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