Effects of gaps in inductors and transformers

[Jan Panteltje]

I don't think that any mass production transistor radios used class A
audio output stages -

from the late 50's onwards the push-pull
transformer coupled class B output stage was the most common, until
the transformerless designs cam in.

Seems you are right:
http://people.msoe.edu/~reyer/regency/parts_placement.jpg

In Eurpe we were a litte later, I think.
first 2 transistor, then 6.
The 2 transistor ones were cheap, and a clever design, used the transistors 2 times,
first as RF amp, and then again as LF amp...
The 6 were not push pull:
Perhaps 1 RF/Mixer, 1 osc, 2 IF, 1 audio drive, 1 audio out?
Then the number of transistors increased, and likely push pull:
http://www.vintage-technology.info/pages/history/histpamtr.htm

The early transistors had very
limited power dissipation capability and the low idle consumption of
class B suited battery power better.

At the end of the fifties or start of the sixties I build little amplifiers with Philips
OC13, OC14 ('power', OC44 (RF) and OC45 transistors.
There also was the OC16 POWER transistor.
Use in class A it really could output _watts_:
http://homepages.nildram.co.uk/~wylie/Mullard/Mullard.htm

Car radios often used class A
even in hybrid designs where the RF and early audio stages were
implemented with valves/tubes.

kevin

It is a long time ago,
OC45 with the paint scraped off was a great photo detector too.
One day I had my pre-amp on, and noise came and went...
It turned out to be clouds in front of the sun, the black paint was damaged a bit.

 

[jasen]

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

 

[Robert Latest]

I can imagine a geometry in which increasing a gap reduces leakage
inductance.

What would that be? Leakage inductance is caused by flux that doesn't go
through all windings. How could any form of air gap keep more flux inside
the windings?

Curious: robert

 

[MassiveProng]

If you look at any hunky arc welder, even a small one is 200A rated
secondary, you will notice that the current adjust dial is mechanically
linked to a chunk of laminated iron that is moved in and out of a big
gap in the core, directly adjusting the reluctance of the magnetic
circuit and the magnitude of flux linked with the secondary.

Oooops! I think you have found one of the GAPs in his logic!

 

[MassiveProng]

Whatever x becomes, it certainly becomes ALLOWED to have a higher
ceiling than without the gap. You need to realize that. The gap
allows the drive to be greater, despite the tiny loss incurred.
Without it, the ceiling for saturation is MUCH lower! Pretty simple
shit.

Gaineth thy selfeth a clue.

Did I say "sinusoidal"?

You didn't say anything worth saying.

 

[John Larkin]

What would that be? Leakage inductance is caused by flux that doesn't go
through all windings. How could any form of air gap keep more flux inside
the windings?

Your question practically answers itself.

John

 

[MassiveProng]

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.

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

 

[John Larkin]

Whatever x becomes, it certainly becomes ALLOWED to have a higher
ceiling than without the gap. You need to realize that. The gap
allows the drive to be greater, despite the tiny loss incurred.
Without it, the ceiling for saturation is MUCH lower! Pretty simple
shit.

Gaineth thy selfeth a clue.

Answer the question.

John

 

[MassiveProng]

Your question practically answers itself.

Is that then a recursive loop, or an eddy current?

Oh... that's right... it's a TardCurrent wave.

 

[MassiveProng]

Answer the question.

John

X drops a LITTLE BIT, you fucking retard (inferred in my post)! Now
observe what I said above about being able to drive it harder to make
up for, and even surpass your petty claim of severe losses.

You are too fucking thick, boy.

 

[Fred Bartoli]

MassiveProng a écrit :

Is that then a recursive loop, or an eddy current?

Oh... that's right... it's a TardCurrent wave.

That's much more simple, but obviously you can't see it.

 

[jasen]

On 23 Feb 2007 19:42:59 GMT, jasen <[email protected]> Gave us:

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.

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

They sure "grumble" when you ground the rod tip (or fuse it to your work)
and the current goes up else why does the rod glow red... it doesn't do
that if used correctly.

Bye.
Jasen

 

[MassiveProng]

MassiveProng a ?crit :


That's much more simple, but obviously you can't see it.

The "recursive loop" remark was about the "question practically
answers itself" comment, having nothing at all to do with the subject
of the discussion. The "eddy current" remark was the closest thing I
could think of trying to be funny about the "practically answers
itself" remark, also not having anything to do with the topic.

You analytical types are too stiff lipped to get humor.

 

[MassiveProng]

They sure "grumble" when you ground the rod tip (or fuse it to your work)
and the current goes up else why does the rod glow red... it doesn't do
that if used correctly.

That is the difference between about one ohm, and about no ohms.

I should have said not much difference, as opposed to virtually no
difference. So yeah, that would make me off on that one.

The tip gets all the heat in the plasma scenario, there is more
current in the dead short, but the welder is certainly designed to
handle them.

 

[John Larkin]

Is that then a recursive loop, or an eddy current?

Oh... that's right... it's a TardCurrent wave.

It's obvious you know almost nothing about magnetics, other than
having some hunches based on working around people who do. That's
fine, but why do you pretend to know stuff that you obviously don't?

If you did understand this stuff, you would have answered my simple
question.

John

 

[John Larkin]

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.

Then from where comes the energy to do the welding?

John

 

[MassiveProng]

Then from where comes the energy to do the welding?

The plasma, and the molten steel are a resistor. The current going
though said resistor gets dissipated as heat at the resistor site,
which is the tip, and the work (weld) location.

 

[The Phantom]

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.

 

[Don Klipstein]

The plasma, and the molten steel are a resistor. The current going
though said resistor gets dissipated as heat at the resistor site,
which is the tip, and the work (weld) location.

It's mostly in the voltage drop of the arc, mainly in the cathode fall
and anode fall regions of the arc.
True, the arc will not limit current, but it has a voltage drop. The
arc somewhat simulates a hypothetical zener diode with a negative
temperature coefficient.

- Don Klipstein ([email protected])

 

[Terry Given]

It's obvious you know almost nothing about magnetics, other than
having some hunches based on working around people who do. That's
fine, but why do you pretend to know stuff that you obviously don't?

If you did understand this stuff, you would have answered my simple
question.

John

X increases.

Cheers
Terry