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Re: [TCML] First notch quenching?

Steve and Antonio

Thanks for your comments.  I suspect that I will have to think about them
for a while before I grasp the implications.

Steve, I would like to explore a couple of your remarks:

On Wednesday, 26 February 2014 at 7:31 AM, Steve Ward wrote:

>> 2.  Because of the freewheeling diodes anti-parallel to the IGBTs, 
>> leaving the IGBTs undriven might not isolate the energy in the 
>> secondary - presumably, after the end of a burst, the mutual 
>> inductance of the primary and secondary still allows energy to be 
>> transferred to the primary and then to the DC storage capacitor.
> Also agree, so its not quite the same as a spark gap clearing an arc.
>  Basically the energy will go to both the arc and back to the DC bus 
> simultaneously.  You can control an H-bridge to "clamp" its output 
> (to nearly 0V, really 2 junction drops) which will keep it from 
> recharging the DC bus. This would be like a spark gap that doesn't 
> quench, but is also very, very, low loss.

I have previously given some thought to this.  Presumably, the way to
'clamp' the output at the end of a burst would be to change the phase of the
drive to one side of a full-bridge so that the IGBTs are still driven (and
hence there is no need to try to run dc though GDTs), but no additional
energy is injected into the primary tank circuit.

Does anyone do this?  Does it work 'better' or 'worse' than simply ceasing
to drive the IGBTs?

> Viewing the primary and secondary currents on an oscilloscope can 
> be very useful to get some intuition on tuning.

Do you have tips on how I could do so with minimal risk to equipment or
body?  The obvious thing would be to use current transformers, but is there
more to it than that?  For example, does the DSO need to be in a Faraday
cage?  Are there transients (particularly on the secondary) that need to be


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