[AMPS] Fuses

[Peter Chadwick]

Rich says:

>A proper glitch resistor needs no fuse.   My guess is that most of the 
>damage caused by peak fault current (delivered by the filter capacitor) 
>takes place in roughly the first couple of milliseconds.  

40swg  (0.0048 ins dia) wire fuses at about 2 amps. Suspended between
suitable supports, it should go in well under 2millisecs, thus reducing the
energy dissipated in the tube. Then it has to be replaced, and if the tube
is a tetrode, some sort of protection is needed for the screen. A suitably
big (physical size/power rating) glitch resistor will presumably hold on
until the primary breaker comes out, but I just wonder if the strain is
worth avoiding. At say 3kV, a 50 ohm glitch resistor can be expected to get
60amps through: that's a fair amount of current for a tube, and for the
capacitor bank. I guess it's case of whether or not the inconvenience of
changing the fuse is worth on the (hopefully!) rare occasion of having to is
worth the reduction of strain on all the other components.


73

Peter G3RZP


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