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Re: High frequency impedance of a neon sign transformer

tesla-at-grendel.objinc-dot-com On Mon, 25 Mar 1996 11:30:58 +0700, you
wrote:


>Ed Phillips EP wrote:


>(1) Any inductor/transformer with a standard 60Hz (thick)  
>laminated core will have an inductance about MU (read 
>magnetic permeability) times bigger than for air at 60Hz.
>MU might be say 1000 for silicon steel... the exact value
>dosen't change the argument just the fact that MU makes the
>inductance much bigger than it would have been if the iron
>core was absent.
>	Now, as the frequency is raised, the skin depth of the
>laminations becomes less than their thcikness. When this happens
>the magnetic field induced by the windings cannot fully penetrate
>into the iron laminations. The effect of this is simply like
>subtracting away the iron deeper than a skin depth. As the frequency
>goes to infinity the skin depth goes to zero and the effective
>permeability goes to that of air! So the inductance and impedance
>go down with frequency even though the winding remains inductive
>in character ( Voltage leads current).

>
>-Ed Harris
>
>
I just received the used LCR bridge that I ordered 2 weeks ago. I
grabbed the good secondary from my blown 15Kv 60ma neon that I
dissembled last month. I measured:

	L       = 8.29H
	Q      = 2.6
	Rdc = 27K ohms

The L and Q measurements were at 1Khz. The coil was "air core", that
is it was not on the neon. Caveats: I've not had a chance to check the
calibration yet and the biggest 1 yet. This was my first inductance
measurement with an LCR bridge, so I may not have done it correctly.
note: Q=Xl/R = 2*pi*1000*8.29/27,000 =1.93 at 1Khz, so I'm off on some
measurement.

more as I get better with measuring known values of inductors and
caps.

	jim