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Re: SG questions cont'd + power factor

At 11:09 PM 01/04/2000 -0500, you wrote:

>Hi Stan, Terry,
>May I please protrude into this discussion. Trying to determine the secondary 
>inductance of a NST is just what I have been matching wits with. Do I have to 
>spend
>$31,000 for a HP LCR bridge?  I used the Wavetek 27-XT to measure Lp at 0.113
>Henrys. Is this a valid measurement? You may have also noticed that several 
>of the 
>postings on this subject all assume values either for XL sec or Lx sec which 
>solve to
>a 60 Hz Fres using a 0.025 uF cap. Fres is 60 Hz and Lx is 312 H. If an LTR 
>system means larger than 60 Hz my problem is solved. I finally understand 
>that we don't care what Lx sec is and simply rely on its large value to 
>charge the cap in a 
>LTR system. That's what you said and if I got this right,  I have gone thru 
>an epihanous moment.
>
>Happy day,
>Ralph Zekelman    
>

Hi Ralph,

	I thought I had it figured out but core losses and low current saturation
characteristics may have distorted my measurements too.  Ed Phillips' post
got me looking into this and the more I look, the more reasons I find that
this is not at all easy to measure.  The MicroSim model may happen to work
because the values just automatically adjust themselves to give the right
answers.  However, the "real" values could be different than what those
models suggest.

Even the big HighPrice bridge will fall victim to not having enough
magnetizing current.

So I have this idea...

If you energize the core with 60mA of DC current and then suddenly remove
the current source and switch a resistor (the resistor could have always
been in the circuit if it is taken into account) across the windings.  Then
you can watch the voltage decay through the resistance and calculate the
inductance.  Since the resistance of the secondary is rather high, you
would probably need around a 300 volt power supply to do this.  However, I
"think" it would give the answer we are looking for here...

Does this approach sound reasonable or is there some other way to measure
this??  Any shunted transformer experts out there??

Cheers,

	Terry