Interesting.
Spark gaps are simple until you go RSG, then looking at solid state
alternatives becomes appealing!
I think that if the speed issue can be dealt with there's some possible
advantages, namely being cheap and robust. You can get single devices in
the 2 - 5kV range that handle thousands of amps continuously for much less
than the equivalent IGBT capability. I can see them working well with a
parallel MOT supply.
I see there are some cheap ultrafast diodes with a 100A+ continuous rating
that might be up to the job of being used to limit the recovery time. Am I
right in my assumption that the these wouldn't need a particularly HV
rating because they should in theory be shielded by the SCR?
On Wed., 5 Dec. 2018, 11:50 pm jimlux <jimlux@xxxxxxxxxxxxx wrote:
> On 12/4/18 11:24 PM, Greg Peters wrote:
> > Hi all,
> >
> > I know this has been discussed before but forget why it was dismissed.
> Can
> > someone remind me?
> >
>
> I think the IGBT approach was found superior -
>
> SCRs are unidirectional, and don't switch very fast.
> You'd need back to back SCRs.
>
> Sort of like the use of a hydrogen thyratron (which has also been
> tried.. they're fast to turn on, not as fast to quench)
>
>
>
> There's also the voltage issue - you'd need to stack them to get the
> voltage you need for a NST.
>
>
> I think that observation is what drove the initial "off line tesla
> coils" - using the rectified power line as a several hundred volt DC
> bus, then using commercial power semiconductors - I seem to recall that
> some folks did start with SCRs, but then IGBTs (which are much faster)
> took over, and the rest is history with the DRSSTC - which is
> essentially a high power switching power supply with an air core
> transformer.
>
>
> When it gets right down to it, a spark gap is a pretty inexpensive and
> decent way to switch high currents at 10s of kV.
>
> > Many thanks,
> >
> > Greg
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxxxxxxxxxx
> > https://www.pupman.com/mailman/listinfo/tesla
> >
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxxxxxx
> https://www.pupman.com/mailman/listinfo/tesla
>
On Wed., 5 Dec. 2018, 11:50 pm jimlux <jimlux@xxxxxxxxxxxxx wrote:
> On 12/4/18 11:24 PM, Greg Peters wrote:
> > Hi all,
> >
> > I know this has been discussed before but forget why it was dismissed.
> Can
> > someone remind me?
> >
>
> I think the IGBT approach was found superior -
>
> SCRs are unidirectional, and don't switch very fast.
> You'd need back to back SCRs.
>
> Sort of like the use of a hydrogen thyratron (which has also been
> tried.. they're fast to turn on, not as fast to quench)
>
>
>
> There's also the voltage issue - you'd need to stack them to get the
> voltage you need for a NST.
>
>
> I think that observation is what drove the initial "off line tesla
> coils" - using the rectified power line as a several hundred volt DC
> bus, then using commercial power semiconductors - I seem to recall that
> some folks did start with SCRs, but then IGBTs (which are much faster)
> took over, and the rest is history with the DRSSTC - which is
> essentially a high power switching power supply with an air core
> transformer.
>
>
> When it gets right down to it, a spark gap is a pretty inexpensive and
> decent way to switch high currents at 10s of kV.
>
> > Many thanks,
> >
> > Greg
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxxxxxxxxxx
> > https://www.pupman.com/mailman/listinfo/tesla
> >
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxxxxxx
> https://www.pupman.com/mailman/listinfo/tesla
>
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