No NEO's: Brushless 17' (20'), is it possible?

[PowerMizer]

Hi!

I am a guy from Sweden and starts to get frustrated... The electricity gets more and more expensive. 1 kWh costs 1,12 SEK (~0,12 USD) incl. taxes.

I have been looking at "otherpower" some time now, and i like the idea and the concept of the 17' and now the 20' turbine. DanB seems to be a good craftsman and also a good father! :-)

Now to the main issue:

Magnets are expensive, copper are "not". Why has no one tried to build a brushless 3-phase alternator? Or has it been done in a "DanB-way"???

My idea was born in Januari 2006.

The theory behind my idea is this picture(have not learnt how to upload pictures):

http://www.alternativ.nu/yabb/attachments/BAC-schema2.jpg

After a day alone up in the snowy mountains here in Lapland i ended up with this idea:

http://www.alternativ.nu/yabb/attachments/skiss_borstlos_rotordisk_nr1.jpg

On the rotor discs there are windings for the "exiter armature" in the inner set of coils and windings for the "main field" in the outer set of coils. There should be a rectifier between the sets to make DC to the main alternator in the outer coilset.

In the stator there is windings for the "exiter field" in the inner set of coils and windings for the "main armature" in the outer set of coils. The stator should have terminals for 3 phase output and DC input for the exiter.

The exiter must have aprox. 5% of the armature power.

If the "remanens" (Swedish for "remaining magnetic field")in the rotordiscs will be enough to get it to take up the voltage, i don't know. Maybe a tiny magnet inside the exiters field-coils will do it? My idea is to only have a pice of steel inside the field-coils (both the exiter and the armature). If so, it might require a separate set of cables from the ground, up to the voltage regulator in the tower...

Please forgive me for my poor English, i'm just a Scandinavian Viking! ;-)

//Powermizer

[asheets]

You might want to check out this ongoing discussion... http://www.fieldlines.com/story/2006/11/8/82820/9683 ... I think the consensus right now is to either rewind an auto generator or try to make do with ceramics in a much smaller generator.

I personally think the best way to go, if money for neos is an issue, is to get friendly with the local computer techie and get ahold of dead hard drives for their mags.

[Ungrounded Lightning Rod]

Magnets are expensive, copper are "not". Why has no one tried to build a brushless 3-phase alternator?

It has been done a number of times and a number of ways.  But it's not popular for small mills.

When the wind is weak there is very little power to be had and that little is precious.  The more you can collect, the longer you can go before your storage drains to the minimum safe point and you have to black out.

Excitation requires power.  That power comes straight out of your output (and may also require some from your stored power to get started).  And it needs the MOST power when the wind is weak and the genny is thus turning slowly.  The result is that using an excited generator raises your cutin windspeed - significantly - in addition to burning power 24/7 when the wind is blowing, so you get less output from your genny at moderate speeds.

If you look at a histogram of wind speeds you'll see that wind spends most of its time at low speeds (where excitation power makes the difference between some output and none) and moderate speeds (where excatation power slows your recharging of the storage that you ran down while the wind was low) and very little of its time at high speeds (where energy is plentiful and excitation power is a minor issue).

The result is that a generator requires a larger turbine for a given amount of output than a magneto, and is usable at a far smaller number of sites due to its higher minimum wind requirements.

Using permanent magnets means you bought your magnetic field with a few bucks when you were building things, rather than renting it continuously with power from your mill.

Also:  Copper isn't all THAT cheap these days (as you'll find out when you start winding your coils).  It takes a lot of copper to make the coils for the excitation (and substituting anything else means higher power requirements).  So you may find that the cost advantage isn't as much as you thought.

That's why people here generally prefer to use permanent magnets - despite the cost, the problems getting them mounted correctly, the hazards of working with very strong magnets, and the greater difficulty harmonizing the magneto output and load voltages.

[scottsAI]

Hello PowerMizer,

Another option:

Use an induction motor as a generator.

Around here a 5 HP 3 phase motor used is less than $100.

You can connect directly to grid. Or with capacitors on the output operation without grid is possible.

Grid connected will need Pitch control, No grid, use capacitors, no pitch.

Search here for induction.

Breezy 5.5 has a complete design using one. No Pitch control needed.

Have fun,

Scott.

[terry5732]

Damn you beat me. Yes, capacitors will do for your excitement rather than the extra coils. You will get little if any power from low RPMs with this arrangement but Lapland it pretty breezy from what I've heard.

I don't get the arguement about losing a percentage of your power on an ongoing basis - your power is FREE to begin with ! The power you lose in years of running will never be near what it took to make neos. Most of the 6 billion people in the world have NO access to buying things like magnets. I'm all for doing what you can with what you have available. In doing so, someone will invariably come up with some great new ideas. Being stuck on ONE way to make gennys isn't progress towards anything. This  forum should not be just about how to make "my" system. It needs much more thought and ideas into new ways to make and store power that is easier, cheaper or more productive/useful. Lead/acid batteries are NINETEENTH CENTURY technology !

I'm drifting into a rant

[Flux]

Yes your brushless alternator is perfectly possible. Someone has already pointed to a link about recent discussion and in that link thefinis kindly found past links to earlier discussion on this issue.

It depends on how much low wind performance you are prepared to loose and how you view costs.

All electromagnetically excited alternators loose a percentage of power in field excitation. They also need closed iron circuits with small air gaps and this brings with it iron losses that also reduce low wind performance.

With larger machines this factor becomes less important. Turbines under about 6ft really will be very poor with wound fields. At 17 to 20 ft the low wind issue becomes more reasonable, but your machine for decent efficiency and direct drive will be large and heavy and will use a lot of copper.

If you use a gearbox to reduce size and cost you compound the low speed loss problem.

It can be done, it has been done, but I question the wisdom of doing it to save the cost of a few magnets.

Flux

[tecker]

 The bugeted amount is the Question here . The 100 to 150 price tag you encounter

with magnets is not that bad .If that's what is holding a builder back you can't make that up by switching to a copper wound field the difference is not that much . The advantages and depenability of the rare earth magnets far outwieghs the copper .

[dinges]

"Now to the main issue: Magnets are expensive, copper are "not". "

I think you're only focusing on one part (the generator), while you should be considering costs of the entire wind generation system:

1. generator
   
2. blades
   
3. tower
   
4. cables
   
5. batteries
   
6. (dumpload) controller
   
7. powershack for the batteries
   
   

...

The generator is only a small fraction of the total costs of your wind generation system. In that generator, the magnets are only a fraction of the cost of the generator. If 200-300$ is too much expense in magnets, it's highly likely that the rest of your system will be even more 'too expensive' for you.

I disagree that copper is not expensive, but not important. You'll find that out yourself when you're going to buy 50 meter of 35mm^2 cable

[mrneutron]

Im very interested with your concept given that I'm constantly wondering myself how wind driven alternators could be more efficient. The majority of alternators have been designed around high speed drives such as combustion engines and steam turbines and geared up. Therefore the optimium speed is around 7000 rpm and above  for steam turbines. Therefore if these alternators are utilised in wind turbines are driven through high ratio gearboxes that drag heavilly on the drive.

I see on the web a few designers trying overcome the transmission losses and looking into low speed alternators and low friction gear systems. I have my own ideas on this for which I would like to prototype and run to patent, so I'd not like to venture on this forum, but as Powermizer has been good to show his ideas

I would be happy to discuss with him moving forward.

Please contact me on my given email

John in Nottingham

[wdyasq]

"- your power is FREE to begin with !""- your power is FREE to begin with !"

Well, I will start off with a rant. A good tower costs real money. Real wire costs. I can't get anyone competent to work at no charge. I know I don't like to work without compensation.

Just the electricity to weld a tower costs. But towers and such can be made of wood. OH, I'm sorry, you mean most of those folks without electricity have burned the wood to cook with?  And they are using the solar panels the 'Relief Groups' supplied to power Televisions rather than keep the free vaccines you supplied from spoiling?

"Lead/acid batteries are NINETEENTH CENTURY technology !"

  Well, the wheel predates that and I doubt you have given up the use of wheels. Broken wheels were fixed at one time, when they were of wood and had the valuable steel tires. At some time a technology is fully developed and it is used with minor improvements until something better is developed.

"This  forum should not be just about how to make "my" system. It needs much more thought and ideas into new ways to make and store power that is easier, cheaper or more productive/useful."

I don't think the Dans would mind if you started your own forum. You can concentrate on what you care to if it is yours. The next "Tesla" may be reading this through the Internet, but I doubt it. Folks like Marcellus Jacobs took the technology about as far as it could go before the advent of  modern magnets and semi-conductors. Many hear would rather rant, 'you are being negative', than research what has been done and wasn't practical. I can't help it, I leaned to read once and remember. Others here propose unworkable designs and want others to spend their money or 'collective money', that taken by threat by our government, to try ideas that may, or may not, show promise. More than likely, they were tried at some time in history and failed the first ten times.

Ron

"Never get mad at a feller who is smarter than you are, it ain't his fault."

Well, I will start off with a rant. A good tower costs real money. Real wire costs. I can't get anyoen compentent

[finnsawyer]

If you want to experiment check out the alternator design I present in my diary.  It would use more coils with a given number of magnets and a larger rotor.

[DanB]

These are my thoughts...

"Damn you beat me. Yes, capacitors will do for your excitement rather than the extra coils. You will get little if any power from low RPMs with this arrangement but Lapland it pretty breezy from what I've heard."

For battery charging I don't think that would work very well and it would be dismally inefficient in low winds I think.  If you're going to use an electromagnetic field you may as well use a DC generator - at least then you can have some control over the field and regulate things.  In my mind that is the only advantge of going that route.

"I don't get the arguement about losing a percentage of your power on an ongoing basis - your power is FREE to begin with !"

The fuel (wind) is free - the equipment and maintenance isnt.  There are lots of ongoing costs with such systems (mainly batteries).  If compromising low wind performance means you need a much larger machine - or a much larger battery, then it may not be worth it.

 "The power you lose in years of running will never be near what it took to make neos."

Thats debatable.  Most of my power comes in very low wind and it adds up to quite a few KWH pretty quickly.

 "Most of the 6 billion people in the world have NO access to buying things like magnets. I'm all for doing what you can with what you have available. In doing so, someone will invariably come up with some great new ideas. Being stuck on ONE way to make gennys isn't progress towards anything. This  forum should not be just about how to make "my" system."

I agree - but there's no sense in repeating past mistakes over and over again.  If you're going to seriously invest time and or money in a system then you may as well build something thats likely to work reasonably well.  In my opinion - we (here on this forum) are not 'stuck' in one way of doing things, but many of us have latched onto a couple of workable ideas and things are always moving forward - if not in the area of overall design, very much so in the area of improving construction methods and in some cases the electronics that support these systems (I feel very behind in that area).  If you think were stuck here... look at what was going on last year - and the year before that, or.. go back and look at the 'old' fieldlines board and perhaps you'll get an idea of the progress over the last 5 or 6 years.

There have been lots of ideas put fourth - most of the 'new' ones may have been clever but few will never get off the drawing board because the outcome is predictable.

 "It needs much more thought and ideas into new ways to make and store power that is easier, cheaper or more productive/useful. Lead/acid batteries are NINETEENTH CENTURY technology !"

I expect if there is break through in that area... it won't come from someones garage (maybe - but I doubt it).  More likely it'll come from General Electric or something like that.  Lead Acid batteries are my least favorite part of the system but I don't see any alternatives in the near future.  Some things have moved forward with storage though, and I think most of it lies in the area of regulation.  It's much easier today to take good care of batteries than it used to be - so perhapst they last longer and get run more efficiently.  That stuff is leaps and bounds beyond where it was 20 years ago.

I'm drifting into a rant

[wdyasq]

Still pimping your design .... why don't YOU spend the time and money to test it?

Ron

[paradigmdesign]

I agree, anyone who thinks copper is not "that" expensive has not bought alot of copper.  Granted the cost of your NEOs will be higher than your copper costs, calling it cheap I belive would be a mistake.

[whatsnext]

He's too busy posting about it.

John.....

[whatsnext]

I don't see the point of going brushless. Brushes are pretty cheap and reliable and your mill will likely need maintainence anyway. I also don't think the power loss has to be so bad if you had some sort of controller to prevent the fields from seeing power when it wasn't needed. And, you could dispence with the cost of a charge controller because someone smart, like Amanda, could probably design a control circuit which would act as one within the field controller.

The currently built mills seem to work pretty well and the build seems pretty straight foward but there are still problems like burnt stators and stuff so they're not without their problems too. So, if you'd rather be an experimenter than just knowing your mill will work the first time it would probably be worth doing if only for science and the next guy who wants to try the same thing. I'm an engineer so I like to control things and complicated things don't look that complicated if it looks like a good bet. Car alts are not that complicated and they seem to work pretty well. They are also quite cheap so I would start there and work out a control system first. Scale up later.

John.......

[Ungrounded Lightning Rod]

The main downside to using capacitors is that it wants regulated RPM on the shaft - which you don't get from the wind.  You CAN get it to run but you'll get no power until it gets up to the RPM corresponding to the resonance.

Flux, check me on this:  I think that if you suck out the excitation, or your load falls off and it overspeeds, you get no load braking and the mill runs away.

With a grid connection to force it the frequency and excitation won't run away - but it can't track the wind very well, either.  It will hard-limit just above the synchronous RPM.

The second downside is that the excitation power losses are still there:  They appear mainly as heating of the squirrel-cage in the rotor and also somewhat as excess heating of the coils from the reactive currents sourced by the capacitor (or the power grid).

[dinges]

Design, design... I've seen no design. I've seen a sketch of an idea. Then again, Edison said it right: 'invention is 99% transpiration and 1% inspiration'.

Personally I like this one better:

http://www.despair.com/inspiration.html

Which reminds me; it's time for my monthly bath again.

[scottsAI]

Enjoyed the replies. I hope you enjoy mine!

This is in response to several post here so posted to the original question.

Generator efficiency is brought up frequently, it's important but not as important as system efficiency.

A good induction motor will be 88 - 92% efficient. Not bad. Heard of 96, not seen. Using 90%.

Bad motor may be 80% even worse. Something to watch out for. Sounds bad?

PMA – what percent is it? Nothing is 100%.

Everybody seems to think it's better so lets say 98% (Not likely).

The induction motor will require speedup gears, additional cost and efficiency cost 95%

People have a bad rap for gears, well your vehicle has many, work just fine when designed correctly.

On the web a 15HP with 16:1 gears for $300. surplus center.

The 15 HP induction motor operates at 220 or 460 vac, wind generator can be far away with acceptable power losses. PMA far away will need to be wound for the high voltage and require a transformer on the other end just like the induction motor will need, unless connected to the grid.

PMA can NOT be directly connected to the grid, no voltage or frequency control.

The induction generator can be connected directly to the grid. No grid, no problem several methods exist for excitation, capacitors are a favorite.

I used 90% motor * 90% gear and excitation = 80% generator efficiency.

The system: Wind turbine 24' dia blades, 10kw at 23mph with Cut in at 5 mph.

Low winds are often listed as reason for using PMA vs induction.

Since this is a large wind gen it needs a large battery 48 volts.

PMA system will have TSR = 7, induction will use TSR = 12 and speedup gears of 26:1

Note: PMA generator output voltage is directly proportional to RPM, which is wind speed.

Induction generator will not be using pitch, fixed, must be furled by 24mph when the wind can over power the generator.

Let's play with the numbers. Do you know what's going to happen?? I have a surprise for you.

Wind PMA I out Battery Efficiency Stator  Induction

        Vout        Power                 Heat   Generator

5      48      2.4    116      100        0      103.55

6      58      3.1    149       83       30      178.93

10     96      9.7    466       50      466      828.36

15    144    21.8  1048       33     2097     2795.73

                            We are cooking!

20    192   38.8   1864       25     5591     6626.91

                                  Sizzling!

25    240   60.7   2912       20    11649     12943.19

Induction generator is more efficient except at cut in, after ten mph 2x to 4x the power generated!

Surprise!

PMA for the cost and simplify are hard to beat for a smaller less than 14'. The larger, the multitude of problems and lack of efficiency make the induction better for the cost. Add pitch control, the generator can continue to produce power to what ever wind speed you want. I target 70mph. Handles gust of wind better to.

Comments? Very dificult to post table here? tried html editors keeps getting errors.

Have fun,

Scott.

[Flux]

ULR

I hopes this turns up in the right place. A grid connected induction generator has a characteristic that is the mirror image of its motoring curve.

Think of the motor, it's more familiar. From no load slip speed the speed falls slightly as you load it. The slope of the fall depends on the rotor characteristics but normally the speed will fall from 5 to 10% from no load to  150 to 200% full load. The thing then goes into a re-entrant state ( pull out) where the torque falls away rapidly and unless you have a very strange load characteristic it will stop. The torque that it finally produces will be the starting torque and again it depends on rotor design. A low slip low loss rotor when running will have a starting torque that may only be 30% of pull out torque,

A high resistance rotor will have a high starting torque but will run with high slip and high loss.

If you turn it into an induction generator linked to the mains it will hold virtually constant speed up to about 150% full load torque and then pull out. Because of the wind cube factor you can regard it as running with no load an it will take off.

Running self excited into capacitors is more complex and is essentially unstable. core saturation is the only thing to limit volts and if you can let the volts rise with speed you may get more load than with grid tie, but it is highly unstable and if you load it too far you loose excitation.

With self excitation it will almost certainly spend most of its life saturated with high core losses.

Flux

[Flux]

John

I tend to agree with you that the brushes are not as big an issue as some seem to imply. A single stage brush fed alternator will be slightly more efficient than a brushless machine when you include the exciter losses. This is a very small issue with big machines and the elimination of brushes from a multi kilowatt machine is a great step forwards. With machines under 5kW the brushless machine will loose out on efficiency.

Replacing the charge controller with field control is not straightforward with wind power, as you maintain constant volts by field reduction you shed load and the speed will rocket up. Unless you have pitch control this is not a viable option. Jacobs did it with their pitch control machines, but for furled machines it is a no go area.

As I said earlier wound fields are not out of the question, but flux from electromagnets comes at a fair cost. Trying to reduce the excitation needs means working with short air gaps and that means greater iron losses and high leakage reactance. The final result is that the thing will be significantly bigger for a given output than a machine with neos and if you aim for low speed and direct drive you will end up with a big heavy brute and probably costing more than you save from the magnets.

Flux

[coldspot]

My thoughts-

Dan's, I love this and you for being kind enough

to share with the world!!!!!!!!! THANK YOU!!!

If I could build  a forum, I wouldn't be here unless to try to pimp you visit it.

"Being stuck on ONE way to make gennys isn't progress towards anything. This  forum should not be just about how to make "my" system"

I agree somewhat.

Dan's-

Like this has hydro, solar and wind.

couldn't it also have-

Wind: PM Motors, airgap, Induction Conversion, ect,... ect,.....

?

[whatsnext]

Flux, Thank you for your comments. I think that pitch control will tend to not work too well for DIYers so a centrifical air brake, ala Jacobs, would likely work much better at limiting overspeed, or at least more consistantly. It would likely be noisy but who cares as it's already noisy in high wind conditions. A physical upper limit on prop speed would make a charge controller/field driver pretty straight foward. I also like the idea of reduced rotating mass and the ability to make adjustments to the output from the ground, both of which can be done with this type of machine.

John....

[finnsawyer]

Yep.  Personally, I don't see any problem with calling attention to alternatives, when appropriate.  The original posting was concerned with lowering the cost of alternators.  One way to do that is make the magnets work harder.  My proposed design (the 3 coils to two magnets) does that, since twice as many coils will be producing a voltage pulse at any time as with a 3:2 three phase design having the same number of magnets.  The larger rotor also means the coils are moving faster relative to the magnets meaning a larger voltage spike.  Faraday' law states that both the magnitude of the flux and the rate at with it changes with time are integral to determining the voltage in a loop or coil.  The magnitude of the flux will be essentially the same since it is mainly determined by the air gaps and not the path length through the iron rotor.  Also, with a greater separation between magnets one would expect less leakage flux.  With each coil moving faster relative to the magnets, the result is a larger voltage pulse.  Considering that some people are still deciding to build single phase alternators I see no problem with making this possibility known.  I'm waiting for someone to pop up with ten magnets looking for a design to use all of the magnets.  It'd be a shame to throw away two of the magnets.

This whole thing reminds me of something that happened before WW11.  There were a number of engineers in the U.S. that advocated developing jet engines.  The Army was not interested, and some 'Experts' said the jet engine was not possible.  Hap Arnold, the head of the army Air Corp happened to make a trip to England and mentioned the crazy idea.  He was taken to see the English jet powered plane that was in development.  Needless to say, things changed over here.  Does this sound familiar?  The conservatism shown by the military is not restricted to military types.  It permeates all of society.  I didn't expect to find it here, but here it is.  You can see it in action.  It has been an education, to say the least.  Bottom line?  I'm sure the 3:4 three phase design didn't just pop up all nicely configured.  It took a number of tries by many people.  The same will hold true for the 3:2 design.  So, why keep it a secret?  Let anyone that wants to have a go at it.      

[dinges]

"With each coil moving faster relative to the magnets, the result is a larger voltage pulse"

Too bad it's not voltage but power we're after.

You familiar with a Dirac pulse?

How much power is available in such a pulse? Note that the amplitude of a Dirac pulse is infinite...

Yes, each pulse is larger in voltage. And also shorter in duration...

I have never heard of Hap Arnold.

Frank Whittle. Now, there is a man I can respect. He didn't just pop an idea. He put in the hard work as well.

You, sir, are no Frank Whittle.

Darn. I'm again getting dragged into the discussion.

At least, why don't you make a proper design? Drawings with the number of coils, wire thickness, number and size of magnets, wiring, expected power at various RPMs, etc. Maybe someone on this board will feel called to build it to end this discussion once and for all. My hands are beginning to itch to build such a thing to get it all over with. I won't. I have done it once before with someone who said that cogless conversions couldn't be built. And of course, after I proved it could, he still wasn't convinced. I will not get into the habit of trying to convince others. But maybe someone else may feel called to prove you right or wrong.

[wdyasq]

http://tinyurl.com/3zozr

Inventors of the jet - maybe.

http://tinyurl.com/yfqrbw

"But the real break through in air powered flight came in 1910. With the first jet powered flight on 16 December in Paris. Henri Coanda designed, built and flew this remarkable aircraft, years before it's time and has never been given the recognition which this remarkable man is entitled to, as the inventor of the Jet engine."

Hap Arnold was an American. I do not doubt you don't recognize him. It seems neither yourself or finsaw can do research.

Ron

[jimjjnn]

Thought his name was Whipple. Gettin' too old to remember. He and the Germans both were working on engine designs at same time

[jimjjnn]

Dang, It is Whittle

[finnsawyer]

If your Dirac pulse is a voltage then the power (into a finite resistance) is infinity squared.  The energy delivered will be dependent on the duration of the pulse and could also be infinite.  Of course, the whole thing is non physical anyway, so let"s forget it.  For the record, the 3:2 design, which gives a single phase waveform, will have a frequency three times that of the 3:4 design, so you get the same number of pulses of current at the same rpm.  Pulse duration is not a major issue.

Every alternator must produce power, and since you brought it up let's take a look at it.  A 9:12 three phase alternator has an internal resistance equal to the sum of the resistance of six coils (six coils produce output at any time).  A 18:12 design would have three times that resistance using the same size wire and coils.  To make a valid power comparison we need to have the internal resistances the same.  While there are different ways to reduce the resistance of the 18:12 design perhaps the most direct would be to use one third as much wire per coil.  This will reduce the number of turns, but not by one third, since it takes more wire for each turn as the coil diameter increases.  Nevertheless, we can use one third as a lower limit for the number of turns per coil.  Now, it happens that the rotor of the 18:12 design can never be less than twice the diameter of the 9:12, even if the coil only has one layer of wire.  But, again we can use twice the rotor diameter as a lower limit.  So, we have twice as many coils (that is, 12 produce at any time) of one third as many turns moving twice as fast, which gives a maximum voltage of 2x2/3 = 4/3.  This in turn implies a minimum power advantage of 16/9, or roughly 2.  I don't know about you, but from an engineering perspective I'd say this makes the alternator worth investigating.  It may be that there really is no advantage for reasons that are not apparent, but I doubt that it would be any worse.

As far as voltage, voltage cut-in is important.  Just ask the VAWT people.  It is common for them to use 24 magnets to keep the cut-in rpm low.  What if they can get the cut-in using 12 magnets instead with the same power output?  One would think any improvement would be welcome.    

[vawtman]

Hmmmm Finsawyer

 Just ask the vawt people.

 Say you have a vawt blade with a tsr of 2 and you want a tsr of lets say 6 one just gears 1:3.

 No need for big expensive unbalanced rotors.

 I know it wouldnt be good for toy turbines.

 v......:<}

[dinges]

You win.

BTW, the power in a Dirac pulse is 1.

[finnsawyer]

So, the power in a Dirac pulse is 'defined' to be one.  Big deal.  It's still non physical.  When I was an EE student at MIT one of the first techniques for simple circuit analysis we were taught was to hit it with a pulse of infinite amplitude, but finite area.  This gave the 'natural' response of the circuit.  Again, big deal.

[finnsawyer]

So, why we do find people making alternators having 24 large Neos?  I have no issues with mechanical gearing.  In fact, I suggested an idea for VAWT people using a large ring (say 5 ft diameter) driving a rubber tire (say 1 ft diameter) for a gearing ratio of 5.  Since VAWTs have a large diameter it would be doable.

I don't know where the toys come in here, but let's assume in my example that we decide to get the resistance down by using the same amount of wire per coil and do it three in hand with the same diameter wire.  So each strand is one third as long for one third the resistance and the three strands are in parallel so each coil now has one ninth the resistance (the 18:12 configuration then has a resistance of one third that of the 9:12.  The number of net turns is now exactly one third per coil.  Just to keep things simple I stick with the doubling of rotor diameter (It will be greater).  We now find that our minimum power gain is (1/3)x2x2/(1/3) = 4.  And we have done this with no loss of voltage.  In effect, by using more copper overall and a considerably larger rotor we predict a considerable increase in power from the same magnets, a result that should be reasonable to everybody.  In other words the cost per magnets per watt goes down.  One would think many people would be interested in such a result.

I think it's pretty well accepted that a large VAWT will need a large difficult to make rotor.  Given that people do make rotors 24 inches in diameter with 24 magnets, then there is no reason they couldn't make rotors 24 inches in diameter with 10 or 12 of the same magnets if the power out will be the same.  In fact the money saved could be put toward even larger rotors.  As usual the devil will be in the details, which is why I put this design out.  There is no way I could make all the incarnations of this design that will be needed to be investigated.  So, where is the spirit of innovation?  How about our Chinese friends?  Are they working on it?

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