Re: 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


.

Relevant Pages

  • Re: Capacitor bank pretty well complete
    ... Charge them with line voltage and discharge into ... short the terminals through a coil. ... will make some generous magnetic field, maybe I can shoot an aluminum plate ... A capacitor is the opposite of an inductor. ...
    (sci.electronics.design)
  • Re: Saturation in transformers.
    ... >> The saturation is a voltage caused phenomena. ... magnetic field depends on current. ... The very field in an inductor opposes the current flow... ...
    (rec.audio.tubes)
  • Re: Saturation in transformers.
    ... >> the saturation ... Once again, it is not a short circuit, ever. ... >> a voltage across a coil? ... > Er, it might, or might not, depending on the time, the resistance ...
    (rec.audio.tubes)
  • Re: Saturation in transformers.
    ... >>> voltage ... >>> and the coil becomes a short circuit when the steels field ... > the saturation ... Er, it might, or might not, depending on the time, the resistance ...
    (rec.audio.tubes)
  • Re: Transformer attenuators
    ... and this may be used to limit the LF response. ... use a transformer then arguably you don't need the ... "Core saturation happens when the magnetic field in the core ... the applied voltage polarity remains the same for a ...
    (rec.audio.tubes)