Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped I
think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK

"amdx" wrote in message
...
Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped
I think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK

"amdx" wrote in message
...
Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped
I think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK



Resonance? (I assume by 1/2 you mean the 4.5 inductor?)

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...
Several years ago while making inductors for tuning a class E amplifier
we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore,
gapped I think,
but it has been awhile. The inductor was driven hard but below
saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK



Resonance? (I assume by 1/2 you mean the 4.5 inductor?)
Yes, a 4 and 1/2 turn inductor had the 1/2 turn overheat.

"amdx" wrote in message
...

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...
Several years ago while making inductors for tuning a class E amplifier
we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore,
gapped I think,
but it has been awhile. The inductor was driven hard but below
saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK



Resonance? (I assume by 1/2 you mean the 4.5 inductor?)
Yes, a 4 and 1/2 turn inductor had the 1/2 turn overheat.


huh?

The half turn and the other turns were ok? This is impossible!?!?! One has
the same current through the whole coil and if the wire was uniform then it
should heat heally well. Not only that copper is a good heat conductor so if
the 1/2 turn was heating up then he heat should spread pretty quickly.

This assumes everything else is uniform along the coil. Something has to be
going on that your not telling us? Ideally the heat should be uniformly
distributed along the coil.

By "HOT" I assume you mean much much hotter than the other coils?

Heat is generated by the current, is it not? and the current should be
uniform throughout the wire? The resistance of the wire itself should also
be uniform. This suggests that the heat dissipated per unit length is
independent of position.

Were both ends hot? If not then something else is going on. Because you are
saying the .5 end of a 4.5 coil got HOT. Yet which end? the 4.5 coil has two
..5 ends and should in theory be symmetric and hence both get equally HOT. If
they wern't then something is aloof.

On Wed, 25 Aug 2010 11:09:35 -0500, "amdx" wrote:

Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped I
think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK


I think it's forcing a substantial portion of the flux to pass through
half of the core and thus increasing the core losses.

There's a half turn technique used in transformer design that ends up
with two half turns in parallel IIRC. Maybe you could use that.

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...
Several years ago while making inductors for tuning a class E amplifier
we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore,
gapped I think,
but it has been awhile. The inductor was driven hard but below
saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK



Resonance? (I assume by 1/2 you mean the 4.5 inductor?)
Yes, a 4 and 1/2 turn inductor had the 1/2 turn overheat.


huh?

The half turn and the other turns were ok? This is impossible!?!?!

Not impossible, there's more than one heating mechanism, not that I can
explain them,
but I know there can be heating in the fringe field of the gap.

One has the same current through the whole coil and if the wire was uniform
then it should heat heally well. Not only that copper is a good heat
conductor so if the 1/2 turn was heating up then he heat should spread
pretty quickly.

This assumes everything else is uniform along the coil. Something has to
be going on that your not telling us? Ideally the heat should be uniformly
distributed along the coil.

By "HOT" I assume you mean much much hotter than the other coils?

Hot enough to burn the insulators used.

Heat is generated by the current, is it not? and the current should be
uniform throughout the wire? The resistance of the wire itself should also
be uniform. This suggests that the heat dissipated per unit length is
independent of position.

Flux my not have been uniform through.

Were both ends hot? If not then something else is going on. Because you
are saying the .5 end of a 4.5 coil got HOT. Yet which end? the 4.5 coil
has two .5 ends and should in theory be symmetric and hence both get
equally HOT. If they wern't then something is aloof.

LOLROTF, ya both ends would be a 1/2 turn??? I'm speechless
and don't know what to say. :-) Don't confuse me with such things!
MikeK

In article ,
"amdx" wrote:

"amdx" wrote in message
...
Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped
I think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK


How do you make a half turn inductor?

Bill

--
An old man would be better off never having been born.

On Wed, 25 Aug 2010 13:36:29 -0700, Salmon Egg
wrote:

In article ,
"amdx" wrote:

"amdx" wrote in message
...
Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped
I think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK


How do you make a half turn inductor?

Bill

Bring wires out opposite slots on a pot core. I've seen it do strange
stuff, too.

John

On 8-25-2010 20:36, Salmon Egg wrote:
In ,
wrote:

wrote in message
...
Several years ago while making inductors for tuning a class E amplifier we
end up with a 4-1/2 turn inductor. The inductor used a 3F3 potcore, gapped
I think,
but it has been awhile. The inductor was driven hard but below saturation.
The problem; the 1/2 turn got HOT. Four turns or five turns were ok.
My physicist friend had an EE verify the problem 2000 miles away.

So, can anyone tell me why 1/2 turn would make such a difference in the
heating?

Thanks, MikeK


How do you make a half turn inductor?

Bill


Half a circle, as used at say 450 MHz and up (the one end is soldered to
one point on a circuit board, goes straight up say 1/4", bends over 180
degrees and the other end soldered to another pad on the PC board...just
like this "U" but flipped over (upsidedown U)...