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#1
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Saturation in transformers.
The simple answer to your toroid question is this:
Saturation occurs when the excitation losses in the core are excessive and reflect an excessive primary no load current. The quantity that you are looking for is VA/lb. loss: i.e If you experience any value over 10VA/lb. you are in or approaching saturation. For example: If your toroid weighs 4 lbs. and you had 40 VA, the primary no load current would be .3333Amperes. That amount of current would occur at 16 kilogausse @ 60Hz. Normally we do not design for any flux density higher than 14kilogausse, so these losses are not prohibitive. I know that Patrick is going to bite his tounge at any flux density over 10KG, but I design for the high volume world where economics do come into play. Also, we use other core materials in the 26Ga. non-oriented steel arena. Most toroids are wound with thin, grain oriented steel. Hope this helps. Jerry |
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#2
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Saturation in transformers.
"Jerry" The simple answer to your toroid question is this: Saturation occurs when the excitation losses in the core are excessive and reflect an excessive primary no load current. ** Defining "excessive" in each case is the problem - maker's opinions differ, a lot. The quantity that you are looking for is VA/lb. loss: i.e If you experience any value over 10VA/lb. you are in or approaching saturation. For example: If your toroid weighs 4 lbs. and you had 40 VA, the primary no load current would be .3333Amperes. That amount of current would occur at 16 kilogausse @ 60Hz. Normally we do not design for any flux density higher than 14kilogausse, so these losses are not prohibitive. ** Toroidal transformers typically have extremely low off load VA readings until the saturation knee voltage is reached - then the VA rises exponentially with a vengeance. A 500 VA rated toroidal I saw recently read only 3 VA at rated voltage ( 230/240V AC) with no load. However, if the supply voltage rose to 250 V AC, the reading climbed sharply to 20VA. At 260V AC it was 110 VA and at 270V AC, 300VA. If the supply developed a small DC offset ( ie 2 volts DC ) the same transformer would draw 300VA at 240V AC. OTOH, e-core types behave rather differently, the off load VA rising steadily with applied AC voltage and saturation onset is a lot more gradual than with toroidals. Small e-cores often run well into saturation at rated voltage with no serious ill effects - it actually improves the regulation factor to allow this since applying the rated load pulls the core out of saturation by reducing the effective primary voltage. You see this with "wall wart" transformers all the time. ......... Phil |
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#3
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Saturation in transformers.
"Phil Allison" wrote in message ... "Jerry" The simple answer to your toroid question is this: Saturation occurs when the excitation losses in the core are excessive and reflect an excessive primary no load current. ** Defining "excessive" in each case is the problem - maker's opinions differ, a lot. The quantity that you are looking for is VA/lb. loss: i.e If you experience any value over 10VA/lb. you are in or approaching saturation. For example: If your toroid weighs 4 lbs. and you had 40 VA, the primary no load current would be .3333Amperes. That amount of current would occur at 16 kilogausse @ 60Hz. Normally we do not design for any flux density higher than 14kilogausse, so these losses are not prohibitive. ** Toroidal transformers typically have extremely low off load VA readings until the saturation knee voltage is reached - then the VA rises exponentially with a vengeance. A 500 VA rated toroidal I saw recently read only 3 VA at rated voltage ( 230/240V AC) with no load. However, if the supply voltage rose to 250 V AC, the reading climbed sharply to 20VA. At 260V AC it was 110 VA and at 270V AC, 300VA. If the supply developed a small DC offset ( ie 2 volts DC ) the same transformer would draw 300VA at 240V AC. OTOH, e-core types behave rather differently, the off load VA rising steadily with applied AC voltage and saturation onset is a lot more gradual than with toroidals. Small e-cores often run well into saturation at rated voltage with no serious ill effects - it actually improves the regulation factor to allow this since applying the rated load pulls the core out of saturation by reducing the effective primary voltage. You see this with "wall wart" transformers all the time. ........ Phil Phil The differences you describe are down to the material used, not the shape. If you use GOSS in an E core it will show sharp saturation characteristics. Graham Holloway |
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#4
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Saturation in transformers.
On Tue, 8 Nov 2005 08:21:52 -0000, "Graham Holloway"
wrote: "Phil Allison" wrote in message ... "Jerry" The simple answer to your toroid question is this: Saturation occurs when the excitation losses in the core are excessive and reflect an excessive primary no load current. ** Defining "excessive" in each case is the problem - maker's opinions differ, a lot. The quantity that you are looking for is VA/lb. loss: i.e If you experience any value over 10VA/lb. you are in or approaching saturation. For example: If your toroid weighs 4 lbs. and you had 40 VA, the primary no load current would be .3333Amperes. That amount of current would occur at 16 kilogausse @ 60Hz. Normally we do not design for any flux density higher than 14kilogausse, so these losses are not prohibitive. ** Toroidal transformers typically have extremely low off load VA readings until the saturation knee voltage is reached - then the VA rises exponentially with a vengeance. A 500 VA rated toroidal I saw recently read only 3 VA at rated voltage ( 230/240V AC) with no load. However, if the supply voltage rose to 250 V AC, the reading climbed sharply to 20VA. At 260V AC it was 110 VA and at 270V AC, 300VA. If the supply developed a small DC offset ( ie 2 volts DC ) the same transformer would draw 300VA at 240V AC. OTOH, e-core types behave rather differently, the off load VA rising steadily with applied AC voltage and saturation onset is a lot more gradual than with toroidals. Small e-cores often run well into saturation at rated voltage with no serious ill effects - it actually improves the regulation factor to allow this since applying the rated load pulls the core out of saturation by reducing the effective primary voltage. You see this with "wall wart" transformers all the time. ........ Phil Phil The differences you describe are down to the material used, not the shape. If you use GOSS in an E core it will show sharp saturation characteristics. Graham Holloway I think maybe he is talking about the amount of flux leakage in a typical E core stack - and even a considerable air gap compared to a toroid. This has the effect of diluting the saturation effects considerably, making for a much softer curve and greatly reduced nasty effects at saturation. Obviously the material is still important, but the construction has a pretty big effect too. d Pearce Consulting http://www.pearce.uk.com |
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#5
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Saturation in transformers.
Jerry wrote: The simple answer to your toroid question is this: Saturation occurs when the excitation losses in the core are excessive and reflect an excessive primary no load current. No. There is no simple rule. Who decides what is 'excessive' anyway ? OTOH if the core is so badly saturated that excessive primary current flows then you're in *big* BIG trouble ! Deciding magnetising current ( and hence working flux ) is a balance between efficiency ( various losses ) and core material properties. Not for the faint hearted or sunday driver. Graham |
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#6
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Saturation in transformers.
Phil Allison wrote: OTOH, e-core types behave rather differently, You're talking ****. It's purely down to material properties. The path shape is utterly irrelevant. Graham |
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#7
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Saturation in transformers.
Jerry wrote: The simple answer to your toroid question is this: Saturation occurs when the excitation losses in the core are excessive and reflect an excessive primary no load current. The quantity that you are looking for is VA/lb. loss: i.e If you experience any value over 10VA/lb. you are in or approaching saturation. For example: If your toroid weighs 4 lbs. and you had 40 VA, the primary no load current would be .3333Amperes. That amount of current would occur at 16 kilogausse @ 60Hz. Normally we do not design for any flux density higher than 14kilogausse, so these losses are not prohibitive. I know that Patrick is going to bite his tounge at any flux density over 10KG, but I design for the high volume world where economics do come into play. Also, we use other core materials in the 26Ga. non-oriented steel arena. Most toroids are wound with thin, grain oriented steel. Your explanation wouldn't be easy for anyone without serious knowledge to follow. The design parameters for all transformers are related as follows :- Fs = 22.6 x V x 10,000 ------------------ B x Np x Afe Where Fs = frequency of saturation, 22.6 is a constant for all equations, V = voltage in rms across the primary, Np = primary turns, B = maximum allowable magnetic field strength in Tesla in the core, Afe = cross sectional area of the central core leg, in square mm. The saturation is a voltage caused phenomena. Power trannies may well be run at 1.6Tesla, but not those in well designed audio gear where 1T is more appropriate. Your reference to W/Lb losses isn't the whole story. GOSS will have much lower W/Lb than non oriented SS. Each type of steel will saturate at nearly the same B. If you want a quiet running tranny that won't get hot, you must use more turns and iron for the same VA compared to what is done in the commercial world where many makers don't care that their trannies are mechanically noisy and/or get roasting hot. There is a whole lot more that helps at my website, http://www.turneraudio.com.au Patrick Turner. Hope this helps. Jerry |
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#8
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Saturation in transformers.
"Graham Holloway" The differences you describe are down to the material used, not the shape. ** WRONG !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!! If you use GOSS in an E core it will show sharp saturation characteristics. ** NEVER with the low loss or near as sharp as a toroidal. YOU have NOT done any tests. ................ Phil |
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#9
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Saturation in transformers.
Graham Stevenson = PSYCHO POMMY **** !!!!!! Phil Allison wrote: OTOH, e-core types behave rather differently, You're talking ****. ** You are ONE criminal, ****ing **** Stevenson. You need a ****ing bullet in the head. HOW DARE YOU STALK ME LIKE THIS !!!!!!!!!! It's purely down to material properties. The path shape is utterly irrelevant. ** Shame about all the ****ING AIR GAPS in an e-core that do not exist with a toroidal core !!!!!!!!!!!!! Go **** your **** ugly mother, your ****wit brother or your mongoloid sister - you pile of sub human pommy GARBAGE !!! ............ Phil |
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#10
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Saturation in transformers.
"Pooh Bear" Deciding magnetising current ( and hence working flux ) is a balance between efficiency ( various losses ) and core material properties. Not for the faint hearted or sunday driver. ** Not for Mother ****ing CRIMINAL IDIOTS like Graham Stevenson either !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ............ Phil |
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#11
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Saturation in transformers.
On Mon, 07 Nov 2005 17:25:52 -0700, Jerry wrote:
The simple answer to your toroid question is this: Saturation occurs when the excitation losses in the core are excessive and reflect an excessive primary no load current. The quantity that you are looking for is VA/lb. loss: i.e If you experience any value over 10VA/lb. you are in or approaching saturation. For example: If your toroid weighs 4 lbs. and you had 40 VA, the primary no load current would be .3333Amperes. That amount of current would occur at 16 kilogausse @ 60Hz. Normally we do not design for any flux density higher than 14kilogausse, so these losses are not prohibitive. I know that Patrick is going to bite his tounge at any flux density over 10KG, but I design for the high volume world where economics do come into play. Also, we use other core materials in the 26Ga. non-oriented steel arena. Most toroids are wound with thin, grain oriented steel. Hope this helps. Jerry Good thinking, guys. The excitation current is in phase quadrature (wow) with the load current meaning that you add the square of the load current to the square of the exciting current and then take the square root. You can then plot the points at which the excitation current makes a real difference in the temperature rise. Now if you want to talk about controlling in-rush current in a transformer that is another whole matter dependent upon those funny little gaps in the laminations. Fusing considerations drove us nuts in the "old tube days." Jerry |
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#12
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Saturation in transformers.
"Jerry": The excitation current is in phase quadrature (wow) with the load current ** The maxima are in quadrature ( ie shifted 90 degrees) but the current waveform is not a sine wave. meaning that you add the square of the load current to the square of the exciting current and then take the square root. ** The problem with that simplistic idea is that load current affects ( diminishes) magnetising current. You can then plot the points at which the excitation current makes a real difference in the temperature rise. ** Easier to just measure temp rise of a sample design to determine VA rating. Once you have that figure, a user only has to measure primary rms current to see if the VA is within the limit. .......... Phil |
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#13
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Saturation in transformers.
Graham Holloway wrote
The differences you describe are down to the material used, not the shape. If you use GOSS in an E core it will show sharp saturation characteristics. No, for several reasons. A toroid is made from a single piece of iron, the grain orientation is consistently in the direction of the field...no corners and no arms at 90 degrees...and all the iron is within the windings so the field strength is more constant throughout. It is this consistency which gives it the sharp saturation. cheers, Ian |
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#14
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Saturation in transformers.
Patrick Turner wrote
Your explanation wouldn't be easy for anyone without serious knowledge to follow. Why not? I followed it OK. I think. Generally there are as many ways of explaining as there are variables. Fs = 22.6 x V x 10,000 ------------------ B x Np x Afe Where Fs = frequency of saturation, 22.6 is a constant for all equations, V = voltage in rms across the primary, Np = primary turns, B = maximum allowable magnetic field strength in Tesla in the core, Afe = cross sectional area of the central core leg, in square mm. The saturation is a voltage caused phenomena. No. Fundamentally, magnetic field depends on current. A voltage without a current will not cause a magnetic field. Saturation arises from a magnetic field, therefore it is directly related to current, not voltage. By your own formula, you should be able to see that saturation depends not just on voltage, but also on frequency. For an inductor, the upshot of voltage and frequency is current. If you think of it as a load resistance in parallel with an iron-cored inductor with a given core and number of windings, it is the current through the inductor that produces the magnetic field, hence too much current leads to saturation. This agrees perfectly with Jerry's point, that the load can be ignored...easily done by testing with no load. cheers, Ian |
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#15
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Saturation in transformers.
"Ian Iveson" The saturation is a voltage caused phenomena. No. ** It is of no interest to transformer users to know what the saturation current level is unless the applied voltage and frequency is specified. Since Imag always increases with increasing applied voltage, that is the practical way to view it - especially when the transformer is intended for connection to the AC supply. Saturation is non-linear behaviour, it cannot be analysed from a model that treats the primary as a simple inductor. Iron cored inductors are designed to behave linearly up to some current figure - no such thing applies to AC supply transformer primaries. .......... Phil |
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#16
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Saturation in transformers.
Daft Phil wrote
No. ** It is of no interest to transformer users to know what the saturation current level is unless the applied voltage and frequency is specified. Since Imag always increases with increasing applied voltage, that is the practical way to view t - especially when the transformer is intended for connection to the AC supply. Rubbish. And how would you know what is of interest to any transformer user other than yourself. Where did I say transformer users *are* interested? And what is the rest of the paragraph for...are you arguing with yourself? What about? I am a transformer user, and I am interested in saturation current. And what's it got to do with "No" anyway... Saturation is non-linear behaviour, it cannot be analysed from a model that treats the primary as a simple inductor. No kidding? Who said anything about a simple inductor? But it can be usefully envisaged as an iron-cored inductor (which it is...you can't hope to be taken seriously if you don't know a transformer is an inductor, clot) in parallel with the reflected secondary load. It is useful to do so, regardless of how complicated the inductor, because it reveals why the current due to the load does not lead to saturation, whereas the current through the inductor can. Note that the usefulness of this model has nothing to do with the simplicity or otherwise of the inductor you envisage. In any event, models and analysis are both *always* simpler than reality. Otherwise there would be no point in using them. Iron cored inductors are designed to behave linearly up to some current figure - no such thing applies to AC supply transformer primaries. Er...what babble is this? Hands up anyone who knows what you think you might be on about. cheers, Ian |
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#17
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Saturation in transformers.
Ian Iveson wrote: Graham Holloway wrote The differences you describe are down to the material used, not the shape. If you use GOSS in an E core it will show sharp saturation characteristics. No, for several reasons. A toroid is made from a single piece of iron, the grain orientation is consistently in the direction of the field...no corners and no arms at 90 degrees...and all the iron is within the windings so the field strength is more constant throughout. It is this consistency which gives it the sharp saturation. cheers, Ian The resulting high µ of the coil of GOSS means that the inductance of the primary is very high compared to ordinary non oriented SiFe which will have a µ of tyipically 1/10 of that of the GOSS toroidal core. Therefore as long as the B max is lower than levels at saturation there is a lower magnetizing current with with less distortion harmonics with a toroid than with a E&I lam core. In practice many tranny winders I have known place the Bmax at 1.3Tesla, and when the tranny is connected to a class A amp drawing some current in a rectifier circuit the darn tranny is mechanically noisy, even though that without a load the input primary current is negligible; ie, the iron losses are very low. I will use a Bmax of below 1Tesla which I find is a sre way to keep the tranny quiet despite the slight extra winding losses. With preamps and old non oriented E&I iron I often use B = 0.9T, and although the design is a little heavier than the modern trannies the tranny runs as cool as a cucumber and noiselesly. And yes, DC bias swings in an audio PP tranny can make saturation problems worse. Try running full range pink noise into an amp up until you get occasional clipping; you can hear the knocking sounds as the high µ material saturates, and heavy anode pulse currents flow, causing serious IMD. Using a CR filter at the front of the amp with a pole at 14Hz reduces the effect considerably. Using Ccores with a slight gap or E&I with a slight gap is another way to get the PP tranny to be far more resiliant to saturation effects at high levels. Patrick Turner. .. ir |
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#18
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Saturation in transformers.
Ian Iveson wrote: Patrick Turner wrote Your explanation wouldn't be easy for anyone without serious knowledge to follow. Why not? I followed it OK. I think. Generally there are as many ways of explaining as there are variables. Fs = 22.6 x V x 10,000 ------------------ B x Np x Afe Where Fs = frequency of saturation, 22.6 is a constant for all equations, V = voltage in rms across the primary, Np = primary turns, B = maximum allowable magnetic field strength in Tesla in the core, Afe = cross sectional area of the central core leg, in square mm. The saturation is a voltage caused phenomena. No. Fundamentally, magnetic field depends on current. A voltage without a current will not cause a magnetic field. Saturation arises from a magnetic field, therefore it is directly related to current, not voltage. By your own formula, you should be able to see that saturation depends not just on voltage, but also on frequency. For an inductor, the upshot of voltage and frequency is current. If you read RDH4, you'd see where they say saturation is a voltage related phenomena, and sure there is a magnetizing current in a tranny, whether loaded or not, and that current is due to voltage applied across an inductance. but once that voltage exceeds a threshold the steel saturates, and the coil becomesa short circuit when the steels field cannot continue to oppose the current flow of the current from the applied voltage. The very field in an inductor opposes the current flow... If you think of it as a load resistance in parallel with an iron-cored inductor with a given core and number of windings, it is the current through the inductor that produces the magnetic field, hence too much current leads to saturation. The too-much-current occurs after a voltage threshold hold has been reached. Patrick Turner. This agrees perfectly with Jerry's point, that the load can be ignored...easily done by testing with no load. cheers, Ian |
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#19
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Saturation in transformers.
Ian Iveson wrote: Daft Phil wrote No. ** It is of no interest to transformer users to know what the saturation current level is unless the applied voltage and frequency is specified. Since Imag always increases with increasing applied voltage, that is the practical way to view t - especially when the transformer is intended for connection to the AC supply. Rubbish. And how would you know what is of interest to any transformer user other than yourself. Where did I say transformer users *are* interested? And what is the rest of the paragraph for...are you arguing with yourself? What about? I am a transformer user, and I am interested in saturation current. And what's it got to do with "No" anyway... Saturation is non-linear behaviour, it cannot be analysed from a model that treats the primary as a simple inductor. No kidding? Who said anything about a simple inductor? But it can be usefully envisaged as an iron-cored inductor (which it is...you can't hope to be taken seriously if you don't know a transformer is an inductor, clot) in parallel with the reflected secondary load. It is useful to do so, regardless of how complicated the inductor, because it reveals why the current due to the load does not lead to saturation, whereas the current through the inductor can. Note that the usefulness of this model has nothing to do with the simplicity or otherwise of the inductor you envisage. In any event, models and analysis are both *always* simpler than reality. Otherwise there would be no point in using them. Iron cored inductors are designed to behave linearly up to some current figure - no such thing applies to AC supply transformer primaries. Er...what babble is this? Hands up anyone who knows what you think you might be on about. cheers, Ian I don't know whether you have ever examined the current wave forms in a tranny hooked up to a variac. But its not very linear with applied voltage; and becomes very non linear at the onset of saturation when the Bmax of around 1.5tesla is reached. Anyway, by examining the current wave form, and its phase relationship and the distortion one gets some idea of what is happening in a typical tranny. Placing 4.7kohms in series between the low Z of the variac drmatically increases the source impedance and the distortion dramatically increases. GOSS in the form of a toroid minimises the Dn, but it is informative to do the experiments to really see what goes on. A dual trace CRO is almost essential to see the phase relationships. Patrick Turner. |
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#20
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Saturation in transformers.
Patrick Turner wrote
Your explanation wouldn't be easy for anyone without serious knowledge to follow. Why not? I followed it OK. I think. Generally there are as many ways of explaining as there are variables. Fs = 22.6 x V x 10,000 ------------------ B x Np x Afe Where Fs = frequency of saturation, 22.6 is a constant for all equations, V = voltage in rms across the primary, Np = primary turns, B = maximum allowable magnetic field strength in Tesla in the core, Afe = cross sectional area of the central core leg, in square mm. The saturation is a voltage caused phenomena. No. Fundamentally, magnetic field depends on current. A voltage without a current will not cause a magnetic field. Saturation arises from a magnetic field, therefore it is directly related to current, not voltage. By your own formula, you should be able to see that saturation depends not just on voltage, but also on frequency. For an inductor, the upshot of voltage and frequency is current. If you read RDH4, you'd see where they say saturation is a voltage related phenomena, The laws of physics won't change if I read RDH. Of course current is related to voltage...look up Ohm's Law. and sure there is a magnetizing current in a tranny, whether loaded or not, and that current is due to voltage applied across an inductance. but once that voltage exceeds a threshold the steel saturates, Rubbish. Only true at a particular frequency. You must know better than this, so I take it you are squirming, as usual. and the coil becomes a short circuit when the steels field cannot continue to oppose the current flow of the current from the applied voltage. No. Some time ago I pointed out an error in RDH. Perhaps you ignored me and failed to amend the diagram? The inductance does not plummet as depicted, but actually trails off more gradually as current increases. The situation is exacerbated by what you, with your crazy notion of feedback, would call positive current feedback: as current increases, reactance falls, so current increases further, etcetera. But, so considered, the feedback is less than unity so the result is finite...whereas with a short it would be infinite. In fact an equilibrium is reached for any given current, and reactance does not disappear as quickly as you think, or as RDH shows. Of course there is also primary resistance, which remains unaffected, so that is two reasons why the coil does *not* become a short. Further, you may notice that a saturated transformer gets hot. A short dissipates no power (only current, no voltage drop), so where do you think the heat is coming from? The very field in an inductor opposes the current flow... If you think of it as a load resistance in parallel with an iron-cored inductor with a given core and number of windings, it is the current through the inductor that produces the magnetic field, hence too much current leads to saturation. The too-much-current occurs after a voltage threshold hold has been reached. Only at a particular frequency (sigh...). Do you remember any school maths? Remember the common questions that ask you to reduce an equation to its simplest form? Why was that an important skill to learn? Because it allows you to see the essential relationship without the complications of mathematical clutter and particular circumstance. In this case you would substitute voltage and frequency for current, and end up with a very simple formula. That would improve your basic grasp of the relationship, which would be true for *all cases*. Armed with this fundamental understanding, you can quite easily derive whatever practical formula you wish, depending on the particular problem you are addressing. If you are interested in frequency and voltage, then you can derive the formula you gave from RDH. Fundamental understanding is, in other words, transferable. Without it, particular knowledge is just empty fact. That's why you have to keep reading the book...you lack the conceptual framework to construct your own thoughts. If you know the core, and how many turns on the windings, and how much current through each, you are home and dry. The only reason you need to drag voltage and frequency in is in order to calculate the current. You won't see what I mean, and neither will Phil. Oh well. cheers, Ian |
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#21
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Saturation in transformers.
Patrick Turner wrote
Iron cored inductors are designed to behave linearly up to some current figure - no such thing applies to AC supply transformer primaries. Er...what babble is this? Hands up anyone who knows what you think you might be on about. I don't know whether you have ever examined the current wave forms in a tranny hooked up to a variac. Yes. Also my transformer model, which behaves the same. But its not very linear with applied voltage; and becomes very non linear at the onset of saturation when the Bmax of around 1.5tesla is reached. Depending on the core material. The best definition of saturation I have seen places it at the point where the peak of the current waveform is double that of the underlying sine wave. Yes it is arbitrary but, without some defined point, expressions such as "saturating" and "approaching saturation" are far too vague for meaningful discussion. Anyway, by examining the current wave form, and its phase relationship and the distortion one gets some idea of what is happening in a typical tranny. Placing 4.7kohms in series between the low Z of the variac drmatically increases the source impedance and the distortion dramatically increases. GOSS in the form of a toroid minimises the Dn, but it is informative to do the experiments to really see what goes on. Perhaps you might try it then. You would discover that the primary never becomes a short, for example. A dual trace CRO is almost essential to see the phase relationships. No kidding? Was that a hands up? Er...is this what you meant, Phil? cheers, Ian |
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#22
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Saturation in transformers.
"Ian Iveson" = Autistic ****wit ** It is of no interest to transformer users to know what the saturation current level is unless the applied voltage and frequency is specified. Since Imag always increases with increasing applied voltage, that is the practical way to view t - especially when the transformer is intended for connection to the AC supply. Rubbish. And how would you know what is of interest to any transformer user other than yourself. Where did I say transformer users *are* interested? And what is the rest of the paragraph for...are you arguing with yourself? What about? ** What a load of mentally retarded drivel. I am a transformer user, and I am interested in saturation current. And what's it got to do with "No" anyway... ** Ian has a reading disability. All autistics do. Saturation is non-linear behaviour, it cannot be analysed from a model that treats the primary as a simple inductor. No kidding? Who said anything about a simple inductor? But it can be usefully envisaged as an iron-cored inductor (which it is...you can't hope to be taken seriously if you don't know a transformer is an inductor, clot) in parallel with the reflected secondary load. ** Wrong. The inductance of a transformer primary is not a defined value like a purpose made inductor - it varies widely with applied voltage and through a single cycle. Iron cored inductors are designed to behave linearly up to some current figure - no such thing applies to AC supply transformer primaries. Er...what babble is this? ** So you know as little about inductors as you do transformers. Never noticed that iron and ferrite cored inductors have max peak current figures ? Just a simple number in amps above which core saturation spoils its usefulness as an inductor. ......... Phil |
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#23
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Saturation in transformers.
