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Re: [TCML] Spark gaps, Solid state switches and diodes
My question is more about "why" the low value. In other words, what
occurs different between 4700 ohms and 680 ohms for Roff? I of course
realize the time base, but I'm more curious as to how the coil, power,
sparks, or whatever is affected? For example, say with a given C1 and
IGBT where we then know gate capacitance for the components used, how
does changing an ensured off time (without charging compromises) differ
from say taking it to the edge with a low value Roff? If the coil
quenches in 2 primary notches and the components are set for 5, so what?
Nanosecond delays are incurred until charging begins. But say I set the
components for 1 primary notch turn off, well, then I'm attempting to
force off current (which doesn't like to be forced off [and in my
experience won't be forced off]).
I'm not saying the 680 ohm is not adequate, I'm simply saying I don't
see the benefit electrically, so I'm asking about anything "else" that
may help me realize why the low value? From my thought process, 5K or
680 ohms should perform similarly in this specific portion of the
circuit (for a narrow band Fr of coils). But what of other frequencies?
Your CM-600 brick is a different flavor than discreet components. I
don't really know how else to ask the question. If a coiler changes say
a resistor value on the SISG (Ron or Roff), then why? What did or did
not happen with original value? So often what is talked about is that
now "I'm using this value". Never is there "why" I'm now using this value.
Finn Hammer wrote:
The 680 ohm seems "on the edge" and specific to your coil. Were you
trying to perform solid state forced quenching? This would be ok for
some coils to a degree, but could be very risky to say my 70kHz coil
that I'm running my SISG on where 330us is 3rd notch primary
quenching. The 4700 ohm provides plenty of ring time without an IGBT
energy crash and doesn't compromise charging. I'm just curious what
you actually gain from setting Roff so low?
I am running 680ohms on my CM600 T-Brisg
The quench time is dependant on gate capacitance, C1 value but also on
current trough IGBT. The gate-emitter capacitance is pumping charge
into the gate by each oscillation.
Cheers, Finn Hammer
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