solid state gap - Cooling

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi All,

Today I ran some numbers and I estimate that a 15/60 system with an IGBT
SSgap would dissipate 3 watts per every 1000 volt section (probabaly
divided between two IGBTs).  So for a say 24 kV gap that works out to 72
watts of power lost (about 1/3 what a convention gap looses best case :-))
At 3 watts, a small conventional air heat sink will do fine so the water,
oil, compressed atmosphere (neat idea!!) should not be an issue.  For those
big 30kW coils I think it will be a case of diminishing returns like MMCs
are for big coils.  The cost of a "big" MMC is just too high for a big coil
where commercial caps are actually cheaper.  I think it will be awhile
before a SSgap is cost effective for a big coil.  It may not even be
terribly cost effective for a small coil... Yet :-))

I also figure it is better to run the whole isolated heat sink "hot"
without a sil pad or anything.  By directly mounting the device to the sink
with a little thermal grease, the thermal transfer is far better.  I also
don't think the sil pad would hold up to the high frequencies and my have
enough leakage current to fail a sil pad.  Since the heatsinks look small,
this is no big deal.

I still dream and wonder what running a coil with a solid state gap would
be like.  No gap noise, RFI, light, or sound...  It could run forever
without another thought...

Cheers,

	Terry