Ian Iveson wrote: Patrick Turner wrote Your explanation wouldn't be easy for anyone without serious knowledge to follow. Why not? I followed it OK. I think. Generally there are as many ways of explaining as there are variables. Fs = 22.6 x V x 10,000 ------------------ B x Np x Afe Where Fs = frequency of saturation, 22.6 is a constant for all equations, V = voltage in rms across the primary, Np = primary turns, B = maximum allowable magnetic field strength in Tesla in the core, Afe = cross sectional area of the central core leg, in square mm. The saturation is a voltage caused phenomena. No. Fundamentally, magnetic field depends on current. A voltage without a current will not cause a magnetic field. Saturation arises from a magnetic field, therefore it is directly related to current, not voltage. By your own formula, you should be able to see that saturation depends not just on voltage, but also on frequency. For an inductor, the upshot of voltage and frequency is current. If you read RDH4, you'd see where they say saturation is a voltage related phenomena, The laws of physics won't change if I read RDH. Of course current is related to voltage...look up Ohm's Law. If you are not into reading RDH, then i suggest many other books may provide a better source of info than I have tendered to the group so far. But we are dealing with the non linear behaviour of transformer iron.... and sure there is a magnetizing current in a tranny, whether loaded or not, and that current is due to voltage applied across an inductance. but once that voltage exceeds a threshold the steel saturates, Rubbish. Only true at a particular frequency. You must know better than this, so I take it you are squirming, as usual. Well look at the formula I quoted above from my website. Its the well known *transfromer equation* that relates the applied voltage, frequency, Bmax, number of turns and the core section area. I am not squirming after having desinged and wound dozens of very fine power and output transformers. and the coil becomes a short circuit when the steels field cannot continue to oppose the current flow of the current from the applied voltage. No. Some time ago I pointed out an error in RDH. Perhaps you ignored me and failed to amend the diagram? The inductance does not plummet as depicted, but actually trails off more gradually as current increases. If you examined the current wave form as V across a winding is increased, you will find there is a sudden increase in the 3H after what is called the saturation phenomena. The iron appears to have magnetic store of energy to oppose the AC flow for *parts* of the cycle, ie, the top and bottom part of the wave, so we see large current *spikes* where the coil acts as if it has become a short circuit for part of the cycle. But for other parts of the cycle around the zero crossing region the iron energy is providing some oposition to the flow of current in the wire. If you looked, you would know. The situation is exacerbated by what you, with your crazy notion of feedback, would call positive current feedback: as current increases, reactance falls, so current increases further, etcetera. There is no crazy notion of FB. Electro magnetics isn't easy to understand. But why does not a large current flow when you apply a voltage across a coil? The magnetic field the applied voltage sets up opposes the flow. But, so considered, the feedback is less than unity so the result is finite...whereas with a short it would be infinite. In fact an equilibrium is reached for any given current, and reactance does not disappear as quickly as you think, or as RDH shows. I didn't say the L dissapears once a threshold has been reached; but it is as if there is a sudden large reduction fall in inductance at saturation. Of course there is also primary resistance, which remains unaffected, so that is two reasons why the coil does *not* become a short. Well when the inductance ceases to oppose the flow during the wave cycles due to saturation, the applied voltage to the primary tends to be a short circuit current, ie, the mains applied voltage sees only the DCR of the primary. This situation *is* regarded as a short circuit. Further, you may notice that a saturated transformer gets hot. A short dissipates no power (only current, no voltage drop), so where do you think the heat is coming from? Two things, core losses, and copper losses. The very field in an inductor opposes the current flow... If you think of it as a load resistance in parallel with an iron-cored inductor with a given core and number of windings, it is the current through the inductor that produces the magnetic field, hence too much current leads to saturation. The too-much-current occurs after a voltage threshold hold has been reached. Only at a particular frequency (sigh...). Do you remember any school maths? See my formula. Seems to me my maths are better than yours. Remember the common questions that ask you to reduce an equation to its simplest form? Why was that an important skill to learn? Because it allows you to see the essential relationship without the complications of mathematical clutter and particular circumstance. The transformer equation is the simplest way to relate the design parameters of a transformer. In this case you would substitute voltage and frequency for current, and end up with a very simple formula. That would improve your basic grasp of the relationship, which would be true for *all cases*. Armed with this fundamental understanding, you can quite easily derive whatever practical formula you wish, depending on the particular problem you are addressing. If you are interested in frequency and voltage, then you can derive the formula you gave from RDH. I did derive my formula from what is in RDH4 and a few other old books that explain everything. Often their explanations are totally incomprehensible. Electro Magnetics was designed by the schitzoprenic brother of the God Of Triodes, and this dude made the use of iron, wire, and volts to be as confusing as possible. Fundamental understanding is, in other words, transferable. Without it, particular knowledge is just empty fact. That's why you have to keep reading the book...you lack the conceptual framework to construct your own thoughts. If you know the core, and how many turns on the windings, and how much current through each, you are home and dry. The only reason you need to drag voltage and frequency in is in order to calculate the current. You won't see what I mean, and neither will Phil. Oh well. I do wind much better transformers than I can buy from anyone. My conceptual understanding levels are good enough. Phil knows more about it than you do, and he can explain it when he isn't acting like a complete fukken idiot. Patrick Turner. cheers, Ian |
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Saturation in transformers.
Ian Iveson wrote: Patrick Turner wrote Iron cored inductors are designed to behave linearly up to some current figure - no such thing applies to AC supply transformer primaries. Er...what babble is this? Hands up anyone who knows what you think you might be on about. I don't know whether you have ever examined the current wave forms in a tranny hooked up to a variac. Yes. Also my transformer model, which behaves the same. So you have not used a CRO and an old tranny. But its not very linear with applied voltage; and becomes very non linear at the onset of saturation when the Bmax of around 1.5tesla is reached. Depending on the core material. The best definition of saturation I have seen places it at the point where the peak of the current waveform is double that of the underlying sine wave. Yes it is arbitrary but, without some defined point, expressions such as "saturating" and "approaching saturation" are far too vague for meaningful discussion. Well, most tranny iron be it NOSS or GOSS saturates with such suddenness it is a definite indicator of when saturation can be deemed to have begun. Anyway, by examining the current wave form, and its phase relationship and the distortion one gets some idea of what is happening in a typical tranny. Placing 4.7kohms in series between the low Z of the variac drmatically increases the source impedance and the distortion dramatically increases. GOSS in the form of a toroid minimises the Dn, but it is informative to do the experiments to really see what goes on. Perhaps you might try it then. You would discover that the primary never becomes a short, for example. See my other post. A dual trace CRO is almost essential to see the phase relationships. No kidding? ? Patrick Turner. Was that a hands up? Er...is this what you meant, Phil? cheers, Ian |
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Saturation in transformers.
"Patrick Turner" wrote in message ... Ian Iveson wrote: Patrick Turner wrote Your explanation wouldn't be easy for anyone without serious knowledge to follow. Why not? I followed it OK. I think. Generally there are as many ways of explaining as there are variables. Fs = 22.6 x V x 10,000 ------------------ B x Np x Afe Where Fs = frequency of saturation, 22.6 is a constant for all equations, V = voltage in rms across the primary, Np = primary turns, B = maximum allowable magnetic field strength in Tesla in the core, Afe = cross sectional area of the central core leg, in square mm. The saturation is a voltage caused phenomena. No. Fundamentally, magnetic field depends on current. A voltage without a current will not cause a magnetic field. Saturation arises from a magnetic field, therefore it is directly related to current, not voltage. By your own formula, you should be able to see that saturation depends not just on voltage, but also on frequency. For an inductor, the upshot of voltage and frequency is current. If you read RDH4, you'd see where they say saturation is a voltage related phenomena, The laws of physics won't change if I read RDH. Of course current is related to voltage...look up Ohm's Law. If you are not into reading RDH, then i suggest many other books may provide a better source of info than I have tendered to the group so far. I dare say. Perhaps you could read one over the weekend. But we are dealing with the non linear behaviour of transformer iron.... No kidding? and sure there is a magnetizing current in a tranny, whether loaded or not, and that current is due to voltage applied across an inductance. but once that voltage exceeds a threshold the steel saturates, Rubbish. Only true at a particular frequency. You must know better than this, so I take it you are squirming, as usual. Well look at the formula I quoted above from my website. Its the well known *transfromer equation* that relates the applied voltage, frequency, Bmax, number of turns and the core section area. I am not squirming after having desinged and wound dozens of very fine power and output transformers. So you say, incessantly. Not one of your claimed customers has ever endorsed any one of your claimed products, and I am not surprised. You spend a lot of fools' money pretending to do what many manufacturers of excellent reputation do for a fraction of the price. and the coil becomes a short circuit when the steels field cannot continue to oppose the current flow of the current from the applied voltage. No. Some time ago I pointed out an error in RDH. Perhaps you ignored me and failed to amend the diagram? The inductance does not plummet as depicted, but actually trails off more gradually as current increases. If you examined the current wave form as V across a winding is increased, Blah de blah...obfuscation again. Wriggle, squirm. you will find there is a sudden increase in the 3H after what is called the saturation phenomena. Wriggle, squirm. The singular of phenomena is phenomenon, but better to avoid the wriggling, squirming obfuscation and just call it saturation. Once you arrive back on earth you may realise that it is necessary to define an arbitrary point in the process you describe at which you say the iron is saturated. It is not sudden like a switch. Look it up, but not in RDH because the diagram is wrong. Or perhaps it would help to look at the RDH diagram and try and see *why* it is in error. As I have said several times, the best definition I have seen is the point at which the current spike is double the magnitude of the underlying current waveform. A more useful definition could be a particular proportion of distortion. The iron appears to have magnetic store of energy to oppose the AC flow for *parts* of the cycle, ie, the top and bottom part of the wave, so we see large current *spikes* where the coil acts as if it has become a short circuit for part of the cycle. No. Once again, it is not a short circuit, ever. It is never a short circuit. Since you are the one claiming to do loads of real measurements, perhaps you could say when you measured this short circuit? But for other parts of the cycle around the zero crossing region the iron energy is providing some oposition to the flow of current in the wire. If you looked, you would know. Before I knew, I did look. But looking is not knowing, as you clearly demonstrate. The situation is exacerbated by what you, with your crazy notion of feedback, would call positive current feedback: as current increases, reactance falls, so current increases further, etcetera. There is no crazy notion of FB. Give you half a chance and you will invent one. Don't you see the parallel with your hopeless notion of triode "internal feedback"? Electro magnetics isn't easy to understand. It would help if you found out about algebra. But why does not a large current flow when you apply a voltage across a coil? Er, it might, or might not, depending on the time, the resistance and the reactance. The magnetic field the applied voltage sets up opposes the flow. No. The current sets up the magnetic field. Otherwise you wouldn't get the phase difference, clot. The changing magnetic field produces an opposing voltage, which opposes the applied voltage (not the current, which I suppose you mean by "flow"). The residual voltage drives the current through the winding resistance. In the case of a transformer, the current in the secondary produces a field opposing that produced by the primary. The residual field is, more or less, the same as that produced by the primary alone when the secondary is open circuit. Hence the transformer can be modelled by a resistance in parallel with an inductor made up of just the primary and the core. Such a model is generally accepted, and can be useful even up to the frequencies used for SMPS, where matters become more complicated because of core losses and skin effect. For the kind of frequencies and waveforms we are talking about, it is hardly a black art But, so considered, the feedback is less than unity so the result is finite...whereas with a short it would be infinite. In fact an equilibrium is reached for any given current, and reactance does not disappear as quickly as you think, or as RDH shows. I didn't say the L dissapears once a threshold has been reached; but it is as if there is a sudden large reduction fall in inductance at saturation. You said ***"short circuit"***. That is the point you are defending. A sudden fall, a large fall...neither of these is a short circuit. A short circuit is somewhere close to zero ohms. The effect you are trying to describe is not a short. The impedance falls quite quickly, the current rises quite rapidly, reaching by my adopted definition twice the instantaneous value which would flow if the iron remained magnetically linear. Of course there is also primary resistance, which remains unaffected, so that is two reasons why the coil does *not* become a short. Well when the inductance ceases to oppose the flow during the wave cycles due to saturation, the applied voltage to the primary tends to be a short circuit current, ie, the mains applied voltage sees only the DCR of the primary. This situation *is* regarded as a short circuit. Squirm, wriggle, obfuscate. Let's just unpick it this time shall we? What is this "DCR" you have thrown in...like the "saturation phenomena (sic)" we saw before. It is a characteristic of your squirming obfuscation that you try to blind people with pathetic grandiose attempts at jargon. You mean resistance, don't you? By "DCR" you just mean resistance, yes? Resistance at DC? Have I worked it out correctly? As opposed to ACR perhaps? Do you perceive a difference between ACR and DCR? Perhaps it would help if you were to realise that it is a defining characteristic of resistance that it is the same for AC and DC? Surely if you pretend to make good transformers, you must also pretend to know the difference between resistance and reactance? So really you just mean resistance. Why then did you call it DCR? What is the purpose of this wriggling, squirming obfuscation? Because you just said that a resistance is regarded as a short circuit. By who, I wonder. You alone, in all the world, sadly. Let's look at that again... the mains applied voltage sees only the DCR of the primary. This situation *is* regarded as a short circuit. Did you really say that? Look, you even underscored the "is". Crikey. Worth another look... the mains applied voltage sees only the DCR of the primary. This situation *is* regarded as a short circuit. Should I bother any further with a conman who thinks that a resistance is a short circuit? And, what is more, it doesn't only see the resistance. It also sees, for much of the time, the full inductance of the transformer and, for that portion of the time when saturation occurs, it also sees a considerable remaining contribution to the inductance by the core, plus it sees the inductance of the windings as if there were no iron there at all. In addition, the apparent resistance it sees in the winding is modified by the core losses. Not a short then, is it? Further, you may notice that a saturated transformer gets hot. A short dissipates no power (only current, no voltage drop), so where do you think the heat is coming from? Two things, core losses, and copper losses. And how would they happen if the primary appears as a short? You haven't seen my point at all as usual. Can't have losses without power, can't have power without voltage, can't have voltage if it's a short. No matter how much I suggest it, you still haven't looked up Ohm's law. The very field in an inductor opposes the current flow... If you think of it as a load resistance in parallel with an iron-cored inductor with a given core and number of windings, it is the current through the inductor that produces the magnetic field, hence too much current leads to saturation. The too-much-current occurs after a voltage threshold hold has been reached. Only at a particular frequency (sigh...). Do you remember any school maths? See my formula. The one you got from RDH? Don't need to, it was burned into my brain aged about 13. Seems to me my maths are better than yours. I can see how it seems like that to you. Remember the common questions that ask you to reduce an equation to its simplest form? Why was that an important skill to learn? Because it allows you to see the essential relationship without the complications of mathematical clutter and particular circumstance. The transformer equation is the simplest way to relate the design parameters of a transformer. Maybe so, depending on what you are designing for. But the thread is not about how to design a transformer, but rather how to understand how transformers saturate. But you won't have noticed that in your rush to con another fool out of his money. In this case you would substitute voltage and frequency for current, and end up with a very simple formula. That would improve your basic grasp of the relationship, which would be true for *all cases*. Armed with this fundamental understanding, you can quite easily derive whatever practical formula you wish, depending on the particular problem you are addressing. If you are interested in frequency and voltage, then you can derive the formula you gave from RDH. I did derive my formula from what is in RDH4 and a few other old books that explain everything. You derived your formula? You mean you copied it from one of the zillion places it appears. Often their explanations are totally incomprehensible. Electro Magnetics was designed by the schitzoprenic brother of the God Of Triodes, and this dude made the use of iron, wire, and volts to be as confusing as possible. I can see your problem... Fundamental understanding is, in other words, transferable. Without it, particular knowledge is just empty fact. That's why you have to keep reading the book...you lack the conceptual framework to construct your own thoughts. If you know the core, and how many turns on the windings, and how much current through each, you are home and dry. The only reason you need to drag voltage and frequency in is in order to calculate the current. You won't see what I mean, and neither will Phil. Oh well. I do wind much better transformers than I can buy from anyone. So you keep saying, but no-one who has bought one agrees. How would you know anyway? You don't test them properly. You don't even know Ohm's law. My conceptual understanding levels are good enough. For conning fools out of their money, perhaps. Phil knows more about it than you do, and he can explain it when he isn't acting like a complete fukken idiot. Then check the last statement of his last post to me, where he finally admits to some approximation to the truth about current. My estimation is that he actually knows less than you, if that is any comfort. But he has had enough failed education to fake a different level of smartness. cheers, Ian |
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Saturation in transformers.
So you say, incessantly. Not one of your claimed customers has ever endorsed any one of your claimed products, and I am not surprised. You spend a lot of fools' money pretending to do what many manufacturers of excellent reputation do for a fraction of the price. I make a living doing repairs, restorations, building complte new amps. I have nothing I want to prove to a disbelieving person like yourself. But I did wind ALL the trannies and chokes in the items at my website. None of my customers would be seen dead posting here. and the coil becomes a short circuit when the steels field cannot continue to oppose the current flow of the current from the applied voltage. No. Some time ago I pointed out an error in RDH. Perhaps you ignored me and failed to amend the diagram? The inductance does not plummet as depicted, but actually trails off more gradually as current increases. If you examined the current wave form as V across a winding is increased, Blah de blah...obfuscation again. Wriggle, squirm. you will find there is a sudden increase in the 3H after what is called the saturation phenomena. Wriggle, squirm. The singular of phenomena is phenomenon, but better to avoid the wriggling, squirming obfuscation and just call it saturation. Once you arrive back on earth you may realise that it is necessary to define an arbitrary point in the process you describe at which you say the iron is saturated. It is not sudden like a switch. Look it up, but not in RDH because the diagram is wrong. Or perhaps it would help to look at the RDH diagram and try and see *why* it is in error. You have not proven the RDH to be in error. And you make silly comments about squirming and obfuscation, but I leave YOU to get off your arse and go and observe something. As I have said several times, the best definition I have seen is the point at which the current spike is double the magnitude of the underlying current waveform. A more useful definition could be a particular proportion of distortion. Depends on the core material. Some say its when the 3H in the current wave exceeds 12% when the tranny is fed from a low Z source like the mains. But you look, and you decide. The iron appears to have magnetic store of energy to oppose the AC flow for *parts* of the cycle, ie, the top and bottom part of the wave, so we see large current *spikes* where the coil acts as if it has become a short circuit for part of the cycle. No. Once again, it is not a short circuit, ever. It is never a short circuit. When the mains voltage can appear across the DCR of the winding wire of the primary for all or part of the wave cycle, it is considered that a continuous or part time short circuit condition. So take you silly idea of never to some other group which understands never. Since you are the one claiming to do loads of real measurements, perhaps you could say when you measured this short circuit? Do your own observations, don't rely on me. But for other parts of the cycle around the zero crossing region the iron energy is providing some oposition to the flow of current in the wire. If you looked, you would know. Before I knew, I did look. But looking is not knowing, as you clearly demonstrate. You refuse to look enough. The situation is exacerbated by what you, with your crazy notion of feedback, would call positive current feedback: as current increases, reactance falls, so current increases further, etcetera. There is no crazy notion of FB. Give you half a chance and you will invent one. Don't you see the parallel with your hopeless notion of triode "internal feedback"? You are a real dumb brute of a fool if you cannot understand the NFB in a triode. Its been explained a thousand times here, but Professor Child had much more precise descriptions of it in T.E.Terman's Radio Engineering book of 1937. I suggest you read a little more before saying leading professors of radio engineering got it all wrong. Electro magnetics isn't easy to understand. It would help if you found out about algebra. I know enough algebra. But why does not a large current flow when you apply a voltage across a coil? Er, it might, or might not, depending on the time, the resistance and the reactance. The magnetic field the applied voltage sets up opposes the flow. No. The current sets up the magnetic field. Otherwise you wouldn't get the phase difference, clot. There is a tiny magnetizing current in the no load condition of most toroidal trannies. The oppsition to the current flow is due to the high inductance of the coil. Ditto in an OPT, where at 1kHz, almost no current flow occurs at all without a load. The changing magnetic field produces an opposing voltage, which opposes the applied voltage (not the current, which I suppose you mean by "flow"). The residual voltage drives the current through the winding resistance. I see you don't design and build any trannies. In the case of a transformer, the current in the secondary produces a field opposing that produced by the primary. The residual field is, more or less, the same as that produced by the primary alone when the secondary is open circuit. Hence the transformer can be modelled by a resistance in parallel with an inductor made up of just the primary and the core. Such a model is generally accepted, and can be useful even up to the frequencies used for SMPS, where matters become more complicated because of core losses and skin effect. For the kind of frequencies and waveforms we are talking about, it is hardly a black art Well since you know all about the black art of winding trannies, go to it, no need to discuss anything with me. But, so considered, the feedback is less than unity so the result is finite...whereas with a short it would be infinite. In fact an equilibrium is reached for any given current, and reactance does not disappear as quickly as you think, or as RDH shows. I didn't say the L dissapears once a threshold has been reached; but it is as if there is a sudden large reduction fall in inductance at saturation. You said ***"short circuit"***. That is the point you are defending. A sudden fall, a large fall...neither of these is a short circuit. A short circuit is somewhere close to zero ohms. See above. The effect you are trying to describe is not a short. The impedance falls quite quickly, the current rises quite rapidly, reaching by my adopted definition twice the instantaneous value which would flow if the iron remained magnetically linear. Go observe a few trannies to examine the saturation behaviour before spouting all this stuff as if you really know. Of course there is also primary resistance, which remains unaffected, so that is two reasons why the coil does *not* become a short. Well when the inductance ceases to oppose the flow during the wave cycles due to saturation, the applied voltage to the primary tends to be a short circuit current, ie, the mains applied voltage sees only the DCR of the primary. This situation *is* regarded as a short circuit. Squirm, wriggle, obfuscate. Let's just unpick it this time shall we? What is this "DCR" you have thrown in...like the "saturation phenomena (sic)" we saw before. It is a characteristic of your squirming obfuscation that you try to blind people with pathetic grandiose attempts at jargon. You mean resistance, don't you? By "DCR" you just mean resistance, yes? Resistance at DC? Have I worked it out correctly? As opposed to ACR perhaps? Do you perceive a difference between ACR and DCR? Perhaps it would help if you were to realise that it is a defining characteristic of resistance that it is the same for AC and DC? Surely if you pretend to make good transformers, you must also pretend to know the difference between resistance and reactance? So really you just mean resistance. Why then did you call it DCR? What is the purpose of this wriggling, squirming obfuscation? DCR is the measured DC resistance of the copper wire in a coil. Because you just said that a resistance is regarded as a short circuit. By who, I wonder. You alone, in all the world, sadly. Let's look at that again... the mains applied voltage sees only the DCR of the primary. This situation *is* regarded as a short circuit. Did you really say that? Look, you even underscored the "is". Crikey. Worth another look... the mains applied voltage sees only the DCR of the primary. This situation *is* regarded as a short circuit. Should I bother any further with a conman who thinks that a resistance is a short circuit? You fail dramatically yo understand one point all engineers agree upon. Say a primary winding has a DCR = 40 ohms. When the magnetic field collapses during part of the waveform due to saturation, ie the iron can no longer be increasingly magnetised to oppose the flow of magnetizing current, then the 240V of the mains sees the 40ohms of the DCR and a 6A flow of AC current can flow during the saturation. This is enough to blow fuses or melt down a tranny, cause loud hum, and generally be a PITA. Its SO obvious you know **** All about trannies, or you would have explored this effect. And, what is more, it doesn't only see the resistance. It also sees, for much of the time, the full inductance of the transformer and, for that portion of the time when saturation occurs, it also sees a considerable remaining contribution to the inductance by the core, plus it sees the inductance of the windings as if there were no iron there at all. In addition, the apparent resistance it sees in the winding is modified by the core losses. Not a short then, is it? The reactance during the saturation events drops to negligible levels. Hence engineers call the sharp saturation current peaks that more easily occurs in high µ material like the GOSS coil of a toroidal tranny short circuits; the long circuit is the one where there is substantial inductance to always provide a high reactance to oppose a high current flow. Further, you may notice that a saturated transformer gets hot. A short dissipates no power (only current, no voltage drop), so where do you think the heat is coming from? Two things, core losses, and copper losses. And how would they happen if the primary appears as a short? Watts = I squared x R; so if the saturation currents are high, then the power dissipated in heat are high. You haven't seen my point at all as usual. Can't have losses without power, can't have power without voltage, can't have voltage if it's a short. No matter how much I suggest it, you still haven't looked up Ohm's law. I use Ohm's Law every day, and have considered it all along in this discussion. The very field in an inductor opposes the current flow... If you think of it as a load resistance in parallel with an iron-cored inductor with a given core and number of windings, it is the current through the inductor that produces the magnetic field, hence too much current leads to saturation. The too-much-current occurs after a voltage threshold hold has been reached. Only at a particular frequency (sigh...). Do you remember any school maths? See my formula. The one you got from RDH? Don't need to, it was burned into my brain aged about 13. Seems to me my maths are better than yours. I can see how it seems like that to you. Well make up your mind, either my formula is right or wrong. Remember the common questions that ask you to reduce an equation to its simplest form? Why was that an important skill to learn? Because it allows you to see the essential relationship without the complications of mathematical clutter and particular circumstance. The transformer equation is the simplest way to relate the design parameters of a transformer. Maybe so, depending on what you are designing for. But the thread is not about how to design a transformer, but rather how to understand how transformers saturate. But you won't have noticed that in your rush to con another fool out of his money. Only a true desperate ****WIT like yourself would, after the last 4 years of discussions and refusals to ever do some real practical electronic engineering observations, make a statement to link me being a conman to whether or not I understand magnetic behaviour. get back to me when you have done the hard yards of observations of what happens. Or else STFU. In this case you would substitute voltage and frequency for current, and end up with a very simple formula. That would improve your basic grasp of the relationship, which would be true for *all cases*. Armed with this fundamental understanding, you can quite easily derive whatever practical formula you wish, depending on the particular problem you are addressing. If you are interested in frequency and voltage, then you can derive the formula you gave from RDH. I did derive my formula from what is in RDH4 and a few other old books that explain everything. You derived your formula? You mean you copied it from one of the zillion places it appears. I didn't invent the standard tranny equation. Loftier minds than I did Mine works for metric measurements, valid for me since I live in Oz which has metric measurements. Using some imperial version would give you identical results as spelled out in the examples in RDH4. Often their explanations are totally incomprehensible. Electro Magnetics was designed by the schitzoprenic brother of the God Of Triodes, and this dude made the use of iron, wire, and volts to be as confusing as possible. I can see your problem... Fundamental understanding is, in other words, transferable. Without it, particular knowledge is just empty fact. That's why you have to keep reading the book...you lack the conceptual framework to construct your own thoughts. If you know the core, and how many turns on the windings, and how much current through each, you are home and dry. The only reason you need to drag voltage and frequency in is in order to calculate the current. You won't see what I mean, and neither will Phil. Oh well. I do wind much better transformers than I can buy from anyone. So you keep saying, but no-one who has bought one agrees. How would you know anyway? You don't test them properly. You don't even know Ohm's law. Again you spit at someone who really knows a shirtload more than you. My conceptual understanding levels are good enough. For conning fools out of their money, perhaps. Again you show you've lost the argument. Phil knows more about it than you do, and he can explain it when he isn't acting like a complete fukken idiot. Then check the last statement of his last post to me, where he finally admits to some approximation to the truth about current. My estimation is that he actually knows less than you, if that is any comfort. But he has had enough failed education to fake a different level of smartness. Phil knows a truckload more than you do despite whatever formal education he may/may not have sustained. He finds it distressingly tedious to deal with your arguments which are never backed up witjh any real observations or practical experiences. That's why he calls you all the names under the sun. He sees you as a dumb cluck who rabbits on and on but there is SFA to be learnt. Its not very nice to be rude, but Phil can't help it when you provoke it. But next time you have a spare sunday, take a couple of trannies and a variac and explore the current flow in the unloaded condition. You can do this using a 110V winding, and watch how the reactance falls as Vin rises, and how inductance falls dramatically once you raise the Vin past 120V. be careful not to burn out the variac. Patrick Turner. cheers, Ian |
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#27
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Saturation in transformers.
Patrick Turner wrote more obfuscating and abusive babble.
Nothing there worth replying to because, as ever, you fail to respond to the key points and when your squirming gets abusive I can't be bothered. Wish I could say you might understand some day but it's too late. If your fire was ever lit it went out some time ago. For anyone else, including Bob, in need of an illuminating mental picture of how a transformer works, the model of a load resistance in parallel with a saturatable inductor explains nearly everything they need to know. Bob, load current doesn't saturate the core because it is in parallel with the inductance. Bob, you can see why saturation depends on frequency and voltage across the inductance, because they determine the current through the inductor, and it is this current, not that through the load, which can cause saturation. It is useful for all transformers, and highlights the importance of primary inductance and impedance matching in audio transformers...it allows you to easily calculate the lower bandwidth limit. Add the leakage inductance in series with the resistance, and capacitance across it, and you have a complete enough picture for most audio purposes. Basically, it gives you a simple filter circuit. Oh, and Bob, don't get confused with the idea that voltage causes a magnetic field in transformers. They aren't that mysterious. Everyone...you learned that current causes a magnetic field, right? Don't worry, it's true. cheers, Ian |
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#28
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Saturation in transformers.
On Sun, 13 Nov 2005 00:24:50 GMT, "Ian Iveson"
wrote: Patrick Turner wrote more obfuscating and abusive babble. Nothing there worth replying to because, as ever, you fail to respond to the key points and when your squirming gets abusive I can't be bothered. Wish I could say you might understand some day but it's too late. If your fire was ever lit it went out some time ago. For anyone else, including Bob, in need of an illuminating mental picture of how a transformer works, the model of a load resistance in parallel with a saturatable inductor explains nearly everything they need to know. Bob, load current doesn't saturate the core because it is in parallel with the inductance. I don't understand that... Bob, you can see why saturation depends on frequency and voltage across the inductance, because they determine the current through the inductor, and it is this current, not that through the load, which can cause saturation. As far as I know, (stop me if I'm wrong ), the primary inductance resists the applied voltage, and a steady state emerges where the only current that flows is due to the losses in the copper and the eddy current, and the leakage inductance. Power loss results from the in-phase loss in the R of the circuit. An increase of primary voltage entails an increase of current flow and an increase of 'back EMF' which matches this increase. Power loss goes up due to copper loss. Extraction of current from the secondary creates another field, which opposes the input field, so an increase of current in the primary is required to match it. This is seen as a decrease in L in the primary. Also it shows that the secondary load is 'reflected' to the primary coil. The increased current all around creates more copper and iron losses. Because the core is iron, it can saturate when the flux goes beyond a certain level. The saturation means that the created field in the primary CAN'T INCREASE! Therefore, any increase in current can't create an out of phase condition, so at that point the L is virtually gone, and no increase of voltage can reflect to the secondary winding. This is a part-cycle phenomenon, and shows up as clipped waveforms. Gotta go do some lab work now! It is useful for all transformers, and highlights the importance of primary inductance and impedance matching in audio transformers...it allows you to easily calculate the lower bandwidth limit. Add the leakage inductance in series with the resistance, and capacitance across it, and you have a complete enough picture for most audio purposes. Basically, it gives you a simple filter circuit. Oh, and Bob, don't get confused with the idea that voltage causes a magnetic field in transformers. They aren't that mysterious. Everyone...you learned that current causes a magnetic field, right? Don't worry, it's true. cheers, Ian |
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#29
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Saturation in transformers.
"Ian Iveson" Patrick Turner wrote more obfuscating and abusive babble. ** Right - so dogs bark and cats go meow ....... For anyone else, including Bob, in need of an illuminating mental picture of how a transformer works, the model of a load resistance in parallel with a saturatable inductor explains nearly everything they need to know. ** It leaves a very great deal out. Eg - it cannot explain this. " I have a 30 VA rated toroidal, as used in a small pro-audio product: 1. With a AC supply of 125 volts and no load it draws 270mA rms. 2. With a 15 watt resistive load the AC draw DROPS to 160mA rms !!!! " If a power transformer was said to saturate at 100mA peak primary current - what do you then know ? Do you know what power rating is ? Do you know what voltage the primary is rated for ? Do you know what frequency the primary can accept at rated voltage ? Nope - not one of them, not even approximately. ........... Phil |
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#30
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Saturation in transformers.
Bob wrote: As far as I know, (stop me if I'm wrong ), the primary inductance resists the applied voltage, I don't really like the use of the word 'resits' to be honest. and a steady state emerges where the only current that flows is due to the losses in the copper and the eddy current, and the leakage inductance. Power loss results from the in-phase loss in the R of the circuit. You've forgotten the losses of the magnetic material itself. It takes work to run it up and down the B-H curve. An increase of primary voltage entails an increase of current flow and an increase of 'back EMF' which matches this increase. Power loss goes up due to copper loss. Extraction of current from the secondary creates another field, which opposes the input field, so an increase of current in the primary is required to match it. This is seen as a decrease in L in the primary. Also it shows that the secondary load is 'reflected' to the primary coil. The increased current all around creates more copper and iron losses. Should only affect copper losses. The working flux is near unaffected by load in a decent transformer. Graham |
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#31
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Saturation in transformers.
Ian Iveson wrote: Patrick Turner wrote more obfuscating and abusive babble. The trouble is that many more people have learnt from my explanations and recommendations than yours. Delete the rest of you post because it does not cast any light on saturation. Patrick Turner. |
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#32
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Saturation in transformers.
Bob wrote: On Sun, 13 Nov 2005 00:24:50 GMT, "Ian Iveson" wrote: Patrick Turner wrote more obfuscating and abusive babble. Nothing there worth replying to because, as ever, you fail to respond to the key points and when your squirming gets abusive I can't be bothered. Wish I could say you might understand some day but it's too late. If your fire was ever lit it went out some time ago. For anyone else, including Bob, in need of an illuminating mental picture of how a transformer works, the model of a load resistance in parallel with a saturatable inductor explains nearly everything they need to know. Bob, load current doesn't saturate the core because it is in parallel with the inductance. I don't understand that... Nobody could. Bob, you can see why saturation depends on frequency and voltage across the inductance, because they determine the current through the inductor, and it is this current, not that through the load, which can cause saturation. As far as I know, (stop me if I'm wrong ), the primary inductance resists the applied voltage, and a steady state emerges where the only current that flows is due to the losses in the copper and the eddy current, and the leakage inductance. Power loss results from the in-phase loss in the R of the circuit. An increase of primary voltage entails an increase of current flow and an increase of 'back EMF' which matches this increase. Power loss goes up due to copper loss. But the core is also heated. Power is lost in both the core and the copper, and good designs favour either copper or core losses to suit the requirement. I suggest a long read of the text books. Extraction of current from the secondary creates another field, which opposes the input field, so an increase of current in the primary is required to match it. This is seen as a decrease in L in the primary. Also it shows that the secondary load is 'reflected' to the primary coil. The increased current all around creates more copper and iron losses. Because the core is iron, it can saturate when the flux goes beyond a certain level. The saturation means that the created field in the primary CAN'T INCREASE! Therefore, any increase in current can't create an out of phase condition, so at that point the L is virtually gone, and no increase of voltage can reflect to the secondary winding. This is a part-cycle phenomenon, and shows up as clipped waveforms. Very few power trannies are run at field strength intensities where the there is serious current wave form distortions, or saturation because of the heavy heat/noise causing currents involved. Gotta go do some lab work now! Do try to read a little more. But examining the saturation phenomena with a variac and tranny and CRO to see how the phase angle difference between input voltage and the winding current is essential to understand the losses, saturation and maths. Patrick Turner. It is useful for all transformers, and highlights the importance of primary inductance and impedance matching in audio transformers...it allows you to easily calculate the lower bandwidth limit. Add the leakage inductance in series with the resistance, and capacitance across it, and you have a complete enough picture for most audio purposes. Basically, it gives you a simple filter circuit. Oh, and Bob, don't get confused with the idea that voltage causes a magnetic field in transformers. They aren't that mysterious. Everyone...you learned that current causes a magnetic field, right? Don't worry, it's true. cheers, Ian |
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#33
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Saturation in transformers.
Bob wrote
Bob, load current doesn't saturate the core because it is in parallel with the inductance. I don't understand that... LOL! :-) It is the standard model used in circuit analysis. It is invariably used in simulation. It is so useful because its electrical properties are simple and, for most purposes it behaves in the same way as a transformer to a good approximation. Current in the secondary produces a field which cancels that of the primary current due to the load. Since the net magnetic effect is zero (to a reasonable approximation blah...), the inductor doesn't see it. Hence it can be considered to be in parallel with the reflected load resistance. You acknowledge this yourself when you refer to "reflected load", so for understanding you need only to consider your own account: "...it shows that the secondary load is 'reflected' to the primary coil." When you consider it reflected, where do you consider it is reflected to? To the primary, of course, where it appears in parallel with the primary inductance. So it must be your model too. Perhaps you couldn't see the wood for the trees. The model works pretty well but is not perfect of course, particularly at high frequencies. Now, this particular debate kicked off when I suggested that a poster take saturation into account when specifying a toroidal power transformer. Phil jumped on me, assuming I had made the common mistake of thinking that secondary current can lead to saturation. That mistake is so common (and hence easy prey for a mantis like Phil) because people tend to associate current with magnetic field, and hence with saturation. In order to dispel this misunderstanding, it is commonly explained that it is primary voltage, not current, that saturates. Assuming a particular frequency, that is a derivative truth. My concern is that, although it may appear to contribute to understanding, it runs counter to a true grasp of the situation, because it is current, not voltage, that produces a field. Everyone knows that, so saying it is voltage won't help. Just to illustrate that point further. When the transformer is used with the secondary open-circuit, the secondary has at normal frequencies virtually no effect, despite the fact that it has a voltage across it. Only when current flows does it impinge on the magnetic circuit. By separating the load current from the current through the saturatable inductor, the model resolves the apparent anomaly. Some comments on the details of your current understanding. Keep in mind I am an amateur...no longer a professional engineer, just a teacher. As far as I know, (stop me if I'm wrong ), the primary inductance resists the applied voltage, and a steady state emerges where the only current that flows is due to the losses in the copper and the eddy current, and the leakage inductance. Power loss results from the in-phase loss in the R of the circuit. Seems OK so far. Careful with the leakage inductance...a perfect inductor dissipates no power although its effect on the circuit may effect losses in the effective resistance (in-phase V/I) An increase of primary voltage entails an increase of current flow and an increase of 'back EMF' which matches this increase. Power loss goes up due to copper loss. True of the inductor part of the equivalent circuit. Add the effect of load current (to which there is no consequent "back EMF") and its attendant primary and secondary copper losses, and we're nearly there. Extraction of current from the secondary creates another field, which opposes the input field, so an increase of current in the primary is required to match it. Excellent...and when they match, the magnetic effects cancel (more or less)... This is seen as a decrease in L in the primary. Hold on, not so fast. Assuming a resistive load, it is better to see this as a decrease in the resistance across the inductance, rather than a decrease in the inductance. Yes you can see it as a decrease in inductance if you like...since that could account for an increase in current, but it's a bit like seeing the sun as going round the earth...it makes the universe much more complicated. Also it shows that the secondary load is 'reflected' to the primary coil. The increased current all around creates more copper and iron losses. See above, good. Watch the iron losses part though. The connection between "current all around" (?) and iron losses is very vague by your account. Also by mine, I must admit. That's because, with a bit of twisting, our models will end up the same anyway, I guess. Because the core is iron, it can saturate when the flux goes beyond a certain level. The saturation means that the created field in the primary CAN'T INCREASE! Therefore, any increase in current can't create an out of phase condition, so at that point the L is virtually gone, and no increase of voltage can reflect to the secondary winding. This is a part-cycle phenomenon, and shows up as clipped waveforms. Yes, but for the hyperbole. What you need to watch out for is the difference between the µ of the iron, and the inductance. This is where RDH gets a key diagram wrong. I posted about this some time ago...see below under "RDH is confused about µ" but in particular note: "But the right hand side of the curve is wrong by miles. µ is shown to plummet towards zero as the gradient of the BH curve flattens towards saturation. This would be true if µ were dB/dH, but if it is B/H then it should drop more gradually with an asymptote along the B axis." So inductance falls much more gradually than perhaps you imagine. But otherwise your comments seem fair enough to me. cheers, Ian ***RDH is confused about µ*** The graph on page 230 (fig 5.15) doesn't fit the definition of µ given on the same page. The authors emphasise that its value is B/H, not dB/dH. The peak value should therefore occur at the knee of the BH curve, from where its tangent passes through the origin. RDH has got the peak in the right place, above the knee rather than above the steepest part of the BH curve, which is where it would be were µ to be dB/dH. But the right hand side of the curve is wrong by miles. µ is shown to plummet towards zero as the gradient of the BH curve flattens towards saturation. This would be true if µ were dB/dH, but if it is B/H then it should drop more gradually with an asymptote along the B axis. The shape of the curve shown on page 216 (fig 5.13D) fits their definition better, but that is for AC, which is another can of worms. Checking several sites and books, there is no agreement on whether µ is B/H or dB/dH. For example, Menno van der Veen says that µ reflects the mobility of the magnetic domains. This observation seems to favour the dynamic definition, because at saturation there is no mobility even though the value of µ may still be high according to the static RDH definition. He shows a graph of inductance versus secondary voltage, in which the inductance plummets to near zero at saturation, which is what I would expect. He also correctly points out that µ is the only variable in the equation for inductance for a given inductor. Hence where the inductance falls to near-zero, so must µ. Further, µ0 is used for the permeability of free space, and also for initial permeability, as in the table on page 208. The unit for µ and µ0 is also generally omitted. It does have a footnote that says "strictly" the unit is gauss/oersted. It also states that µ0 = 1. Actually its unit depends on what system of units you are using, as does its value. In a table using both gauss and lines per inch, the unit of µ should be stated. The confusion is everywhere. It has infected various spice core models that don't work properly. Much data is barely intelligible because units and definitions are not clear. Incidentally, Van der Veen, of Plitron fame, gets the formula for inductance wrong in his book, transposing core area and magnetic path length. I assume this is a misprint, otherwise Plitron transformers would be very long and thin. cheers, Ian |
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#34
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Saturation in transformers.
