Heating in 4-1/2 turn inductor

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

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" <amdx_at_knology.net> wrote in message
news:7baf9$4c754008$45013905$14209_at_KNOLOGY.NET...
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.

"Jeff Johnson" <Jeff_Johnson_at_Hotmail.com> wrote in message
news:i53m65$s2c$1_at_news.eternal-september.org...


"amdx" <amdx_at_knology.net> wrote in message
news:7baf9$4c754008$45013905$14209_at_KNOLOGY.NET...
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.

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" <amdx_at_knology.net> wrote in message
news:7f589$4c755cac$45013905$6863_at_KNOLOGY.NET...

"Jeff Johnson" <Jeff_Johnson_at_Hotmail.com> wrote in message
news:i53m65$s2c$1_at_news.eternal-september.org...


"amdx" <amdx_at_knology.net> wrote in message
news:7baf9$4c754008$45013905$14209_at_KNOLOGY.NET...
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.

LOLROTF, ya both ends would be a 1/2 turn??? I'm speechless

"amdx" <amdx_at_knology.net> wrote in message
news:7baf9$4c754008$45013905$14209_at_KNOLOGY.NET...
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

In article <8c64b$4c755b30$45013905$6500_at_KNOLOGY.NET>,
"amdx" <amdx_at_knology.net> wrote:

"amdx" <amdx_at_knology.net> wrote in message
news:7baf9$4c754008$45013905$14209_at_KNOLOGY.NET...
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

In article<8c64b$4c755b30$45013905$6500_at_KNOLOGY.NET>,
"amdx"<amdx_at_knology.net> wrote:

"amdx"<amdx_at_knology.net> wrote in message
news:7baf9$4c754008$45013905$14209_at_KNOLOGY.NET...
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

"Jeff Johnson" <Jeff_Johnson_at_Hotmail.com> wrote in message
news:i53nja$2qd$1_at_news.eternal-september.org...


"amdx" <amdx_at_knology.net> wrote in message
news:7f589$4c755cac$45013905$6863_at_KNOLOGY.NET...

"Jeff Johnson" <Jeff_Johnson_at_Hotmail.com> wrote in message
news:i53m65$s2c$1_at_news.eternal-september.org...


"amdx" <amdx_at_knology.net> wrote in message
news:7baf9$4c754008$45013905$14209_at_KNOLOGY.NET...
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
BTW we were use the inductor at about 660 khz.

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" <amdx_at_knology.net> wrote in message
news:7f589$4c755cac$45013905$6863_at_KNOLOGY.NET...

"Jeff Johnson" <Jeff_Johnson_at_Hotmail.com> wrote in message
news:i53m65$s2c$1_at_news.eternal-september.org...


"amdx" <amdx_at_knology.net> wrote in message
news:7baf9$4c754008$45013905$14209_at_KNOLOGY.NET...
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.

I got some confirmation from my collaborator, The 1/2 turn as were

On 8/25/2010 11:09 AM, 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



This kind of odd-ball result can be caused by "parasitics" - in other
words, a high overtone excited by just the right length of inductor
paired with just the right stray capacitance, and energized by something
that can hit the high notes....

Brian W

I got some confirmation from my collaborator, The 1/2 turn as were
describing it
was the LAST 1/2 turn wound on the bobbin.