[Amps] HV fuse

[Ian White, G3SEK]

Oleg Skydan wrote:
>Hi, All !
>
>> On the other hand, for tubes up to the 1500W class, Eimac's and Rich's
>> recommendation is a good one:
>> >> limit I-peak with a suitable HV glitch R and use circuit breakers, or
>> >>250v fuses, in the primaries of the PS transformers.
>
>What do you think about switching HV off with the vacuum relay ?
>Is it better than fuses/circuit breakers in the primaries of the PS
>transformer ?

It doesn't need to be as fast as a vacuum relay. With conventional mains 
switching relays and an electronic anode current sensing circuit, a 
crowbar short will usually shut down the HV without blowing any fuses.

The glitch resistor protects the tube against the first current surge 
out of the HV capacitor, so there is no great strain on the relay.

You must always have mains fuses or breakers as well, but hopefully 
these will only be a backup.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek