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From: George Herold on 14 Jun 2010 12:28 On Jun 11, 2:20 am, Jon Kirwan <j...(a)infinitefactors.org> wrote: > On Thu, 10 Jun 2010 19:26:20 -0700 (PDT), George Herold > > <gher...(a)teachspin.com> wrote: > ><snip of what I wrote> > >Hi Jon, I hope you re not offended if I say that the first time I > >read this I thought it sounded crazy. > > Not at all. Cripes, can you imagine what would have happened > if Rutherford had gotten all offended when meeting with his > young students who might have proposed some idea? I had > loved reading, somewhere, that he would listen to any and all > if they thought they had _any_ idea, no matter how modest or > odd it may have been. They would take a break every > afternoon for tea, cake and buttered bread and just sit on > stools talking. Nice. 11 of his students went on to receive > Nobel Prizes, not to mention some of the collatborators who > also attended and also won Nobels. Not that I think what I > wrote is anything much. I'm just saying... > > >I took vol. 2 of The Feynman Lectures of Physics down to the creek > >when I got home this evening. In chapter 36 he does ferromagnetism. > >(do you have a copy?) > > I do have a copy and have carefully read the first 5 or 6 > chapters of the first book, only. I have not read chapter > 36. > > >He does an electro-magnet near the end. > >(36-5). Early in the chapter he says that if you are willing to > >accept the fiction of magnetic monopoles, you can think of > >ferromagnetism as the magnetic analog of the polarization of > >dielectrics. > > I'll read it, tonight. Though I may need to _also_ go back > and read on polarization to refresh that, as well. > > >And so I totally accept your picture though I understand it > >differently. Thanks! > > It's the way I imagine it and it works to solve any questions > I've had about the concepts others teach differently (and to > me with less clarity.) I am sure, someday, there will be > some behavior that requires me to modify it. But so far for > my limited experience, it works well. I like it better > because I don't have to think about how recoverable EM energy > (which in my imagination can ONLY be stored in a vacuum) > might be one figure for vacuum, another figure for atom A, > another figure for aligned atom A, another figure for atom A > in an excited state, and so on. I just have to keep one > thing in mind... energy is stored in vacuum, only, and > permeability is simply a fudge factor used to estimate the > effective ratio of the vacuum path length and the vacuum path > length less the magnetic short circuit length (once alignable > atoms are aligned.) L_vacuum / (L_vacuum - L_shorted). It's > a fictitious parameterization so that we humans can use basic > measuring tools and simple observations plus that figure to > estimate the effective vaccum psth length remaining for > energy storage. But the recoverable energy really only goes > into vacuum, I believe. > > >Oh Feynman says the energy loss is the area enclosed by the B/H > >curve. > > Which makes complete sense. I mentioned before that I also > imagine aligning the atoms takes energy, but it isn't > recoverable. The work involved in aligning is largely ('all' > probably, unless there is a wound up spring recoil effect > which I don't at all imagine exists) converted to heat. If > you reverse the alignments, you do more work. And so on. But > you don't get it back. That goes into heat. > > It's only the energy stored in vacuum (energy cannot be > created or destroyed) where there is no possibility of "heat" > that you can recover. (Would be interesting to imagine the > case where you could actually lose energy as work converted > to heat in a vacuum... hmm... could you cause the vacuum to > heat up enough to create 'vacuum ash?' Enough letting my > imagination get away with me... ;) > > Jon Hi Jon, I had a great time this weekend playing with magnetic equations and thinking about magnetization.. ala Feynman. (chaps 36+37, vol. 2) (If you read the chapters you might have found that he does things a bit differently than others. He defines the H field so that it has the same units as the B field. He also doesnt like mu- sub zero, but instead just writes it as 1/(epsilonsub zero times c- squared. = u0)) (Ill use u0 below because its easier to write.) Anyway for his system, If you make the approximation that the B and H fields in the magnetic material are linearly related then you can solve everything. (B=uH) With L1 being the gap length and L2 being the length in the magnetic material I found B to be given by, B = u0*N*I*(1/(L1+L2/u)) So if L1 is much greater than L2/u, then the gap determines the field. (u is the permeability of the material) And you can also solve for the energy density in the material and in the gap. And from that calculate the inductance. For which I get, (A is the area of the material and gap) L = u0 *A*N^2*I^2*(1/(L1+L2/u)) And the energy stored in the gap is proportional to L1 and that in the magnetic material to L2/u! This is totally cool, I never knew! Its a relatively simple calculation; I wonder why no one had me do it in college? (Course they dont teach you anything about real components in college.) George H. Say it seems like toriods are the perfect topology for inductors, do they make toriods with a built in air gaps? (It doesn't have to be air.)
From: Archimedes' Lever on 14 Jun 2010 12:47 On Mon, 14 Jun 2010 09:28:06 -0700 (PDT), George Herold <gherold(a)teachspin.com> wrote: >On Jun 11, 2:20�am, Jon Kirwan <j...(a)infinitefactors.org> wrote: >> On Thu, 10 Jun 2010 19:26:20 -0700 (PDT), George Herold >> >> <gher...(a)teachspin.com> wrote: >> ><snip of what I wrote> >> >Hi Jon, �I hope you re not offended if I say that the first time I >> >read this I thought it sounded crazy. >> >> Not at all. �Cripes, can you imagine what would have happened >> if Rutherford had gotten all offended when meeting with his >> young students who might have proposed some idea? �I had >> loved reading, somewhere, that he would listen to any and all >> if they thought they had _any_ idea, no matter how modest or >> odd it may have been. �They would take a break every >> afternoon for tea, cake and buttered bread and just sit on >> stools talking. �Nice. �11 of his students went on to receive >> Nobel Prizes, not to mention some of the collatborators who >> also attended and also won Nobels. �Not that I think what I >> wrote is anything much. �I'm just saying... >> >> >I took vol. 2 of The Feynman Lectures of Physics down to the creek >> >when I got home this evening. �In chapter 36 he does ferromagnetism. >> >(do you have a copy?) >> >> I do have a copy and have carefully read the first 5 or 6 >> chapters of the first book, only. �I have not read chapter >> 36. >> >> >He does an electro-magnet near the end. >> >(36-5). �Early in the chapter he says that if you are willing to >> >accept the fiction of magnetic monopoles, you can think of >> >ferromagnetism as the magnetic analog of the polarization of >> >dielectrics. >> >> I'll read it, tonight. �Though I may need to _also_ go back >> and read on polarization to refresh that, as well. >> >> >And so I totally accept your picture though I understand it >> >differently. �Thanks! >> >> It's the way I imagine it and it works to solve any questions >> I've had about the concepts others teach differently (and to >> me with less clarity.) �I am sure, someday, there will be >> some behavior that requires me to modify it. �But so far for >> my limited experience, it works well. �I like it better >> because I don't have to think about how recoverable EM energy >> (which in my imagination can ONLY be stored in a vacuum) >> might be one figure for vacuum, another figure for atom A, >> another figure for aligned atom A, another figure for atom A >> in an excited state, and so on. �I just have to keep one >> thing in mind... energy is stored in vacuum, only, and >> permeability is simply a fudge factor used to estimate the >> effective ratio of the vacuum path length and the vacuum path >> length less the magnetic short circuit length (once alignable >> atoms are aligned.) �L_vacuum / (L_vacuum - L_shorted). �It's >> a fictitious parameterization so that we humans can use basic >> measuring tools and simple observations plus that figure to >> estimate the effective vaccum psth length remaining for >> energy storage. �But the recoverable energy really only goes >> into vacuum, I believe. >> >> >Oh Feynman says the energy loss is the area enclosed by the B/H >> >curve. >> >> Which makes complete sense. �I mentioned before that I also >> imagine aligning the atoms takes energy, but it isn't >> recoverable. �The work involved in aligning is largely ('all' >> probably, unless there is a wound up spring recoil effect >> which I don't at all imagine exists) converted to heat. �If >> you reverse the alignments, you do more work. �And so on. But >> you don't get it back. �That goes into heat. >> >> It's only the energy stored in vacuum (energy cannot be >> created or destroyed) where there is no possibility of "heat" >> that you can recover. �(Would be interesting to imagine the >> case where you could actually lose energy as work converted >> to heat in a vacuum... �hmm... could you cause the vacuum to >> heat up enough to create 'vacuum ash?' �Enough letting my >> imagination get away with me... �;) >> >> Jon > >Hi Jon, I had a great time this weekend playing with magnetic >equations and thinking about magnetization.. ala Feynman. (chaps >36+37, vol. 2) (If you read the chapters you might have found that he >does things a bit differently than others. He defines the H field so >that it has the same units as the B field. He also doesn�t like mu- >sub zero, but instead just writes it as 1/(epsilon�sub zero times c- >squared. = u0)) (I�ll use u0 below because it�s easier to write.) > >Anyway for his system, If you make the approximation that the B and H >fields in the magnetic material are linearly related then you can >solve everything. (B=uH) >With L1 being the gap length and L2 being the length in the magnetic >material I found B to be given by, > >B = u0*N*I*(1/(L1+L2/u)) So if L1 is much greater than L2/u, then the >gap determines the field. (u is the permeability of the material) And >you can also solve for the energy density in the material and in the >gap. And from that calculate the inductance. For which I get, (A is >the area of the material and gap) > >L = u0 *A*N^2*I^2*(1/(L1+L2/u)) > >And the energy stored in the gap is proportional to L1 and that in the >magnetic material to L2/u! > >This is totally cool, I never knew! It�s a relatively simple >calculation; I wonder why no one had me do it in college? (�Course >they don�t teach you anything about �real� components in college.) > >George H. > >Say it seems like toriods are the perfect topology for inductors, do >they make toriods with a built in air gaps? (It doesn't have to be >air.) Yes, you can buy physically severed and epoxied, gapped toroids, or you can have a formulation made or buy one that incorporates it into the medium itself homogeneously.
From: Tim Williams on 14 Jun 2010 13:31 "George Herold" <gherold(a)teachspin.com> wrote in message news:bef75813-b0ee-4178-b630-1db31fa97c2c(a)w31g2000yqb.googlegroups.com... > B = u0*N*I*(1/(L1+L2/u)) So if L1 is much greater than L2/u, then the > gap determines the field. (u is the permeability of the material) And > you can also solve for the energy density in the material and in the > gap. And from that calculate the inductance. For which I get, (A is > the area of the material and gap) > > L = u0 *A*N^2*I^2*(1/(L1+L2/u)) > > And the energy stored in the gap is proportional to L1 and that in the > magnetic material to L2/u! Ah yes, I recently did that. Except, L = Phi/I (compare: C = Q/V), so you forgot to cancel the I somewhere. I wrote about it and more here: http://webpages.charter.net/dawill/tmoranwms/Elec_Magnetics.html Should be useful to lots of people who, like you, never got instruction in what the hell a real transformer or inductor is, or how to design one. > Say it seems like toriods are the perfect topology for inductors, do > they make toriods with a built in air gaps? (It doesn't have to be > air.) Well, mix 61 and 67 ferrites have low permeability. I'm not sure if that's due to fillers or magnetic properties. The B-H curve shows a rather wide hysteresis loop (about 7 Oe across), suggesting disturbingly high losses. I don't think powdered irons are even that high, though they lose energy through eddy current as much as hysteresis. Powdered irons could be said to have built in air gaps, since they're usually made from a fine powder (like carbonyl iron, which is spheroidial), compacted and bonded with a resin. The metal density might be 70-90%, I suppose, which is a lot of airgap. Actually, I suppose density would have to be at least 97% for most types, as there are powdered irons with mu_r >= 75 (and I think I saw MPPs as high as 750, but those might be sintered, I'm not sure). Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
From: George Herold on 14 Jun 2010 14:05 On Jun 14, 1:31 pm, "Tim Williams" <tmoran...(a)charter.net> wrote: > "George Herold" <gher...(a)teachspin.com> wrote in message > > news:bef75813-b0ee-4178-b630-1db31fa97c2c(a)w31g2000yqb.googlegroups.com... > > > B = u0*N*I*(1/(L1+L2/u)) So if L1 is much greater than L2/u, then the > > gap determines the field. (u is the permeability of the material) And > > you can also solve for the energy density in the material and in the > > gap. And from that calculate the inductance. For which I get, (A is > > the area of the material and gap) > > > L = u0 *A*N^2*I^2*(1/(L1+L2/u)) > > > And the energy stored in the gap is proportional to L1 and that in the > > magnetic material to L2/u! > > Ah yes, I recently did that. Except, L = Phi/I (compare: C = Q/V), so you > forgot to cancel the I somewhere. Opps quite right. I set the total energy equal to 1/2L I^2 and forgot to take out the I^2 from both sides... Thanks, George H. > I wrote about it and more here:http://webpages.charter.net/dawill/tmoranwms/Elec_Magnetics.html > Should be useful to lots of people who, like you, never got instruction in > what the hell a real transformer or inductor is, or how to design one. > > > Say it seems like toriods are the perfect topology for inductors, do > > they make toriods with a built in air gaps? (It doesn't have to be > > air.) > > Well, mix 61 and 67 ferrites have low permeability. I'm not sure if that's > due to fillers or magnetic properties. The B-H curve shows a rather wide > hysteresis loop (about 7 Oe across), suggesting disturbingly high losses. I > don't think powdered irons are even that high, though they lose energy > through eddy current as much as hysteresis. > > Powdered irons could be said to have built in air gaps, since they're > usually made from a fine powder (like carbonyl iron, which is spheroidial), > compacted and bonded with a resin. The metal density might be 70-90%, I > suppose, which is a lot of airgap. Actually, I suppose density would have > to be at least 97% for most types, as there are powdered irons with mu_r >= > 75 (and I think I saw MPPs as high as 750, but those might be sintered, I'm > not sure). > > Tim > > -- > Deep Friar: a very philosophical monk. > Website:http://webpages.charter.net/dawill/tmoranwms
From: Jim Thompson on 14 Jun 2010 14:15
On Mon, 14 Jun 2010 10:50:58 -0700 (PDT), dagmargoodboat(a)yahoo.com wrote: >On Jun 14, 12:08�pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On- >My-Web-Site.com> wrote: >> On Mon, 14 Jun 2010 09:49:09 -0700 (PDT), dagmargoodb...(a)yahoo.com >> wrote: [snip] >> >> > � � � � Vcc = +5v >> > � �--+--------------+------+-- >> > � � �| � � � � � � �| � � �| >> > � � �| � � � � � � �| � � .-. >> > � � �| � � � � � � �| � � | | e.s.r. = 1 ohm >> > � � �| � � � � � � �| � � | | >> > � � �| � � � � � � �| � � '-' >> > � � �| � � � � � � �| � � �| >> > � � �| � � � � � � �| � � �|_ || >> > � � �| � � � � � � �| � � � _)|| >> > � � .-. � � � � � �--- �L1a _)|| >> > Rb �| | � � � � C1 --- �1mH _)|| >> > 47k | | � � � � 1uF | � � � _)|| >> > � � '-' � � � � � � | � � � _)|| >> > � � �| � � � � � � �| � � *| �|| >> > � � �| � � � � � � �'---+--' �|| >> > � � �| � �R1 � � D1 � � | � � || >> > � � �| � 220r �schottky | � � || >> > � � �+--/\/\/----|>]----+ � � || >> > � � �| � � � � � � � � �| � � || >> > � � �| � � .------------' � � || >> > � � �| � |/ � � � � � � � � � || >> > � � �+---| � �Q1 � � � � � � �|| >> > � � �| � |>. 2n3904 � � � � � || >> > � � �| � � | � � � � � � � * �|| >> > �C2 --- � �+----------------. || >> > 1uF --- � �| � � � � � L1b �_)|| >> > � � �| � � | � � � � 100nH �_)|| >> > � � �| � � | � � � � � � � | >> > � � === � �| � � � � � � �=== >> > � � � � � �| >> > � � � � � �'--------------------> 5KHz output >> >> >Cheers, >> >James Arthur >> >> [snip LTspice Schematic] >> >> James, �How can you call it "class-A" when the emitter current is >> _not_linear_, _not_linear_, _not_linear_, _not_linear_ !! > >True, the emitter current isn't linear, but it is continuous and non- >zero, so I call that "class-A." > > >> All you've done is use a Schottky bypassing the C-B junction... >> otherwise it's identical. > >That makes a big difference. It prevents Q1 saturating and from >conducting b-c. And, without it Q1 conducts in reverse mode during >negative peaks, making the i(c) not just discontinuous, but reversing >in direction. That loads the tank, obviously. "Obviously"? Q1 doesn't conduct in reverse with your values, but no Schottky... the current is always out of the emitter... though it does get awfully close to zero: -376uA and -12.5mA peak. > >> I liken such oscillators to how you push your kid on a swing set. >> Giving a "nudge" every cycle. > >That's exactly how I think of them too. A "nudge" each cycle (short >conduction cycle) is what I did first. I call that "class-C." > >> To be "class-A" you'd need to sit upon the top bars and _continuously_ >> push and pull the ropes. > >Or you can pull continuously, harder at some times, not as hard at >others. That gives the swing position a d.c. bias, but is otherwise >the same, yes? Class-A implies _linear_, does it not? Or do we have a Larkin definition for today ?:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy |