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12AX7
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| Quote: | Originally posted by ShadowWarrior4444
It’s simply mystifying how I can be insulted by people who suggested feeding an unregulated alternator into a battery and believe that a
transformer's quadranture current is actually called "self-inductance."
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You seem to be confusing me with someone else. You should check out my website, perhaps it will clear up some of your confusion. In particular for
this thread,
http://webpages.charter.net/dawill/tmoranwms/Electronics.htm...
Bye.
Tim
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len1
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| Quote: | | the magnetic field is constant regardless of load current. Primary amps cancel with secondary amps in exact proportion, leaving magnetizing current
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Thats an interesting observation. Interesting because it would tend to suggest that since the flux in the core is - to a first approximation -
independent of the current, whether the transformer is being run at full power or at no load, the size of the core to this approximation has no
bearing on the power of the transformer.
To rephrase how does the power-handling of the transformer manifest itself in the amount of iron that needs to be used if the iron carries almost the
same flux throught its regime of operation.
The key word here is carries. To a first (torroidal) approximation the amount of iron must be sufficient to store the entire energy transformed from
primary to secondary in a half-period
E = P / 2 f
where P is the power rating of the transformer. This explains why switchmode transformers (or flyback) are so much smaller than their 50Hz
equivalents.
The other feature is the maximum sustainable field in the core Bm. If V is the volume of iron required then the power formula becomes
Hm x Bm V > P / f
and power is proportional to volume.
What then fails in the first analysis? It will break down, and the secondary flux will cease to be linked to the primary when the energetically most
favourable path for it ceases to be linked with the secondary winding - which will occur roughly when the inequality fails.
[Edited on 29-7-2008 by len1]
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12AX7
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| Quote: | Originally posted by len1
To rephrase how does the power-handling of the transformer manifest itself in the amount of iron that needs to be used if the iron carries almost the
same flux throught its regime of operation.
The key word here is carries. To a first (torroidal) approximation the amount of iron must be sufficient to store the entire energy transformed from
primary to secondary in a half-period
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No, it doesn't. A flyback transformer does (commonly used in small switching supplies), but power transformers do not operate this way. In fact,
these are only reasonably efficient at low power levels and high frequencies (typically 50-200kHz), where price and physical size aren't too bad.
Power is transferred essentially instantaneously. No magnetic middle-man. It goes directly from primary to secondary. The core just hangs around to
increase inductance.
The basic idea is, since you must have a core to build a reasonable 50/60Hz transformer, you have to figure out how much you can get before reaching
its limits. Limits are defined by inductivity and saturation field strength. And inductivity determines how many turns you need to avoid saturation.
All those turns take up space, a well-defined amount of space because the winding has to handle load current. So you need a bigger core to handle
more VAs.
Tim
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len1
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| Quote: | Originally posted by 12AX7
| Quote: | Originally posted by len1
To rephrase how does the power-handling of the transformer manifest itself in the amount of iron that needs to be used if the iron carries almost the
same flux throught its regime of operation.
The key word here is carries. To a first (torroidal) approximation the amount of iron must be sufficient to store the entire energy transformed from
primary to secondary in a half-period
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No, it doesn't. A flyback transformer does (commonly used in small switching supplies), but power transformers do not operate this way. In fact,
these are only reasonably efficient at low power levels and high frequencies (typically 50-200kHz), where price and physical size aren't too bad.
Power is transferred essentially instantaneously. No magnetic middle-man. It goes directly from primary to secondary. The core just hangs around to
increase inductance.
The basic idea is, since you must have a core to build a reasonable 50/60Hz transformer, you have to figure out how much you can get before reaching
its limits. Limits are defined by inductivity and saturation field strength. And inductivity determines how many turns you need to avoid saturation.
All those turns take up space, a well-defined amount of space because the winding has to handle load current. So you need a bigger core to handle
more VAs.
Tim |
Tim I think this is something you wrote someone
| Quote: | | Please read up more on electronics before taking an authoritative stand on the subject! |
It would do you well to listen to your own advice. If not sure - ask, you might be dealing with someone who knows more than you, and you should
always take that eventuallity into account.
This
| Quote: | | Power is transferred essentially instantaneously. No magnetic middle-man. It goes directly from primary to secondary. The core just hangs around to
increase inductance. |
if you pardon my French is absolute rubbish. I have lectured electronics in unversities for many years and you would get a very low mark for this -
in fact repeat the course.
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ShadowWarrior4444
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| Quote: | Originally posted by len1
| Quote: | | Power is transferred essentially instantaneously. No magnetic middle-man. It goes directly from primary to secondary. The core just hangs around to
increase inductance. |
if you pardon my French is absolute rubbish. I have lectured electronics in unversities for many years and you would get a very low mark for this -
in fact repeat the course. |
Len is correct in this case, though particularly insulting.
A flyback operates by storing energy in the magnetic field which then rapidly collapses to produce high voltage. The core has an air-gap to increase
magnetic reluctance.
Ancillary: Explaining this in plain terms instead of posturing would make you a better professor.
[Edited on 7-29-2008 by ShadowWarrior4444]
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12AX7
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| Quote: | Originally posted by len1
| Quote: | | Please read up more on electronics before taking an authoritative stand on the subject! |
It would do you well to listen to your own advice. If not sure - ask, you might be dealing with someone who knows more than you, and you should
always take that eventuallity into account.
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So if you have a problem, would you be so kind as to show specifically what is wrong? As an academic, I'm sure you must understand my preference for
fact over heresay.
I had prepared a more in-depth explanation of the phenomenon, but I've decided to hold off until we resolve these issues.
Tim
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Texium
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Thread Moved
19-11-2023 at 12:32 |
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