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

Heating in 4-1/2 turn inductor
 

"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

Heating in 4-1/2 turn inductor
 

"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?)

Heating in 4-1/2 turn 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.

Heating in 4-1/2 turn inductor
 

"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.

Heating in 4-1/2 turn inductor
 

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.

Heating in 4-1/2 turn inductor
 

"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

Heating in 4-1/2 turn inductor
 

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.

Heating in 4-1/2 turn inductor
 

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

Heating in 4-1/2 turn inductor
 

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)...

Heating in 4-1/2 turn inductor
 

"amdx" wrote in message
...

"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
BTW we were use the inductor at about 660 khz.
Mike

Heating in 4-1/2 turn inductor
 

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

Heating in 4-1/2 turn inductor
 

"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!?!?! 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
describing it
was the LAST 1/2 turn wound on the bobbin.
MikeK

Heating in 4-1/2 turn inductor
 

"brian whatcott" wrote in message
...
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

Maybe, but we had it confirmed by someone else and I doubt very much
they developed the circuit we were using to do the test. We used it to
cancel
out the capacitance of a piezo transducer. Driving about 250 watts into a
20 ohm load, at about 600 khz.
MikeK

Heating in 4-1/2 turn inductor
 

"amdx" wrote in message
...
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.

It doesn't happen to be nicked, forming a shorted turn perhaps?

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Heating in 4-1/2 turn inductor
 

"Tim Williams" wrote in message
...
"amdx" wrote in message
...
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.

It doesn't happen to be nicked, forming a shorted turn perhaps?

verified more than once.

Heating in 4-1/2 turn inductor
 

"amdx" wrote in message
...

"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!?!?! 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
describing it
was the LAST 1/2 turn wound on the bobbin.
MikeK

What you describing is,

L1 V L2
V1--/\/\--+--/--0

on the same core?

L2, the 1/2 turn part of the coil is behaving wildly different than expect?

After all, ideally L2 has resistance in direct proportion to the total
winding which in this case 0.5*/4.5 ~ 11% of the total resistance of the
coil.

In a single coil the power dissipation of the 1/2 turn would also be ~ 11%
and this is quite easy to see. You are saying that it is much more than this
as if the ratio's were turned up side down. Something like the 1/2 part
dissipating 90% and the 4 turns part dissipating 10%?

if you agree with the layout of

L1 V L2
V1--/\/\--+--/--0

Then it is easy to see that in ideal circumstances the current through L1
should equal that of L2 and the I^2R heating would produce the results I
described first.

Instead of assuming the two inductors are on the same core we can assume
they are on different cores. This will help us understand if differences in
flux could cause such problems.

You mentioned in another post that you were using AC to drive the coil? Did
the effect happen with DC?

Did you measure the voltage on the 1/2 turn?

Was the core itself generating the heat or was it due to the 1/2 turn?

What was the total current through the coil?

Was it possible the coil could have been shorting out on another turn or the
core?

Was it really 1/2 a turn getting hot or "just the end of it"?

Was the coil tested by itself outside the circuit? If so did it exhibit the
same phenomena?

What was the end of the coil that generated the heat connected to? Was the
connection itself possible cause for the heat?

Was the coil reversed in the circuit? If so did it exhibit the same problem
with the ends switched?

You mentioned that you tried 4 turns and 5 turns and the problem went away.
Did it go away completely or partially? Was those two coils made exactly the
same way and connected the same or were they in any way different besides
just the turn difference?

Was the coil one continuous piece? the 1/2 turn was not spliced on?

Did you try a 5.5 and/or 6 turn coil?

Did the 1/2 turn end get hot very quick or did it take a while? Basically
seconds or minutes?

Did you try to change the direction of the core relative to the coil? If so
did it make any difference?

Is there any possible way the core itself could have been generating the
heat at the 1/2 turn and the effect you experienced was just the core
heating up that 1/2 first?

Did you allow the inductor to run a long time? If so, What was the effect
still? Was the whole coil hot or still just the 1/2 turn?

Hopefully you can answer some of these questions. It sounds to me like you
didn't do much troubleshooting so I expect most of them can't be answered so
the true reason probably will not be known.

Heating in 4-1/2 turn inductor
 

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...

"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!?!?! 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
describing it
was the LAST 1/2 turn wound on the bobbin.
MikeK

What you describing is,

L1 V L2
V1--/\/\--+--/--0

on the same core?

L2, the 1/2 turn part of the coil is behaving wildly different than
expect?

After all, ideally L2 has resistance in direct proportion to the total
winding which in this case 0.5*/4.5 ~ 11% of the total resistance of the
coil.

In a single coil the power dissipation of the 1/2 turn would also be ~ 11%
and this is quite easy to see. You are saying that it is much more than
this as if the ratio's were turned up side down. Something like the 1/2
part dissipating 90% and the 4 turns part dissipating 10%?

if you agree with the layout of

L1 V L2
V1--/\/\--+--/--0

Then it is easy to see that in ideal circumstances the current through L1
should equal that of L2 and the I^2R heating would produce the results I
described first.

Instead of assuming the two inductors are on the same core we can assume
they are on different cores. This will help us understand if differences
in flux could cause such problems.

You mentioned in another post that you were using AC to drive the coil?
Did the effect happen with DC?

Never tried it with dc.

Did you measure the voltage on the 1/2 turn?

No.

Was the core itself generating the heat or was it due to the 1/2 turn?

It's been ten years, all I recall is the insulation on the last 1/2 turn
of the coil
got charred.

What was the total current through the coil?


I think about a litle over 2 amps at 600khz.

Was it possible the coil could have been shorting out on another turn or
the core?

No

Was it really 1/2 a turn getting hot or "just the end of it"?

It was the 1/2 turn.

Was the coil tested by itself outside the circuit? If so did it exhibit
the same phenomena?

Not by us, but someone else confirmed our observation.

What was the end of the coil that generated the heat connected to? Was the
connection itself possible cause for the heat?

Naw.

Was the coil reversed in the circuit? If so did it exhibit the same
problem with the ends switched?

No

You mentioned that you tried 4 turns and 5 turns and the problem went
away. Did it go away completely or partially? Was those two coils made
exactly the same way and connected the same or were they in any way
different besides just the turn difference?

We shipped the product, as far as I know the didn't it back for replacement
smoke.

Was the coil one continuous piece? the 1/2 turn was not spliced on?

One continuous piece.

Did you try a 5.5 and/or 6 turn coil?
No


Did the 1/2 turn end get hot very quick or did it take a while? Basically
seconds or minutes?

Minutes.

Did you try to change the direction of the core relative to the coil? If
so did it make any difference?

No

Is there any possible way the core itself could have been generating the
heat at the 1/2 turn and the effect you experienced was just the core
heating up that 1/2 first?

I don't think so.

Did you allow the inductor to run a long time? If so, What was the effect
still? Was the whole coil hot or still just the 1/2 turn?

The whole think would have got hot, we were pushing limits.

Hopefully you can answer some of these questions. It sounds to me like you
didn't do much troubleshooting so I expect most of them can't be answered
so the true reason probably will not be known.

Probably, won't know the answer, once we learned the 1/2 turn overheated we
didn't do it again.
But it stuck as a curiosity. I had one of the overheated 4-1/2 turn bobbins
hanging on a cord over my
bench for years. It's been ten years but my old bench is still the same,
next time I stop in I'll see if it
the bobbins is still hanging.

MikeK

Heating in 4-1/2 turn inductor
 

On 8/26/2010 6:41 AM, amdx wrote:
"brian wrote in message
...
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

Maybe, but we had it confirmed by someone else and I doubt very much
they developed the circuit we were using to do the test. We used it to
cancel
out the capacitance of a piezo transducer. Driving about 250 watts into a
20 ohm load, at about 600 khz.
MikeK



You don't have to guess whether I am right or wrong: you just have to
hang a 200MHz bandwidth scope on the hot end, and see what you get.

Brian W

Heating in 4-1/2 turn inductor
 

On 8/26/2010 7:51 AM, amdx wrote:
"Tim wrote in message
...
wrote in message
...
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.

It doesn't happen to be nicked, forming a shorted turn perhaps?

verified more than once.



There isn't a cold solder joint at the heating end of the coil? This
would result in localized heating to one end of the coil ... strange is
all I can say.

Regards,
JS

Heating in 4-1/2 turn inductor
 

On 8/26/2010 4:45 PM, John Smith wrote:
On 8/26/2010 7:51 AM, amdx wrote:
"Tim wrote in message
...
wrote in message
...
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.

It doesn't happen to be nicked, forming a shorted turn perhaps?

verified more than once.



There isn't a cold solder joint at the heating end of the coil? This
would result in localized heating to one end of the coil ... strange is
all I can say.

Regards,
JS


Never mind, the confirmation you mention, done by another, was obviously
done on another coil ... duh, should have read all the posts before
commenting ...

Regards,
JS

Heating in 4-1/2 turn inductor
 

"amdx" wrote in message
...

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...

"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!?!?! 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
describing it
was the LAST 1/2 turn wound on the bobbin.
MikeK

What you describing is,

L1 V L2
V1--/\/\--+--/--0

on the same core?

L2, the 1/2 turn part of the coil is behaving wildly different than
expect?

After all, ideally L2 has resistance in direct proportion to the total
winding which in this case 0.5*/4.5 ~ 11% of the total resistance of the
coil.

In a single coil the power dissipation of the 1/2 turn would also be ~
11% and this is quite easy to see. You are saying that it is much more
than this as if the ratio's were turned up side down. Something like the
1/2 part dissipating 90% and the 4 turns part dissipating 10%?

if you agree with the layout of

L1 V L2
V1--/\/\--+--/--0

Then it is easy to see that in ideal circumstances the current through L1
should equal that of L2 and the I^2R heating would produce the results I
described first.

Instead of assuming the two inductors are on the same core we can assume
they are on different cores. This will help us understand if differences
in flux could cause such problems.

You mentioned in another post that you were using AC to drive the coil?
Did the effect happen with DC?

Never tried it with dc.

Did you measure the voltage on the 1/2 turn?

No.

Was the core itself generating the heat or was it due to the 1/2 turn?

It's been ten years, all I recall is the insulation on the last 1/2 turn
of the coil
got charred.

What was the total current through the coil?


I think about a litle over 2 amps at 600khz.

Was it possible the coil could have been shorting out on another turn or
the core?

No

Was it really 1/2 a turn getting hot or "just the end of it"?

It was the 1/2 turn.

Was the coil tested by itself outside the circuit? If so did it exhibit
the same phenomena?

Not by us, but someone else confirmed our observation.

What was the end of the coil that generated the heat connected to? Was
the connection itself possible cause for the heat?

Naw.

Was the coil reversed in the circuit? If so did it exhibit the same
problem with the ends switched?

No

You mentioned that you tried 4 turns and 5 turns and the problem went
away. Did it go away completely or partially? Was those two coils made
exactly the same way and connected the same or were they in any way
different besides just the turn difference?

We shipped the product, as far as I know the didn't it back for
replacement smoke.

Was the coil one continuous piece? the 1/2 turn was not spliced on?

One continuous piece.

Did you try a 5.5 and/or 6 turn coil?
No


Did the 1/2 turn end get hot very quick or did it take a while? Basically
seconds or minutes?

Minutes.

Did you try to change the direction of the core relative to the coil? If
so did it make any difference?

No

Is there any possible way the core itself could have been generating the
heat at the 1/2 turn and the effect you experienced was just the core
heating up that 1/2 first?

I don't think so.

Did you allow the inductor to run a long time? If so, What was the effect
still? Was the whole coil hot or still just the 1/2 turn?

The whole think would have got hot, we were pushing limits.

Hopefully you can answer some of these questions. It sounds to me like
you didn't do much troubleshooting so I expect most of them can't be
answered so the true reason probably will not be known.

Probably, won't know the answer, once we learned the 1/2 turn overheated
we didn't do it again.
But it stuck as a curiosity. I had one of the overheated 4-1/2 turn
bobbins hanging on a cord over my
bench for years. It's been ten years but my old bench is still the same,
next time I stop in I'll see if it
the bobbins is still hanging.



I don't know what to say. Just not enough information. If your looking from
some exotic possibility I don't think you'll find one.

The reason is that the current through the wire will almost be surely the
same through out all points along the wire. That precisely means that the
heat generated per unit length will be the same. Even if you have some crazy
resonance or core flux/transformer effect going on, that current in the wire
has to be the same through the whole wire(assuming no shorts).

You can't have electrons bunch up on part of the wire and not on any other
part. Even if you could, that bunch would have to flow through the wire from
one part to another and on average it would heat it up uniformly.

The reason is simple, We all know that for a power supply when one electron
is supplied on the wire one electron leaves it so there really is no way to
"bunch" it up.

Now, if the wire is not uniform in size or resistance then the heating
effect is not uniform. As smith mentioned about the joint connecting the
coil. In this case it is possible that the joint could be heating up and it
was being passed along to the 1/2 turn and it just happens that you didn't
let it run long enough to heat up any more turns.

The 1/2 turn was really a point at the joint and the heat just spread about
about 1/2 turn.

To me this is the most plausable case. I'm not sure if it's physically
possible any other way that involves the coil itself generating generating
the heat. (I gave a good reason about about electron flow being uniform in
the wire)

It may be possible using some type of standing wave or transformer like
effect but even here I can't see it possible if the wire's restance per unit
length is constant.

Heating in 4-1/2 turn inductor
 

"Jeff Johnson" wrote in message
...
big ****in snip
The reason is that the current through the wire will almost be surely
the same through out all points along the wire.

Well, no:
http://en.wikipedia.org/wiki/Proximi...romagnetism%29

the current density varies strongly, especially if the wire is thick
(curiously, it was never stated what size wire is in question, nor what
type; 600kHz suggests fine stranded litz!).

Wire near the gap (which is usually placed in the center, right underneath
the winding) experiences fringing fields, which dramatically increases
losses.

That precisely means that the heat generated per unit length will be the
same.

Eddy currents in the center of the coil are much stronger than at the
ends, so the center of a solenoid heats up much more strongly.

The uncooled coil in this video demonstrates proximity effect:
http://www.youtube.com/watch?v=nY66rBJvbpY
See the connections are clean and coppery, but the coil has seen better
days. You can't really tell if the center turns are hotter; they probably
are by a little bit.


Of course Kirchoff is harder to fool, obviously the total current flowing
along the wire is the current flowing along the wire period. Unless
there's a short, which supposedly was inspected as to have none.


None of these are an "end" effect. The only possible explanation is a
short, or else, "look harder". It's plainly obvious that the cause is NOT
"an additional half turn". It is only a coincidence that this symptom
showed up between turns 4 and 5.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Heating in 4-1/2 turn inductor
 

Hey OM:

First how many newsgroups do you have this thread cross posted on?

Second: A 1/2 turn is equal to 1 turn in a pot core so 4 and 1/2 turns
is the same as 5 turns.

Lastly OM: I think you are looking at a classic case of proximity
effect.

73 OM
de n8zu





On Aug 25, 4:09*pm, "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

Heating in 4-1/2 turn inductor
 

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...

"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!?!?!
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
describing it
was the LAST 1/2 turn wound on the bobbin.
MikeK

What you describing is,

L1 V L2
V1--/\/\--+--/--0

on the same core?

L2, the 1/2 turn part of the coil is behaving wildly different than
expect?

After all, ideally L2 has resistance in direct proportion to the total
winding which in this case 0.5*/4.5 ~ 11% of the total resistance of the
coil.

In a single coil the power dissipation of the 1/2 turn would also be ~
11% and this is quite easy to see. You are saying that it is much more
than this as if the ratio's were turned up side down. Something like the
1/2 part dissipating 90% and the 4 turns part dissipating 10%?

if you agree with the layout of

L1 V L2
V1--/\/\--+--/--0

Then it is easy to see that in ideal circumstances the current through
L1 should equal that of L2 and the I^2R heating would produce the
results I described first.

Instead of assuming the two inductors are on the same core we can assume
they are on different cores. This will help us understand if differences
in flux could cause such problems.

You mentioned in another post that you were using AC to drive the coil?
Did the effect happen with DC?

Never tried it with dc.

Did you measure the voltage on the 1/2 turn?

No.

Was the core itself generating the heat or was it due to the 1/2 turn?

It's been ten years, all I recall is the insulation on the last 1/2 turn
of the coil
got charred.

What was the total current through the coil?


I think about a litle over 2 amps at 600khz.

Was it possible the coil could have been shorting out on another turn or
the core?

No

Was it really 1/2 a turn getting hot or "just the end of it"?

It was the 1/2 turn.

Was the coil tested by itself outside the circuit? If so did it exhibit
the same phenomena?

Not by us, but someone else confirmed our observation.

What was the end of the coil that generated the heat connected to? Was
the connection itself possible cause for the heat?

Naw.

Was the coil reversed in the circuit? If so did it exhibit the same
problem with the ends switched?

No

You mentioned that you tried 4 turns and 5 turns and the problem went
away. Did it go away completely or partially? Was those two coils made
exactly the same way and connected the same or were they in any way
different besides just the turn difference?

We shipped the product, as far as I know the didn't it back for
replacement smoke.

Was the coil one continuous piece? the 1/2 turn was not spliced on?

One continuous piece.

Did you try a 5.5 and/or 6 turn coil?
No


Did the 1/2 turn end get hot very quick or did it take a while?
Basically seconds or minutes?

Minutes.

Did you try to change the direction of the core relative to the coil? If
so did it make any difference?

No

Is there any possible way the core itself could have been generating the
heat at the 1/2 turn and the effect you experienced was just the core
heating up that 1/2 first?

I don't think so.

Did you allow the inductor to run a long time? If so, What was the
effect still? Was the whole coil hot or still just the 1/2 turn?

The whole think would have got hot, we were pushing limits.

Hopefully you can answer some of these questions. It sounds to me like
you didn't do much troubleshooting so I expect most of them can't be
answered so the true reason probably will not be known.

Probably, won't know the answer, once we learned the 1/2 turn overheated
we didn't do it again.
But it stuck as a curiosity. I had one of the overheated 4-1/2 turn
bobbins hanging on a cord over my
bench for years. It's been ten years but my old bench is still the same,
next time I stop in I'll see if it
the bobbins is still hanging.



I don't know what to say. Just not enough information. If your looking
from some exotic possibility I don't think you'll find one.

The reason is that the current through the wire will almost be surely the
same through out all points along the wire. That precisely means that the
heat generated per unit length will be the same. Even if you have some
crazy resonance or core flux/transformer effect going on, that current in
the wire has to be the same through the whole wire(assuming no shorts).

You can't have electrons bunch up on part of the wire and not on any other
part. Even if you could, that bunch would have to flow through the wire
from one part to another and on average it would heat it up uniformly.

The reason is simple, We all know that for a power supply when one
electron is supplied on the wire one electron leaves it so there really is
no way to "bunch" it up.

Now, if the wire is not uniform in size or resistance then the heating
effect is not uniform. As smith mentioned about the joint connecting the
coil. In this case it is possible that the joint could be heating up and
it was being passed along to the 1/2 turn and it just happens that you
didn't let it run long enough to heat up any more turns.

The 1/2 turn was really a point at the joint and the heat just spread
about about 1/2 turn.

To me this is the most plausable case. I'm not sure if it's physically
possible any other way that involves the coil itself generating generating
the heat. (I gave a good reason about about electron flow being uniform in
the wire)

It may be possible using some type of standing wave or transformer like
effect but even here I can't see it possible if the wire's restance per
unit length is constant.

I'm sure it was not a bad connection.
I know all about heat caused by I^2 x R at connections.
In fact just yesterday I was checking for bad connections on my electric
gokart and I burned my finger! I found a loose connection between a
5/16" post and a ring terminal connected to a 6 gauge wire.
It was some oddity about the 1/2 turn in a potcore. I suspect the low
turns count is also important to the phenomena.
I thought I'd ask and see if anybody else ever had the problem.
Closest I got was when John Larkin said,
"I've seen it do strange stuff, too."
John, would you care to elaborate?
MikeK

Heating in 4-1/2 turn inductor
 

"Tim Williams" wrote in message
...
"Jeff Johnson" wrote in message
...
big ****in snip
The reason is that the current through the wire will almost be surely the
same through out all points along the wire.

Well, no:
http://en.wikipedia.org/wiki/Proximi...romagnetism%29

the current density varies strongly, especially if the wire is thick
(curiously, it was never stated what size wire is in question, nor what
type; 600kHz suggests fine stranded litz!).


Again it has been 10 years, but I think the coil in question had something
like 4-24 gauge wires in parallel, maybe 28 gauge.

Wire near the gap (which is usually placed in the center, right underneath
the winding) experiences fringing fields, which dramatically increases
losses.

Yes, we learned to space our wire away from the gap, after finding burned
wire and melted bobbins in the center where the gap was.

That precisely means that the heat generated per unit length will be the
same.

Eddy currents in the center of the coil are much stronger than at the
ends, so the center of a solenoid heats up much more strongly.

The uncooled coil in this video demonstrates proximity effect:
http://www.youtube.com/watch?v=nY66rBJvbpY
See the connections are clean and coppery, but the coil has seen better
days. You can't really tell if the center turns are hotter; they probably
are by a little bit.


Of course Kirchoff is harder to fool, obviously the total current flowing
along the wire is the current flowing along the wire period. Unless
there's a short, which supposedly was inspected as to have none.


None of these are an "end" effect. The only possible explanation is a
short, or else, "look harder". It's plainly obvious that the cause is NOT
"an additional half turn". It is only a coincidence that this symptom
showed up between turns 4 and 5.

Tim

And some people don't believe in DDWFTTW! :-)
But thanks, MikeK

Heating in 4-1/2 turn inductor
 

On Fri, 27 Aug 2010 09:57:31 -0500, "amdx" wrote:


"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...

"Jeff Johnson" wrote in message
...


"amdx" wrote in message
...

"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!?!?!
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
describing it
was the LAST 1/2 turn wound on the bobbin.
MikeK

What you describing is,

L1 V L2
V1--/\/\--+--/--0

on the same core?

L2, the 1/2 turn part of the coil is behaving wildly different than
expect?

After all, ideally L2 has resistance in direct proportion to the total
winding which in this case 0.5*/4.5 ~ 11% of the total resistance of the
coil.

In a single coil the power dissipation of the 1/2 turn would also be ~
11% and this is quite easy to see. You are saying that it is much more
than this as if the ratio's were turned up side down. Something like the
1/2 part dissipating 90% and the 4 turns part dissipating 10%?

if you agree with the layout of

L1 V L2
V1--/\/\--+--/--0

Then it is easy to see that in ideal circumstances the current through
L1 should equal that of L2 and the I^2R heating would produce the
results I described first.

Instead of assuming the two inductors are on the same core we can assume
they are on different cores. This will help us understand if differences
in flux could cause such problems.

You mentioned in another post that you were using AC to drive the coil?
Did the effect happen with DC?

Never tried it with dc.

Did you measure the voltage on the 1/2 turn?

No.

Was the core itself generating the heat or was it due to the 1/2 turn?

It's been ten years, all I recall is the insulation on the last 1/2 turn
of the coil
got charred.

What was the total current through the coil?


I think about a litle over 2 amps at 600khz.

Was it possible the coil could have been shorting out on another turn or
the core?

No

Was it really 1/2 a turn getting hot or "just the end of it"?

It was the 1/2 turn.

Was the coil tested by itself outside the circuit? If so did it exhibit
the same phenomena?

Not by us, but someone else confirmed our observation.

What was the end of the coil that generated the heat connected to? Was
the connection itself possible cause for the heat?

Naw.

Was the coil reversed in the circuit? If so did it exhibit the same
problem with the ends switched?

No

You mentioned that you tried 4 turns and 5 turns and the problem went
away. Did it go away completely or partially? Was those two coils made
exactly the same way and connected the same or were they in any way
different besides just the turn difference?

We shipped the product, as far as I know the didn't it back for
replacement smoke.

Was the coil one continuous piece? the 1/2 turn was not spliced on?

One continuous piece.

Did you try a 5.5 and/or 6 turn coil?
No


Did the 1/2 turn end get hot very quick or did it take a while?
Basically seconds or minutes?

Minutes.

Did you try to change the direction of the core relative to the coil? If
so did it make any difference?

No

Is there any possible way the core itself could have been generating the
heat at the 1/2 turn and the effect you experienced was just the core
heating up that 1/2 first?

I don't think so.

Did you allow the inductor to run a long time? If so, What was the
effect still? Was the whole coil hot or still just the 1/2 turn?

The whole think would have got hot, we were pushing limits.

Hopefully you can answer some of these questions. It sounds to me like
you didn't do much troubleshooting so I expect most of them can't be
answered so the true reason probably will not be known.

Probably, won't know the answer, once we learned the 1/2 turn overheated
we didn't do it again.
But it stuck as a curiosity. I had one of the overheated 4-1/2 turn
bobbins hanging on a cord over my
bench for years. It's been ten years but my old bench is still the same,
next time I stop in I'll see if it
the bobbins is still hanging.



I don't know what to say. Just not enough information. If your looking
from some exotic possibility I don't think you'll find one.

The reason is that the current through the wire will almost be surely the
same through out all points along the wire. That precisely means that the
heat generated per unit length will be the same. Even if you have some
crazy resonance or core flux/transformer effect going on, that current in
the wire has to be the same through the whole wire(assuming no shorts).

You can't have electrons bunch up on part of the wire and not on any other
part. Even if you could, that bunch would have to flow through the wire
from one part to another and on average it would heat it up uniformly.

The reason is simple, We all know that for a power supply when one
electron is supplied on the wire one electron leaves it so there really is
no way to "bunch" it up.

Now, if the wire is not uniform in size or resistance then the heating
effect is not uniform. As smith mentioned about the joint connecting the
coil. In this case it is possible that the joint could be heating up and
it was being passed along to the 1/2 turn and it just happens that you
didn't let it run long enough to heat up any more turns.

The 1/2 turn was really a point at the joint and the heat just spread
about about 1/2 turn.

To me this is the most plausable case. I'm not sure if it's physically
possible any other way that involves the coil itself generating generating
the heat. (I gave a good reason about about electron flow being uniform in
the wire)

It may be possible using some type of standing wave or transformer like
effect but even here I can't see it possible if the wire's restance per
unit length is constant.

I'm sure it was not a bad connection.
I know all about heat caused by I^2 x R at connections.
In fact just yesterday I was checking for bad connections on my electric
gokart and I burned my finger! I found a loose connection between a
5/16" post and a ring terminal connected to a 6 gauge wire.
It was some oddity about the 1/2 turn in a potcore. I suspect the low
turns count is also important to the phenomena.
I thought I'd ask and see if anybody else ever had the problem.
Closest I got was when John Larkin said,
"I've seen it do strange stuff, too."
John, would you care to elaborate?
MikeK


One of my engineers, a real magnetics guy who used to work for Signal
Transformer, designed a push-pull forward dc/dc converter using a pot
core. This was in the power supply of a laser controller [1] where the
customer, for reasons never rationalized, wanted our +24 power to be
isolated. One center-tapped winding included a half turn on each side,
and efficiency was terrible. Going to full turns, and wasting a bit
more power in a downstream linear regulator, worked much better.
Neither of us understood why.

John

[1] The controller is still in production. It manages the firing of a
series of deep-UV MOPA lasers that expose some fraction of the
fine-pitch ICs made in the world.

Heating in 4-1/2 turn inductor
 

"raypsi" wrote in message
...
Hey OM:

First how many newsgroups do you have this thread cross posted on?

How many do you see it on?

Second: A 1/2 turn is equal to 1 turn in a pot core so 4 and 1/2 turns
is the same as 5 turns.

I don't think so. If I put 4-1/2 turns on a potcore and measure inductance,
then unwind the 1/2 turn, do you think the inductance will measure the same?

Lastly OM: I think you are looking at a classic case of proximity
effect.

It may be, but I can't explain to myself how that would happen. I do think
it has
something to do with the flux through the coil though.
Thanks, MikeK


73 OM
de n8zu





On Aug 25, 4:09 pm, "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

Heating in 4-1/2 turn inductor
 

On 8/27/2010 1:07 AM, Jeff Johnson wrote:
...Even if you
have some crazy resonance or core flux/transformer effect going on, that
current in the wire has to be the same through the whole wire(assuming
no shorts).

Hmmm...it is easy to demonstrate two coils in series, loaded with two
caps to provide two (different Fx) resonant paths - the coil in the part
that resonates carries way more current than the path that is not
resonating...

Brian w

Heating in 4-1/2 turn inductor
 

"John Larkin" wrote in
message ...
big ****ing snip
One of my engineers, a real magnetics guy who used to work for Signal
Transformer, designed a push-pull forward dc/dc converter using a pot
core. This was in the power supply of a laser controller [1] where the
customer, for reasons never rationalized, wanted our +24 power to be
isolated. One center-tapped winding included a half turn on each side,
and efficiency was terrible. Going to full turns, and wasting a bit
more power in a downstream linear regulator, worked much better.
Neither of us understood why.

Well that's obvious, it's acting like two transformers. Huge LL between
halves. Imagine the full path of each turn, it's effectively a full turn
around one outer limb or the other, but not both.

Whether or not you curve it tightly around the center limb doesn't matter,
intensions are lost on inanimate objects. :)

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Heating in 4-1/2 turn inductor
 

I'm sure it was not a bad connection.
I know all about heat caused by I^2 x R at connections.
In fact just yesterday I was checking for bad connections on my electric
gokart and I burned my finger! I found a loose connection between a
5/16" post and a ring terminal connected to a 6 gauge wire.
It was some oddity about the 1/2 turn in a potcore. I suspect the low
turns count is also important to the phenomena.

And I think these is exactly why you are pursing it. You believe it must be
due to some fanciful effect because of the "1/2" turn as if 0.5 was more
special than 0.73524 or 1.0.

You have the mindset to those people that think 3.141592... is special. This
causes you to overlook the obvious. First, pi in another base is not
3.1415.... but in any case it must have been some number. In some alternate
universe we could imagine it being 5.43524. In is only special in the sense
that we make it special because it seems different than most other decimals.
In fact though there are a ton of "special numbers".


The theory of ideal inductors does not give any reason why a 1/2 turn should
at all be important. Tim mentioned the promixity effect which would produce
heating throughout the windings and more so for inner windings so it is not
the correct effect here.

Most other phenomena that stand any chance of creating the effect would do
it symmetrical. Why? Because both ends have no special preference for the
heat. This should be completely obvious.

The only chance is if you wrapped the windings in such a strange and crazy
way and a totally screwed up core as to make a retard jealous of your work.

We think of other possibilities that would work in a non-symmetric way but
they just don't seem to gel with physics. No one can say for sure since you
obviously don't have any good investigative information to provide about it.

Almost always things that seem phenomenal are due to simple mistakes. If you
are really serious about it then I would suggest you attempt to reproduce
the result then do a bit more investigation. Until then you might want to
drop it because we don't need another cold fusion story circulating around.
(I'm being facetious)

Heating in 4-1/2 turn inductor
 

"Jeff Johnson" wrote in message
...


I'm sure it was not a bad connection.
I know all about heat caused by I^2 x R at connections.
In fact just yesterday I was checking for bad connections on my electric
gokart and I burned my finger! I found a loose connection between a
5/16" post and a ring terminal connected to a 6 gauge wire.
It was some oddity about the 1/2 turn in a potcore. I suspect the low
turns count is also important to the phenomena.

And I think these is exactly why you are pursing it. You believe it must
be due to some fanciful effect because of the "1/2" turn as if 0.5 was
more special than 0.73524 or 1.0.

You have the mindset to those people that think 3.141592... is special.
This causes you to overlook the obvious. First, pi in another base is not
3.1415.... but in any case it must have been some number. In some
alternate universe we could imagine it being 5.43524. In is only special
in the sense that we make it special because it seems different than most
other decimals. In fact though there are a ton of "special numbers".


The theory of ideal inductors does not give any reason why a 1/2 turn
should at all be important. Tim mentioned the promixity effect which would
produce heating throughout the windings and more so for inner windings so
it is not the correct effect here.

Most other phenomena that stand any chance of creating the effect would do
it symmetrical. Why? Because both ends have no special preference for the
heat. This should be completely obvious.

The only chance is if you wrapped the windings in such a strange and crazy
way and a totally screwed up core as to make a retard jealous of your
work.

We think of other possibilities that would work in a non-symmetric way but
they just don't seem to gel with physics. No one can say for sure since
you obviously don't have any good investigative information to provide
about it.

Almost always things that seem phenomenal are due to simple mistakes. If
you are really serious about it then I would suggest you attempt to
reproduce the result then do a bit more investigation. Until then you
might want to drop it because we don't need another cold fusion story
circulating around.
OH, you think I might have some overunity thing going on?
Let me get my magnet motor out!
(I'm being facetious)
Me to.
MikeK

Heating in 4-1/2 turn inductor
 

On Aug 27, 10:31*am, "Jeff Johnson" wrote:

The theory of ideal inductors does not give any reason why a 1/2 turn should
at all be important.

Oh, yes, it DOES give a reason. A pot core (or E cores) has a pair of
return
flux arms flanking the central element, and a '1/2 turn' winding
imbalances
those return fluxes.

That means the 3-d flux inside the core is very different in the
two cases, and if one return arm saturates, that flux distribution
alters
considerably during the cycle. That causes (1) the material to heat
due to remagnetization in an asymmetric way, (2) the forces of the
pole pieces to modulate as the field builds. The first effect (caused
by material hysteresis) might have been expected. The second
effect, though, will cause ultrasonic excitation of the core, maybe
creating cracks by mechanical stress.

Heating in 4-1/2 turn inductor
 

"whit3rd" wrote in message
...
On Aug 27, 10:31 am, "Jeff Johnson" wrote:

The theory of ideal inductors does not give any reason why a 1/2 turn
should
at all be important.

Oh, yes, it DOES give a reason. A pot core (or E cores) has a pair of
return
flux arms flanking the central element, and a '1/2 turn' winding
imbalances
those return fluxes.


In the ideal case the fringe effects are usually ignored. Atleast every book
I've read about inductance supposes the fringe effects can be ignored.
Remember, we are talking about the inductive effects on heating those ends
and not the inductance itself.

That means the 3-d flux inside the core is very different in the
two cases, and if one return arm saturates, that flux distribution
alters
considerably during the cycle. That causes (1) the material to heat
due to remagnetization in an asymmetric way, (2) the forces of the
pole pieces to modulate as the field builds. The first effect (caused
by material hysteresis) might have been expected. The second
effect, though, will cause ultrasonic excitation of the core, maybe
creating cracks by mechanical stress.

In all causes if the the ends are relatively symmetric then both should heat
up equally. Also the fringe effects tend to reduce the heat on the ends and
not increase it. Also all the effects you describe should heat the central
windings more than the outside and have little to do with the end turn
amount. Again, In all cases it would be symmetric unless the core or
windings themselfs were wound in some weird way. 99.99999% of all inductors
are wound to be symmetric.

So if there is some effect that is due to the reasons you describe then it
must be because they let a 2 year old create the winding.

Now, you'll have to excuse me if I make some assumptions about what is going
on. When he says inductor I think of basically something that looks like an
inductor and acts like one. So if he did something non-standard then he
should include that information.

I cannot totally exclude some physical reason why such a thing could happen
because I don't know all the possibities. Given the assumption that what
they created was very much inductor like no one has presented any reason why
only one side would heat up and the rest of the coil would be fine that is
due to the coil/core.

The most likely effect is that the connection on that one end was bad or was
shorting out. This is the best guess given the little amount of information
that was provided.

Since he said the same result was produced independently then this possibly
suggests something else but the same mistake could have been made twice.

It would be quite easy to create a partially laminated core that was not
laminated near one end. The core would heat up due to eddy currents which
would heat up the 1/2 turn first. Who the hell would use such a core? Such
behavior is to be expected when someone doesn't know what they are doing.

Heating in 4-1/2 turn inductor
 

On Aug 27, 1:30*pm, "Jeff Johnson" wrote:
"whit3rd" wrote in message

...

On Aug 27, 10:31 am, "Jeff Johnson" wrote:

The theory of ideal inductors does not give any reason why a 1/2 turn
should
at all be important.

Oh, yes, it DOES give a reason. *A pot core (or E cores) has a pair of
return
flux arms flanking the central element, and a '1/2 turn' winding
imbalances
those return fluxes.

In the ideal case the fringe effects are usually ignored.

What 'fringe effects'? This is about the flux contained in the
magnetic arms of the core, not outside somewhere

That means the 3-d flux inside the core is very different in the
two cases, and if one return arm saturates, that flux distribution
alters
considerably during the cycle. *That causes (1) the material to heat
due to remagnetization in an asymmetric way, (2) the forces of the
pole pieces to modulate as the field builds. *The first effect (caused
by material hysteresis) might have been expected. *The second
effect, though, will cause ultrasonic excitation of the core, maybe
creating cracks by mechanical stress.

...all the effects you describe should heat the central
windings more than the outside and have little to do with the end turn
amount.

Oh, this has nothing to do with ohmic heating in the windings. It
concerns
the B-H curve, which (for a hysteretic material) loops around some
area.
At 600 kHz, the area, multiplied by 6e6, is the power lost when the
magnetic material is forced to traverse that loop.
If part of the material saturates, its loop is of greater area than
the rest of
the material. A core that should handle 2A without overheating, then
would overheat.

Heating in 4-1/2 turn inductor
 

"whit3rd" wrote in message
...
On Aug 27, 10:31 am, "Jeff Johnson" wrote:

The theory of ideal inductors does not give any reason why a 1/2 turn
should
at all be important.

Oh, yes, it DOES give a reason. A pot core (or E cores) has a pair of
return
flux arms flanking the central element, and a '1/2 turn' winding
imbalances
those return fluxes.

That means the 3-d flux inside the core is very different in the
two cases, and if one return arm saturates, that flux distribution
alters
considerably during the cycle. That causes (1) the material to heat
due to remagnetization in an asymmetric way, (2) the forces of the
pole pieces to modulate as the field builds. The first effect (caused
by material hysteresis) might have been expected. The second
effect, though, will cause ultrasonic excitation of the core, maybe
creating cracks by mechanical stress.

Some may find interest in this.
A turn around an outside leg of an E-core is called a half-turn because it
encloses only one-half of the cross-sectional area of a turn around the
center leg. It is well known that a half-turn in a secondary winding of a
power transformer greatly increases the leakage inductance between windings,
thus causing an adverse effect on cross-regulation. However, the increased
leakage inductance of a half-turn can be very beneficial in tapped inductors
for boost circuits and in coupled output chokes. This paper explains some of
these little-known applications of a half-turn. The theory and formulae for
prediction of leakage inductance added by such a half-turn are presented
http://ieeexplore.ieee.org/Xplore/lo...hDecision=-203

Heating in 4-1/2 turn inductor
 

In article , "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

** Is it a 5-turn inductor with 1/2 turn shorted?

--
Richard L. Measures. AG6K, 805-386-3734, www.somis.org

Heating in 4-1/2 turn inductor
 

In article ,
"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

Only two ideas from me, and they seem weak.

A half turn means the current goes in and out on separate sides. That
makes one turn of inductance perpendicular to the rest of the turns that
would skew the magnetic field.

If it is a powdered iron core, the volts per turn could be high enough
that it conducts electricity.
--
I won't see Google Groups replies because I must filter them as spam

Heating in 4-1/2 turn inductor
 

On Fri, 27 Aug 2010 14:23:13 -0700 (PDT), whit3rd
wrote:

On Aug 27, 1:30*pm, "Jeff Johnson" wrote:
"whit3rd" wrote in message

...

On Aug 27, 10:31 am, "Jeff Johnson" wrote:

The theory of ideal inductors does not give any reason why a 1/2 turn
should
at all be important.

Oh, yes, it DOES give a reason. *A pot core (or E cores) has a pair of
return
flux arms flanking the central element, and a '1/2 turn' winding
imbalances
those return fluxes.

In the ideal case the fringe effects are usually ignored.

What 'fringe effects'? This is about the flux contained in the
magnetic arms of the core, not outside somewhere

That means the 3-d flux inside the core is very different in the
two cases, and if one return arm saturates, that flux distribution
alters
considerably during the cycle. *That causes (1) the material to heat
due to remagnetization in an asymmetric way, (2) the forces of the
pole pieces to modulate as the field builds. *The first effect (caused
by material hysteresis) might have been expected. *The second
effect, though, will cause ultrasonic excitation of the core, maybe
creating cracks by mechanical stress.

...all the effects you describe should heat the central
windings more than the outside and have little to do with the end turn
amount.

Oh, this has nothing to do with ohmic heating in the windings. It
concerns
the B-H curve, which (for a hysteretic material) loops around some
area.
At 600 kHz, the area, multiplied by 6e6, is the power lost when the
magnetic material is forced to traverse that loop.
If part of the material saturates, its loop is of greater area than
the rest of
the material. A core that should handle 2A without overheating, then
would overheat.

You may be on to something. Maybe. At least it make physics sense to
me, but then i are enguneer. It does show a path to have thermal
non-uniformity that is regenreative.

Say Mike just how big is that pot core?

Heating in 4-1/2 turn inductor
 

"JosephKK" wrote in message
...
On Fri, 27 Aug 2010 14:23:13 -0700 (PDT), whit3rd
wrote:

On Aug 27, 1:30 pm, "Jeff Johnson" wrote:
"whit3rd" wrote in message

...

On Aug 27, 10:31 am, "Jeff Johnson" wrote:

The theory of ideal inductors does not give any reason why a 1/2 turn
should
at all be important.

Oh, yes, it DOES give a reason. A pot core (or E cores) has a pair of
return
flux arms flanking the central element, and a '1/2 turn' winding
imbalances
those return fluxes.

In the ideal case the fringe effects are usually ignored.

What 'fringe effects'? This is about the flux contained in the
magnetic arms of the core, not outside somewhere

That means the 3-d flux inside the core is very different in the
two cases, and if one return arm saturates, that flux distribution
alters
considerably during the cycle. That causes (1) the material to heat
due to remagnetization in an asymmetric way, (2) the forces of the
pole pieces to modulate as the field builds. The first effect (caused
by material hysteresis) might have been expected. The second
effect, though, will cause ultrasonic excitation of the core, maybe
creating cracks by mechanical stress.

...all the effects you describe should heat the central
windings more than the outside and have little to do with the end turn
amount.

Oh, this has nothing to do with ohmic heating in the windings. It
concerns
the B-H curve, which (for a hysteretic material) loops around some
area.
At 600 kHz, the area, multiplied by 6e6, is the power lost when the
magnetic material is forced to traverse that loop.
If part of the material saturates, its loop is of greater area than
the rest of
the material. A core that should handle 2A without overheating, then
would overheat.

You may be on to something. Maybe. At least it make physics sense to
me, but then i are enguneer. It does show a path to have thermal
non-uniformity that is regenreative.

Say Mike just how big is that pot core?

I think it may have been a 3622 but could have been a 4229.
MikeK