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Re: High frequency impedance of a neon sign transformer



Ed:
	You wrote
"It dosn't appear to be capacitive since the measurement shows that
the time dependent voltage leads the current by about 90 degrees no
matter what frequency is used. If I understand you concern correctly,
you're saying that in a pure inductance the impedance always goes up
with frequency, right? So why does my measurement show an inductive
impedance which goes down with frequency - is that it?"
That sure sounds like the current lags the voltage, which implies
an inductive reactance.  My assumption is that the transformer secondary
input impedance should look capacitive above resonance (wherever
that occurs, and I would think it would be pretty low with the
high inductance and inter-winding capacitance).  Since your
measurements appear to show otherwise I guess I will be forced
to CLEAN UP MY WORK BENCH TO FIND ROOM (!!!!) so I can put a
transformer on it and make similar measurements before I comment
further.
	Subject is of current interest as I am looking into protective
filters for the neon xformers, and trying to guess what will really
happen with different configurations.  I am pretty sure that under
some circumstances a typical L section LC filter may have transient
response which will actually stress the transformer more than
operation without it, but the approximations for transformer
impedance at high frequency aren't good enough to trust.
More later,
Ed