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Re: [TCML] final word on inductance



Thanks Paul.  That's what I've been trying to tell everyone.

With a very small and critical window for zero cross these changes will
affect the cross over point and the prediktor circuit will not track the
thermal, capacitive, and resistive changes accurately enough to be effective
when these effects are integrated over time

Also the thermal changes of inductance and capacitance in the sec coil with
1 - 50 Amps peak flowing certainly will not be a linear match for the
capacitive and resistive changes in the primary circuit with perhaps
hundreds or thousands (large coils) of peak Amps.

The prediktor circuit operates way back on the primary side of the gate
drive transformer and does not monitor primary or secondary currents.  It
works fine without a load in static condition, but in the real world of
operating DRSSTCs it will not function as designed.  It monitors neither the
tank circuit current values nor the sec circuit current values, all which
effect the zero cross over point.

Dr. Resonance




On Thu, Jun 25, 2009 at 6:20 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:

> Hey Paul. When I read Terry's reply to my own brain phart, I thought to
> myself "DOH, I'm and idiot"! I had in mind the physics of current in the
> conductor changing the conductors usable portion and how that affects the
> current in the conductor as well as the inductance. However, increased
> frequency is what causes that in the first place.
>
> I certainly confused myself.. however, it's easy for me to say "hey, I'm
> wrong".
>
> Take care,
> Bart
>
>
> Paul Nicholson wrote:
>
>> > L= Volt second / Amps = Henry
>> > ...
>> > The bottom line is really (volt seconds/Amps) - - -
>> > change either one and the inductance changes.
>>
>> Change either one (volts or current), and the other one changes
>> by the same proportion, so the inductance remains constant.
>>
>> At low frequencies where self-capacitance can be ignored,
>> inductance is a constant for the coil, based only on the
>> geometry and is independent of frequency.  That's the
>> inductance measured by an LCR meter and estimated by
>> Wheeler, etc.
>>
>> At frequencies high enough for self capacitance to matter,
>> the current may no longer be uniform in the coil and the
>> 'effective' inductance is likely to be different from the DC
>> value and will vary slowly with frequency.
>>
>> --
>> Paul Nicholson
>> --
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