[AMPS] perfect amplifiers

[Rich Measures]

>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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