[Amps] Serious design stage

[Ian White, G3SEK]

Jim Isbell wrote:
>After collecting parts for most of a year I am in the serious design 
>stage of a 4-1000A linear.  The power supply, because of its size is to 
>be external and connected by a cable.
>
>In the first design I was going to bring the 6500VDC power through a 
>cable to the linear.  But then it occurred to me that since the main 
>reason for the separate supply was the size...which is MOSTLY the 12KVA 
>transformer I am using.  It might be safer to just make the transformer 
>external and have the rectifiers and filter capacitors in the 
>transmitter case thus allowing the only the transmission of AC, at a 
>lower potential, (using a voltage doubler circuit) in the cable.  Thus, 
>by just turning off the input power I could eliminate the potential on 
>the cable instantly...or almost so...while the filter capacitors which 
>are the biggest danger would be in the transmitter cage and would be 
>connected to shorting circuits controlled by the safety switches on the 
>lid of the transmitter.
>
>There must be some reason this is not a good idea as I have never seen 
>it done.
>
It's mostly the inconvenience of running several high-voltage, 
high-current cables - and also multiple redundant safety ground bonding.

You also need to think *very* carefully about the right locations for 
mains and HV-AC fuses, to protect against a short if any wire breaks... 
or any pair of wires... or...

In all other respects, it's not much different from 'remoting' the 
complete HV power supply, and that's a routine thing to do.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)

http://www.ifwtech.co.uk/g3sek