Re: Effects of gaps in inductors and transformers

On Fri, 23 Feb 2007 17:38:03 -0800, MassiveProng
<MassiveProng@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On 23 Feb 2007 19:42:59 GMT, jasen <jasen@xxxxxxxxxxx> Gave us:

On 2007-02-22, John Larkin <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
On Wed, 21 Feb 2007 23:34:47 -0800, MassiveProng
<MassiveProng@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Thu, 22 Feb 2007 02:28:01 -0500, "Paul E. Schoen"
<pstech@xxxxxxxxx> Gave us:

but I observed that they are generally
present in iron core inductors, but not in most transformers.


You observed incorrectly.

No, he's generally correct. Power and audio iron-lam transformers are
almost never gapped; ferrite power transformers are usually not; iron
core and ferrite inductors are usually gapped, either with a distinct
gap or just an open magnetic structure; it prevents dc saturation and
helps better define their inductance.

Ferroresonant power transformers were gapped, but they're pretty rare
these days.

arc welders use them (well, mine did). something like that needs to
withstand frequent short cuircuits (especially in my hands :) )

Bye.
Jasen


An arc welder is ALWAYS a short circuit when there is a plasma arc
struck up, and during its entire duration. There is virtually no
difference between the resistance of the plasma, and a dead short.

The *incremental* resistance of the plasma may be very low, maybe even
nearly as low as a short, but there is a voltage drop across the plasma,
and (essentially) no voltage drop across a short. This makes all the
difference. It means that substantial power is dissipated in the plasma,
but (essentially) no power is dissipated in a short.


They are designed to be at maximum secondary current at all times
during actual use (not talking about at idle but on).

.

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