>Phil, K5PC says
>
>>The use of variacs with capacitor input power supplies is not good
>>engineering practice. It can reduce a nice, stiff 240 volt line to mush
>>in many >cases.
Amen - although this is much less the case when a resonant-choke dc
filter is used instead of C-input dc filter
>
>Depends on how far up the variac you are. .
..snip...
agreed.
>
RE: Big Bangs:
>....... I'm looking into using a hydrogen
>thyratron as a crowbar. OTH, my company makes big thyristors (2000volt,
>1200Amp sort of level) for controlling electric trains and the
>like..........unfortunately, it's another plant, so it's not too easy to
>get samples....but I'm trying! But certainly a bit of protection is
>desirable........and it doesn't cost much.......even if its only the 50
>ohm resistor in the HV and diodes across the meters.
Svetlana's recommended 10 to 25 ohms of peak fault current limiting
resistance (a.k.a., a glitch R) is probably plenty. IMO, a reasonable
rule-of-thumb is to limit fault current to 200A-peak, and to use
200A-peak glitch diodes (1N5400-series, or similar). However, the glitch
resistor that is used must be able to discharge the filter capacitors
without breaking down between adjacent turns. Bigger/longer is better.
>
Rich---
R. L. Measures, 805-386-3734, AG6K
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