amdx said:
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.