Topband: measuring transformer core inductance

[Robert Kavanagh <ve3osz@rac.ca>]

Steve KK7UV wrote:

> .  My question to the group is what do you use to measure the inductance 
> of the windings so you know when you reach the desired ratios?  I've had 
> miserable luck doing it by formula and thought the meter would cinch it for me.

Just one point to add to what Nick and Tom have said, if by any chance the 
application for your transformer has a d.c. flowing in one of the windings, 
then the situation changes drastically. The inductance factors in the 
Fair-Rite data are based upon the "initial permeability" of the material 
and that is fine when the coils carry no d.c. If there is d.c. in a winding 
the hysteresis loop of the material comes into play. The inductance is then 
determined by the "incremental permeability".which is less than the 
"initial permeability".

If anybody is interested in this behaviour (and a practical application) 
see my article in the May/June 2003 issue of QEX.

73

Bob
VE3OSZ 

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