Phil Allison wrote For anyone else, including Bob, in need of an illuminating mental picture of how a transformer works, the model of a load resistance in parallel with a saturatable inductor explains nearly everything they need to know. ** It leaves a very great deal out. Like what? Of course the model in not perfect, but a close enough approximation for most purposes. Eg - it cannot explain this. Try it... " I have a 30 VA rated toroidal, as used in a small pro-audio product: OK, so have I, maybe...what's the "pro-audio product" part all about? Dunno if I have one to hand...is it significant to your essential argument? 1. With a AC supply of 125 volts and no load it draws 270mA rms. 2. With a 15 watt resistive load the AC draw DROPS to 160mA rms !!!! " What's the "!!!!" for? The standard model does offer a possible explanation, although your example does seem extreme. If the point of saturation is taken to be when the current spike is double the underlying sine wave, then considering this is only for a part of the cycle, your transformer must be well saturated with the secondary open circuit. Once you have an appreciable load on the secondary, the consequent current through the winding resistance, which is in series with the primary inductance, drops the voltage, and hence the current, through the saturatable inductor, enough to relieve the saturation. If a power transformer was said to saturate at 100mA peak primary current - what do you then know ? In combination with its inductance and a precise definition of saturation, I could accurately predict the point at which it would saturate. Do you know what power rating is ? No electrical model will tell you that because it is mostly a thermal management problem. Given the regulation or the winding resistances, and assuming that the power rating is for a non-saturated condition, and given the core material, the power dissipation in the transformer due to winding losses and most significant core losses could be calculated. The rate of heat loss and maximum allowable temperature would be need to be added to get a power rating. Do you know what voltage the primary is rated for ? As above, and if I know where on the BH curve the design is intended to be. Do you know what frequency the primary can accept at rated voltage ? As above. Nope - not one of them, not even approximately. Yes, nearly all, to a good degree of accuracy. Of course information is necessary for a model to work...it would be silly to expect otherwise. Do you have a better model? Of course I could just use the published quoted ratings when I buy a transformer. But as you know, they often don't tell you much of the story either. Going back to the question of the external magnetic field of a toroid...how often is that quoted? Never, in my experience. So there is a need to analyse a little further, and in that case to find out where the design places itself on the BH curve, etc. There is a need for analysis, and hence for a model. Once again, do you have a better one? I am not proposing anything other than what is widely accepted. cheers, Ian |
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#35
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Saturation in transformers.
Yo, Patrick, now you see what happens when you encourage these pommy
wreckers. -- Andre Jute Ian Iveson wrote lots of obfuscating and abusive babble: Patrick Turner wrote more obfuscating and abusive babble. Nothing there worth replying to because, as ever, you fail to respond to the key points and when your squirming gets abusive I can't be bothered. Wish I could say you might understand some day but it's too late. If your fire was ever lit it went out some time ago. For anyone else, including Bob, in need of an illuminating mental picture of how a transformer works, the model of a load resistance in parallel with a saturatable inductor explains nearly everything they need to know. Bob, load current doesn't saturate the core because it is in parallel with the inductance. Bob, you can see why saturation depends on frequency and voltage across the inductance, because they determine the current through the inductor, and it is this current, not that through the load, which can cause saturation. It is useful for all transformers, and highlights the importance of primary inductance and impedance matching in audio transformers...it allows you to easily calculate the lower bandwidth limit. Add the leakage inductance in series with the resistance, and capacitance across it, and you have a complete enough picture for most audio purposes. Basically, it gives you a simple filter circuit. Oh, and Bob, don't get confused with the idea that voltage causes a magnetic field in transformers. They aren't that mysterious. Everyone...you learned that current causes a magnetic field, right? Don't worry, it's true. cheers, Ian |
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#36
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Saturation in transformers.
"Ian Iveson" Now, this particular debate kicked off when I suggested that a poster take saturation into account when specifying a toroidal power transformer. ** This is the only comment to Bob from Ian on the issue: " You should ensure that both transformers are adequately specified so they don't saturate. " Readers can see that it came with no context and is utterly ambiguous. What is to be specified " adequately " ? What does Bob have to look for in the maker's specs ? Do buyers of commercial power transformers have to be vigilant lest they get sold a unusable device? Phil jumped on me, assuming I had made the common mistake of thinking that secondary current can lead to saturation. ** Mind readers like Ian ought to be on stage - with rabbits emerging from a top hats. I suppose blowing obnoxious pongs out his arse on usenet is all the fool can really manage. ......... Phil |
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#37
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Saturation in transformers.
"Ian ****wit Iveson" Phil Allison For anyone else, including Bob, in need of an illuminating mental picture of how a transformer works, the model of a load resistance in parallel with a saturatable inductor explains nearly everything they need to know. ** It leaves a very great deal out. Like what? ** Read the whole post - ****hed - before asking ****wit questions. Eg - it cannot explain this. Try it... ** **** off - ****wit. " I have a 30 VA rated toroidal, as used in a small pro-audio product: OK, so have I, maybe...what's the "pro-audio product" part all about? ** The tranny really exists and is NOT a standard shelf line. 1. With a AC supply of 125 volts and no load it draws 270mA rms. 2. With a 15 watt resistive load the AC draw DROPS to 160mA rms !!!! " What's the "!!!!" for? ** It just a ***tad surprising*** to most when the connection of a resistive load to a power transformer results in the VA draw dropping by nearly half and (by implication) also the heat dissipation. ( snip ****e) If a power transformer was said to saturate at 100mA peak primary urrent - what do you then know ? In combination with its inductance and a precise definition of saturation, I could accurately predict the point at which it would saturate. ** Ridiculous drivel - that point has been specified. Do you know what power rating is ? Do you know what voltage the primary is rated for ? Do you know what frequency the primary can accept at rated voltage ? Nope - not one of them, not even approximately. Yes, nearly all, to a good degree of accuracy. ** What a cretinous, bloody LIAR !!! .............. Phil |
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Saturation in transformers.
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#39
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Saturation in transformers.
Daft Phil whinged:
In combination with its inductance and a precise definition of saturation, I could accurately predict the point at which it would saturate. ** Ridiculous drivel - that point has been specified. Given the point in terms of current, the model can predict the point in terms of voltage, as pointed out in the part of my explanation you cut. ** It just a ***tad surprising*** to most when the connection of a resistive load to a power transformer results in the VA draw dropping by nearly half and (by implication) also the heat dissipation. That's why I suggest the simple standard model is adopted. Then the truth won't be such a surprise, and the needless complication you appear to crave will vanish. cretinous ** What !!! LIAR a bloody, eh? cheers, Ian "Phil Allison" wrote in message ... "Ian ****wit Iveson" Phil Allison For anyone else, including Bob, in need of an illuminating mental picture of how a transformer works, the model of a load resistance in parallel with a saturatable inductor explains nearly everything they need to know. ** It leaves a very great deal out. Like what? ** Read the whole post - ****hed - before asking ****wit questions. Eg - it cannot explain this. Try it... ** **** off - ****wit. " I have a 30 VA rated toroidal, as used in a small pro-audio product: OK, so have I, maybe...what's the "pro-audio product" part all about? ** The tranny really exists and is NOT a standard shelf line. 1. With a AC supply of 125 volts and no load it draws 270mA rms. 2. With a 15 watt resistive load the AC draw DROPS to 160mA rms !!!! " What's the "!!!!" for? ( snip ****e) If a power transformer was said to saturate at 100mA peak primary urrent - what do you then know ? Do you know what power rating is ? Do you know what voltage the primary is rated for ? Do you know what frequency the primary can accept at rated voltage ? Nope - not one of them, not even approximately. Yes, nearly all, to a good degree of accuracy. ............. Phil |
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#40
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Saturation in transformers.
"Ian ****wit Autistic Iveson" ** What a cretinous, bloody LIAR !!! ............. Phil |
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