PM by mbouwer »

joestue

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Re: Active Pitchcontrol
« Reply #583 on: March 22, 2017, 09:19:06 PM »
the best configuration is similar to what is in any car alternator.

three phases that overlap each other. the cross section is approximately 50% copper and 50% steel as viewed from the rotor, but the slot teeth cover the opening to capture all that leakage flux we don't want crossing through the conductors.  if you don't have any steel teeth sticking through, then you can double the amount of copper you shove through the air gap. so your coils are about 1cm wide, 2 cm inside diameter and 4cm outside diameter. mashed through the middle of the 2 cm wide inside diameter of one coil is two other coils.

when dealing with overlapping coils you have to press the coils together so that the cross section looks like this https://motoredbikes.com/attachments/cross-section-png.26611/


if you do not mash the coils together and fit them in the same air gap as what you can get from a single layer coil structure like this: 000 then you get no improvement, no increased copper density. compared to a single layer coil. and this should be easy to understand why. its like trying to fit washers in a box, there is a fundamental limit that you can't break through without bending them to fit inside each other.

here is a very creative way of achieving a fairly high copper fill density.
http://johansense.com/bulk/dayton90v34hp.JPG
i have no idea how they did that, other than to say they wound all the coils at the same time.
« Last Edit: March 22, 2017, 09:30:30 PM by joestue »

mbouwer

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Re: Active Pitchcontrol
« Reply #584 on: March 23, 2017, 04:15:59 AM »
The 64 magnets I have are 20-10 mm and 3 mm thick with a hole.
Attaching them with a normal steel screw and then a layer of epoxy over it?

joestue

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Re: Active Pitchcontrol
« Reply #585 on: March 23, 2017, 11:30:48 PM »
counter sunk hole on every north (or south) pole?

what a mess. it may be possible for you to screw only the countersunk magnets down and epoxy the others. if you put a screw in there it sticks up above the magnet and that's where you really do not want anything to be.

mbouwer

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Re: Active Pitchcontrol
« Reply #586 on: March 24, 2017, 03:00:52 AM »
You are right. I am going to buy new magnets without a hole.
But then I can also take the size 20-4 so I can place 160 magnets

hiker

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Re: Active Pitchcontrol
« Reply #587 on: March 24, 2017, 06:18:09 PM »
still good mags--screw down half...make tight fitting gap..between mags..so it will help keep the glued down mags secure..looks great..
WILD in ALASKA

mbouwer

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Re: Active Pitchcontrol
« Reply #588 on: March 25, 2017, 03:04:48 AM »
Making the mast and the yaw bearing now I have a lot of questions about the design of the stator.
« Last Edit: March 25, 2017, 03:11:35 AM by mbouwer »

mbouwer

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Re: Active Pitchcontrol
« Reply #589 on: March 26, 2017, 10:22:02 AM »
Yaw slide bearing. Later I can make grooves in it to get a ball bearing.

mbouwer

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Re: Active Pitchcontrol
« Reply #590 on: March 27, 2017, 04:07:43 AM »
The stuff mounted.
64 magnets 20x10x2  are in order.

mbouwer

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Re: Active Pitchcontrol
« Reply #591 on: March 28, 2017, 01:36:30 AM »
Wire 0.5 mm
Now there is the shape and configuration of the coils.

hiker

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Re: Active Pitchcontrol
« Reply #592 on: March 28, 2017, 09:15:53 AM »
Is it going to be wave wound ...like a car alt ?  what kind of voltage and amps are you looking for..? Is the stator going to have lams built in as well..iron ? Looks great ....
WILD in ALASKA

mbouwer

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Re: Active Pitchcontrol
« Reply #593 on: March 28, 2017, 01:38:38 PM »
Thank you for your interest. The goal is a model of the Enercon.
So I would like the blades a low number of r.p.m. and yet a high voltage.